U.S. patent application number 13/428830 was filed with the patent office on 2012-08-16 for cationic polymer coated mesoporous silica nanoparticles and uses thereof.
This patent application is currently assigned to The Regents of the University of California. Invention is credited to Zhaoxia Ji, Zongxi Li, Monty Liong, Huan Meng, Andre E. Nel, Derrick Y. Tarn, Tian Xia, Min Xue, Jeffrey I. Zink.
Application Number | 20120207795 13/428830 |
Document ID | / |
Family ID | 46637045 |
Filed Date | 2012-08-16 |
United States Patent
Application |
20120207795 |
Kind Code |
A1 |
Zink; Jeffrey I. ; et
al. |
August 16, 2012 |
CATIONIC POLYMER COATED MESOPOROUS SILICA NANOPARTICLES AND USES
THEREOF
Abstract
A submicron structure having a silica body defining a plurality
of pores is described. The submicron body may be spherical or
non-spherical, and may include a cationic polymer or co-polymer on
the surface of said silica body. The submicron structure may
further include an oligonucleotide and be used to deliver the
oligonucleotide to a cell. The submicron structure may further
include a therapeutic agent and be used to deliver the therapeutic
agent to a cell. An oligonucleotide and therapeutic agent may be
used together. For example, when the oligonucleotide is an siRNA,
the composition may be used to decrease cellular resistance to the
therapeutic agent by decreasing translation of a resistance
gene.
Inventors: |
Zink; Jeffrey I.; (Sherman
Oaks, CA) ; Nel; Andre E.; (Sherman Oaks, CA)
; Xia; Tian; (Los Angeles, CA) ; Ji; Zhaoxia;
(Los Angeles, CA) ; Meng; Huan; (Torrance, CA)
; Li; Zongxi; (Los Angeles, CA) ; Liong;
Monty; (Charlestown, MA) ; Xue; Min; (Los
Angeles, CA) ; Tarn; Derrick Y.; (Irvine,
CA) |
Assignee: |
The Regents of the University of
California
Oakland
CA
|
Family ID: |
46637045 |
Appl. No.: |
13/428830 |
Filed: |
March 23, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2011/043874 |
Jul 13, 2011 |
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13428830 |
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61363945 |
Jul 13, 2010 |
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61466581 |
Mar 23, 2011 |
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61469190 |
Mar 30, 2011 |
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61479751 |
Apr 27, 2011 |
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Current U.S.
Class: |
424/400 ;
428/402; 435/375; 514/44A; 514/44R; 977/773; 977/915 |
Current CPC
Class: |
A61K 31/713 20130101;
B82Y 5/00 20130101; Y10T 428/2982 20150115; A61K 9/5192 20130101;
A61P 35/00 20180101; A61K 2300/00 20130101; A61K 2300/00 20130101;
A61K 9/5115 20130101; A61K 31/704 20130101; A61K 9/0019 20130101;
A61K 9/5146 20130101; A61K 31/713 20130101; A61K 31/704
20130101 |
Class at
Publication: |
424/400 ;
428/402; 514/44.A; 514/44.R; 435/375; 977/773; 977/915 |
International
Class: |
A61K 31/713 20060101
A61K031/713; A61P 35/00 20060101 A61P035/00; A61K 9/00 20060101
A61K009/00; B32B 3/26 20060101 B32B003/26; C12N 5/071 20100101
C12N005/071 |
Goverment Interests
[0002] This invention was made with Government support under Grant
Nos. CA133697, ES016746, ES018766, and ES019528 awarded by the
National Institutes of Health and Grant No. 0830117 awarded by the
National Science Foundation. The Government has certain rights in
this invention.
Claims
1. A submicron structure, comprising: a silica body defining a
plurality of pores and an outer surface between pore openings of
said plurality of pores, a cationic polymer on the surface of said
silica body, and wherein said submicron structure has a maximum
dimension less than one micron.
2. The submicron structure of claim 1, further comprising a
cationic therapeutic compound and an oligonucleotide
electrostatically bound to the cationic polymer wherein the
oligonucleotide is an siRNA that reduces translation of a protein
causing resistance in a cell.
3. The submicron structure of claim 2, wherein the siRNA reduces
translation of a protein that causes resistance to said therapeutic
compound in the cell.
4. The submicron structure of claim 2, wherein the siRNA reduces
translation of p-glycoprotein.
5. The submicron structure of claim 2, wherein the cationic
therapeutic compound is doxirubicin.
6. The submicron structure of claim 1, wherein the cationic polymer
is electrostatically bound to the silica body.
7. The submicron structure of claim 1, wherein the cationic polymer
is selected from the group consisting of polyethyleneimine,
polyamidoamine, polylysine, poly(allylamine), and
poly(diallyldimethylammonium chloride).
8. The submicron structure of claim 1, wherein the cationic polymer
is polyethyleneimine.
9. The submicron structure of claim 1, wherein the cationic polymer
is a cationic co-polymer.
10. The submicron structure of claim 1, wherein the cationic
co-polymer is a co-polymer of poly(ethyleneimine) and poly(ethylene
glycol).
11. The submicron structure of claim 1, comprising an
oligonucleotide electrostatically bound to said cationic
polymer.
12. The submicron structure of claim 11, wherein the
oligonucleotide is DNA.
13. The submicron structure of claim 11, wherein the
oligonucleotide is RNA.
14. The submicron structure of claim 13, wherein the RNA is
siRNA.
15. The submicron structure of claim 1, comprising a therapeutic
compound within the silica body or pores of the silica body.
16. The submicron structure of claim 15, wherein the therapeutic
compound is hydrophobic.
17. The submicron structure of claim 15, wherein the therapeutic
compound is cationic.
18. The submicron structure of claim 15, wherein the therapeutic
compound is anionic.
19. The submicron structure of claim 1, wherein the silica body is
mesoporous.
20. The submicron structure of claim 1, wherein the pores are
substantially cylindrical pores having an ensemble average diameter
between about 1 nm and about 10 nm.
21. The submicron structure of claim 1, wherein the silica body is
substantially spherical having a diameter between about 50 nm and
about 1000 nm.
22. The submicron structure of claim 1, wherein the silica body is
substantially spherical having a diameter between about 100 nm and
about 500 nm.
23. The submicron structure of claim 1, wherein the silica body is
substantially spherical having a diameter between about 20 nm and
about 200 nm.
24. The submicron structure of claim 23, wherein the silica body is
substantially spherical having a diameter less than 100 nm.
25. The submicron structure of claim 1, further comprising a
plurality of anionic molecules attached to an outer surface of said
silica body.
26. A submicron structure according to claim 25, wherein said
plurality of anionic molecules comprise a phosphonate moiety.
27. A submicron structure according to claim 25, wherein said
plurality of anionic molecules are trihydroxysilylpropyl
methylphosphonate.
28. The submicron structure according to claim 1, further
comprising a light-emitting compound, peptide, protein,
oligonucleotide, sugar, oligosaccharide, or polysaccharide
covalently bonded to the surface of the silica body.
29. The submicron structure according to claim 1, further
comprising a light-emitting compound covalently bonded to the
surface of the silica body.
30. The submicron structure of claim 1 further comprising a core
structure within said silica body.
31. The submicron structure of claim 30, wherein said core
structure is a superparamagnetic nanocrystal, silver nanocrystal,
or gold nanocrystal.
32. The submicron structure of claim 31, wherein the
superparamagnetic nanocrystal is an iron oxide nanocrystal.
33. A submicron structure, comprising: a silica body defining a
plurality of pores and an outer surface between pore openings of
said plurality of pores, wherein the submicron structure has an
aspect ratio greater than 1.3, and wherein said submicron structure
has a maximum dimension less than one micron.
34. The submicron structure of claim 33, further comprising a
therapeutic compound.
35. The submicron structure of claim 33, further comprising a
cationic polymer on the surface of said silica body.
36. A therapeutic method comprising administering to a subject in
need of treatment an effective amount of a submicron structure
according to claim 1.
37. A therapeutic method comprising administering to a subject in
need of treatment an effective amount of a submicron structure
according to claim 33.
38. The method of claim 36 for treating drug resistant cancer
wherein the submicron structure comprises an siRNA that reduces
translation of a protein causing resistance in the drug resistant
cancer.
38. The method of claim 37 for treating drug resistant cancer
wherein the submicron structure comprises an siRNA that reduces
translation of a protein causing resistance in the drug resistant
cancer.
39. A method for transfecting a cell comprising administering to
the cell a submicron structure according to claim 1 comprising an
oligonucleotide.
40. A method for transfecting a cell comprising administering to
the cell a submicron structure according to claim 33 comprising an
oligonucleotide.
Description
CROSS-REFERENCE OF RELATED APPLICATION
[0001] This application claims is a Continuation-in-Part of
International Application Number PCT/US11/43874, filed Jul. 13,
2011, which claims priority to U.S. Provisional Application No.
61/363,945 filed Jul. 13, 2010. This application claims priority to
U.S. Provisional Application No. 61/466,581 filed Mar. 23, 2011,
U.S. Provisional Application No. 61/469,190 filed Mar. 30, 2011,
and U.S. Provisional Application No. 61/479,751 filed Apr. 27,
2011. The entire contents of each are hereby incorporated by
reference.
BACKGROUND
[0003] 1. Field of Invention
[0004] The current invention relates to submicron structures having
a silica body defining a plurality of pores and an outer surface
between pore openings of said plurality of pores and a cationic
polymer on the surface of said silica body. Such submicron
structures may be combined with oligonucleotides and therapeutic
compounds for drug delivery, transfection, and cancer therapy.
[0005] 2. Discussion of Related Art
[0006] Based on properties such as large surface area and ordered
porous channels that can be used to encapsulate molecules,
mesoporous silica nanoparticles (MSNP) have emerged as an efficient
drug delivery platform (Kim et al., Angew. Chem., Int. Ed., vol.
47, pp. 8438-8441, 2008; Liong et al., ACS Nano, vol. 2, pp.
889-896, 2008; Lu et al., Small, vol. 3, pp. 1341-1346, 2007;
Slowing et al., Adv. Drug Delivery Rev., vol. 60, pp. 1278-1288,
2008; Vallet-Regi et al., Angew. Chem., Int. Ed., vol. 46, pp.
7548-7558, 2007). In addition to the well-developed surface
chemistry, silica materials are known to be safe, biodegradable and
potentially biocompatible (Borm et al., Toxicol. Sci., vol. 90, pp.
23-32, 2006; Finnie et al., J. Sol-Gel. Sci. Techn., vol. 49, pp.
12-18, 2009). This drug transport system is suitable for the
delivery of anticancer drugs, including camptothecin, paclitaxel,
and doxorubicin (Kim et al., Angew. Chem., Int. Ed., vol. 47, pp.
8438-8441, 2008; Liong et al., ACS Nano, vol. 2, pp. 889-896, 2008;
Vivero-Escoto et al., J. Am. Chem. Soc., vol. 131, pp. 3462-3463,
2009). The chemical stability of the particles contribute to their
therapeutic utility by allowing the attachment of functional groups
for imaging and targeting applications along with the placement of
a series of nanovalves for on-demand drug release (Liong et al.,
ACS Nano, vol. 2, pp. 889-896, 2008; Nguyen et al., Org. Lett.,
vol. 8, pp. 3363-3366, 2006; Rosenholm et al., ACS Nano, vol. 3,
pp. 197-206, 2009).
[0007] RNA interference describes natural processes that lead to
gene silencing by siRNA (Moazed et al., Nature, vol. 457, pp.
413-420, 2009). siRNA has been widely used as an experimental tool
that is now also becoming the focus of the pharmaceutical industry
(Blow et al., Nature, vol. 450, pp. 1117-1120, 2007). Currently
there are a number of clinical trials underway that include the use
of siRNAs to treat various disease processes (Davis et al., Mol.
Pharm., vol. 6, pp. 659-668, 2009; Judge et al., Mol. Ther., vol.
13, pp. 494-505, 2006). As for most molecular therapies, in vivo
delivery is a major hurdle in successful implementation and has
sparked a number of strategies to increase siRNA circulatory
half-life, facilitate transduction across biological membranes, and
achieve cell-specific delivery (Davis et al., Mol. Pharm., vol. 6,
pp. 659-668, 2009; Judge et al., Mol. Ther., vol. 13, pp. 494-505,
2006).
[0008] There are a number of circumstances where drug and siRNA
delivery could achieve a synergistic therapeutic outcome. One
example is the restoration of drug sensitivity in cancer cells by
knockdown of genes that are involved in the resistance to one or
more chemotherapeutic agents. An example is the inducible
P-glycoprotein (Pgp) gene that encodes for a gene product known as
the multiple drug resistance protein 1 (MDR-1) (Gottesman et al.,
Annu. Rev. Med., vol. 53, pp. 614-627, 2002). Pgp is constitutively
expressed in normal cells such as capillary endothelial cells in
the blood brain barrier but also is selectively overexpressed in
carcinomas of the stomach, breast, pancreas and cervix in response
to a number of chemotherapeutics agents (Szakacs et al., Nat. Rev.
Drug Discov., vol. 5, pp. 219-234, 2006). If overexpressed, Pgp
could lead to drug resistance because MDR-1 contributes to the
formation of a drug efflux pump that prevents the intracellular
buildup of chemotherapeutic agents (Jabr-Milane et al., Cancer
Treat. Rev., vol. 34, pp. 592-602, 2008).
[0009] Mesoporous silica nanoparticle (MSNP) is a multifunctional
delivery platform that has been shown at cellular and in vivo
levels to be capable of delivering chemotherapeutic agents and
DNA/siRNA to a variety of cancer cell types (Lu et al., Small, vol.
3, pp. 1341-1346, 2007; He et al., Small, vol. 7, pp. 271-280,
2011; Lee et al., Adv. Funct. Mater., vol. 19, pp. 215-222, 2009;
Liong et al., ACS Nano, vol. 2, pp. 889-896, 2008; Meng et al., ACS
Nano, vol. 4, pp. 4539-4550, 2010; Meng et al., J. Am. Chem. Soc.,
vol. 132, pp. 12690-12697, 2010; Xia et al., ACS Nano, vol. 3, pp.
3273-3286, 2009; Radu et al., J. Am. Chem. Soc., vol. 126, pp.
13216-13217, 2004; Slowing et al., J. Am. Chem. Soc., vol. 129, pp.
8845-8849, 2007). This delivery platform allows effective and
protective packaging of hydrophobic and charged anticancer drugs
for controlled and on demand delivery, with the additional
capability to also image the delivery site (Liong et al., ACS Nano,
vol. 2, pp. 889-896, 2008). The key challenge now is to optimize
the design features for efficient and safe in vivo drug delivery
(He et al., Small, vol. 7, pp. 271-280, 2011; Lee et al., Angew.
Chem. Int. Ed., vol. 49, pp. 8214-8219, 2010; Liu et al.,
Biomaterials, vol. 32, pp. 1657-1668, 2011; Al Shamsi et al., Chem.
Res. Toxicol., vol. 23, pp. 1796-1805, 2010), which be assessed
through the use of human xenograft tumors in nude mice (Lu et al.,
Small, vol. 6, pp. 1794-1805, 2010).
[0010] While the availability of nanocarrier drug delivery systems
is an exciting development that holds the promise of a fundamental
change in cancer chemotherapy, it remains at a relatively early
stage of the implementation of this technology that often contains
overblown claims of drug delivery nanoparticles acting as magic
bullets. Such claims include the putative ability of active tumor
targeting with the ability of selectively sparing all normal
tissues. However, the reality is that most nanocarriers are
particulates that are recognized by and are effectively removed by
the mononuclear phagocytic cells in the reticuloendothelial system
(RES) of the liver and spleen (Davis et al., Nat. Rev. Drug
Discov., vol. 7, pp. 771-782, 2008). This sequestration is often
enhanced by the surface coating of nanoparticles with a corona of
proteins that lead to opsonization and enhance phagocytosis by the
RES (Nel et al., Nat. Mater., vol. 8, pp. 543-557, 2009). Moreover,
there is also a possibility that the encapsulated drugs could be
lost from the carrier or degraded, as well as the fact that the
colloidal instability of the carrier could lead to agglomeration in
the circulation and may therefore be excluded from the intended
"target site". It is also possible that the nanocarrier may reach
the target site but that the drug is not released from the particle
or that the carrier is not taken up effectively in the tumor cells.
Both effects will conspire to insufficient intracellular drug
delivery. Finally, there is also the concern that the heterogeneity
among different tumor types could lead to considerable variation in
the magnitude of the enhanced permeability and retention (EPR)
effect due to differences in vascularity or lymphatic drainage
(Ruenraroengsak et al., J. Controlled Release, vol. 141, pp.
265-276, 2010). Given these constraints, it is not a surprise that
drug delivery to the tumor site seldom achieves more than 10% of
the total administered dose. In fact, few publications show the
actual calculation of the EPR effect of the nanocarriers being
described (de Wolf et al., Int. J. Pharm., vol. 331, pp. 167-175,
2007).
[0011] There are a number of nanomaterial design options for
improving the pharmacokinetics, biodistribution and delivery of
anticancer drugs to the tumor site (Nie et al., Annu. Rev. Biomed.
Eng., vol. 9, pp. 12.1-12.32, 2007; Perrault et al., Nano Lett.,
vol. 9, pp. 1909-1945, 2009; Ferrari et al., Nat. Rev. Cancer, vol.
5, pp. 161-171, 2005). The EPR effect is due to a combination of
the abnormally large fenestrations of tumor vasculature and the
inefficient lymphatic drainage, which generates the retention
effect (Maeda et al., Eur. J. Pharm. Biopharm., vol. 71, pp.
409-419, 2009; Torchilin et al., Adv. Drug Deliver. Rev., vol. 63,
pp. 131-135, 2011; Iyer et al., Drug Discov. Today, vol. 11, pp.
812-818, 2006). A frequent strategy that is being used is to
decorate the particle surface with polyethylene glycol (PEG) to
provide steric hindrance to improve particle dispersion (Xia et
al., ACS Nano, vol. 3, pp. 3273-3286, 2009). Because this feature
also leads to interference in particle opsonization, there is a
concomitant increase in circulatory half-life as well as an
improvement in the EPR effect (He et al., Small, vol. 7, pp.
271-280, 2011; Maeda et al., Eur. J. Pharm. Biopharm., vol. 71, pp.
409-419, 2009; Maeda et al., Factors and Mechanism of "EPR" Effect
and the Enhanced Antitumor Effects of Macromolecular Drugs
Including SMANCS. In Polymer Drugs in the Clinical Stage, Springer
US, vol. 519, pp. 29-49, 2004). The potential downside of surface
coating is that PEG may also interfere in particle uptake by the
tumor cells and that the longer circulation time may increase drug
leakage from the carrier (Xia et al., ACS Nano, vol. 3, pp.
3273-3286, 2009).
SUMMARY
[0012] Embodiments of the invention include a submicron structure
having a silica body defining a plurality of pores and an outer
surface between pore openings of said plurality of pores, and a
cationic polymer on the surface of said silica body. Said submicron
structure has a maximum dimension less than one micron.
[0013] In some embodiments, the submicron structure also includes a
cationic therapeutic compound. The cationic therapeutic compound
may be, for example, in the interior or in the pores of the
submicron structure. In some embodiments, the submicron structure
also includes an oligonucleotide electrostatically bound to the
cationic polymer. Some embodiments include both a cationic
therapeutic compound and an oligonucleotide. In some embodiments,
the oligonucleotide is an siRNA that reduces translation of a
protein that causes resistance in a cell. In some embodiments, the
siRNA reduces translation of a protein that causes resistance to
the therapeutic compound in the cell. In some embodiments, the
siRNA reduces translation of p-glycoprotein. In some embodiments,
the therapeutic compound is doxirubicin.
[0014] In some embodiments, the cationic polymer is
electrostatically bound to the silica body. In some embodiments,
the cationic polymer is selected from the group consisting of
polyethyleneimine, polyamidoamine, polylysine, poly(allylamine),
and poly(diallyldimethylammonium chloride). In some embodiments,
the cationic polymer is polyethyleneimine.
[0015] Some embodiments include an oligonucleotide
electrostatically bound to the cationic polymer. The
oligonucleotide may be DNA or RNA. When the oligonucleotide is RNA,
is may be a small inhibiting RNA (siRNA).
[0016] Some embodiments include a therapeutic compound within the
silica body or pores of the silica body. The therapeutic compound
may be hydrophobic, neutral (i.e. uncharged), cationic or anionic
at physiologic pH.
[0017] In some embodiments, the silica body is mesoporous. In some
embodiments, the pores are substantially cylindrical and have an
ensemble average diameter between about 1 nm and about 10 nm.
[0018] In some embodiments, the silica body is substantially
spherical and has a diameter between about 50 nm and about 1000 nm.
In some embodiments, the substantially spherical silica body has a
diameter between about 100 nm and about 500 nm.
[0019] In some embodiments, the silica body has a plurality of
anionic molecules attached to an outer surface of the silica body.
In some embodiments, the plurality of anionic molecules have a
phosphonate moiety. In some embodiments, the plurality of anionic
molecules are derived from reaction between the silica body surface
and trihydroxysilylpropyl methylphosphonate.
[0020] In some embodiments, the submicron structure further
includes a light-emitting compound, peptide, protein,
oligonucleotide, sugar, oligosaccharide, or polysaccharide
covalently bonded to the surface of the silica body. Some
embodiments have a light emitting compound covalently bonded to the
surface of the silica body.
[0021] In some embodiments, the submicron structure further
includes a core structure within the silica body. In some
embodiments, the core structure is a superparamagnetic nanocrystal,
silver nanocrystal or gold nanocrystal. In some embodiments, the
core structure is a superparamagnetic iron oxide nanocrystal
[0022] Embodiments of the invention include pharmaceutical
compositions having a submicron structure according to the
invention and a pharmaceutically acceptable carrier or excipient.
Embodiments of the invention include use of the submicron
structures according to the invention for the manufacture of a
medicament or pharmaceutical composition for the treatment of a
disease or disorder.
[0023] Embodiments of the invention include therapeutic methods
have the step of administering an effective amount of a submicron
structure according to the invention to a subject in need of
treatment. Embodiments include use of the submicron structures
according to the invention for the treatment of a disease or
disorder by administering the submicron structure to a subject in
need of treatment.
[0024] Embodiments of the invention include methods of treating
drug resistant cancer where the submicron structure includes an
siRNA that reduces translation of a protein causing resistance in
the drug resistant cancer. Embodiments of the invention includes
the use of a submicron structure according to the invention having
an siRNA that reduces translation of a protein causing drug
resistance to treat drug resistant cancer.
[0025] Embodiments of the invention include methods of transfecting
a cell by administering a submicron structure according to the
invention having an oligonucleotide. Embodiments of the invention
include the use of a submicron structure according to the invention
including an oligonucleotide to transfect a cell.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0027] Further objectives and advantages will become apparent from
a consideration of the description, drawings, and examples.
[0028] FIG. 1 shows transmission electron microscopy (TEM) of the
MSNP and cell viability detection by the MTS assay. FIG. 1A shows
TEM image shows the particle size and the ordered pore structure.
FIG. 1B shows cell viability after addition of appropriately
dispersed MSNP exhibiting a range of surface modifications to
pancreatic cancer cell lines at doses ranging from 12.5-50 .mu.g/ml
for 16 hrs, cells were incubated with the MTS reagent for 30 min
and the absorbance was measured at 490 nm. All the MTS values were
normalized according to the value of the control (no particle
exposure)--this was regarded as 100% cell viability. The IC.sub.50
values of MSNP-PEI-25 KD in PANC-1 and BxPC3 cells were 37 .mu.g/ml
and 46 .mu.g/ml, respectively. The results were reproduced 3
times.
[0029] FIG. 2 shows cellular uptake of FITC-labeled MSNP in PANC-1
cells. MSNP were labeled with FITC as described in Example 1. FIG.
2A shows a representative histogram showing the shift in
fluorescence intensity in PANC-1 cells treated with 25 .mu.g/ml
FITC-MSNP that contain different surface modifications (left
panel). The fold-increase in MFI after 3 hr was calculated and used
to generate the graph. RITC-labeled MSNP-Phos served as a control
particle to show that coating with PEI leads to enhanced uptake in
the same particle type in the same cell (right panel). FIG. 2B
shows confocal microscopy used to study the cellular uptake of
FITC-MSNP in PANC-1 cells. Cells were exposed to 25 .mu.g/ml
FITC-labeled particles for 3 hr. After cell membrane staining with
5 .mu.g/ml red fluorescent wheat germ agglutinin (WGA), cells were
visualized using a Confocal 1P/FCS Inverted microscope. Data are
representative of 3 separate experiments. *p<0.01 compared with
control.
[0030] FIG. 3 shows cellular uptake of FITC-labeled MSNP in BxPC3
cells. BxPC3 cells were exposed to FITC-labeled MSNP and flow
cytometry and confocal microscopy were conducted as in FIG. 2. FIG.
3A shows a representative histogram showing the shift in
fluorescence intensity (left panel). The fold-increase in MFI after
3 hr was calculated and used to generate the graph. RITC-labeled
MSNP-Phos served as a control particle to show that coating with
PEI leads to enhanced uptake in the same particle type in the same
cell (right panel). FIG. 3B shows confocal microscopy used to study
the cellular uptake of FITC-MSNP. Cells were exposed to 25 .mu.g/ml
FITC-labeled particles for 3 hr. After cell membrane staining with
5 .mu.g/ml red fluorescent wheat germ agglutinin (WGA), cells were
visualized using a Confocal 1P/FCS Inverted microscope. Data are
representative of 3 separate experiments. *p<0.01 compared with
control.
[0031] FIG. 4 shows Cell viability detection by the MTS assay.
After incubation with particles coated with polymers of MW 0.6-25
KD at doses of 6-100 .mu.g/ml for 16 hrs, PANC-1 (FIG. 4A), BxPC3
(FIG. 4B), and HEPA-1 (FIG. 4C) cells were incubated with the MTS
reagent for 30 min and the absorbance was measured at 490 nm. All
the MTS values were normalized as described in FIG. 1. The
experiment was reproduced 3 times.
[0032] FIG. 5 shows Gel retardation and DNase I protection assays.
Agarose gel electrophoresis of PEI-MSNP/plasmid DNA (pEGFP) (FIG.
5A) and PEI-MSNP/siRNA (FIG. 5B) complexes at various nanoparticle
to nucleic acid (N/P) ratios. Anionic phosphonate-coated MSNP was
used as a control. M=MW marker. FIG. 5C shows DNase I protection
assay. M: DNA marker. .PHI.: naked plasmid DNA (pEGFP), as negative
control. Lane 1, pDNA/PEI-1.2 KD complex. Lane 2, pDNA/PEI 25 KD
complex. Lane 3, naked pDNA treated with DNase I, positive control.
Lane 4, pDNA/PEI 1.2 KD complex treated with DNase I before pDNA
was released by 1% SDS. Lane 5, pDNA/PEI 25 KD complex treated with
DNase I before pDNA was released by 1% SDS. Lane 6, pDNA/PEI 1.2 KD
complex treated with 1% SDS. Lane 7, pDNA/PEI 25 KD complex treated
with 1% SDS.
[0033] FIG. 6 shows GFP knockdown by siRNA in stable transfected
GFP-HEPA cells. HEPA-1 cells with stable GFP expression were used
for siRNA knockdown assays. MSNP coated with different size PEI
polymers were used to transfect GFP-specific or scrambled siRNA and
the results compared with Lipofectamine 2000 as transfection agent.
FIG. 6A shows GFP knockdown assessed by flow cytometry in which GFP
MFI was normalized to the value of control untransduced cells
(100%). FIG. 6B shows confocal pictures showing GFP knockdown in
GFP-HEPA cells. TEX 615-labeled siRNA was used to show the cellular
localization of the nucleic acid bound particles (red dots). "X"
represents scrambled siRNA. The experiment was reproduced 3
times.
[0034] FIG. 7 shows GFP plasmid DNA transfection into HEPA-1 cells.
HEPA-1 cells were used for GFP plasmid DNA transfection. MSNP
coated with different size PEI polymers were used to transfect GFP
plasmid DNA and the results were compared with Lipofectamine 2000
as transfection agent. FIG. 7A shows a representative histogram
showing the shift in green fluorescence intensity in HEPA-1 cells
after transfection with Lipofectamine 2000 or MSNP-PEI-10 KD. FIG.
7B shows confocal pictures showing GFP expression in transfected
HEPA-1 cells. This demonstrates differences in the transfection
efficiency as judged by fluorescent intensity and proportion of
cells in the population showing GFP expression. The experiment was
reproduced 3 times.
[0035] FIG. 8 shows Drug delivery to PANC-1 and BxPC3 cells using
PEI-MSNP. A MTS assay was conducted for the paclitaxel-loaded MSNP
delivered to these cells at doses of 3-50 .mu.g/ml over a 48 hrs
period in PANC-1 (FIG. 8A) and BxPC3 (FIG. 8B) cells. The controls
were cells treated with particles only and cells treated with
paclitaxel suspended in culture medium with and without the
addition of DMSO carrier. The experiment was reproduced 2
times.
[0036] FIG. 9 shows MSNP size distribution in aqueous solutions.
Dynamic light scattering (DLS) for MSNP exhibiting different
surface modifications was performed in water, DMEM plus 10% FCS,
BEGM or BEGM plus 2 mg/ml BSA. The presence of serum and BSA in the
cell culture media improves MSNP dispersity.
[0037] FIG. 10 shows assessment of cell viability and mitochondrial
membrane potential (MMP) in RAW 264.7 and BEAS-2B cells. FIG. 10A
shows cell viability following treatment with MSNP displaying
different surface modifications, wise determined by the MTS assay
as described in FIG. 1. Cells were exposed to MSNP at doses of
12.5-50 .mu.g/ml for 16 hrs. All the MTS values were normalized as
outlined in FIG. 1. The IC.sub.50 values for image NP-PEI-25 KD in
RAW 264.7 and BEAS-2B cells are 40.6 .mu.g/ml and 9.7 .mu.g/ml,
respectively. FIG. 10B shows cell death and mitochondrial
depolarization after treatment with MSNP-phosphonate and MSNP-PEI
backspace-25 kD was determined using PI and JC-1, respectively.
[0038] FIG. 11 shows effect on cell viability after conversion of
primary amines to COOH. Succinic anhydride was used to convert the
primary NH.sub.2-- to COOH-- groups on MSNP-PEI-25 KD. FIG. 11A
shows cell viability comparing non-modified with succinic anhydride
treated particles in RAW 264.7 cells using MTS assay. FIG. 11B
shows the conversion confirmed using fluorescamine, which yields
green fluorescence when complexed to the primary NH.sub.2 groups.
The decline in fluorescence intensity was followed in a
fluorometer.
[0039] FIG. 12 shows determination of the stability of PEI coating
on the MSNP surface. Rhodamine-B labeled PEI was used to coat the
surface of FITC-labeled MSNP and the dual-labeled particles were
added to RAW 264.7 cells prior to the performance of confocal
microscopy. The composite overlay confirms that the polymer and the
particle co-localize at the same intracellular site at 3 and 6
hrs.
[0040] FIG. 13 shows cellular uptake of FITC-labeled MSNP in RAW
264.7 cells. MSNP were FITC labeled as described in the Examples.
FIG. 13A shows a representative histogram showing the shift in
fluorescence intensity in RAW 264.7 cells treated with 25 .mu.g/ml
FITC-MSNP exhibiting different surface modifications for 3 hrs
(left panel). The fold-increase in MFI was calculated and used to
generate the graph. RITC-labeled MSNP was used as a control as
discussed in FIG. 2 (right panel). FIG. 13B shows confocal
microscopy to study the cellular uptake of FITC-MSNP in RAW 264.7
cells. Cells were exposed to 25 .mu.g/ml FITC-labeled particles for
3 hr. After the cell membrane was stained with 5 .mu.g/ml red
fluorescent wheat germ agglutinin (WGA), cells were visualized in a
Confocal 1P/FCS Inverted microscope. Data are representative of 3
separate experiments. *p<0.01 compared with control.
[0041] FIG. 14 shows Cell viability detection by the MTS assay in
RAW 264.7 (FIG. 14A) and BEAS-2B (FIG. 14B) cells. After incubation
with particles coated with different length PEI polymers at doses
from 6.25-100 .mu.g/ml for 16 hrs, the MTS assay and data
calculation were performed as described in FIG. 1.
[0042] FIG. 15 shows detection of GFP knockdown by siRNA using
western blotting in HEPA-1 cells. FIG. 15A shows HEPA-1 cells with
stable GFP expression was used for siRNA knockdown as described in
FIG. 6. The procedure, including use of particles coated with
different polymer lengths and the control agent, Lipofectamine
2000, was carried out as described in FIG. 6. However, instead of
using confocal microscopy, cells were lyzed and the lysates used to
conduct anti-GFP immunoblotting. The blotting membrane was also
overlaid with an antibody recognizing .beta.-actin to correct for
protein loading. FIG. 15B shows MFI of siRNA was calculated to show
relative quantity of siRNA uptake into cells transfected by
PEI-MSNP in HEPA-1 cells (arbitrary units).
[0043] FIG. 16 shows quantification of paclitaxel (Pac) loading
capacity in MSNP. MSNP with different surface modifications were
loaded with paclitaxel. Methanol was used for complete release of
the drug from washed particles and the amount of paclitaxel in the
supernatant was determined by UV absorbance at 230 nm.
[0044] FIG. 17 shows animal weight and histology of major organs.
FIG. 17A shows animal weight was monitored after particle
injections. FIG. 17B shows histology of liver, kidney, spleen was
performed by UCLA Division of Laboratory Animal Medicine (DLAM)
diagnostic laboratory services. The sections were stained with
hematoxylin-eosin and examined by light microscopy.
[0045] FIG. 18 shows physicochemical characterization of PEI coated
MSNP. FIG. 18A shows TEM images of phosphonate-MSNP before and
after coating with the 10 kD PEI polymer. The arrows indicate that
the polymer decorates the MSNP surface but leaves the porous
interior accessible to drug loading. FIG. 18B shows particle size
and zeta potential in pure water, after stabilization with 1 mg/mL
BSA in water, or in DMEM cell culture medium were measured. All of
the size and zeta potential data do no significantly unchanged when
the MSNP were loaded with Dox and siRNA (Table 3).
[0046] FIG. 19 shows effective Pgp siRNA delivery and gene
knockdown in KB-V1 cells. FIG. 19A shows agarose gel
electrophoresis of PEI-coated MSNP to which Pgp siRNA was complexed
at various nanoparticle to nucleic acid (N/P) ratios. M is
molecular weight marker. The .PHI. lane contains Pgp siRNA only.
Dox loading did not change the N/P ratio or the electrophoretic
mobility. The results indicate that all siRNA was bound when the
N/P ratio >16 (PEI 1.8 kD), >16 (PEI 10 kD), and >8 (PEI
25 kD). FIG. 19B shows confocal microscopy to demonstrate Texas
red-labeled siRNA uptake in association with FITC-labeled PEI
coated MSNP. The cell membrane and nucleus were stained by WGA 633
and Hoechst 33342, respectively. The panels on the right show
merging of the images to show Pgp siRNA co-localization with
FITC-MSNP. FIG. 19C shows quantitative comparison of labeled Pgp
siRNA uptake by measuring fluorescent intensity of Texas red in
various PEI groups, using Imaging J software. *p<0.05. FIG. 19D
shows detection of Pgp knockdown by siRNA-PEI-MSNP using western
blotting. Lipofectamine 2000 was used as positive control. The
relevant Pgp expression was calculated by the signal intensity of
the protein bands. "X" stands for cells treated by scrambled
siRNA-PEI-MSNP.
[0047] FIG. 20 shows that phosphonate-MSNP effectively binds Dox
via a proton-sensitive mechanism. FIG. 20A shows modeling studies
using positively and negatively charged MSNP under abiotic
conditions. Loading yield of Dox in MSNP with various surface
modifications. A photograph of the Dox-loaded MSNP (20 mg/ml)
containing various surface modifications were taken. Consistent
with loading yield, the phosphonate-MSNP was more intensively
stained (red) than other particle types. FIG. 20B shows loading
yield measurements for PEI-coated phosphonate MSNP. The yields were
similar to that of non-coated particles in (A). FIG. 20C shows
time-dependent release profile of Dox from drug loaded phosphonate
MSNP in phenol red free DMEM acidified to pH 5.0. The effect of PBS
or treatment with PBS containing 10% ethanol is shown for
comparison. *P<0.05. I.sub.t is the fluorescent intensity of
released Dox at certain time point; I.sub.0 as the total Dox
fluorescence signal intensity that can be recovered by repeated
acid washing (considered as 100% release). The release percentage
equals (I.sub.t/I.sub.0).times.100%. FIG. 20D shows Dox release
from phosphonate-MSNP coated with the 10 kD PEI polymer under
similar acidification conditions; this demonstrates that the
polymer does not interfere in drug release. FIG. 20E shows Confocal
microscopy showing FITC-labeled MSNP uptake into the LAMP-1.sup.+
compartment in KB-V1 cells. The yellow spots in the merged image
show the co-localization. Calculation of co-localization ratio by
Imaging J software indicates >55% co-localization of the
green-labeled particles with the red-labeled lysosomes. FIG. 20F
shows confocal microscopy showing Dox release from the MSNP to the
nucleus in KB-V1 cells 72 hrs after the introduction the particles.
The bottom panel shows that the lysosomal pH neutralizer,
NH.sub.4Cl, interferes in drug release.
[0048] FIG. 21 shows simultaneous delivery of Dox and Pgp siRNA to
the nucleus leads to a synergistic increase in cellular and nuclear
Dox levels in KB-V1 cells. FIG. 21A shows quantitative comparison
of Dox levels using a fluorescent readout of cellular drug levels
72 hrs after introduction of treatment, using 2 .mu.g/ml free Dox
or the equivalent amount of drug loaded into MSNP before or after
PEI coating or PEI coating followed by the attachment of Pgp siRNA.
FIG. 21B shows confocal images showing drug uptake in KB-V1 cells
that treated by 5 .mu.g/ml free Dox or the equivalent amount of
drug loaded into various MSNPs for 72 hrs. Please note that while
free Dox could not be maintained intracellularly, Dox delivered by
MSNP (Dox-MSNP) were retained in the particles that localized in
the peri-nuclear region. PEI-Dox-MSNP significantly enhanced
particle uptake compared to the unmodified MSNP. However, while
much of the drug remained confined to the particles, nuclear
staining could be observed when Pgp siRNA was added to this
platform. Thus, Pgp knockdown is likely effective at maintaining
the Dox that is released from the particles long enough to allow
the drug to find its way to the nucleus. The cell membrane was
stained by Alexa 633-conjugated WGA (cyan color). Dox staining is
in red. FIG. 21C shows quantitative analysis of the nuclear
fluorescence signal in KB-V1 nuclei was performed by the use of
Image J software.
[0049] FIG. 22 shows comparison of the cytotoxic effects of
different delivery modalities of Dox in KB-V1 cells. FIG. 22A shows
MTS cell viability assay showing that MSNP delivery of Dox
concomitant with Pgp siRNA is capable of improving the induction of
cytotoxicity by free Dox or Dox delivered by PEI-coated MSNP not
attached to siRNA. The broken line is the cell killing curve of
free Dox in parental cell line (KB-31, Dox sensitive). FIG. 22B
shows annexin V-SYTOX staining showing enhanced apoptosis and cell
death by siRNA-PEI-Dox compared to the other Dox modalities
mentioned in FIG. 22A. The flow cytometry data was further
confirmed by TUNEL staining assay (FIG. 29).
[0050] FIG. 23 shows identification of Dox sensitivity in KB-31 and
KB-V1 cells. FIG. 23A shows cytotoxicity profiles of Dox in KB-31
(parental line) and KB-V1 cells (resistant cell line). FIG. 23B
shows immunoblotting showing Pgp expression in KB-31 and KB-V1
cell.
[0051] FIG. 24 shows agarose gel electrophoresis of PEI 10
kD-coated MSNP to which Pgp siRNA was complexed at various
nanoparticle to nucleic acid (N/P) ratios. The .PHI. lane contains
Pgp siRNA only. The threshold N/P ratio (N/P=16) remains the same
with or without Dox loading (FIG. 19A, middle panel).
[0052] FIG. 25 shows Pgp expression was significantly knocked down
(.about.80%) by siRNA-PEI 10 kD-Dox-MSNP treatment at the dose of
10 .mu.g/ml for 72 hrs. Knockdown of Pgp expression by siRNA is not
influenced by Dox loading.
[0053] FIG. 26 shows assessment of PEI-MSNP safety in KB-V1 cells.
FIG. 26A shows MTS assay assessment of the viability of the cells
incubated with the polymer-coated MSNP. FIG. 26B shows MTS assay
assessment of cell viability in response to 100 .mu.g/ml MSNP
coated with the 10 kD polymer. The cell viability began to decrease
at 36 hrs time-point (*p<0.05)
[0054] FIG. 27 shows loading and release profile of Hoechst 33342
loaded MSNP with various surface modifications. FIG. 27A shows
loading yield of Hoechst 33342 in MSNP with different surface
modifications. Positively charged Hoechst 33342 dye (pKa=11.9), has
a strong interaction with the particles with a negatively charged
porous surface, showing higher loading yield. FIG. 27B shows
Hoechst 33342-loaded MSNP was incubated in H.sup.+ (pH=5.0) and 10%
(v/v) ethanol containing DMEM for 3 hrs. The supernatant was
collected for released dye measurement. H.sup.+ induced Hoechst
33342 release is significantly higher than ethanol induced release
(*p<0.05).
[0055] FIG. 28 shows that the Dox release profile remains same with
or without siRNA binding on PEI 10 kD-MSNP. The experiment was
performed in acidifying phenol red free DMEM medium (pH=5) at the
12 hr time point. PBS was used as control. The date show that Dox
release will not be influenced by siRNA that binds to PEI polymer
where locates at the exterior of MSNP.
[0056] FIG. 29 shows a TUNEL detection kit used according to the
manufacturer's instructions to study Dox-induced apoptosis.
Percentage of TUNEL positive cell showing enhanced apoptosis by
siRNA-PEI-Dox compared to the other Dox modalities. The result
shows the same trend of flow cytometry data (FIG. 22B)
[0057] FIG. 30 shows cell viability analyzed after longer exposure
periods (4 days) because Pgp knockdown by siRNA may need a certain
amount of time, but did not observe a significant improvement in
cytotoxicity.
[0058] FIG. 31 shows that co-administration of free Dox and
Tariquidar (50 nM) partially restores drug sensitivity in KB-V1
cells for 72 hrs. This combination significantly improved cell
killing capability in KB-V1 cells, but was not able to completely
restore Dox sensitivity to the level seen in KB-31 cells.
[0059] FIG. 32 shows loading and release profile of CPT loaded MSNP
with various surface modifications. FIG. 32A shows loading yield of
CPT in modified MSNP. As shown in FIG. 32A, MSNP with different
surface modifications were compared for their loading capacity to
CPT. The loading yield of MSNP varied from 3.8% (w/w) to 6.2% (w/w)
when different surface modifications were used. The amounts of CPT
stored within the surface functionalized particles were similar,
although storing lesser amounts than the silanol surface. FIG. 32B
shows the release profile of CPT loaded into phosphonate-MSNP in
response to acidification or induction of ethanol into the wash
medium. PBS treatment was set as control. The ethanol-induced CPT
release is significantly higher than acid-induced release. The
loading and release mechanisms for hydrophilic cargo (e.g. Dox) and
hydrophobic cargo (e.g. CPT) are different since there is a phase
transfer process for hydrophobic cargo during drug loading. Loading
capacity is independent of the functional groups that are used, and
the cargo can be quickly released by an organic solvent in which
the cargo is dissolvable.
[0060] FIG. 33 shows a graphical representation of the MSNP design.
NP1 refers to the first generation phosphonate-coated MSNP with a
primary particle size of 100 nm. NP2 was PEGylated with a
mesoporous silica core size of 50 nm and coated with a 5 kD PEG
polymer. NP3 represents the same core size as NP2, but was coated
with a 1.2 kD PEI polymer in which some of the amines were reacted
with 5 kD PEG. The pore diameter of all three generations of
particles was 2.5 nm. The TEM images at the bottom demonstrate the
primary particle size and ordered pore structure.
[0061] FIG. 34 shows physicochemical characterization of the
different MSNPs. FIG. 34A shows particle size and zeta potential in
pure water and saline were assessed with a ZetaSizer Nano
(Malvern), with the particle concentrations at 100 .mu.g/mL. Note
that the size and zeta potential were not significantly changed
before and after doxorubicin loading (not shown). FIG. 34B shows
TEM images to demonstrate particle size and dispersal in saline.
FIG. 34C shows photographs of the particles suspended in saline at
20 mg/mL against an appropriate background were taken and
supplemented with the illustrations to show that NP3 coated with
PEI-PEG had optical transparency because of electrostatic
monodispersion while the other particle types agglomerated for
reasons discussed in the manuscript.
[0062] FIG. 35 shows the biodistribution of NIR dye-labeled MSNP to
the KB-31-luc tumor xenograft model in nude mice. Particle labeling
was performed with Dylight 680 dye as described in Materials and
Methods. FIG. 35A shows an IVIS optical imaging system (Xenogen)
was used to study the biodistribution of NIR dye labeled-MSNP in
the tumor-bearing mice. To visualize the luciferase expression in
the KB-31 cells, anesthetized mice received intraperitoneal
injection of 75 mg/kg D-Luciferin, followed 8 min later by
obtaining the bioluminescence images using 10 s exposure time.
Reference fluorescence images were captured before intravenous
injection of 50 mg/kg NIR-labeled particles into the tumor-bearing
mice. Pronate and supine images were obtained at the indicated time
intervals following the particle injection. FIG. 35B shows results
72 h after injection, the animals were sacrificed and tumor tissues
as well as major organs (heart, lung, spleen, liver, kidney, brain
and muscle) were collected for ex vivo imaging. FIG. 35C shows the
fluorescence intensities of individual organs from mice treated
with each particle type. Around 100-200 mg tissue for each organ
was accurately weighted, homogenized and the fluorescence intensity
obtained at excitation and emission wavelength of 680/715 nm in a
microplate reader (SpectraMax M5e, Molecular Device, USA). The data
represent the mean fluorescence intensity of 1 mg of tissue from
the tumor or each organ. *, p<0.05, compared with NP1 and NP2.
FIG. 35D shows the biodistribution of each particle type was
expressed as % of total load of each nanoparticle distributing to
the individual organs. This % is determined according to the
formula: [(tissue fluorescent intensity per mg mass
tissue.times.tissue weight in mg)/(total injected particle
fluorescent intensity)].times.100%. NP3 yielded a passive tumor
accumulation of .about.12% of the injected dose, which is
significantly higher compared to the treatments using NP1 and NP2.
*, p<0.05, compared to NP1 and NP2.
[0063] FIG. 36 shows dual color fluorescence to show the tumor
localization of the doxorubicin in relation to the tumor blood
vessels detected by a CD31 biomarker. Tumor-bearing mice received
intravenous administration of doxorubicin-loaded particles, each at
a dose of 50 mg/kg for 72 h. Tumor tissues were collected
immediately following animal sacrifice. Histological staining of
the OCT embedded frozen tumor tissues in each group was performed
by the UCLA Division of Laboratory Animal Medicine (DLAM)
diagnostic laboratory services. The sections were incubated with a
CD31 primary antibody and visualized by FITC-conjugated secondary
antibody. The red fluorescence of doxorubicin was also captured for
the same slide view and merged images were prepared to show
intratumoral distribution of the drug in relation to the blood
vessels. Slides were visualized under a fluorescence microscope
(Zeiss, Germany). It is possible to discern some speckled
fluorescence in the lower panels, suggesting that some of the drug
is still encapsulated in the particles.
[0064] FIG. 37 shows tumor growth inhibition of doxorubicin loaded
NP3 in tumor-bearing nude mice. FIG. 37A shows a comparison of the
tumor inhibition effect of doxorubicin-loaded NP3 (Dox-NP3) versus
free drug (free Dox), empty particles and saline in the KB-31
xenograft model. The tumor-bearing mice were intravenously injected
with 120 mg/kg doxorubicin-loaded NP3 weekly for 3 weeks. This
particle dose is equivalent to 4 mg/kg doxorubicin being delivered
to each animal. The animals receiving the free drug were injected
with the same amount of doxorubicin weekly for 3 weeks. To compare
the effect of NP3 alone, empty particles were intravenously
injected at 120 mg/kg, weekly for 3 weeks. The saline group
received intravenous saline administration at the same time points.
Tumor size was accurately measured twice a week by the same
observer. Tumor weight was calculated according to the formula:
Tumor weight (mg)=(length in mm).times.(width in mm).sup.2/2. *,
p<0.05, compared to saline; $, p<0.05, compared to free
doxorubicin. FIG. 37B shows results at the end of this experiment,
tumor tissue was collected from each sacrificed animal and a
photograph of the tumor tissue was obtained.
[0065] FIG. 38 shows a TUNEL staining assay showing enhanced
apoptosis and cell death by doxorubicin-loaded NP3 (Dox-NP3)
compared to the free drug. FIG. 38A shows doxorubicin-induced
apoptosis in the tumor tissue, where tumor sections were used for
TUNEL staining and visualized under a fluorescence microscope.
Briefly, a TUNEL detection kit (Invitrogen) was used according to
the manufacturer's instructions. Slides of the tumors were washed,
fixed, and permeabilized before TUNEL staining. The number of TUNEL
positive cells (in green) was scored under the fluorescence
microscope (200.times.). Utilizing its red fluorescence properties,
the doxorubicin signal could be captured in the same tumor section.
After merging of the images, the composite yellow spots suggest the
presence of delivered drug inside the apoptotic cells. Higher
magnification images, including Hoechst nuclear staining of regions
"I" and "II" were obtained to further distinguish between free drug
and NP3 encapsulated doxorubicin (see panel C). FIG. 38B shows
quantitative analysis of TUNEL positive cells for each treatment.
At least three fields were counted by the same investigator to
calculate the percentage of TUNEL positive cells. *, p<0.05,
compared to free doxorubicin. FIG. 38C shows Higher magnification
images of regions "I" and "II" representing free or Dox-NP3 treated
animals. Hoechst dye staining was used to demonstrate the
localization of the red fluorescent specks in relation to the
nucleus (as indicated by number). In contrast, the free drug
yielded more diffuse and dull fluorescence, suggesting that the
specks may indeed represent particles, some being displayed in a
perinuclear distribution. This is indicative of particle uptake in
the tumor cells.
[0066] FIG. 39 shows Assessment of treatment on animal weight as
well as liver and kidney histology. FIG. 39A shows animal weights
recorded twice a week and expressed for the three-week experimental
duration. FIG. 39B shows histological analysis of liver and kidney
sections were performed by UCLA DLAM diagnostic laboratory
services. The sections were stained with hematoxylin/eosin
(H&E) and examined by light microscopy. Representative images
are shown. The hepatic histology reveals steatosis of the liver in
the free doxorubicin treated group. In contract, the liver
histology was normal for animal treated with the same amount of
drug encapsulated in NP3. The liver histology of animals receiving
empty NP3 or saline was also documented as normal (see FIG. 43).
The kidney histology demonstrates the generation of glomerular
swelling and nephrotoxicity by free doxorubicin while animals
treated with the encapsulated drug had no histological
abnormalities. The histology was also reported as normal in animals
receiving empty NP3 or saline (see FIG. 43).
[0067] FIG. 40 shows fluorescent labeling efficiencies of NP1-NP3
were determined in a microplate reader. The Dylight 680-labeled
different particles were washed and suspended in water at 100
.mu.g/mL. 100 .mu.L of each particle suspension was loaded into a
96-well plate and the fluorescent intensity was detected at
excitation and emission wavelength of 680/715 nm with a microplate
reader (M5e, Molecular Device). The fluorescent intensities of NP2
and NP3 were expressed as a unit of the fluorescence intensity of
NP1, which was considered as 100%. The results indicate that there
is no significant difference (p<0.05) in the fluorescent
labeling efficiency among different particle types.
[0068] FIG. 41 shows the biodistribution data determined by
fluorescence intensity measurement, where the Si content of tumor,
liver, lung and spleen tissue was detected by ICP-MS in animals
intravenously injected one with saline or empty NP3 at 50 mg/kg.
The animals were sacrificed 3 days after injection. Briefly, each
tissue was accurately weighed and soaked in ultrahigh purity
HNO.sub.3 and H.sub.2O.sub.2 overnight. This solution was heated at
80.degree. C. for 1 h the next day. At the same time,
H.sub.2O.sub.2 solution was added to drive off nitrogen oxide vapor
until the solution became colorless and clear. The aqueous
solutions were analyzed by a Perkin-Elmer SCIEX Elan DRCII to
determine the Si concentration. Elemental indium at 20 ng/mL was
used as an internal standard. FIG. 41A shows ICP-MS analysis
showing the Si concentrations in the collected organs of NP3 vs
saline treated animals. FIG. 41A shows NP3 biodistribution was
expressed as a % of the total particle amount for each of the
indicated organs. This % was determined according to the formula:
[(Si concentration per unit amount of tissue.times.tissue total
weight)/(total injected Si mass)].times.100%.
[0069] FIG. 42 shows morphological observation of tumor xenografts
at the end of the tumor treatment experiment in intact mice.
Tumor-bearing animals were treated with saline, free doxorubicin
(free Dox), unloaded NP3 and doxorubicin loaded NP3 (Dox-NP3) as
described in FIG. 39. The localization of the tumor is outlined by
a broken line. Compared with free doxorubicin that is dissolved in
saline, the drug delivery by NP3 exhibited a significantly
improvement in tumor shrinkage. No cancer growth inhibition was
found using unloaded NP3 or saline only.
[0070] FIG. 43 shows a comparison of liver and kidney histology in
animals receiving saline only or empty particles. The animals
received weekly intravenous administration of saline or empty NP3
at 50 mg/kg for 3 weeks. The animals were sacrificed 3 weeks after
the first treatment. Histological analysis of liver and kidney
sections were performed by the UCLA DLAM diagnostic laboratory
services. The sections were stained with hematoxylin/eosin
(H&E) and examined by light microscopy. Representative images
are shown. Both the liver and kidney histology of animals receiving
empty NP3 or saline was interpreted as normal.
[0071] FIG. 44 shows histological examination of the lung tissue of
tumor-bearing animals after the various treatments. These animals
the same animal groups as in FIGS. 7B and S4. The results did not
show any gross changes in lung pathology among different
groups.
[0072] FIG. 45 shows histological examination of the heart tissue
of tumor-bearing animal after its various treatments. These animals
are from the same experiment shown in FIGS. 39 and 43. The results
did not show any gross histological differences among the different
groups.
[0073] FIG. 46 shows a hemolysis assay to determine membrane lysis
of heparinized mouse red blood cells (RBC). Briefly, heparinized
mouse blood was collected and washed by PBS. The RBC were suspended
at 1.times.10.sup.9 cells per mL and exposed to the indicated
concentrations of empty NP3 for 4 h at 37.degree. C. PBS and 0.025%
Triton X-100 served as negative and positive controls,
respectively. The samples were centrifuged and the absorbance of
hemoglobin in the supernatants at 500-650 nm was measured by a
microplate reader (M5e, Molecular Device). There was no hemoglobin
release in response to particle concentration of up to 2500
.mu.g/mL.
[0074] FIG. 47 shows neutralization of amine groups in NP3 to show
the effects of particle size. Free amine groups in PEI were
neutralized with phthalic anhydride. 10 mg of NP3 was suspended in
1 mL of N,N-Dimethylformamide (DMF) and mixed with 1.0-3.0 mg of
phthalic anhydride to obtain an increasing mass ratio (w/w) of the
neutralizer with respect to the NP3 weight. Each mixed solution was
stirred for 24 h and the neutralized NP3 was washed with DMF and
H.sub.2O before use. Size and zeta potential were determined by
ZetaSizer Nano (Malvern Instruments Ltd., Worcestershire, UK). The
data demonstrate the importance of the addition of cationic charge
in controlling the particle size after coating with a PEI-PEG
co-polymer.
[0075] FIG. 48 shows physicochemical characterization of MSNP. FIG.
48A shows scanning electron microscope and transmission electron
microscope images of MSNP exhibiting different AR values. The
arrows point out the periodical "fringes" along the short axes of
the rod-shaped particles; these represent ordered helical hexagonal
pore arrangements. FIG. 48B shows XRD profiling of MSNP. The peaks
confirm the two-dimensional hexagonal symmetry (p6m) in the
particles. The d-spacing of the rods was calculated to be 4 nm,
using the first diffraction peak and the cell parameter, a=4.6
nm.
[0076] FIG. 49 shows the abundance and rate of cellular uptake of
FITC-labeled MSNP in Hela cells. FIG. 49A shows Hela cells treated
with 20 .mu.g/mL FITC-labeled particles for 6 h. The fold-increase
in mean fluorescence intensity (MFI) compared to spherical
FITC-labeled MSNP (MSNP0) was used for comparison. RITC-labeled
nanosphere uptake was used as another internal control for
comparing each FITC-labeled particles type to an alternatively
labeled sphere. The RITC-labeled particles were introduced 1 h
prior to the PBS washing and introduction of the FITC-labeled
particles and PBS washing. Prior experimentation have shown that
pre-incubation with RITC-labeled spheres do not interfere in
subsequent uptake of FITC-labeled particles. *, p<0.05, compared
with spherical FITC-labeled particle (MSNP0); #, p<0.05,
compared with FITC-labeled MSNP1; $, p<0.05, compared with
FITC-labeled MSNP3. FIG. 49B shows Hela cells seeded into 8-well
chamber slides before addition of the FITC-labeled particles at 20
.mu.g/mL for 6 h. After fixation and permeabilization, cells were
stained with 5 .mu.g/mL wheat germ agglutinin 633 and Hoechst 33342
dye, following by visualization under a confocal 1P/FCS inverted
microscope. FIG. 49C shows the fold-increase in MFI of FITC-labeled
rods compared to sphere at 0 to 6 h. Hela cells were exposed to
different FITC-labeled MSNP at 20 .mu.g/mL, and flow cytometry were
conducted at the indicated time points. *, p<0.05 compared with
spherical FITC-labeled particle (MSNP0); #, p<0.05 compared with
FITC-labeled MSNP1; $, p<0.05 compared with FITC-labeled
MSNP3.
[0077] FIG. 50 shows TEM Ultrastructural analysis and confocal
microscopy elucidating the role of MSNP uptake by macropinocytosis
in Hela cells. FIG. 50A shows Electron microscopy to determine the
ultrastructural changes in Hela cells following exposure to 20
.mu.g/mL MSNP for 3 h. Please notice the increased pinocytotic
activity in cells treated with MSNP2 compared to larger or shorter
rod-shaped particles. Not only was exposure to MSNP2 accompanied by
more prominent membrane ruffles and filopodia formation but these
particles were also taken up more abundant than MSNP1 and MSNP3.
"N" denotes nuclear. Additional TEM images are displayed in FIG.
55, while a 3D reconstruction using electron tomography is shown in
FIG. 56. FIG. 50B shows Confocal microscopy showing the
rearrangement of actin fibers as determined by phalloidin staining.
Cells were treated with 20 .mu.g/mL spheres or rods for 6 h, fixed,
permeabilized, and then stained with Alexa 594-labeled phalloidin.
Confocal microscopy was performed as in FIG. 49. FIG. 50C shows
quantitative image analysis to determine the number of filopodia
per cell. At least 20 cells for each exposure in FIG. 50B were used
to count the number of actin spikes that comprise the filopodium
core. * demotes a significant increase (p<0.05) in cells treated
with MSNP2 compared with other particle types. FIG. 50D shows
confocal microscopy showing inhibition of filopodia formation and
FITC-labeled MSNP2 uptake in the presence of amiloride (which is
capable of inhibiting Na.sup.+/H.sup.+ exchange) or cytochalasin D
(Cyto D) (which is capable of binding to actin filaments and
inhibiting actin polymerization). The effect of cooling of the
sample to 4.degree. C. was determined as well as ATP depletion
(NaN.sub.3 plus 2-DG) on filopodia formation and particle uptake.
FIG. 50E shows quantitative expression of the effect of above
inhibitors on particle uptake and filopodia formation. * and #
denote a significant decrease of the number of MSNP2 or the number
of filopodia, respectively, under the various inhibitory conditions
compared with treatments using MSNP2 alone.
[0078] FIG. 51 shows confocal microscopy showing the effect of the
different particle types on Rac1 activation in Hela cells. FIG. 51A
shows cells that were serum-starved for 4 h before introduction of
the particles, which were dispersed in complete RPMI. In order to
correct for effect of serum growth factors on Rac1 activity, a
serum-starved control was included that was treated with complete
RPMI for 30 min Particles were introduced at 20 .mu.g/mL for 30 min
After fixation and permeabilization, cells were stained with
primary antibodies recognizing GTP-Rac1 or total Rac1, which were
subsequently visualized with Alexa 594 or FITC-labeled secondary
antibodies, respectively. Nuclei were stained with Hoechst dye.
FIG. 51B shows the fluorescence intensity of GTP-Rac1 in FIG. 51A
was quantitatively analyzed using Image J software. The
fluorescence intensity of serum-starved control cells exposed to
complete medium for 30 min (FIG. 51A, first row) was used as the
reference value for calculating the particle-induced increase in
Rac1 activation. At least 20 cells from the selection shown in
panel FIG. 51A were used to perform the analysis. * demotes a
significant decrease (p<0.05) for each particle type with the
control. #, p<0.05, compared with MSNP1; $, p<0.05, compared
with MSNP3.
[0079] FIG. 52 shows MTS assay comparing the cytotoxic effects of
free CPT and Taxol delivered by the different MSNP types. FIG. 52A
shows comparison of the CPT effects in Hela cells. After incubation
with the particles for 36 h at doses of 6.25-200 .mu.g/mL (which
agrees with CPT concentrations of 0.1-8.0 .mu.g/mL), the cells were
incubated with the MTS reagent for 2 h and the absorbance measured
at 490 nm. FIG. 52B shows the same experiment performed using
Taxol. The cells were treated for 36 h at particle concentration at
6.25-200 .mu.g/mL, which equals Taxol concentrations of 0.1-2.0
.mu.g/mL for 36 h. The MTS assay was performed as in panel FIG.
52A.
[0080] FIG. 53 shows fluorescent labeling efficiency of the
different particle types determined in a microplate reader. The
FITC-labeled MSNPs were washed and suspended in water at 100
.mu.g/mL. 100 .mu.L each particle suspensions were loaded into a
96-well plate and the fluorescent intensity was detected at
excitation and emission wavelength of 488/525 nm with a microplate
reader (M5e, Molecular Device). The fluorescent intensities of
MSNP1-MSNP3 were expressed as a unit of the fluorescence intensity
of MSNP0, which was regarded as 1.0. The result indicated that
there was no significant difference (p>0.05) in the fluorescent
labeling efficiency among different MSNPs.
[0081] FIG. 54 shows cellular uptake of FITC-labeled MSNP in A549
lung cancer cells. FIG. 54A shows A549 cells treated with 20
.mu.g/mL FITC-labeled particles for 6 h. The fold increase in mean
fluorescence intensity (MFI) compared to spherical FITC-labeled
MSNP (MSNP0) was used for making comparisons. RITC-labeled
nanosphere uptake was used as an internal control for comparing to
each FITC-labeled particle type. The RITC-labeled particles were
introduced 1 h prior to the PBS washing and introduction of the
FITC-labeled particles followed by another PBS washing. *,
p<0.05, compared with spherical FITC-labeled particle (MSNP0);
#, p<0.05, compared with FITC-labeled MSNP1; $, p<0.05,
compared with FITC-labeled MSNP3. FIG. 54B shows A549 cells seeded
into 8-well chamber slides before addition of the FITC-labeled
particles at 20 .mu.g/mL for 6 h. After fixation and
permeabilization, cells were stained with 5 .mu.g/mL wheat germ
agglutinin 633 and Hoechst dye, following by visualization under a
confocal 1P/FCS inverted microscope.
[0082] FIG. 55 shows additional ultrastructure analysis using TEM
to elucidate MSNP uptake by macropinocytosis in Hela cells. Hela
cells were exposed to 20 .mu.g/mL MSNP2 for 3 h. The arrows in the
figures point out filopodia and MSNP2 nanoparticles, respectively.
"N" denotes nuclear.
[0083] FIG. 56 shows electron tomography analysis and 3D image
reconstruction of the TEM images generated during Hela cell
incubation with 20 .mu.g/mL MSNP2. TEM grids were used for the
tomography analysis on an FEI Tecnai F20 microscope operated at 200
kV. Images were captured by tilting the specimen from -70.degree.
to 70.degree. with 1.degree. steps. Tilt series images were
captured with a TIETZ F415MP 16 megapixel CCD camera at a
magnification of 26,600.times. and then aligned using the Etomo
program in the IMOD package. The aligned tilt series were further
processed using the reconstruction features of the FEI software,
Inspect3d's SIRT, to improve the contrast. Videos of the aligned
tilt series were generated using both Inspect3d and Windows movie
maker (still images shown in FIG. 60). These data confirm MSNP2
uptake by macropinocytosis and actually yield resolution of the
particles pores inside the cell. M: macropinosome. N: nuclear.
[0084] FIG. 57 shows confocal microscopy to study the subcellular
localization of FITC-labeled MSNP2 in Hela cells. Hela cells were
treated with 20 .mu.g/mL FITC-labeled MSNP for the indicated time
periods. After fixation and permeabilization, cells were stained
with anti-clathrin (Santa Cruz, Biotechnology), anti-caveolin-1 (BD
BioSciences), and anti-LAMP-1 (Abeam) antibodies, and visualized
with Alexa 594-conjugated secondary antibody. The colocalization
ratio, as determined by Imaging J software, indicates <1%
colocalization of the green-labeled nanoparticles with the
red-labeled clathrin and caveolae at 36 h. The colocalization
ratios with the LAMP-1 positive compartment were estimated to be
<5% and 75%, respectively, at the 6 h and 36 h time points.
[0085] FIG. 58 shows Confocal microscopy to show the effects of the
chemical inhibitors and low temperature on Rac1 activation in Hela
cells. FIG. 58A shows cells pre-cultured for 3 h in serum free RPMI
1640 medium containing amiloride (75 .mu.M), Cyto D (2.5 .mu.g/mL),
or 0.1% NaN.sub.3/50 mM 2-DG for 3 h. Alternatively, cells were
placed at 4.degree. C. for 3 h. Subsequently, the media was
exchanged using fresh complete RPMI 1640 that contained 20 .mu.g/mL
FITC-labeled MSNP2 as well as one of the chemical inhibitors
(amiloride, Cyto D or NaN.sub.3/50 mM) for a further 6 h. The
4.degree. C. culture was maintained at this temperature. After
fixation and permeabilization, cells were stained with a primary
antibody recognizing GTP-Rac1 and an Alexa 594-labeled secondary
antibody. Nuclei were stained with Hoechst dye. FIG. 58B shows the
fluorescence intensity of GTP-Rac1 was analyzed by Image J
software. The fluorescence intensity of GTP-Rac1 in cells incubated
with MSNP2 was regarded as 100% for comparison with the
fluorescence intensity of cells treated with MSNP2 in the presence
of inhibitors. *, p<0.05, demotes a significant decrease
compared with the treatment using MSNP2 alone.
[0086] FIG. 59 shows cell viability determination using a MTS
assay. 1.times.10.sup.4 Hela cells in 100 .mu.L completed RPMI were
plated onto 96-multi-well plates (Costar; Corning, N.Y.). After
incubation with various empty particles at doses of 200 .mu.g/mL
for 36 h, Hela cells were incubated with the MTS reagent for 2 h
and the absorbance measured at 490 nm. The treatment by adding 5
.mu.L PBS into cultured cells serves as control. The MSNP
themselves were devoid of toxicity.
[0087] FIG. 60 shows Electron tomography analysis and 3D image
reconstruction of the TEM images generated during HeLa cell
incubation with 20 .mu.g/mL MSNP rod with an aspect ratio of
2.1-2.5 for 3 h. TEM grids were used for the tomography analysis on
an FEI Tecnai F20 microscope operated at 200 kV. Images were
captured by tilting the specimen from -70.degree. to 70.degree.
with 1.degree. steps. Tilt series images were captured with a TIETZ
F415MP 16 megapixel CCD camera at a magnification of 26,600.times.
and then aligned using the Etomo program in the IMOD package. The
aligned tilt series were further processed using the reconstruction
features of the FEI software, Inspect3d's SIRT, to improve the
contrast. Videos of the aligned tilt series were generated using
both Inspect3d and Windows movie maker. Still shots from the video
were shown in FIG. 60A (Image 1 to Image 6). Similarly, a higher
magnification of the region of interest (box) in FIG. 60A was
imaged (FIG. 60B). MSNP rod with an aspect ratio of 2.1-2.5 were
taken up by a process of macropinocytosis as evidenced by the
presence of filopodia and formation of macropinocytotic vesicles.
Noteworthy, the number of filopodia and extent of membrane ruffling
were dramatically enhanced in cells exposed to MSNP rods with an
aspect ratio of 2.1-2.5. Electron tomography and 3D image
reconstruction was powerful enough to capture the porous structure
of the particles inside the cells, an ultrastructural feature that
has not previously been accomplished.
DETAILED DESCRIPTION
[0088] Some embodiments of the current invention are discussed in
detail below. In describing embodiments, specific terminology is
employed for the sake of clarity. However, the invention is not
intended to be limited to the specific terminology so selected. A
person skilled in the relevant art will recognize that other
equivalent components can be employed and other methods developed
without departing from the broad concepts of the current invention.
All references cited anywhere in this specification are
incorporated by reference as if each had been individually
incorporated.
[0089] Embodiments of the invention include submicron structures of
a silica body defining a plurality of pores and an outer surface
between pore openings of said plurality of pores and a cationic
polymer on the surface of said silica body. The submicron structure
has a maximum dimension less than one micron (.mu.m).
[0090] Compared with an existing anticancer drug delivery system
(e.g. Doxil.RTM., doxorubicin HCl liposome injection, Centocor
Ortho Biotech Products), MSNP is a multifunctional delivery
platform that has been shown at cellular and in vivo levels to be
capable of delivering multiple pharmaceutical components (e.g.
chemotherapeutic agents and DNA/siRNA) to a variety of cancer cell
types and the tumor site in nude mice. This delivery platform
allows effective and protective packaging of hydrophobic and
charged anticancer drugs for controlled and on demand delivery,
with the additional capability to also image the delivery site.
Advantages of using MSNP to deliver anticancer drugs can include:
(1) MSNP have minimal cytotoxicity, they are used extensively as
food additives; MSNP is biologically inert when injected
intravenously at high dose in rodents and are also biologically
degradable and excretable. (2) Low cost and ease of large-scale
production; (3) Easy to modify physicochemical characteristics
(e.g. particle size, surface charge, hydrophilicity) and simple
purification procedures (centrifugation); (4) Establish the
possibility to co-deliver of two or more drugs or therapeutic
modalities for combination therapy; (5) Versatile functionalization
methods (organo-silanes) allows ligand (e.g. folate, transferrin)
conjugation for targeted delivery of drugs in a cell- or
tissue-specific manner; (6) visualization of sites of drug delivery
by combining therapeutic agents with imaging modalities such as
iron oxide nanoparticles for MRI or probes for fluorescent imaging;
(7) extension of the economic life of proprietary drugs.
[0091] Preliminary studies using MSNP with a .about.100 nm primary
particle size has shown that these particles could be taken up and
accumulate in a human breast cancer (MCF-7) xenograft in nude
mouse. However, the EPR effect was not calculated in that study and
it has subsequently been recognized that the original synthesis
method yielded particles that tend to agglomerate considerably in
biological media. This could make them relatively ineffective from
the perspective that particle sizes <200 nm are better suited
for achieving improved EPR effects. Thus, size reduction may be
helpful to increase their passive targeting but has to take into
consideration that to overcome this agglomeration by salt and
protein in biological fluids may require an additional design
feature.
[0092] In some embodiments, size reduction and surface
functionalization of mesoporous silica nanoparticles (MSNP) with
cationic polymers, including cationic co-polymers reduces particle
opsonization while enhancing the passive delivery of monodisperse,
50 nm doxorubicin-laden MSNP to a human squamous carcinoma
xenograft in nude mice following intravenous injection. Using near
infrared (NIR) fluorescence imaging and elemental Si analysis,
accumulation of .about.12% of the injected particle load at the
tumor site, where there is effective cellular uptake and the
delivery of doxorubicin to HeLa cells. This was accompanied by the
induction of apoptosis and an enhanced rate of tumor shrinking
compared to free doxorubicin. The improved drug delivery was
accompanied by a significant reduction in systemic side effects
such as animal weight loss as well reduced liver and renal injury.
These results demonstrate that it is possible to achieve effective
passive tumor targeting by MSNP size reduction as well as
introducing steric hindrance and electrostatic repulsion through
coating.
[0093] Some embodiments of the current invention can be implemented
in practice to deliver anticancer drugs (e.g. doxorubicin,
camptothecin, paclitaxel) in carcinoma disease that can benefit
from a nanotherapeutic MSNP platform, and eventually in human
beings. However, some embodiments of the current invention can also
be practiced for diseases other than cancer where increased
vascular fenestration could lead to passive delivery and
accumulation of a wide range of drugs. An example, without
limitation, is inflammatory disease processes.
Silica Body
[0094] The submicron structure includes a silica body that defines
a plurality of pores therein. For example, the silica body can be a
mesoporous silica nanoparticle. The fact that we refer to the body
as a silica body does not preclude materials other than silica from
also being incorporated within the silica body. In some
embodiments, the silica body may be substantially spherical with a
plurality of pore openings through the surface providing access to
the pores. However, the silica body can have shapes other than
substantially spherical shapes in other embodiments of the current
invention. Generally, the silica body defines an outer surface
between the pore openings, as well as side walls within the pores.
The pores can extend through the silica body to another pore
opening, or can extend only partially through the silica body such
that it has a bottom surface of the pore defined by the silica
body.
[0095] In some embodiments, the silica body is non-spherical. As
used herein, a non-spherical silica body has an average aspect
ratio (AR) greater than 1.3, and where said submicron structure has
a maximum dimension less than one micron. In some embodiments the
silica body may have an average aspect ratio greater than 1.4,
greater than 1.5, greater than 1.7, greater than 1.8, greater than
1.9, greater than 2.0, greater than 2.1, greater than 2.2, or
greater than 2.5. In some embodiments, the silica body may have an
aspect ratio less than about 5, less than about 4.7, less than
about 4.5, less than about 4.3, less than about 4.0, less than
about 3.7, less than about 3.5, less than about 3.3, less than
about 3.0, or less than about 2.7. As used herein, the average AR
values were determined by a Transmission Electron Microscope (TEM),
measuring the length and diameter of at least 30 randomly selected
particles and averaging the individual AR values to produce the
average AR.
[0096] In some embodiments, the silica body is mesoporous. In other
embodiments, the silica body is microporous. As used herein,
"mesoporous" means having pores with a diameter between 2 nm and 50
nm, while "microporous" means having pores with a diameter smaller
than 2 nm. In general, the pores may be of any size, but in some
embodiments are large enough to contain one or more therapeutic
compounds therein. In such embodiments, the pores allow small
molecules, for example, therapeutic compound such as anticancer
compounds to adhere or bind to the inside surface of the pores, and
to be released from the silica body when used for therapeutic
purposes. In some embodiments, the pores are substantially
cylindrical.
[0097] Some embodiments of the invention include nanoparticles
having pore diameters between about 1 nm and about 10 nm in
diameter. Other embodiments include nanoparticles having pore
diameters between about 1 nm and about 5 nm. Other embodiments
include particles having pore diameters less than 2.5 nm. In other
embodiments, the pore diameters are between 1.5 and 2.5 nm. Silica
nanoparticles having other pore sizes may be prepared, for example,
by using different surfactants or swelling agents during the
preparation of the silica nanoparticles.
[0098] The submicron structures according to some embodiments of
the current invention may be referred to as nanoparticles. The term
nanoparticles as used herein is intended the include particles as
large as 1000 nm. In general, particles larger than 300 nm become
ineffective in entering living cells. In some embodiments,
colloidal suspensions may be formed using a plurality of submicron
structures according to some embodiments of the invention. In that
case, larger particles can tend to settle rather than remaining
suspended in Brownian motion. As used herein, size of the submicron
structure refers to the size of the primary particles, as measured
by transmission electron microscopy (TEM) or similar visualization
technique. Particle size does not refer to agglomerates in solution
or suspension. Some embodiments include nanoparticles having an
average maximum dimension between about 50 nm and about 1000 nm.
Other embodiments include nanoparticles having an average maximum
dimension between about 50 nm and about 500 nm. Other embodiments
include nanoparticles having an average maximum dimension between
about 50 nm and about 200 nm. In some embodiments, the average
maximum dimension is greater than about 20 nm, greater than about
30 nm, greater than 40 nm, or greater than about 50 nm. Other
embodiments include nanoparticles having an average maximum
dimension less than about 500 nm, less than about 300 nm, less than
about 200 nm, less than about 100 nm or less than about 75 nm.
[0099] In some embodiments, the surface of the submicron structure
or nanoparticle is unmodified. As used herein, an "unmodified"
nanoparticle has had no other functional groups added to the
surface after formation of the nanoparticle. Unmodified
nanoparticles have an anionic charge due to free silyl hydroxide
moieties present on the surface.
Cationic Polymer
[0100] As used herein, the term "polymer" is a macromolecule
composed of repeating structural units, usually in a linear or
branched sequence.
[0101] The cationic polymer may be any polymer bearing an overall
positive charge, such as, for example, poly(ethyleneimine) (PEI),
polyamidoamine, polylysine, poly(allylamine) or
poly(diallyldimethylammonium chloride). Other cationic polymers
will be apparent to those of skill in the art, and may be found,
for example, in "Polymer Handbook, 4th Edition, Edited by: Brandrup
et al.; John Wiley & Sons, 1999; and De Smedt et al.,
Pharmaceutical Research, vol. 17, no. 2, pp. 113-126). Other
examples include, chitosan, poly(N-isopropyl
acrylamide-co-Acrylamide), Poly(N-isopropyl acrylamide-co-acrylic
acid), poly(L-lysine), diethylaminoethyl-dextran,
poly-(N-ethyl-vinylpyridinium bromide), poly(-dimethylamino)ethyl
methacrylate), poly(ethylene
glycol)-co-poly(trimethylaminoethylmethacrylate chloride). Cationic
polymer modified nanoparticles have a positive charge. In some
embodiments, the cationic polymer is poly(ethyleneimine) (PEI).
[0102] In some embodiments, the cationic polymer is a co-polymer. A
co-polymer contains more than one repeating unit. Any co-polymer
may be used, so long as the co-polymer bears an overall positive
charge. The co-polymer may be a random co-polymer, alternating
co-polymer, periodic co-polymer, statistical co-polymer, graft
co-polymer, or block co-polymer. In some embodiments, the
co-polymer may be a block co-polymer of poly(ethyleneimine) (PEI)
and poly(ethylene glycol) (PEG).
[0103] The cationic polymer may be bound covalently or
electrostatically to the surface of the silica body. In some
embodiments, the cationic polymer is electrostatically bound to the
surface of the silica body. For example, the cationic polymer may
bind electrostatically to an unmodified silica body, which has an
overall negative charge, or to a surface-modified silica body
bearing a plurality of negatively charged surface modifying groups
such that the silica body has an overall negative charge. Surface
modification of the silica body is described in detail below.
[0104] In some embodiments, the cationic polymer has a weight
average molecular weight less than about 30,000, less than about
25,000, less than about 20,000, less than about 15,000, or less
than about 10,000. In some embodiments, the cationic polymer has a
weight average molecular weight greater than about 600, greater
than about 1000, greater than about 1500, or greater than about
1800, greater than about 2000, greater than about 3000, or greater
than about 4000, or greater than about 5000. The range of molecular
weight may be between any recited endpoints.
[0105] When a block co-polymer is used, each portion may have a
weight average molecular weight within the above ranges. For
example, if PEG is used, the PEG may have a weight average
molecular weight, greater than about 2000, greater than about 3000,
greater than 4000, or greater than about 5000. Alternatively, the
PEG may have a weight average molecular weight less than about
20,000, less than about 16,000, less than about 12,000, or less
than about 10,000.
Core Structure
[0106] In some embodiments, the silica body may have a core
structure. As used herein, a core structure is a metal crystal or
nanocrystal in the interior of the silica body. In some
embodiments, the silica body does not include a metal nanoparticle
or metal nanocrystal as a core structure. In some embodiments, the
core structure is superparamagnetic metal, silver, or gold. Other
embodiments include submicron structures having more than one core
structure in the nanoparticle, such as, for example, a silver and
gold nanocrystal in the core structure, or a silver nanocrystal and
superparamagnetic iron nanocrystal. In some embodiments, the core
structure is a superparamagnetic nanocrystal, such as, for example,
an iron oxide nanocrystal. A superparamagnetic nanocrystal core
makes the particles visible using magnetic resonance imaging (MRI).
The nanoparticle may be used as MRI contrast agents in addition to
any transfection or anti-cancer activity. The superparamagnetic
nanocrystal in the core of the nanoparticle also allows the
particles to be manipulated or collected by a magnetic field, for
example. In other embodiments, the core structure is a gold
nanocrystal.
Surface Modification
[0107] Other embodiments include submicron structures as described
above, which further include a surface modification. As used
herein, "surface modification" means attaching or appending
molecules or other materials to the surface of the silica body, in
addition to the cationic polymer. Surface modification also
modifies the surface of the pores of the silica body. The surface
modification may be covalent, electrostatic or a combination of
both. For example, the surface may include a covalent surface
modification and an electrostatic surface modification on the same
nanoparticle. In some embodiments, the surface modification may be
further derivatized, for instance, by further covalent or
electrostatic bonds. Surface modifications, as described herein,
may be used on any silica body having an unreacted silica surface,
including nanodevices having stoppers, impellers or valves, as
described below.
[0108] In some embodiments, the surface modification comprises a
plurality of anionic or electrostatic molecules attached to an
outer surface of said silica body, wherein the anionic or
electrostatic molecules provide hydrophilicity or aqueous
dispersability to the nanoparticle and are suitable to provide
repulsion between other similar submicron structures. Anionic
surface modified nanoparticles are described, for example, in
International Application No. PCT/US2008/013476, filed Dec. 8,
2008, published as WO 2009/078924, the contents of which are
incorporated herein by reference in its entirety.
[0109] In some embodiments, the plurality of anionic molecules
include at least one phosphonate moiety. In some embodiments, the
plurality of anionic molecules are trihydroxysilylpropyl
methylphosphonate. Trihydroxysilylpropyl methyl phosphonate surface
modifications are prepared, for example, by treating the silica
body with trihydroxysilyl propyl methylphosphonate.
[0110] In some embodiments, the surface modification is covalently
bonded to the surface of the silica body. In other words, the
surface modification has a functional group covalently bonded to
the surface. As used herein, the "functional group" defines a
chemical moiety linked to the surface of the nanoparticle, either
directly, or via a linker. In some embodiments, the functional
group is a phosphonate, amine, sulfhydryl, disulfide, carboxylic
acid, epoxide, halide (i.e. fluorine, chorine, bromine, or iodine),
azide, alkyne, or hydrophobic moiety. In some embodiments, the
functional group is a phosphonate or an amide. In some embodiments,
the functional group may be further bonded, covalently or
electrostatically to a further compound.
[0111] In general, any reaction capable of reacting with the silyl
hydroxide surface of the silica body may be used to covalently
modify the surface. For example, the surface of the silica body may
be treated with a trialkoxysilyl compound or trihydroxysilyl
compound. The compound reacts with the silyl hydroxide surface of
the silica body, forming covalent silicon-oxygen bonds.
Trialkoxysilyl and trihydroxysilyl compounds bearing various
functional groups may be used to modify the surface of the
nanoparticle.
[0112] In some embodiments, the covalent surface modification
comprises a phosphonate, amine, sulfhydryl, disulfide, carboxylic
acid, epoxide or hydrophobic organic moiety. As discussed above,
various functional groups may be present on the surface
modification, depending on the reagents used to modify the surface.
In some embodiments, the functional group (i.e. phosphonate, amine,
sulfhydryl, disulfide, carboxylic acid, epoxide, halide, azide,
alkyne, or hydrophobic organic moiety) may be separated from the
silica surface by a linker. In some embodiments, the functional
group is covalently bonded to the silica surface via a C.sub.1 to
C.sub.12 alkyl linker. In other words, a C.sub.1 to C.sub.12 alkyl
group is present between the atom covalently bonded to the surface
and the functional group (i.e. phosphonate, amine, sulfhydryl,
disulfide, carboxylic acid, epoxide or hydrophobic organic moiety).
In other embodiments, the functional group is covalently bonded to
the silica surface via a C.sub.1 to C.sub.6 alkyl linker.
Nanoparticles bearing a surface modification are called
surface-modified nanoparticles.
[0113] As used herein a C.sub.1 to C.sub.12 alkyl chain includes
linear, branched and cyclic structures having 1 to 12 carbon atoms,
and hybrids thereof, such as cycloalkylalkyl. Examples of alkyl
chains include methylene (CH.sub.2), ethylene (CH.sub.2CH.sub.2),
propylene (CH.sub.2CH.sub.2CH.sub.2), and so forth.
[0114] As used herein, surface modification having a phosphonate
(also known as phosphonate-modified nanoparticles) have at least
one phosphonic acid (--P(O)(OH).sub.2) group or phosphinic acid
(--P(O)(OH)R, where R is an C.sub.1 to C.sub.12 alkyl group). The
phosphonic or phosphinic acid may be charged or uncharged,
depending on the pH. At physiological pH, phosphonic acids and
phosphinic acids are negatively charged, or anionic. Phosphonate
modifications may be prepared, for example, by treating the silica
body surface with a phosphonate bearing trialkylsiloxane compound
or phosphonate-bearing trihydroxylsilyl compound, such as
(trihydroxylsilyl)propyl methylphosphonate.
[0115] In some embodiments, the surface modification has a
phosphate (i.e. phosphonic acid or phosphinic acid) group.
Functionalization of the particle surface with a phosphonate group
provides electrostatic binding of positively charged (i.e.
cationic) hydrophilic therapeutic compounds (e.g. doxorubicin) to
the porous interior, from where the drug could be released by
acidification of the medium under abiotic and biotic conditions. In
addition, phosphonate modification also improves exterior coating
with the cationic polymer, PEI, which endows the MSNP with the
ability to contemporaneously bind and deliver siRNA.
[0116] As used herein, surface modifications having an amine (also
known as amine modified nanoparticles) will have at least one
primary (--NH.sub.2), secondary (--NHR), tertiary (--NR.sub.2) or
quaternary amine. An amine-modified surface may be charged or
uncharged, depending on the amine and pH. Amine modifications may
be prepared, for example, by treating the silica body surface with
an amine bearing trialkoxysilane compound, such as
aminopropyltriethoxysilane,
3-(2-aminoethylamino)propyl-trimethoxysilane, or
3-trimethoxysilylpropyl ethylenediamine. An amine modified silica
body may have an overall negative charge at certain pH, and when
combined with anionic surface modifications, as discussed
above.
[0117] As used herein, surface modifications having a sulfhydryl
(or thiol) group will have at least one --SH moiety. Such a
modification may be prepared, for example, by treating the surface
of the nanoparticle with a sulfhydryl bearing trialkoxysilane
compound, such as 3-mercaptopropyltriethoxysilane.
[0118] As used herein, surface modifications having a disulfide
group will have at least one --S--S-- moiety. Such a modification
may be prepared, for example, by treating the surface of the
nanoparticle with a disulfide bearing trialkoxysilane compound, or
by treating a sulfhydryl modified surface with
2,2'-dithiodipyridine or other disulfide.
[0119] Surface modifications having a carboxylic acid group will
have at least one --CO.sub.2H, or salt thereof. Such a modification
may be prepared, for example, by treating the surface with a
carboxylic acid bearing trialkoxysilane compound, or by treating
the surface with a trialkoxysilane compound bearing a functional
group that may be converted chemically into a carboxylic acid. For
example, the surface may be treated with
3-cyanopropyltriethoxysilane, followed by hydrolysis with sulfuric
acid.
[0120] Surface modifications having an epoxide will have at least
one epoxide present on the surface of the nanoparticle. Such a
modification may be prepared, for example, by treating the surface
with an epoxide bearing trialkoxysilane compound, such as
glycidoxypropyltriethoxysilane.
[0121] Surface modifications having a hydrophobic moiety will have
at least one moiety intended to reduce the solubility in water, or
increase the solubility in organic solvents. Examples of
hydrophobic moieties include long chain alkyl groups, fatty acid
esters, and aromatic rings.
[0122] Different surface modifications may be combined. For
example, an anionic surface modification (such as, for example, a
phosphonate modification) may be combined with an amine
modification, thiol modification, or hydrophobic modification if
desired. In some embodiments, the modified silica body has an
overall negative charge before being combined with a cationic
polymer. If the silica body has an overall negative charge, a
cationic polymer may bind electrostatically to the surface of the
silica body.
Surface Derivitization
[0123] Any of the covalent surface modifications described above
may be further derivatized, for example, by further covalent or
electrostatic bonds. In some embodiments, the surface modification
is further covalently bonded to another compound, such as a
light-emitting molecule, targeting compound, polymer, peptide,
protein, nucleic acid, sugar, oligosaccharide, or polysaccharide.
Light emitting molecules include compounds which emit light by
either fluorescence or phosphorescence. Light emitting molecules
include dyes, such as fluorescent dyes. Examples of light emitting
molecules include fluorescent dyes such as fluorescein, and
rhodamine B. Light emitting molecules may be covalently bonded to
the surface modified silica body by any useable method. For
example, amine-modified nanoparticles having a free NH.sub.2 group
may be reacted with fluorescent dyes bearing amine-reactive groups
such as isocyanates, isothiocyanates, and activated esters, such as
N-hydroxysuccinimide (NHS) esters. Examples of fluorescent dyes
bearing amine reactive groups include, for example, fluorescene
isothiocyanate, N-hydroxysuccinimide-fluorescein, rhodamine B
isothiocyanate, or tetramethylrhodamine B isothiocyanate. Other
dyes will be apparent to those of skill in the art. Nanoparticles
bearing light-emitting molecules may be used, for example, for
fluorescence imaging, for instance when the nanoparticles interact
with the surface of a microbe.
[0124] In some embodiments, the surface modification is further
bonded to a polymer, such as, for example, polyethylene glycol
(PEG). Polymers covalently bonded to the surface modification
should be covalently bonded at only one location to prevent
crosslinking. For example, the surface may be modified with
poly(ethylene glycol) methyl ether, which has only one reactive
end. The reactive end may be activated, for example with an
N-hydroxysuccinimide ester. Activated PEG may react, for example,
with free amines, including PEI. For example, modification of a
PEI-coated MSNP with polyethylene glycol (PEG) would produce an
MSNP with a block-copolymer of PEI and PEG (PEI-PEG).
[0125] In some embodiments, the surface modification is further
bonded to a peptide or protein. Peptides include polypeptides
having at least 2 amino acids. Various amino acid residues on
peptides or proteins may form a covalent bond with surface-modified
nanoparticles. For example, carboxylic acid residues (from aspartic
acid and glutamic acid) may react with amine-modified nanoparticles
bearing a free NH.sub.2 group. Likewise, amine residues on proteins
(i.e. from lysine) may react with carboxylic acid bearing surface
modifications or with epoxide bearing surface modifications.
Sulfhydryl surface modifications may react with disulfide bonds
(e.g. from cystine residues) in the protein via thiol exchange.
Disulfide surface modifications, such as 2-thiopyridine disulfides
may react with free thiols (e.g. from cysteine residues) in the
protein to form a covalent bond with the protein. Other suitable
methods for conjugating the proteins to the surface-modified
nanoparticles will be evident to those of skill in the art.
[0126] In some embodiments, the polymer, protein, peptide,
oligonucleotide, sugar, oligosaccharide, or polysaccharide is
covalently attached to the surface modifying group via a linker.
Various bifunctional crosslinkers are known to those in the art for
covalently bonding to proteins, any of which may be used to
covalently link a surface modified nanoparticle to a protein. For
example, heterodifunctional crosslinkers such as
succinimidyl-4-[N-maleimidomethyl]cyclohexane-1-carboxylate (SMCC)
and melaimidobutyryloxysuccinimide ester (GMBS) may be used to
react with amine-modified nanoparticles (via the succinimide
esters), and then form a covalent bond with a free thiol in the
protein (via the maleimide). Other crosslinkers, such as
succinimidyl 3-(2-pyridyldithio)-propionate (SPDP) may react with
amine-modified nanoparticles (via the succinimide ester), and form
a covalent bond with a free thiol in the protein via thiol
exchange. Other difunctional crosslinkers include suberic acid
bis(N-hydrosuccinimide ester), or disuccinimidyl carbonate which
can react with amine-modified, hydroxyl-modified, or unmodified
nanoparticles, and free amines or hydroxyl groups on the polymer
(such as poly(ethyleneglycol) methyl ether) or protein (e.g. from
lysine residues). Other bifunctional and heterobifunctional
crosslinkers useable with various surface modifications will be
evident to those of skill in the art.
[0127] In some embodiments, the surface modifying material is a
polymer, protein, peptide, nucleic acid, sugar, oligosaccharide,
polysaccharide, or combination thereof.
[0128] Surface-modified nanoparticles bearing a protein are also
called protein-modified nanoparticles. The protein may be bonded
covalently (directly to the surface modification or via a linker)
or may be electrostatically bonded to the modified or unmodified
nanoparticles as discussed above. The protein may be a targeting
protein or an antibody. A "targeting protein" as used herein, means
a protein which binds to a particular surface feature of a cell.
Antibodies and peptides are also used to bind to particular surface
features of cells, and may be used to modify the nanoparticles of
the invention. Protein-modified nanoparticles may be used to
selectively target specific cells, by interacting specifically or
selectively to a cell of interest.
[0129] In some embodiments, the surface modification is
electrostatically bonded to the surface. As used herein
"electrostatically bonded" means bonded based on the attraction of
opposite charges. An unmodified nanoparticle has a negative charge,
due to the presence of free silyl hydroxide residues on the surface
of the nanoparticle. The particle may also bear a surface
modification having a negative charge (such as a phosphonate
modification), such that the overall charge of the surface is
negative. The surface may be modified with material bearing a
positive charge, which will bind to the surface
electrostatically.
[0130] In other embodiments, in addition to the cationic polymer, a
protein may bind to the surface electrostatically. A protein having
a net positive charge will bind electrostatically to unmodified
nanoparticles or surface modified nanoparticles bearing a negative
charge. For example, proteins such as Bovine Serum Albumin (BSA)
and protein solutions such as Fetal Bovine Serum (FBS) bind
electrostatically to unmodified or negatively charged
nanoparticles.
[0131] A protein having a net negative charge will bind
electrostatically to modified nanoparticles having a positive
charge, such as amine-modified nanoparticles, or nanoparticles
modified by cationic polymers. For example, negatively charged
proteins bind electrostatically to nanoparticles bearing a cationic
polymer, as described herein.
Oligonucleotides
[0132] In some embodiments, the submicron structure further
includes an oligonucleotide. The oligonucleotide binds
electrostatically to the cationic polymer and outside surface of
the silica body.
[0133] As used herein, an oligonucleotide is a nucleic acid
polymer, and may be a ribonucleic acid polymer (RNA) or
deoxyribonucleic acid polymer (DNA). DNA may be double stranded,
and may be, for example a plasmid. RNA may be single stranded or
double stranded and may be, for example a siRNA. Other
oligonucleotides include, for example, microRNA (miRNA) and small
hairpin RNA (shRNA).
[0134] Without wishing to be bound by theory, the cationic polymer
envelopes and protects the oligonucleotide from degradation.
Oligonucleotide-containing structures according to the invention
may, for example, deliver oligonucleotides to the interior of a
cell when the submicron structure enters the cell. Genes or
therapeutic oligonucleotides (such as siRNA) may thus be
successfully delivered into a cell. In other words,
oligonucleotide-containing submicron structures may be used for
transfection.
Therapeutic Compounds
[0135] In some embodiments, the submicron structure further
includes a therapeutic compound within the silica body or pores of
the silica body. As used herein, a therapeutic compound is a small
molecule used to treat a disease or disorder. In principle any type
of therapeutic compound may be incorporated into the pores of the
silica body. In some embodiments, the therapeutic compound is an
anticancer compound (i.e. used to treat cancer). In some
embodiments, the therapeutic compound is hydrophobic. Examples of
hydrophobic therapeutic compounds include, for example paclitaxel
and camptothecin and related compounds. In some embodiments, the
therapeutic compound is cationic. Cationic compounds
electrostatically bind to the surface of the silica body. Even in
the presence of a cationic polymer on the surface of the silica
body, cationic compounds may bind to the interior of the silica
body or within the pores of the silica body. Examples of cationic
therapeutic compounds include, for example, daunomycin, doxorubicin
or related compounds. In some embodiments, the therapeutic compound
is anionic. Anionic compounds may bind in pores or surface of the
silica body, for example, by binding electrostatically to
amine-modified surfaces or to cationic-polymer bound silica
bodies.
Oligonucleotide-Therapeutic Compound Combinations
[0136] In some embodiments, the submicron structure includes both
an oligonucleotide and therapeutic compound. The benefits of both
the oligonucleotide and therapeutic compound may be realized. In
some embodiment, the oligonucleotide may be a DNA plasmid. In some
embodiments, the oligonucleotide may be an RNA polymer. In some
embodiments, the oligonucleotide may be a small interfering RNA
(siRNA). In some embodiments, the oligonucleotide may be a siRNA
that decreases translation of a gene that produces drug resistance.
In some embodiments, the siRNA decreases translation of a gene that
produces drug resistance in a cancer cell, and the therapeutic
compound is an anticancer compound. By co-delivering siRNA and
therapeutic compounds, the siRNA may decrease the resistance of the
cell to the therapeutic compound. In the context of cancer, for
example, the siRNA may reduce translation of the p-glycoprotein
(pgp), implicated in multiple drug resistance (MDR). Other
resistance genes that may be suppressed by siRNA include, for
example, MRP1 (ABC transporters), breast cancer resistance protein
(BCRP, ABC transporters), glucosylceramide synthase (GCS) and c-Myc
(oncogene regulating MDR1 expression. Other resistance genes will
be apparent to one of ordinary skill in the art.
[0137] The therapeutic compound, may be, for example doxirubicin.
As a result, a cancer cell that is normally resistant to
doxirubicin may become susceptible to doxirubicin activity. In this
way, multiple drug resistant cancers may be treated.
Additional Structural Features
[0138] In some embodiments, the submicron structure described above
further includes a stopper assembly attached to the silica body.
The stopper assembly has a blocking unit arranged proximate at
least one pore and has a structure suitable to substantially
prevent material from entering or being released when the blocking
unit is arranged in a blocking configuration. The stopper assembly
is responsive to the presence of a predetermined stimulus such that
the blocking unit is released in the presence of the predetermined
stimulus to allow material to enter or be released. The
predetermined stimulus is a predetermined catalytic activity that
is suitable to cleave, hydrolyze, oxidize, or reduce a portion of
the stopper assembly. Examples of stopper assemblies are described,
for example, in International Application No. PCT/US2009/031891,
filed Jan. 23, 2009, now published as WO 2009/094580 and
incorporated herein by reference in its entirety.
[0139] In some embodiments the stopper assembly can include a
thread onto which the blocking unit can be threaded. The thread has
a longitudinal length that is long relative to a transverse length
and is suitable to be attached at one longitudinal end to the
silica body. The stopper assembly can also have a stopper attached
to a second longitudinal end of the thread in some embodiments. The
stopper can be selected among a wide range of possible stoppers
based on the type of environment
[0140] For example, according to some embodiments, a synthetic
strategy can involve the use of a snap-top "precursor". The
assembly of the snap-top precursors can be performed step-wise from
the silica nanoparticle surfaces outward. For instance, the silica
nanoparticles are treated with aminopropyltriethoxysilane (APTES)
to achieve an amine-modified nanoparticle surface. An azide
terminated tri(ethylene)glycol thread is attached to the
amine-modified nanoparticles. The precursor is completed through
the addition of .alpha.-cyclodextrin as the blocking unit at
5.degree. C., which complexes with the threads at the low
temperature. The precursor can enable the preparation of many
different systems based on a common general structure in which
different stoppers can be attached depending on the specific
desired application. For example, stoppers may be selected that
respond to enzymes (for example, ester linked or peptide linked),
pH (for example, vinyl ether linked), and redox (for example
disulfide linked) stimulation. However, the broad concepts of the
current invention are not limited to only these specific examples.
There are a wide range of possible stoppers that may be selected
according to the particular application.
[0141] Other embodiments include submicron structures further
including an impeller attached to the silica body. Silica bodies
modified by impellers are described, for example in International
Application No. PCT/US2009/031871, filed Jan. 23, 2009, published
as WO 2009/094568, the contents of which are incorporated herein in
their entirety. The term "impeller" as used herein is intended to
have a broad meaning to include structures which can be caused to
move and which can in turn cause molecules located proximate the
impeller to move in response to the motion of the impeller.
[0142] In operation, the impellers are driven by an energy transfer
process. The energy transfer process can be, but is not limited to,
absorption and/or emission of electromagnetic energy. For example,
illuminating with light at an appropriate wavelength can cause the
plurality of impellers to wag back and forth between two molecular
shapes. The motion of the plurality of impellers causes motion of
molecules (for example, peptides, proteins, ions, drugs or
antibiotics) of interest into and/or out of the silica body. On the
other hand, in the absence of excitation energy, the plurality of
impellers can remain substantially static, at least for time
periods long enough for the desired application, to act as
impediments to block molecules from exiting and/or entering the
storage chamber.
[0143] The impellers can be, but are not limited to, azobenzenes
according to some embodiments of the current invention. For
example, the azobenzenes can include the following: 1) One phenyl
ring derivatized with a functional group that enables attachment
directly to the silica surface or to a modified silica surface as
described later. The list of suitable functional groups contains
but is not limited to: alcohols, (--ROH), anilinium amines
(--NH.sub.2) primary amines (--RNH.sub.2), secondary amines
(--R.sub.1R.sub.2NH), azides (N.sub.3), alkynes (RC.ident.CH),
isocyanates (--RNCO), isothiocyanates (--RNCS), acid halides
(RCOX), alkyl halides (RX) and succinimidyl esters. 2) other
functional groups on the other phenyl ring (which is the moving end
of the machine). The list of these functional groups includes but
is not limited to: --H (here the phenyl ring is underivatized),
esters (--OR), primary and secondary amines, alkyl group,
polycyclic aromatics, and various generations of dendrimers. The
bulkiness of these functional groups can be designed for specific
systems. For example, large dendritic functionalities might be
required when very large pore openings or very small guest
molecules are employed.
[0144] When illuminated or irradiated with light of a particular
wavelength, the azobenzene undergoes photoisomerization, causing
the second phenyl group to move.
[0145] In other embodiments, impellers are based on redox of copper
complexes. The copper complexes can include bifunctional bidentate
stators that contain diphosphine and/or diimine bidentate metal
chelators on one end of the stator, while at the other end
functionalities such as alkoxysilanes (for immobilization on silica
and silicon substrates) and thiols (for immobilization on gold
substrates) are present. The copper complexes can contain a rotator
that is a rigid bidentate diimine metal chelator, which rotates and
changes the shape of the overall molecule upon redox or photons.
These copper complexes exist in two oxidation states, each of which
corresponds to a specific shape. Copper (I) is tetrahedral while
copper (II) is square planar. The different oxidation states, and
hence different shapes that are caused by a 90.degree. rotation of
the rotator, can be generated in three ways: Reduction and
oxidation (1) using electrodes and an electric current (2) by use
of chemical reducing and oxidizing agents, and (3) by the
photo-excitation of light of the appropriate wavelength.
[0146] Some embodiments include submicron structure further
including a valve assembly attached to the silica body. Porous
nanoparticles having valves are described, for example, in
International Application No. PCT/US2009/032451, filed Jan. 29,
2009, published as WO 2009/097439, the contents of which are
incorporated herein in their entirety. In some embodiments, the
valve assembly is operable in an aqueous environment. The valve
assembly has a valve arranged proximate the at least one pore and
has a structure suitable to substantially prevent material from
entering or being released while the valve is arranged in a
blocking configuration. The valve assembly is responsive to a
change in pH such that the valve moves in the presence of the
change in pH to allow the material to enter or be released from the
silica body.
[0147] According to some embodiments of the current invention, the
pH-responsive valve assembly relies on the ion-dipole interaction
between cucurbit[6]uril (CB[6]) and bisammonium stalks, and that
can operate in water. CB[6], a pumpkin-shaped polymacrocycle with
D.sub.6h symmetry consisting of six glycouril units strapped
together by pairs of bridging methylene groups between nitrogen
atoms has received considerable attention because of its highly
distinctive range of physical and chemical properties. Of
particular interest in the field of supramolecular chemistry is the
ability of CB[6] to form inclusion complexes with a variety of
polymethylene derivatives, especially diaminoalkanes: the
stabilities of these 1:1 complexes are highly pH-dependent. The
pH-dependent complexation-decomplexation behavior of CB[6] with
diaminoalkanes has enabled the preparation of dynamic
supramolecular entities which can be controlled by pH. In some
embodiments, [2]pseudorotaxanes having bisammonium stalks and CB[6]
rings, may be constructed on the surface of the mesoporous silica
nanoparticles, and the pH-dependent binding of CB[6] with the
bisammonium stalks is exploited to control the entry or release of
molecules from the silica nanoparticles. At neutral and acidic pH
values, the CB[6] rings encircle the bisammonium stalks tightly,
blocking the nanopores efficiently when employing suitable lengths
of tethers. Deprotonation of the stalks upon addition of base
results in spontaneous dethreading of the CB[6] rings and
unblocking of the pores.
Pharmaceutical Compositions
[0148] Embodiments include pharmaceutical compositions comprising
any of the submicron structures according to the invention.
[0149] In certain embodiments, the composition may be in any
suitable form such as a solution, a suspension, an emulsion, an
infusion device, or a delivery device for implantation or it may be
presented as a dry powder to be reconstituted with water or another
suitable vehicle before use. The composition may include suitable
parenterally acceptable carriers and/or excipients.
[0150] In certain embodiments, the compositions may be in a form
suitable for administration by sterile injection. To prepare such a
composition, the nanoparticles are dissolved or suspended in a
parenterally acceptable liquid vehicle. Among acceptable vehicles
and solvents that may be employed are water, water adjusted to a
suitable pH by addition of an appropriate amount of hydrochloric
acid, sodium hydroxide or a suitable buffer, 1,3-butanediol,
Ringer's solution, and isotonic sodium chloride solution and
dextrose solution. The aqueous formulation may also contain one or
more preservatives (e.g., methyl, ethyl or n-propyl
p-hydroxybenzoate). For parenteral formulations, the carrier will
usually comprise sterile water, though other ingredients, for
example, ingredients that aid solubility or for preservation, may
be included. Injectable solutions may also be prepared in which
case appropriate stabilizing agents may be employed.
[0151] Formulations suitable for parenteral administration usually
comprise a sterile aqueous preparation, which may be, for example,
isotonic with the blood of the recipient (e.g., physiological
saline solution). Such formulations may include suspending agents
and thickening agents and liposomes or other microparticulate
systems which are designed to target the compound to blood
components or one or more organs. The formulations may be presented
in unit-dose or multi-dose form.
[0152] Parenteral administration may comprise any suitable form of
systemic delivery or localized delivery. Administration may for
example be intravenous, intratumoral, intra-arterial, intrathecal,
intramuscular, subcutaneous, intramuscular, intra-abdominal (e.g.,
intraperitoneal), etc., and may be effected by infusion pumps
(external or implantable) or any other suitable means appropriate
to the desired administration modality.
Methods
[0153] Embodiments include methods for using the submicron
structures according to any embodiment of the invention for
treatment of a disease or disorder by administering to a subject in
need of treatment an effective amount of a submicron structure of
the invention.
[0154] The submicron structures may be administered, for example,
as a pharmaceutical composition. Administration may be achieved by
any suitable means. In certain embodiments, the compositions may be
administered systemically, for example, formulated in a
pharmaceutically-acceptable buffer such as physiological saline.
Routes of administration include, for example, subcutaneous,
intravenous, intraperitoneal, intramuscular, or intradermal
injections that provide continuous, sustained levels in the
patient. Administration to human patients or other animals is
generally carried out using a physiologically effective amount of a
compound of the invention in a physiologically-acceptable carrier.
Suitable carriers and their formulation are described, for example,
in Remington's Pharmaceutical Sciences by E. W. Martin.
[0155] The composition may be administered parenterally by
injection, infusion or implantation in dosage forms, formulations,
or via suitable delivery devices or implants containing
conventional, non-toxic pharmaceutically acceptable carriers and/or
adjuvants. In some embodiments, the compositions are added to a
retained physiological fluid, such as cerebrospinal fluid, blood,
or synovial fluid. The compositions of the invention can be
amenable to intravenous (i.v.) injection and direct injection (i.e.
intratumoral injection), application or infusion at a site of
disease or injury.
[0156] By "disease" is meant any condition or disorder that damages
or interferes with the normal function of a cell, tissue, organ or
subject.
[0157] By "effective amount" is meant the amount of an agent
required to ameliorate the symptoms of a disease relative to an
untreated subject. The effective amount of an active therapeutic
agent for the treatment of a disease or injury varies depending
upon the manner of administration, the age, body weight, and
general health of the subject. Ultimately, the attending clinician
will decide the appropriate amount and dosage regimen.
[0158] By "subject" is meant an animal. In some embodiments, a
subject may be a mammal, including, but not limited to, a human or
non-human mammal, such as a bovine, equine, canine, ovine, or
feline.
[0159] As used herein, the terms "treat," treating," "treatment,"
"therapeutic" and the like refer to reducing or ameliorating a
disorder and/or symptoms associated therewith. It will be
appreciated that, although not precluded, treating a disorder or
condition does not require that the disorder, condition or symptoms
associated therewith be completely eliminated.
[0160] Embodiments of the invention include methods of treating
drug resistant cancer by administering to a patient in need a
submicronstructure according to the invention having an siRNA that
reduces the translation of a gene responsible for the drug
resistance, and an anticancer compound. The anticancer compound is
a compound to which the cancer is resistant but becomes susceptible
to treatment upon co-administration with an siRNA that reduces the
translation of a resistance gene.
[0161] In addition to being used for the delivery of chemical
therapeutic agents, MSNP have the potential as hybrid
organic-inorganic materials that can act as carriers for nucleic
acids and therefore potentially useful for the delivery of small
interfering RNAs (siRNAs) and other forms of gene therapy (Park et
al., Int. J. Pharm., vol. 359, pp. 280-284, 2008; Radu et al., J.
Am. Chem. Soc., vol. 126, pp. 13216-13217, 2004; Torney et al.,
Nat. Nanotechnol., vol. 2, pp. 295-300, 2007). As opposed to other
gene delivery systems based on inorganic materials, the porous
structure of MSNP allows both the binding of nucleotides on the
surface as well as the encapsulation of small molecules within the
particles. It is even possible to combine these modules to achieve
dual delivery of drugs and nucleic acids (Torney et al., Nat.
Nanotechnol., vol. 2, pp. 295-300, 2007). To maximize the delivery
of negatively charged nucleic acids to cells, the silica surface
may be converted into positive charge in order to bind DNA and
siRNA. Some of the methods for introducing cationic charge on
inorganic materials, which include silica, iron oxide, and gold,
typically involve surface grafting with amine groups and coating
with cationic polymers (e.g. polyethyleneimine, polyamidoamine,
polylysine) through either covalent or electrostatic association
(Radu et al., J. Am. Chem. Soc., vol. 126, pp. 13216-13217, 2004;
Bharali et al., Proc. Natl. Acad. Sci. U.S.A., vol., 102, pp.
11539-11544, 2005; Bonoiu et al., Proc. Natl. Acad. Sci. U.S.A.,
vol. 106, pp. 5546-5550, 2009; Elbakry et al., Nano Lett., vol. 9,
pp. 2059-2064, 2009; Fuller et al., Biomaterials, vol. 29, pp.
1526-1532, 2008; Kneuer et al., Bioconjugate Chem., vol. 11, pp.
926-932, 2000; McBain et al., J. Mater. Chem., vol. 17, pp.
2561-2565, 2007; Zhu et al., Biotechnol. Appl. Biochem., vol. 39,
pp. 179-187, 2004. The gene delivery capabilities of these surface
modified materials have been demonstrated and may prove useful as
alternatives to traditional viral vectors.
[0162] The effects of polyethyleneimine (PEI) coating on the MSNP
in terms of cellular uptake, cytotoxicity, and efficiency of
nucleic acid delivery were studied. PEIs are synthetic cationic
polymers that compact DNA and siRNA into complexes that are
effectively taken up in cells to make nucleic acid delivery and
gene therapy possible (Boussif et al., Proc. Natl. Acad. Sci.
U.S.A., vol. 92, pp. 7297-7301, 1995; Godbey et al., Proc. Natl.
Acad. Sci. U.S.A., vol. 96, pp. 5177-5181, 1999; Urban-Klein et
al., Gene Ther., vol. 12, pp. 461-466, 2005). Although the polymer
itself is used as a delivery vehicle, PEI can also be attached to
nanoparticle surfaces through covalent and electrostatic
interactions to achieve the same goal (Park et al., Int. J. Pharm.,
vol. 359, pp. 280-284, 2008; Elbakry et al., Nano Lett., vol. 9,
pp. 2059-2064, 2009; Fuller et al., Biomaterials, vol. 29, pp.
1526-1532, 2008; McBain et al., J. Mater. Chem., vol. 17, pp.
2561-2565, 2007; Liong et al., Adv. Mater., vol. 21, pp. 1684-1689,
2009). Complexing the polymer with the nanoparticles has the
potential advantage of facilitating DNA and siRNA delivery by a
multifunctional platform that also allows imaging, targeting and
concurrent drug delivery. PEI was chosen as the polymer coating to
enhance the particle uptake into cells and facilitate endosomal
escape for the nucleotide delivery (Duan et al., J. Am. Chem. Soc.,
vol. 129, pp. 3333-3338, 2006). It is documented that while low MW
PEI is not cytotoxic, these polymers are ineffective at
transfecting nucleotides in contrast to the high MW PEI. In this
regard, it has been demonstrated that the size (MW), compactness
and chemical modification of PEI affect the efficacy and toxicity
of this polymer (Florea et al., AAPS Pharm Sci., vol. 4, p. E12,
2002; Neu et al., J. Gene. Med., vol. 7, pp. 992-1009, 2005).
Therefore, several PEI polymer sizes ranging from MW of 0.6 to 25
KD were investigated in order to balance the efficiency of nucleic
acid delivery and cellular toxicity, which proceed by the proton
sponge effect that involves proton sequestration on the polymer
surface, heightened activity of the proton pump, osmotic swelling
lysosomal injury, intracellular Ca.sup.2+ flux and mitochondrial
damage (Xia et al., Nano Lett. Vol. 6, pp. 1794-1807, 2006; Xia et
al., ACS Nano, vol. 2, pp. 85-96, 2008). The large number of amine
groups of PEI also allows the polymer-coated particles to move
across cell membranes through rapid endocytosis. Cellular uptake of
PEI-coated MSNP may be enhanced by at least two orders of magnitude
compared to that of the MSNP which are unmodified (silanol surface)
or coated with phosphonate or poly(ethylene glycol) groups.
Furthermore, with coating of PEI MW 10 KD, it is possible to
achieve both increased cellular uptake and high transfection
efficacy while minimizing the toxicity normally observed with
higher molecular weight PEI.
[0163] In some embodiments, surface functionalization with
polyethyleneimine (PEI) polymers may enhance oligonucleotide (i.e.
DNA, RNA, shRNA or siRNA) binding. The tight complexing between PEI
and nucleic acids on the particle surface protects these cargo
molecules from enzymatic degradation. The positive charge of
PEI-coated nanoparticles may also lead to strong electrostatic
interaction with the negatively charged cell surface membrane,
which may facilitate particle cellular uptake and lysosomal release
via a proton sponge mechanism. In addition, the molecular weight of
PEI polymer may be carefully selected in order to reduce possible
cytotoxicity.
[0164] Surface coating with PEI yields cationic MSNP with
therapeutically useful nucleic acid delivery properties that
include high binding avidity of DNA and siRNA as well as a high
rate of cellular uptake. siRNA complexed to the MSNP-PEI surface is
quite effective to achieve green fluorescent protein (GFP)
knockdown in transduced HEPA-1 cells, while plasmid DNA delivery is
comparable to a commercially available transfection agent. The
facilitated cellular uptake of cationic particles may enhance the
ability of MSNP to deliver hydrophobic chemotherapeutic agents,
such as paclitaxel, to pancreatic cancer cells. A potential
downside of cationic functionalization to achieve drug or nucleic
delivery is induction of cytotoxicity, best demonstrated by the use
of MSNP-PEI-25 KD. However, this toxicity could be reduced or
eliminated by attaching shorter length polymers that retain nucleic
acid and drug delivery capabilities. Thus, the therapeutic use of
the MSNP platform can be extended to delivery of DNA and siRNA
constructs.
[0165] Packaging siRNA on the surface of cationic MSNP may provide
several benefits. First, the MSNP surface can be functionalized to
enhance siRNA binding through the attachment of PEI polymers, for
example, which in their own right have been used as effective siRNA
compacting and transducing agents. The tight complexing between PEI
and nucleic acids on the particle surface protects these molecules
from enzymatic degradation as demonstrated for DNA. Furthermore,
the positive charge of PEI-coated nanoparticles leads to strong
electrostatic interaction with the negatively charged cell surface
membrane, leading to facilitated particle wrapping and cellular
uptake. This is in agreement with the recent demonstration that
PEI-coated nanoparticles is taken up into cells at high efficiency
(Rosenholm et al., ACS Nano, vol. 3, pp. 197-206, 2009; Duan et
al., J. Am. Chem. Soc., vol. 129, pp. 3333-3338, 2006). However,
the latter study did not look at nucleic acid delivery but did show
that the attachment of the ligand such as folic acid further
enhance uptake in cancer cells (Liong et al., ACS Nano, vol. 2, pp.
889-896, 2008; Rosenholm et al., ACS Nano, vol. 3, pp. 197-206,
2009). While PEI can be used in various ways to make siRNA delivery
complexes, coating it onto the surface of MSNP utilizes this
therapeutic platform as a carrier with large surface area, which is
inexpensive and simple to synthesize, and which can be decorated
with functional groups and fluorescent tags and can be used for
magnetic resonance imaging through the inclusion of
superparamagnetic iron oxide nanocrystals (Liong et al., ACS Nano,
vol. 2, pp. 889-896, 2008). Not only may PEI coating enhance siRNA
delivery, but the particles also are capable of anticancer compound
such as paclitaxel delivery, which constitutes a significant
advance for the use of MSNP as a therapeutic platform. One can
envisage using siRNA and drug delivery simultaneously, e.g.,
delivery of siRNA that knocks down the expression of the
P-glycoprotein (Pgp) drug exporter at the same time as delivering a
chemotherapeutic agent that is exported by Pgp (Ludwig et al.,
Cancer Res., vol. 66, pp. 4808-4815, 2006). This may be an
effective strategy for the treatment of cancers that have developed
a drug resistance due to the activity of this exporter.
[0166] Several advantages of MSNP-PEI for the delivery of siRNA
also hold true for plasmid DNA transduction. In fact, a number of
modifications of the PEI polymer, including various polymer sizes,
degrees of branching, thiol cross-linking and covalent attachment
have been used as gene transfer agents since the 90's and are
enjoying increasing popularity because of the high transfection
efficiency of plasmid DNA and siRNA into cells and live animals
(Boussif et al., Proc. Natl. Acad. Sci. U.S.A., vol. 92, pp.
7297-7301, 1995; Godbey et al., Proc. Natl. Acad. Sci. U.S.A., vol.
96, pp. 5177-5181, 1999; Urban-Klein et al., Gene Ther., vol. 12,
pp. 461-466, 2005; Kircheis et al., J. Gene. Med., vol. 1, pp.
111-120, 1999). An advantage of using PEI for gene transfer lies in
the simplicity with which the polymer can be mixed with DNA/siRNA
without involving covalent attachment. Moreover, PEI protects the
nucleic acids from degradation by nucleases. In all of these
therapeutic applications, however, one has to keep in mind that
high MW polymer could cause toxicity (Florea et al., AAPS Pharm
Sci., vol. 4, p. E12, 2002). As demonstrated by the present
invention, it is now possible to deal with a toxicity problem while
maintaining effective nucleic acid delivery by using intermediate
length polymers. These intermediate length polymers may provide
effective cellular uptake and siRNA/plasmid DNA delivery. Moreover,
this approach may produce transfection of >70% cells in the
population, which may increase effectiveness from the perspective
of gene therapy.
[0167] Other than mediating its effect through high cellular
uptake, the efficient gene transduction ability of PEI proceed via
the proton sponge effect, implying that the primary amines buffer
the protons being pumped into the lysosomal compartment by the
v-ATPase (proton pump) (Boussif et al., Proc. Natl. Acad. Sci.
U.S.A., vol. 92, pp. 7297-7301, 1995; Xia et al., ACS Nano, vol. 2,
pp. 85-96, 2008; Yezhelyev et al., J. Am. Chem. Soc., vol. 130, pp.
9006-9012, 2008). This results in heightened pump activity, leading
to the accumulation of a Cl.sup.- and a water molecule for each
proton that is retained; ultimately this leads to osmotic rupture
of the endosome (Sonawane et al., J. Biol. Chem., vol. 277, pp.
5506-5513, 2002). While effective for delivering the nucleic acid
cargo to the cytosol, the effect of PEI or cationic particles on
the proton pump is a major contributory factor in cationic
cytotoxicity (Xia et al., ACS Nano, vol. 2, pp. 85-96, 2008).
Cationic nanoparticle toxicity can lead to clinically significant
adverse health effects (Clottens et al., Occup. Environ. Med., vol.
54, pp. 376-387, 1997; Hoet et al., Toxicol. Appl. Pharmacol., vol.
175, pp. 184-190, 2001; Hoet et al., Toxicol. Sci., vol. 52, pp.
209-216, 1999). Methods to reduce cationic toxicity while
maintaining effective cargo delivery are therefore desired (Nel et
al., Nat. Mater., vol. 8, pp. 543-557, 2009). Experimental examples
of how PEI toxicity has been reduced include neutralizing the
cationic charge by anhydride, differential ketalization, altering
PEI crosslinking through adjustment of disulfide content and using
shorter polymers (Xia et al., ACS Nano, vol. 2, pp. 85-96, 2008;
Shim et al., J. Control. Release., vol. 133, pp. 206-213, 2009;
Veiseh et al., Biomaterials, vol. 30, pp. 649-657, 2009; Hobel et
al., Eur. J. Pharm. Biopharm., vol. 70, pp. 29-41, 2008 Peng et
al., Bioconjugate Chem., vol. 20, pp. 340-346, 2009). The latter
principal can also be applied to PEI-coated MSNP, cytotoxicity may
be reduced or eliminated while maintaining efficient nucleic acid
delivery. Thus, by attaching a 10 KD polymer, it was possible at
particle doses <50 .mu.g/ml to obtain highly efficient
transduction without any cell death. Preliminary data also indicate
that the PEI-coated MSNP can be intravenously injected into mice
without causing acute toxicity. It appears, therefore, that
cationic toxicity can be controlled to achieve a therapeutically
useful outcome. While the gene transduction efficiency is
significantly reduced with lower MW (0.6-1.8 KD) polymers, the
facilitated MSNP uptake is good enough for delivering paclitaxel
(FIG. 8).
[0168] To use the MSNP delivery system, the first step is to
conduct toxicity test in mice. Results show that i.v. injection of
MSNP in mice has no obvious toxic effects to the major organs or
systems of the animals. It is interesting that MSNP-PEI 25 KD
showed toxicity to cultured cells while no toxicity in vivo. This
may be because of the dilution of the MSNP in the blood system, the
huge number of cells in the body, and strong defense/clearance
capability in living organisms. Until now, there are only limited
in vivo data regarding the toxicity, biodistribution, and
biopersistence of mesoporous silica nanoparticles (Kim et al.,
Angew. Chem., Int. Ed., vol. 47, pp. 8438-8441, 2008; Barb et al.,
Adv. Mater., vol. 16, pp. 1959-1966, 2004; Taylor et al., J. Am.
Chem. Soc., vol. 130, pp. 2154-2155, 2008; Wu et al., Chem Bio
Chem, vol. 9, pp. 53-57, 2008). Several groups used MRI agent to
coat mesoporous silica nanoparticles for in vivo imaging, they
found that MSNP were in the blood vessel 30 min after
administration, then MSNP tended to accumulate more in the RES
systems such as liver and spleen tissue than in kidney, lung, and
heart; in fact MSNP appeared to have cleared kidney after 2 h (Kim
et al., Angew. Chem., Int. Ed., vol. 47, pp. 8438-8441, 2008; Wu et
al., Chem Bio Chem, vol. 9, pp. 53-57, 2008). Long-term MRI
tracking study revealed that the MRI signal gradually disappeared
after 90 days, which means that MSNP were resistant to
decomposition and not easily excreted from the body, suggesting a
potential candidate for long-term liver/spleen MRI monitoring and
targeted drug delivery (Wu et al., Chem Bio Chem, vol. 9, pp.
53-57, 2008). Another interesting finding is MSNP accumulate
preferentially at tumor sites through their enhanced permeability
and retention (EPR) effect in tumor targeting (Kim et al., Angew.
Chem., Int. Ed., vol. 47, pp. 8438-8441, 2008). To achieve the full
potential of MSNP, more in vivo tests may be done regarding to
their toxicity, biodistribution, pharmacokinetics, and
targeting.
[0169] Due to its unique structure and ease with which the surface
can be functionalized, mesoporous silica nanoparticles (MSNP)
constitute a multi-functional platform that can be used for drug
(Lu et al., Small, vol. 4, pp. 421-426, 2008; Coti et al.,
Nanosacle, vol. 1, pp. 16-39, 2009; Slowing et al., Adv. Drug
Deliv. Rev., vol. 60, pp. 1278-1288, 2008; Liong et al., ACS Nano,
vol. 2, pp. 889-896, 2008) and nucleic acid delivery (Xia et al.,
ACS Nano, vol. 3, pp. 3273-3286, 2009). For therapeutic purposes,
nanoparticles that contain a phosphonate surface coating may be
beneficial because of the ease of particle dispersal, good
bio-safety index as well as the ability to adsorb cationic
polyethylenimine (PEI) polymers for complexing and delivery of DNA
and siRNA (Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
Since the polymer attachment leaves the porous interior free for
drug binding and delivery, it establishes the potential to achieve
simultaneous drug and nucleic acid delivery (Astrid et al., J. Am.
Ceram. Soc., vol. 84, pp. 806-812, 2001). It was envisaged that
there some disease conditions such as multidrug resistant cancer
might benefit from the delivery of both agents. Dual delivery
might, therefore achieve simultaneous drug and siRNA delivery,
leading to a synergistic therapeutic outcome.
[0170] Significant uncertainties remained, however. For example, it
was uncertain whether the cationic polymer would interfere with a
therapeutic compound binding to the porous interior of the silica
body. For example, binding a cationic polymer to the surface might
block access to the interior of the silica body. Particularly for
cationic therapeutic compounds, a cationic polymer might displace
any cationic therapeutic compound bound to the silica body, whether
in the interior or on the surface. It was unknown whether a
therapeutic compound could even be loaded into the silica body with
the cationic polymer pre-bound. Assuming a therapeutic compound
could bind to the interior of the silica body in the presence of
the cationic polymer, it was unclear whether the cationic polymer
would prevent drug release inside a cell.
[0171] Through experimentation, the inventors successfully met
these challenges and prepared a dual delivery system. As
demonstrated in the present invention, for example, a cationic
polymer, such as PEI, will not interfere in drug binding to the
porous interior. Furthermore, as demonstrated herein, cationic
therapeutic compounds, such as doxirubicin can be loaded into the
silica body, but only after a cationic polymer, such as PEI is
coated on the surface of the silica body. Furthermore, loading
therapeutic compounds, such as doxirubicin or paclitaxel did not
disturb siRNA binding, as demonstrated herein. Finally, as
demonstrated herein, the dual delivery system could be
preferentially taken up by drug resistant cancer cells and was
capable of acting synergistically to overcome drug resistance. In
other words, the cationic polymer did not prevent release of the
therapeutic compound in the cell.
[0172] In order to test the utility of MSNP as a dual delivery
platform, drug-resistant squamous carcinoma cell line, KB-V1, was
investigated to see if Pgp knockdown restores doxorubicin (Dox)
sensitivity. KB-V1 cells exhibit MDR as a result of Pgp
overexpression (Ludwig et al., Cancer Res., vol. 66, pp. 4808-4815,
2006). In order to effectively engineer particles to deliver Dox as
well as Pgp siRNA, particle functionalization by the attachment of
negative (phosphonate) as well as positive (PEI) surface groups are
functionally effective. Moreover, because PEI delivery of siRNA
constructs to the cytosol may require intermediary lysosomal
processing, it was uncertain whether this endocytic route was
appropriate for doxorubicin (Dox) delivery. As shown in the current
invention, Dox can be stably attached to the porous interior by a
proton-sensitive electrostatic binding interaction that allows
effective drug release from the acidifying LAMP-1-positive
compartment. Pgp siRNA co-delivery increases intracellular Dox
concentrations with improved cytotoxic killing. The improvement of
Dox resistance provides proof-of-principal testing that MSNP can be
engineered to provide contemporaneous drug and siRNA delivery by
effective use of charge and the state of protonation or
deprotonation at the particle surface.
[0173] As shown herein, MSNP can be functionalized to deliver a
chemotherapeutic agent as well as Pgp siRNA to a drug-resistant
cancer cell line. The functionalization of the particle surface
with a phosphonate group allows electrostatic binding of Dox to the
porous interior, from where the drug could be released by
acidification of the medium under abiotic and biotic conditions. In
addition, phosphonate modification also allows exterior coating
with the cationic polymer, PEI, which endows the MSNP with the
ability to contemporaneously bind and deliver Pgp siRNA. The dual
delivery of Dox and siRNA in KB-V1 cells was capable of increasing
the intracellular as well as intranuclear drug concentration to
levels exceeding that of free Dox or the drug being delivered by
MSNP without siRNA co-delivery. This reflects the ability of the
siRNA to effectively knock down Pgp expression and therefore
interfering in drug efflux as one of the resistance mechanisms in
KB-V1 cells. Unlike hydrophobic cargo (FIG. 32), Dox can be
released from the lysosome by a proton-sensitive mechanism. While
clearly effective at improving cytotoxic killing through its dual
delivery capabilities, siRNA-PEI-MSNP could not restore Dox
sensitivity in KB-V1 to the level seen in drug-sensitive KB-31
cells. This may be due to the extremely high levels of Pgp
expression, as confirmed in FIG. 23.
[0174] Two of the major problems in cancer chemotherapy are toxic
side effects as well as development of MDR in cancer cells.
Nanoparticle drug delivery is capable of overcoming both problems
through tumor cell targeting as well as the capability to overcome
drug resistance (Jabr-Milane et al., Cancer Treat. Rev., vol. 34,
pp. 592-602, 2008; Ferrari et al., Nat. Rev. Cancer, vol. 5, pp.
161-171, 2005). MDR can basically be divided into two distinct
categories, namely pump and non-pump resistance (Jabr-Milane et
al., Cancer Treat. Rev., vol. 34, pp. 592-602, 2008; Saad et al.,
Nanomedicine, vol. 3, pp. 761-776, 2008). Pump resistance refers to
the inducible formation of membrane-bound channels or pores that
actively expel a series of structural and functionally distinct
chemotherapeutic agents from the cell. Drug efflux significantly
decreases the intracellular concentration that limits their
cytotoxic potential. The key proteins involved in pump resistance
are Pgp and MRP-1, while the major mechanism in non-pump resistance
is activation of cellular anti-apoptotic defense pathways,
including drug-induced expression of Bcl-2 protein (Saad et al.,
Nanomedicine, vol. 3, pp. 761-776, 2008). Moreover, the pump and
non-pump resistance mechanisms could be mutually interactive
(Jabr-Milane et al., Cancer Treat. Rev., vol. 34, pp. 592-602,
2008). Given this background, a number of nanomaterial design
strategies can be used to overcome drug resistance:
[0175] The first is co-delivery of the chemotherapeutic drug with a
pharmaceutical agent that interferes in pump activity or in
non-pump pathways. One example is the use of verapamil as a Pgp
inhibitor that have been combined with Dox, aimed at reducing
cardiotoxicity of Dox as well as overcoming Pgp-mediated MDR (Wu et
al., J Pharm. Pharmaceut. Sci., vol. 10, pp. 350-357, 2007). In
Dox-resistant K562 leukemia cells, a liposomal Dox-verapamil
complex doubled the cytotoxicity index (IC.sub.50=11.4 .mu.M) of
free Dox (IC.sub.50=23.4 .mu.M) (Wu et al., J Pharm. Pharmaceut.
Sci., vol. 10, pp. 350-357, 2007). Another example is using a
polymeric nanoparticle formulation of
poly(ethyleneoxide)-poly(epsilon-caprolactone) to co-administer
ceramide that is capable of lowering the apoptotic threshold to
paclitaxel, thereby enhancing paclitaxel-induced cytotoxicity in a
MDR human ovarian cancer cell line (van Vlerken et al., Cancer
Res., vol. 67, pp. 4843-4850, 2007).
[0176] A second strategy is to use nanoparticles to deliver the
chemotherapeutic together with siRNA that interfere in key protein
expression in pump-dependent or independent drug resistance
pathways, as demonstrated herein. There are reports demonstrating
that compared to the free drug, dual delivery with a nucleic acid
is capable of enhancing the efficacy in a synergistic fashion (Chen
et al., Small, vol. 5, pp. 2673-2677, 2009; Patil et al.,
Biomaterials, vol. 31, pp. 358-365, 2009). Chen et al showed that
MSNP served as a drug delivery vehicle to deliver Dox and Bcl-2
siRNA that can effectively silence the Bcl-2 mRNA and significantly
suppress the non-pump resistance, and therefore result in enhanced
cell killing capability of Dox in multidrug resistant A2780/AD
human ovarian cancer cells (Chen et al., Small, vol. 5, pp.
2673-2677, 2009). Another example is paclitaxel that was delivered
by poly(d,l-lactide-co-glycolide) nanoparticles along with Pgp
siRNA to the MDR murine mammary cancer cell line, JC. The dual
delivery system showed significantly higher cytotoxicity in vitro
and significantly greater inhibition of tumor growth in vivo than
nanoparticles loaded with paclitaxel alone (Patil et al.,
Biomaterials, vol. 31, pp. 358-365, 2009).
[0177] The third strategy is to deliver the drug together with a
combination of siRNA's that interfere in both pump (e.g. Pgp) and
non-pump (e.g. Bcl-2) mechanisms. Such an approach may be
necessitated by the co-existence of pump and non-pump resistance
mechanisms (Jabr-Milane et al., Cancer Treat. Rev., vol. 34, pp.
592-602, 2008; Saad et al., Nanomedicine, vol. 3, pp. 761-776,
2008). In this regard, it has been demonstrated that the increase
in intracellular drug concentration as a result of the suppression
of drug efflux pumps leads to almost proportional activation of
anti-apoptotic cellular defense (Gottesman et al., Annu. Rev. Med.,
vol. 53, pp. 614-627, 2002; Jabr-Milane et al., Cancer Treat. Rev.,
vol. 34, pp. 592-602, 2008). As one example, a cationic liposome
carrier system was developed to deliver Dox contemporaneously with
two species of siRNA targeting of MRP-1 as well as Bcl-2 (Saad et
al., Nanomedicine, vol. 3, pp. 761-776, 2008). This triple
component (Dox, MRP-1 siRNA, and Bcl-2 siRNA) delivery system
demonstrated enhanced Dox cytotoxicity in human MDR H69AR lung
cancer cells which showed >100 fold enhancement in cytotoxicity
(Saad et al., Nanomedicine, vol. 3, pp. 761-776, 2008). Similar
attempts in experiments in KB-V1 cells where Bcl-2 was combined
with Pgp siRNA and Dox did not improve the cytotoxicity or
IC.sub.50 significantly (not shown).
[0178] In some embodiments, this invention demonstrates how MSNP
can be engineered to effectively deliver a drug together with
siRNA. Because Dox (pKa=8.2) is positively charged at physiological
pH, a number of surface charge modifications were used to
demonstrate the utility of using electrostatic charge to bind and
deliver Dox from the MSNP surface (FIG. 20A, 21B). These studies
demonstrated that Dox as well as the cationic dye, Hoechst 33342
(pKa=11.9) (FIG. 27), are capable of binding to negatively charged
surfaces from where both agents could be released by dropping the
environmental pH (FIG. 20C-F). Thus, when the MSNP are suspended in
buffered cell culture medium (pH=7.4), the attached phosphonate
(pKa=2) and carboxylate (pKa=5) groups are de-protonated and assume
a negative charge, whereas unmodified OH-MSNP (pKa=7) is near its
isoelectric point and therefore not quite as effective for
electrostatic binding (FIG. 20A). By contrast, the amine groups
(pKa .about.9) are protonated at physiological pH and exhibit a
positive charge that prevents electrostatic binding of the same
agents (Bagwe et al., Langmuir vol. 22, pp. 4357-4362, 2006; Santra
et al., Chem. Commun., pp. 2810-2811, 2004). From a therapeutic
perspective, phosphonate-MSNP exhibit good particle dispersibility
and biocompatibility. The ability to release Dox from the interior
surface by proton interference allowed Dox delivery inside the cell
in an acidifying compartment (FIG. 20F, upper panel). The role of
the lysosomal proton pump is supported by the finding that
NH.sub.4Cl interferes in Dox release to the nucleus (FIG. 20F,
lower panel). Phosphonate attachment also facilitates the binding
of cationic PEI to the particle exterior (FIG. 18, right panel).
This binding interaction is sufficiently strong to allow the
polymer and attached siRNA to stay on the particle surface until
entry into the lysosomal compartment. PEI may play a role in firm
cellular attachment and selection of the initial endosomal
compartment. Importantly, the polymer is attached to the particle
surface to leave the pores accessible to Dox binding (FIG.
20B).
[0179] It is important to briefly mention the importance of
selecting the correct PEI polymer size to prevent particle toxicity
(Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009; Meng et al.,
ACS Nano, vol. 3, pp. 1620-1627, 2009; Lin et al., Chem. Mater.,
vol. 21, pp. 3979-3986, 2009). It is well known that PEI exerts
cytotoxic effects when used by itself or attached to the
nanoparticle surface as a polyplexing agent (Xia et al., ACS Nano,
vol. 3, pp. 3273-3286, 2009). In this regard, 25 kD PEI polymer as
well as high doses of the 10 kD polymer can render the MSNP toxic
as a result of the proton sponge effect in the lysosome (Xia et
al., ACS Nano, vol. 3, pp. 3273-3286, 2009). For these reasons, the
particle dose and exposure time may be limited to within safe
limits to conduct Dox and siRNA delivery with PEI 10 kD polymer
(FIG. 26). Curiously and somewhat paradoxically, siRNA delivery to
the cytosol is also dependent on the proton sponge effect of the
PEI-coated particle and in this case, the lysosome appears to be a
key organelle in the dual drug delivery paradigm.
[0180] Above design features extend the utility of MSNP as a drug
delivery platform for chemotherapeutic agents. In addition to being
able to deliver hydrophobic drugs such as camptothecin and
paclitaxel, it is also possible to deliver water soluble drugs by a
packaging and release mechanism that is quite different from the
phase transition principle involved in hydrophobic drug delivery
(see FIG. 32). While it is not possible to release hydrophobic
drugs through an acidification mechanism, camptothecin can be
extracted from phosphonate-MSNP pores by ethanol treatment (FIG.
32). The release characteristics of Dox are exactly opposite,
namely a release response to protons but not ethanol (FIGS. 20C and
D). Taken together, these results demonstrate the dynamic features
of MSNP for obtaining optimal drug packaging and delivery.
[0181] Because Pgp overexpression is one of the major mechanisms of
multiple drug resistance (MDR) in cancer cells, knockdown of Pgp
gene expression by nanoparticle siRNA delivery could help to
restore the intracellular drug levels to the concentrations
required for induction of apoptosis and cytotoxicity. Thus, dual
drug and siRNA delivery by nanoparticles can be used to overcome
drug resistance in MDR cancer cells. The feasibility of the MSNP
platform to improve the cytotoxicity of Dox by co-delivery of Pgp
siRNA is demonstrated as proof-of-principle. Downregulation of Pgp
expression allowed the intranuclear Dox levels to increase above
the threshold required for inducing apoptosis and cell death.
However, since the KB-V1 cell line expresses very high Pgp level
that may go beyond the clinically relevant expression level, it may
not be possible to restore drug sensitivity to the level seen in
KB-31. It is reasonable to expect that the MSNP delivery platform
will be more effective in a lesser Pgp expressing cell type. In
addition, the MDR phenotype is quite complex and often involve a
combination of drug resistance mechanisms such as increased efflux,
blocked apoptosis, decreased drug influx, increased drug
metabolism, and increased DNA repair (Gottesman et al., Annu. Rev.
Med., vol. 53, pp. 614-627, 2002; Jabr-Milane et al., Cancer Treat.
Rev., vol. 34, pp. 592-602, 2008). Preliminary research has
revealed that 36 genes were either up- or down-regulated in KB-V1
cells compared to KB-31 cells. These genes can be categorized into
several groups, including oxidative stress regulation (HBB, IDH),
drug metabolism (HMGCS1, ACAT1), signal transduction (CGA, SGK),
tumor suppression (PTEN), etc (Wang et al., Chin. J. Cancer Res.,
vol., 14, pp. 5-10, 2002). It is possible that these gene products
could contribute to MDR besides Pgp overexperssion. What additional
mechanisms are involved is still uncertain but apparently does not
involve Bcl-2 as inclusion of Bcl-2 with Pgp siRNA did not
significantly improved cell killing. Understanding of
abovementioned MDR mechanisms may provide new opportunity to
develop more therapeutic components or combinations to achieve
better therapeutic effects.
[0182] In conclusion, MSNP can be functionalized to act as a dual
delivery vehicle for Dox as well as Pgp siRNA in a drug-resistant
cancer cell line. To improve the drug sensitivity of KB-V1 cells,
phosphonate attachment was used to deliver the therapeutic compound
as well as the siRNA via a lysosomal processing pathway. This dual
delivery system increased the intracellular Dox levels to the
extent that it improves cytotoxic killing in this KB-V1 MDR cell
line. This strategy could be an effective new approach for the
treatment of cancers that develop multiple drug resistance.
Tuning Aspect Ratio of Mesoporous Silica Nanoparticles
[0183] Embodiments of the invention include submicron structure
having a silica body defining a plurality of pores and an outer
surface between pore openings of said plurality of pores, where the
submicron structure has an average aspect ratio (AR) greater than
1.3, and where said submicron structure has a maximum dimension
less than one micron.
[0184] In some embodiments the silica body may have an average
aspect ratio greater than 1.4, greater than 1.5, greater than 1.7,
greater than 1.8, greater than 1.9, greater than 2.0, greater than
2.1, greater than 2.2, or greater than 2.5. In some embodiments,
the silica body may have an aspect ratio less than about 5, less
than about 4.7, less than about 4.5, less than about 4.3, less than
about 4.0, less than about 3.7, less than about 3.5, less than
about 3.3, less than about 3.0, less than about 2.7, or less than
about 2.5.
[0185] As used herein, the average AR values were determined by a
Transmission Electron Microscope (TEM), measuring the length and
diameter of at least 30 randomly selected particles and averaging
the individual AR values to produce the average AR.
[0186] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include a core structure.
Any core structure described herein may be used in these submicron
structures, and may be prepared in the same way as spherical
particles as modified to produce structures having AR greater than
1.3.
[0187] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include a surface
modification. Any surface modification described herein may be used
in these submicron structures, and may be prepared in the same way
as spherical particles described previously.
[0188] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include a surface
derivitization. Any surface derivitization described herein may be
used in these submicron structures, and may be prepared in the same
way as spherical particles.
[0189] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include an oligonucleotide.
Any oligonucleotide described herein may be used in these submicron
structures, and may be prepared in the same way as spherical
particles.
[0190] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include a therapeutic
compound. Any therapeutic compound described herein may be used,
and may be prepared in the same way as spherical particles.
[0191] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include an
oligonucleotide-therapeutic compound combination. Any
oligonucleotide-therapeutic compound composition described herein
may be used, and may be prepared in the same way as spherical
particles.
[0192] In some embodiments, the submicron structure having an
average AR greater than 1.3 may further include an additional
structural feature. Any additional structure feature described
herein may be used, and may be prepared in the same way as
spherical particles.
[0193] Submicron structure having an average AR greater than 1.3
may be used in any pharmaceutical compositions described herein,
and may be prepared in the same way as pharmaceutical compositions
of spherical particles.
[0194] Submicron structure having an average AR greater than 1.3
may be used in any method described herein, and may be used in the
same way as spherical particles.
[0195] Although the aspect ratio (AR) of engineered nanomaterials
(ENMs) is one of the key physicochemical parameters that could
determine biological outcome, not much is understood about how this
material property generates biological effects. By using a
mesoporous silica nanoparticle (MSNP) library that has been
constructed by a new anisometric synthesis method to cover a range
of different lengths, it was discovered that the AR of rod-shaped
particles determines the rate and abundance of MSNP uptake by an
act of cellular uptake process in Hela and A549 cancer cell lines.
For example, MSNPs with an AR of 2.1-2.5 were taken up in larger
quantities compared to shorter or longer length rods by a process
that is sensitive to amiloride, cytochalasin D, azide and 4 degrees
C. inhibition, though all non-spherical MSNPs showed improved
uptake. In some embodiments, rods with intermediary AR also induced
the maximal number of filopodia, actin polymerization and
activation of a small GTP-binding protein, Rac1, which controls the
actin assembly and filopodia formation. When assessing the role of
AR in the delivery of paclitaxel or camptothecin, rods with AR
2.1-2.5 may be the most efficient for drug delivery and generation
of cytotoxic killing in Hela cells. These data suggest an active
sensoring mechanism by which Hela and A549 cells are capable of
detecting AR differences in MSNP to the extent that accelerated
macropinocytosis can be used for more efficient drug delivery.
[0196] Some embodiments of the current invention may include
non-spherical MSNP nanocarriers that are capable of maximizing
delivering efficiency and bioavailability to a variety of cancer
cells. Moreover, there is active recognition of particles with a
long AR, which may form the basis for developing nanoparticle
shapes that can be used for studying biological response pathways
that can be used for understanding basic cellular mechanisms of
improved drug delivery by nanocarriers.
[0197] Compared with spherical MSNP nanocarrier, key advantages of
rod-shaped MSNP can include:
[0198] (1) Unlike existing technology for enhancing cellular uptake
by cationic surface functionalization of MSNP, AR tuning of MSNP is
capable of promoting cellular uptake and thereby improving the
bio-availability of MSNP nanocarrier by activating a specific
cellular acute uptake process (macropinocytosis). This method of
enhancing MSNP uptake is not associated with the potential
cytotoxicity of cationic carriers.
[0199] (2) The AR effect allows us to add a shape design feature to
the list of tunable MSNP properties that can be exploited to
improve drug delivery. This additional feature may be combined with
other approaches, described herein, to deliver therapeutic
compounds.
[0200] In general, compared with other nanocarriers capable of drug
delivery, advantages of MSNP based nanocarriers can include:
[0201] (1) MSNP has little or no intrinsic toxic potential, are
extensively used as food additives; MSNP is biologically inert when
injected intravenously at high dose in rodents and are also
biologically degradable and excretable.
[0202] (2) MSNP constitute an efficient multi-functional platform
including cargo delivery (e.g. anticancer drugs, siRNA/DNA),
targeting, controlled release, and for the purposes of bio-imaging
because of its unique silica-based composition and ease of surface
modification.
[0203] (3) Ease of chemical synthesis and versatile
functionalization methods allowing us to design various and
customized MSNP including changing AR. Physicochemical
characteristics (e.g. particle size, surface charge,
hydrophilicity, pore size) are tunable.
[0204] (4) Improved ability to deliver poorly water-soluble drugs
by making use of phase transition trapping in the pores;
[0205] (5) Allows co-delivery of two or more drugs or therapeutic
modalities (e.g., drugs and siRNA) for combination therapy;
[0206] (6) Versatile functionalization methods (organo-silanes)
allowing ligand (e.g. folate, transferrin) conjugation for targeted
delivery of drugs in a cell- or tissue-specific manner;
[0207] (7) Visualization of sites of drug delivery (theranostics)
by combining therapeutic agents with imaging modalities such as
iron oxide nanoparticles for MRI or probes for fluorescent
imaging;
[0208] (8) Potential to extend of the patent life of proprietary
drugs that are being delivered more efficiently as a new drug
formulation.
[0209] (9) Low cost and ease of large-scale production; It is
simple for particle purification through centrifugation
procedures.
[0210] Briefly, MSNP with different AR may be chemically
synthesized by a sol-gel approach using a surfactant/co-structure
direct agent (CSDA) mixture as template.
[0211] In some non-limiting embodiments described further in the
examples below, different shaped MSNP and AR were synthesized by
varying the PFOA/CTAB molar ratio as follows: 0 (AR=1), 0.015
(AR=1.5-1.7); 0.03 (AR=2.1-2.5), 0.06 (AR=4-4.5). The PFOA/CTAB
mixture was stirred at 600 rpm for 1 h at room temperature before
the addition of 2.1 mL 2 M NaOH. Subsequently, the solution
temperature was raised to 80.degree. C. before the addition of 4.1
mL of silica precursor. This mixture was stirred for an additional
2 h and the precipitate was carefully collected by filtration. The
MSNP templates were removed by extracting the CTAB with HCl
containing methanol under nitrogen protection. The resulting MSNP
were collected by filtration, washed by methanol, and dried
overnight in air.
[0212] To visualize the particles under a confocal microscope or
perform flow cytometry, fluorescent-labeled MSNP were prepared. In
order to determine the uptake mechanism of rod-shaped MSNP,
confocal microscope, flow cytometry, transmission electron
microscopy, electron tomography, macropinocytosis inhibitor
experiments were performed. In order to determine the capability of
drug delivery using different particle types, two hydrophobic
anticancer drugs, Taxol and camptothecin (CPT), were loaded into
different MSNP using 20 mg of each type of particles suspended into
a solution containing 0.5 mg of each drug in 1 mL DMSO. After 24 h,
the particles were collected by centrifugation, and the trace
amounts of DMSO were removed by drying under vacuum. The loading
capacity of the particles was measured by microplate reader. MSNP,
loaded with CPT or Taxol, were incubated with the cancer cells. The
cell killing capability was assessed by an MTS assay.
[0213] Some embodiments of the current invention can best be
implemented in practice to deliver anticancer drugs in human
carcinoma disease that can benefit from a nanotherapeutic MSNP
platform. The examples described below demonstrates the improvement
of cellular uptake, bio-availability and cell killing capability of
drug loaded MSNP in cancer cells. Some practical implementations
can include the non-spherical platform used with FDA approved drugs
to treat cancers in human subjects. However, the invention is not
limited to this example. It is also envisaged that the use of MSNP
shape and AR can be useful for other therapeutic areas where drug
uptake could be enhanced by AR modification.
[0214] Due to the rapid evolution in the techniques that are used
to synthesize engineered nanomaterials (ENMs), it is possible to
construct different shapes from a single base material, including
spheres, rods, disks, ellipsoids and cylinders..sup.1-5 Besides
spherical nanoparticles that have been intensively investigated,
non-spherical ENMs with a high aspect ratio (AR) are of great
interest since this physicochemical feature has been shown to have
a disproportionate impact on biological outcome,.sup.1, 3 including
determining the rate of cellular uptake,.sup.1 the mechanism of
uptake,.sup.1, 6 particle transportation,.sup.7, 8 biodistribution,
and biocompatibility..sup.9, 10 How exactly AR impacts cellular
function is unknown but of considerable importance in understanding
how to improve nanomaterial safety and delivery through the use of
a physical design feature. In order to understand the impact of AR
on cellular function, it is necessary to construct a series of ENMs
that show AR variation of the same base material. One example has
been the synthesis of triacrylate or monomethacrylate nanoparticles
through the PRINT fabrication technique, allowing these
investigators to look at the uptake of cylindrical particles that
exhibit an AR of 1-3 in Hela cells..sup.1 The authors demonstrated
that the particles with an AR of 3 (450 nm.times.150 nm) were taken
up four times more rapidly than the particles with an AR of 1.
Another example is the use of a batch of colloidal gold
nanoparticles, composed of spheres (14 nm and 74 nm) and rods (14
nm.times.74 nm) to study cellular uptake in Hela cells..sup.4 This
demonstrated a 2-4 times higher uptake of spherical gold
nanoparticles compared to rod-shaped particles with an AR of 5.
[0215] A mesoporous silica nanoparticle (MSNP) library was prepared
composed of spherical and rod-shaped particles to study the impact
of AR variation on cellular uptake in Hela and A549 cancer cells.
The advantage of using mesoporous silica is that this material is
useful for drug delivery studies as well as safety studies on
ENMs..sup.11-13 AR effects on MSNP cellular uptake would add
another design feature that will extend the utility of this
multifunctional platform that can be tuned for drug delivery by
controlling pore opening with nanovalves, surface ligation, surface
charge variation, etc..sup.12-18 In some examples, described below,
data demonstrate that rod-shaped MSNP with an AR of 2.1-2.5 is
preferentially endocytosed by an active uptake mechanism that is
able of distinguishing these intermediary length from longer and
shorter rods, though all non-spherical particles produced exhibited
higher active uptake than spherical particles. This implies a
cellular mechanism capable of discerning and responding to rod
length. Further investigation of the molecular pathway that
controls filopodia formation and macropinocytosis demonstrated that
intermediary length rods that are capable of stimulating GFP uptake
in Rac1, leading to cytoskeletal activation and formation of
filopodia. Intermediary length rods may be more effective for the
delivery of chemotherapeutic agents to Hela cells.
[0216] The examples below demonstrate that Hela and A549 cells
endocytose rod-shaped MSNP through a macropinocytosis process that
is capable of discerning the AR and adapting the cellular response.
In some examples, uptake is maximal for particles with an AR of
2.1-2.5. This differential effect involves filopodia formation that
is linked to activation of the actin cytoskeleton by a small
GTP-binding protein. Without wishing to be bound by theory, These
findings suggest a mechanosensitive mechanism that is capable of
translating variations in AR into GTP loading of Rac1. Particles
taken up into the pinocytotic vesicles are shuttled into an
acidifying lysosomal compartment and can be used to deliver of
hydrophobic chemotherapeutic drugs. This utility was demonstrated
by the delivery of Taxol and CPT in Hela cells, with maximum
cytotoxicity being achieved when the drugs are loaded into rods
with an AR of 2.1-2.5.
[0217] Current research in the field of biomaterials is witnessing
the emergence of a powerful set of new design parameters, including
the use of physical shape at micron and nanoscale levels to control
biological responses..sup.3, 8, 10, 39 Shape is an important
physical characteristic and has an important role in modeling
cellular responsiveness and associated applications in
biotechnology..sup.1 Theoretical models and experimental studies
have confirmed the benefits of using non-spherical particles for
drug delivery based on their effects on cellular internalization
and vascular dynamics..sup.1, 2, 7, 40 This includes a
demonstration that for micron-size particles the local geometry at
the point of contact with the cell membrane rather than the overall
particle shape dictates whether macrophages initiate
internalization..sup.39 In this regard, it has been demonstrated
that when a macrophage encounters an elliptical disc at its pointed
edge or side, the particle is rapidly phagocytosed within minutes
whereas attachment of the flat side of the disc failed to initiate
phagocytosis for an extensive time period..sup.6, 8, 39, 41 The
effect of geometry in phagocytosis could be quantified by measuring
the angle between the membrane at the point of initial contact and
the line defining the particle curvature at this point. If this
angle exceeds a critical value of >45.degree., the cells lost
the ability to entrap the particles..sup.3, 39 The authors proposed
that the particle shape at the point of attachment determines the
type of actin rearrangements that are required for cellular
uptake..sup.3, 39 According to this view, the requisite actin
structures can not form if the angle is >45.degree., leading the
macrophages to instead switch to spreading behavior..sup.39
[0218] At a much smaller length scale, Gratton et al. demonstrated
that internalization of cylindrical particles depends on AR..sup.1
There, the authors evaluated internalization pathways of three
different series of micro- and nanoparticles made from the
cross-linked PEG-based hydrogels produced by the "particle
replication in non-breaking templates" (PRINT) technique..sup.1 The
synthesized materials included cubic microparticles, cylindrical
microparticles and cylindrical nanoparticles (200.times.200 nm;
100.times.300 nm; 150.times.450 nm). While all the particles were
internalized by Hela cells, the nanoparticles entered more rapidly,
with the longer cylinders (150.times.450 nm) being captured more
rapidly than cubic particles of nearly same volume (200.times.200
nm) or shorter cylinders of lower volume (100.times.300 nm).
Particles with an AR of 3 were internalized about four times more
rapidly than spheres of the same volume..sup.1 In contrast to the
results for hydrogel particles, other studies have found that
receptor-mediated endocytosis of Au nano-objects was significantly
decreased with increased AR..sup.4, 42, 43 For instance, Au
nanospheres with diameters of 14 nm or 74 nm were taken up three
times more readily by Hela cells compared to 74.times.14 nm
rods..sup.4 Muro et al. compared targeted accumulation of spheres
of various diameters (ranging from 100 nm to 10 .mu.m) or
elliptical discs of microscale dimensions (1.times.3 .mu.m) in
tissues and found that the targeting efficiency of micron-scale
discs is better than spheres, even those with nanoscale
dimensions..sup.44
[0219] The examples below enhance the understanding of the role of
AR by demonstrating that for MSNP of the same chemical composition
there is differential macropinocytosis of particles with an AR
2.1-2.5. Moreover, this effect is mediated through a pathway that
involves Rac1 activation, the actin cytoskeleton and filopodia
formation..sup.45 Not only is the demonstration that rod-shaped
MSNP being capable of inducing macropinocytosis through Rac1
activation a novel finding, but also provides a platform for
understanding how specific shape variations can be used to modulate
cellular function. Macropinocytosis refers to the formation of
large endocytic vesicles of irregular shape and size that is
generated by actin-driven evaginations of the plasma
membrane..sup.26 Macropinocytosis is an efficient route for the
non-selective uptake of soluble macromolecules, and is either
constitutive or stimulated by growth factors such as epidermal
growth factor, platelet derived growth factor, macrophage
colony-stimulating factor, interleukin-4 or phorbol esters..sup.26,
30, 46 Interestingly, these agents are all capable of initiating
signaling pathways that activate Rac GTPase, which has also been
shown to play a role in regulating macropinocytosis..sup.34 The
occurrence of macropinocytosis in a variety of different cell types
suggests that it contributes to cellular functions such as nutrient
uptake,.sup.47 host-pathogen interactions,.sup.48 antigen
processing.sup.49 and directed cell movement..sup.47
Macropinocytosis differs from other endocytic mechanisms that are
involved in the uptake of individual nanoparticles by smaller
vesicles..sup.26 Different from clathrin-dependent,
caveolae-mediated or caveolae- and clathrin-independent
pathways,.sup.50 macropinocytosis is dependent on signaling to the
actin cytoskeleton and actin-driven membrane movement..sup.26, 33
This results in membrane ruffling and the formation of filopodia
that are necessary for the closure of the macropinocytotic
vesicles..sup.26 The intracellular fate of macropinosomes varies
depending on the cell type but in most cases end up fusing with
lysosomes and shrinking..sup.47
[0220] A key question that remains is how the differences in AR are
being discerned and translated into Rac1 activation and actin
assembly in Hela and A549 cells? Whilte an exact explanation is
unavailable, it is worthwhile considering the role of the
integrated-adhesome network that responds to complex chemosensitive
and mechanosensitive environmental cues in the extracellular matrix
(ECM)..sup.51 Cells demonstrate an extraordinary ability to respond
to a wide range of physical signals, either locally or globally and
are capable of reacting to ECM topography, including its
rigidity,.sup.52 spatial organization and anisotropy..sup.51, 53
The crucial scaffolding interactions involved in the link of the
ECM to the actin cytoskeleton involve actin-polymerizing and
actin-linking modules associated with the integrin-receptor
system..sup.51 This system as a whole is mechanoresponsive and
numerous studies have demonstrated that the biochemical
characteristics of the ECM, including its spatial organization, are
recognized by cells as a result of differential signaling from
integrin-based molecular complexes..sup.51, 54 This molecular
machinery can be viewed as a network of tightly interconnected
modules that contains .about.700 links, most of involve binding
interactions with the rest consisting of pathways that modify those
interactions..sup.51 The biological activities of the adhesome
components are quite diverse and include several actin regulators
that affect the organization of the attached cytoskeleton. These
include adapter proteins that link actin to integrins (directly or
indirectly) as well as a wide range of signaling molecules,
including kinases, phosphatases and G-proteins and their
regulators..sup.51
[0221] How could this model apply to the sensing and response to AR
variations of a nanomaterial? While it is unlikely that integrins
are directly involved in this process, MSNPs may be decorated with
serum proteins that could act as ligands on the particle surface.
However, this is an unlikely explanation because macropinocytosis
differs from receptor-mediated endocytosis that classically proceed
via caveolae or clathrin-mediated uptake. Another possibility is
that AR variation could be detected at the contact site of the
nanoscale spheres and rods with the cell surface membrane or the
interior of the lipid bilayer that enwraps the macropinocytotic
vesicles. In this regard, it has been demonstrated that silanol
groups on silica nanoparticles are capable of interacting with
membrane lipid compounds and possibly also with electrostatically
charged membrane proteins..sup.55, 56 It is possible that the
number and spatial distribution of these contact sites may be
capable of relaying information to Rac1 by a transduction process
that either involves GTP loading via a guanine nucleotide exchange
factor or inhibiting the activity of a Rac1 GTPase. The exquisite
sensitivity of cells to variations in adhesive patch spacing at the
nanoscale level has been demonstrated through the use of
nano-lithography approaches, e.g., positioning of nanoscale gold
particles (1-15 nm) in spatial arrangements or formation of spacing
gradients that can be tuned at 10-200 nm scales..sup.51, 57, 58
Examination of cellular spreading on these surfaces have
demonstrated that the weakest gradient to which cells can respond
corresponds to a strength of .about.15 nm per mm, provided that the
interparticle spacings remained at 58-73 nm..sup.51, 59, 60 Given a
typical spreading length of 60 .mu.m, the implication is that cells
can respond to 1 nm differences in average ligand patch spacing
between the front and rear end of the cell..sup.51 Thus, the
sensitivity to small variations in interparticle spacing is quite
remarkable and probably achievable in a time-integrated
manner.sup.51 Interestingly, these variations are much smaller than
the typical variations in the inter-ligand spacing that governs
integrin interactions with the ECM. Thus, given this exquisite
sensitivity at the nanoscale level, a related mechanism may be
involved in detecting AR differences in rod-shaped MSNP.
[0222] Not only do these results advance understanding of the
mechanism by which AR differences change cellular uptake, but also
adds a shape design feature to the list of tunable MSNP properties
that can be exploited to improve drug delivery..sup.11, 15, 61, 62
Accumulated evidence indicates that spherical nano carriers may not
be optimal drug delivery devices due to the poor cellular uptake
and unsatisfactory biodistribution compared to disc-shaped objects
or particles exhibiting a long AR..sup.1, 2, 7 To improve cellular
uptake of MSNP, better uptake can be achieved by non-covalent
attachment of the cationic polymer, polyethyleneimine, to the
particle surface..sup.12, 13 However, cationic functionalization
may lead to cytotoxicity..sup.12, 13 Improved delivery and killing
in Hela cells may be achieved using particles with higher aspect
ratio, for example, an AR of 2.1-2.5 (FIGS. 52 and 59). To further
understand the bio-behavior of AR particles in vivo, animal
experiments are being performed to test the efficacy of a
non-spherical MSNP delivery system.
[0223] Through the use of AR variation in a designed batch of MSNPs
it can be demonstrated that cells actively respond to the shape
change by changing particle uptake through a macropinocytosis
process. Not only can Hela and A549 cells distinguish between
specific ARs, but also are capable of translating this recognition
into activation of Rac1, control actin assembly and optimal
filopodia formation that leads to maximal uptake of intermediary
length rods. This active uptake process can be inhibited by a list
of inhibitors (amiloride, Cyto D and NaN.sub.3/2-DG) or dropping
the culture temperature to 4.degree. C. In some examples,
intermediary length MSNP with an AR of 2.1-2.5 are more efficient
at delivery hydrophobic chemotherapeutic agents to Hela cells.
[0224] From the foregoing description, it will be apparent that
variations and modifications may be made to the invention described
herein to adopt it to various usages and conditions. Such
embodiments are also within the scope of the following claims.
[0225] The recitation of a listing of elements in any definition of
a variable herein includes definitions of that variable as any
single element or combination (or subcombination) of listed
elements. The recitation of an embodiment herein includes that
embodiment as any single embodiment or in combination with any
other embodiments or portions thereof.
[0226] Terms listed in single tense also include multiple unless
the context indicates otherwise.
[0227] Where a range of values is provided in the present
application, it is understood that each intervening value, to the
tenth of the unit of the lower limit unless the context clearly
dictates otherwise, between the upper and lower limit of that range
and any other stated or intervening value in that stated range, is
encompassed within the invention. The end values of any range are
included in the range.
[0228] The examples disclosed below are provided to illustrate the
invention but not to limit its scope. Other variants of the
invention will be readily apparent to one of ordinary skill in the
art and are encompassed by the appended claims. All publications,
databases, and patents cited herein are hereby incorporated by
reference for all purposes.
[0229] Methods for preparing, characterizing and using the
compounds of this invention are illustrated in the following
Examples. Starting materials are made according to procedures known
in the art or as illustrated herein. The following examples are
provided so that the invention might be more fully understood.
These examples are illustrative only and should not be construed as
limiting the invention in any way.
EXAMPLES
Reagents
[0230] Tetraethylorthosilicate (98%), cetyltrimethylammonium
bromide (CTAB, 95%), fluorescein isothiocyanate (FITC, 90%),
polyethyleneimine (MW 1.2 and 25 KD), poly(ethylene glycol) methyl
ether (MW 5 KD), N,N'-disuccinimidyl carbonate (DSC, 95%),
4-(dimethylamino)pyridine (DMAP, 99%), aminopropyltriethoxysilane
(APTS, 99%), 3-(trihydroxysilyl)propyl methylphosphonate (42%),
succinic anhydride (99%), fluorescamine, paclitaxel, propidium
iodide (PI), .beta.-actin antibody, and bovine serum albumin (BSA)
were from Sigma (St. Louis, Mo.). Polyethyleneimine (MW 0.6, 1.8,
and 10 KD) were from Alfa Aesar (Ward Hill, Mass.). The MTS assay
kit was from Promega (Madison, Wis.). Dulbecco's Modified Eagle's
medium (DMEM), penicillin/streptomycin, and L-glutamine were
purchased from Invitrogen (Carlsbad, Calif.). Fetal calf serum
(FCS) was from Atlanta Biologicals, Inc (Lawrenceville, Ga.). siRNA
for GFP knock down was purchased from IDT Technologies (Coralville,
Iowa). For all experiments and analyses, water was de-ionized and
filtered with a 0.45 .mu.m pore size polycarbonate syringe filter
(Millipore, Billerica, Mass.). All chemicals were reagent grade and
used without further purification or modification.
MSNP Dispersion and Use to Perform Tissue Culture
[0231] All cell cultures were maintained in 25 cm.sup.2 cell
culture flasks in which the cells were passaged at 70-80%
confluency every 2-4 days. RAW 264.7, BxPC3, PANC-1, and HEPA-1
cell lines were cultured in Dulbecco's Modified Eagle Medium (DMEM)
(Carlsbad, Calif.) containing 10% fetal calf serum (FCS), 100 U/ml
penicillin, 100 .mu.g/ml streptomycin, and 2 mM L-glutamine
(complete medium). BEAS-2B cells were cultured in BEGM (Charles
City, Iowa) in type I rat tail collagen-coated flasks or plates.
Cells were cultured at 37.degree. C. in a humidified 5% CO.sub.2
atmosphere. To disperse MSNP, the stock solution (in water) was
sonicated (Tekmar Sonic Disruptor probe) for 15 sec prior to
aliquoting. In order to coat the surface of MSNP with bovine serum
albumin (BSA), the aliquoted NP suspension (.about.10 .mu.l) was
mixed with an equal volume of 4% BSA. Tissue culture media (1 ml)
was added to the BSA coated MSNP suspension. Cell culture media
deprived of serum (e.g. BEGM) was modified by addition of BSA at a
concentration of 2 mg/ml. The cell culture media containing MSNP at
the desired concentration was sonicated for 15 sec and
characterized as described before.
Assays for Cellular Viability and Mitochondrial Function
[0232] Cellular viability was determined by the MTS assay, which
looks at the reduction of
(3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl-
)-2H-tetrazolium (MTS) to formazan in viable cells. Briefly,
2.times.10.sup.4 cells were plated onto 96 multi-well plates
(Costar; Corning, N.Y.). After incubation with the indicated dose
of MSNP for various lengths of time at 37.degree. C., formazan
absorbance was measured at 490 nm. The mean absorbance of
non-exposed cells served as the reference for calculating 100%
cellular viability.
[0233] Cell death and mitochondrial function were detected using
propidium iodide (PI) uptake and JC-1 fluorescence. Fluorescent
probes were diluted in DMEM before the addition to cells for 30 min
at 37.degree. C. in the dark: (i) 5 .mu.g/ml propidium iodide (PI)
in 200 .mu.l DMEM (assessment of cell death); (ii) 5 .mu.M JC-1
(assessment of .DELTA..PSI.m). Flow cytometry was performed using a
LSR (Becton Dickinson, Mountain View, Calif.). PI was analyzed in
FL-2 and JC-1 was analyzed in both FL-1 and FL-2. Forward and side
scatter were used to gate out cellular fragments.
Assessment of Cellular MSNP Uptake by Flow Cytometry and Confocal
Microscopy
[0234] For the performance of flow cytometry, aliquots of
5.times.10.sup.4 cells (RAW 264.7, BEAS-2B, PANC-1, and BxPC3) were
cultured in 48-well plates in 0.4 ml medium. RITC-labeled MSNP with
a phosphonate surface coating were added to the above cultures at a
dose of 25 .mu.g/ml for 30 minutes, followed by incubation with the
FITC-labeled MSNP-PEI series at final concentrations of 25 .mu.g/ml
for 3 hr. All cell types were trypsinized and washed with trypan
blue to quench the fluorescence of cell surface attached MSNP.
Cells were analyzed in a LSR flow cytometer using mean FL-2 and
FL-1 to assess RITC and FITC fluorescence, respectively. Data are
reported as fold increase above control (cells without MSNP).
[0235] Cellular uptake of MSNP was performed by adding 25 .mu.g/ml
of the various MSNP to 8-well chamber slides (Nunc) in which
5.times.10.sup.4 cells were cultured in each well containing 0.4 ml
culture medium. Cell membranes were stained with 5 .mu.g/ml wheat
germ agglutinin (WGA) Alexa Fluor.RTM. 594 conjugate in PBS for 30
min. Slides were mounted with DAPI (Molecular Probes, Eugene,
Oreg.) and visualized under a confocal microscope (Leica Confocal
1P/FCS) in the UCLA/CNSI Advanced Light Microscopy/Spectroscopy
Shared Facility. High magnification images were obtained with a
63.times. objective. Optical sections were averaged 2-4 times to
reduce noise. Images were processed using Leica Confocal
Software.
Example 1
Synthesis and Surface Modification of Mesoporous Silica
Nanoparticles MSNP
[0236] The basic synthesis of MSNP was conducted by mixing the
silicate source tetraethylorthosilicate (TEOS) with the templating
surfactants cetyltrimethylammonium bromide (CTAB) in basic aqueous
solution (pH 11). In a round bottom flask, 100 mg CTAB was
dissolved in a round-bottom flask containing solution of 48 ml
distilled water and 1.75 ml sodium hydroxide (2 M). The solution
was heated to 80.degree. C. and stirred vigorously. After the
temperature had stabilized, 0.5 ml TEOS was added slowly into the
heated CTAB solution. After 15 min, 0.23 mmol of the organosilane
solution was added into the mixture. 3-trihydroxysilylpropyl
methylphosphonate was used for phosphonate surface modification,
and aminopropyltriethoxy silane (APTS) was used for amine surface
modification. After 2 hr, the solution was cooled to room
temperature and the materials were washed with methanol using
centrifugation. In order to incorporate fluorescent dye molecules
in the silicate framework, fluorescein-modified silane was first
synthesized and then mixed with TEOS. To synthesize
fluorescein-modified silane, 2.4 .mu.L APTS was mixed with 1 mg
fluorescein isothiocyanate (FITC) in 0.6 ml absolute ethanol, and
stirred for 2 hr under inert atmosphere. In another formulation,
rhodamine B isothiocyanate (RITC) was used instead of FITC to
synthesize rhodamine B-modified APTS. The dye-modified silane was
then mixed with TEOS before adding the mixture into the heated CTAB
solution. The surfactants were removed from the pores by refluxing
the particles in a mixture of 20 ml methanol and 1 ml hydrochloric
acid (12.1 M) for 24 hr. The materials were then centrifuged and
washed with methanol.
[0237] For the poly(ethylene glycol) modification, 1 g of
poly(ethylene glycol) methyl ether (MW 5 KD, mPEG) was dried under
vacuum for 30 min and dissolved in 5 ml dioxane (with slight
heating). mPEG has only one reactive end that can be attached to
the particle surface and limits the coupling process only to that
end, whereas normal PEG has two reactive ends and may cause
particle cross-linking. 307.4 mg disuccinimidyl carbonate (DSC) was
dissolved in 2 ml anhydrous DMF (with slight heating) and mixed
with the mPEG solution. 146.6 mg 4-(dimethylamino)pyridine was
dissolved in 2 ml acetone and added slowly into the mPEG solution
The mixture was stirred for 6 hours under an inert atmosphere. The
polymer was precipitated by the addition of 30 ml diethyl ether to
the solution and separated by centrifugation. After washing the
polymer twice with diethyl ether, the activated mPEG was dried
under vacuum. 60 mg of amine-modified MSNP was washed and
resuspended in 2 ml anhydrous DMF. 300 mg of the activated mPEG was
dissolved in 9 ml DMF and mixed with the particles. The mixture was
stirred for 12 hr and washed thoroughly with DMF and PBS.
[0238] To perform polyethyleneimine (PEI) modification, 5 mg of
phosphonate-modified MSNP were dispersed in a solution of 2.5 mg
PEI (MW 25 KD) and 1 ml absolute ethanol. The process to coat the
particles with other PEI polymers (MW 0.6, 1.2, 1.8, 10 KD) was
carried out similarly. After the mixture was sonicated and stirred
for 30 min, the particles coated with PEI were washed with ethanol
and PBS. Thermogravimetric analysis showed that the amount of PEI
on the particles was approximately 5 weight percent. To succinylate
the PEI 25K-coated particles, 1 mg particles were resuspended in
0.25 ml anhydrous DMF and mixed with different amounts of succinic
anhydride (0.15 mg, 0.075 mg, and 0.015 mg). The mixture was
sonicated and stirred overnight. The succinylated particles were
washed with DMF and resuspended in PBS. To fluorescently label PEI
(MW 25 KD), 60 mg of PEI 25 KD was dissolved in 10 ml carbonate
buffer (pH 9) and mixed with 1 mg rhodamine B isothiocyanate
dissolved in 1 ml DMSO. The mixture was stirred for 24 hr at
4.degree. C. and dialyzed against distilled water. The rhodamine
B-labeled PEI 25K was attached to the particles by using similar
procedure for the unlabeled PEI.
Example 2
Physicochemical Characterization of the NP
[0239] MSNP were synthesized according to a modified procedure
previously described (Radu et al., J. Am. Chem. Soc., vol. 126, pp.
13216-13217, 2004; Cai et al., Chem. Mater., vol. 13, no. 2, pp.
258-263, 2001). All MSNP were characterized for size, size
distribution, shape, and charge (Table 1).
TABLE-US-00001 TABLE 1 Size distribution of MSNPs in aqueous
solutions. Zeta Size (nm) Potential (mV) DMEM BEGM H.sub.2O/DMEM +
10% 2 mg/ml serum/ H.sub.2O serum BEGM BSA BEGM + BSA MSNP-OH 1966
408 1096 416 -10.5/-6.8/-7.2 MSNP-Phosphate 1975 306 867 439
-8.9/-6.5/-5.8 MSNP-PEG 2675 405 1215 542 -10.4/-5.9/-4.5 MSNP-PEI
0.6 1689 415 1243 474 +29.5/-7.8/-6.5 KD MSNP-PEI 1.2 1684 452 1298
502 +38.7/-6.5/-7.1 KD MSNP-PEI 1.8 1053 510 1087 550
+36.9/-5.4/-3.2 KD MSNP-PEI 10 614 702 917 684 +34.1/-7.5/-6.9 KD
MSNP-PEI 25 1473 1043 1544 825 +30.8/-5.9/-4.0 KD Particle size and
zeta potential in solution were measured by a ZetaSizer Nano
(Malvern). DMEM = Complete Dulbecco's Modified Eagle Media, which
contains 10% fetal calf serum (FCS). BEGM = Bronchial Epithelial
Growth Medium, which includes growth factors, cytokines, and
supplements (no serum).
[0240] The shape and structure were characterized using a
transmission electron microscope (JEOL JEM 2010, JEOL USA, Inc.,
Peabody, Mass.). Microfilms for TEM imaging were made by placing a
drop of the respective particle suspension onto a 200-mesh copper
TEM grid (Electron Microscopy Sciences, Washington, Pa.) and then
drying at room-temperature overnight. A minimum of 5 images of each
sample was collected to obtain representative views. Particle size
and zeta potential in solution were measured by ZetaSizer Nano
(Malvern Instruments Ltd., Worcestershire, UK). This instrument
measures the light scattering (DLS) from a suspension at an angle
of 173.degree.. Size measurements were performed on dilute
suspensions in water or complete cell culture media at pH 7.4. The
ZetaSizer Nano was also used to measure the electrophoretic
mobility of the MSNP suspended in solution. Electrophoretic
mobility is used as an approximation of particle surface charge and
can be used to calculate zeta potential. The Helmholtz-Smoluchowski
equation was used to recalculate electrophoretic mobility into zeta
potential.
[0241] The primary particle size is in the 100-130 nm range with a
uniform pore size .about.2.5 nm as shown by TEM (FIG. 1). To
conduct biological experimentation, particle size and zeta
potential were measured in water as well as tissue culture media
(Xia et al., ACS Nano, vol. 2, pp. 2121-2134, 2008). For the
purposes of this study DMEM supplemented with 10% fetal calf serum
(FCS) or BEGM was used as is or supplemented with 2 mg/ml BSA
(Table 1). The addition of protein leads to improved particle
dispersal by countering the colloidal forces that promote particle
aggregation in salt containing media (FIG. 9). While all of the
non-PEI coated particles exhibited a negative zeta potential,
PEI-coated particles showed a positive charge (Table 1). However,
with the addition of FCS or BSA, all PEI-coated particles assumed a
negative zeta potential.
Example 3
Differences in the Cytotoxic Potential of Anionic Vs Cationic
MSNP
[0242] To screen for particle hazard, the MTS assay was used, which
reflects dehydrogenase activity in healthy cells (Xia et al., ACS
Nano, vol. 2, pp. 85-96, 2008). While most of the MSNP did not
interfere in MTS activity in the PANC-1 and BxPC3 pancreatic cancer
cell lines, particles coated with the 25 KD PEI polymer showed
decreased cellular viability (FIG. 1). The particles coated with
the 25 KD polymer also induced toxicity in macrophage (RAW 264.7)
and bronchial epithelial (BEAS-2B) cell lines staining (FIG. 10).
The toxicity was confirmed by propidium iodide (PI) staining, which
showed that the rate of cell death was progressive over 15 hour
period (FIG. 10). Similar to previous results with cationic
polystyrene nanoparticles (Xia et al., ACS Nano, vol. 2, pp. 85-96,
2008), the toxicity of cationic MSNP involves an effect on
mitochondria as determined by JC-1 fluorescence (FIG. 10). JC-1
measures mitochondrial membrane potential (MMP). In contrast,
phosphonate-coated nanoparticles (MSNP-Phos) were non-toxic and did
not perturb the mitochondrial function (FIG. 10).
[0243] To confirm that PEI toxicity is due to cationic charge,
succinic anhydride was used to convert the primary NH.sub.2 to COOH
groups (Xia et al., ACS Nano, vol. 2, pp. 85-96, 2008). FIG. 11A
demonstrates that this conversion reduced the toxicity of
MSNP-PEI-25 KD in a dose-dependent fashion. Depletion of the
primary NH.sub.2 groups was confirmed by fluorescamine, which
yields green fluorescence when it reacts with primary amines (FIG.
11B). Thus, succinic anhydride reduced the mean fluorescence
intensity (MFI) in a dose-dependent fashion. The stability of PEI
attached to the MSNP surface was confirmed by coating FITC-labeled
MSNP with rhodamine-B labeled PEI. Confocal microscopy confirmed
that both labels co-localize as shown by the composite yellow
fluorescent spots in the cell (FIG. 12).
Example 4
Differences in the Cellular Uptake of Anionic Versus Cationic
MSNP
[0244] Cellular toxicity of cationic polystyrene nanoparticles
involves a high rate of cellular uptake due to tight surface
membrane binding, which facilitates particle wrapping and cellular
uptake (Xia et al., Nano Lett. Vol. 6, pp. 1794-1807, 2006; Xia et
al., ACS Nano, vol. 2, pp. 85-96, 2008). Cellular uptake of
FITC-labeled MSNP was assessed by flow cytometry and confocal
microscopy (Xia et al., ACS Nano, vol. 2, pp. 85-96, 2008).
FITC-labeled MSNP were incubated with PANC-1, BxPC3, RAW 264.7, and
BEAS-2B cells. This resulted in a clear shift in the MFI of the
different cellular populations following treatment with particles
coated with 1.2 and 25 KD PEI polymers as compared to the
phosphonate-coated MSNP (FIGS. 2 and 3; FIG. 13). When expressed as
fold-increase in the MFI compared to untreated cells, the relative
abundance of MSNP-PEI-25 KD and MSNP-PEI-1.2 KD uptake was two
orders of magnitude higher than the phosphonate or PEG-coated
particles (FIGS. 2 and 3; FIG. 13). In contrast, there was no
difference in the uptake of RITC-labeled MSNP in the same cells
treated with the FITC-labeled particles. This confirms that the
cationic charge is responsible for high cellular uptake. The flow
data was corroborated by confocal studies that showed a significant
increase in the number of PEI-coated particles in all cell types
(FIGS. 2, 3 and 13). Please notice that a large fraction of the
MSNP-PEI-25 KD particles localized at the cell membrane as
demonstrated by the composite yellow fluorescence in pancreatic
cancer cells stained with the red-fluorescent wheat germ agglutinin
(FIGS. 2 and 3). It is possible that this membrane binding might
contribute to the toxicity of these particles.
Reducing PEI Polymer Length Maintains Effective Nucleic Acid
Delivery but Eliminates Cellular Toxicity
[0245] While PEI is quite effective for complexing and delivering
nucleic acids, polymer-based delivery of DNA and siRNA often leads
to cytotoxicity due to damage to the surface membrane, lysosomes
and mitochondria (Boussif et al., Proc. Natl. Acad. Sci. U.S.A.,
vol. 92, pp. 7297-7301, 1995; Florea et al., AAPS Pharm Sci., vol.
4, p. E12, 2002; Xia et al., ACS Nano, vol. 2, pp. 85-96, 2008).
However, based on the observation that decoration of MSNP with a
1.2 KD polymer resulted in a non-toxic particle, a range of PEI
polymers were explored in terms of achieving cellular delivery
versus reduction of toxicity. MSNP were coated with 0.6, 1.2, 1.8,
10 and 25 KD polymers and their cytotoxic potential assessed in
various cell types. This included the use of HEPA-1 cells for which
there is a commercial variant expressing green fluorescent protein
(GFP) for the purposes of assessing siRNA knockdown. No toxicity
was seen with particles coated with 0.6, 1.2 and 1.8 KD PEI
polymers (FIGS. 4 and 14). While MSNP-PEI-10 KD exerted toxic
effects at the highest dose (50 .mu.g/ml) tested, MSNP-PEI-25 KD
was responsible for the decline in MTS activity at doses
.gtoreq.12.5 .mu.g/ml (FIGS. 4 and 14). This demonstrates that it
is possible to adjust MSNP toxicity according to the polymer length
used and is the first demonstration that the choice of the PEI
polymer length can be used to modify the toxicity of MSNP while
still maintaining a useful function.
Preparation of PEI-MSNP-pDNA/siRNA Polyplexes and Agarose Gel
Retardation
[0246] Agarose gel retardation assay was used to determine the
DNA/siRNA binding ability of PEI-coated MSNP. 0.1 .mu.g plasmid DNA
(pEGFP) or siRNA in aqueous solution was used to mix with
PEI-coated nanoparticles to obtain particle to pDNA ratios (N/P)
ratios of 5-600. The mixture was incubated at room temperature for
30 min for complex formation. 10 .mu.L of the polyplex solution
mixed with 2 .mu.L of 6.times. loading buffer was electrophoresed
on 1% agarose gel containing 0.5 .mu.g/ml ethidium bromide (EB)
with Tris-boric acid (TBE) running buffer (pH 8) at 100 V for 30
min. DNA/RNA bands were visualized by an UV (254 nm) illuminator
and photographed with a Bio-Rad imaging system (Hercules, Calif.).
The binding capacity was expressed by the N/P ratio that shows
total retardation of DNA or siRNA migration (as reflected by the
disappearance of DNA/RNA bands on the gel).
DNase I Protection Assay:
[0247] Particle/pDNA complexes were prepared at a MSNP/pDNA ratio
of 100 with 100 ng pDNA in 10 .mu.l total volume. The complex
solutions were incubated with 1 .mu.l DNase I (2.7 U/.mu.l) in 50
mM Tris-Cl, 10 mM MgCl.sub.2, pH 7.4. at 37.degree. C. for 30 min.
The DNase I was inactivated by adding 1 .mu.l of 100 mM
ethylenediaminetetraacetic acid (EDTA). The pDNA was then released
from the complex by adding 1% sodium dodecyl sulfate (SDS), and
analyzed by 1% agarose gel electrophoresis.
[0248] To assess the efficacy of different PEI-coated MSNP in terms
of siRNA and plasmid DNA delivery, the nucleic acid binding
capacity of the particles was determined using a gel retardation
assay. The data show high siRNA and plasmid DNA binding capacity
that was mostly independent of the PEI MW (FIG. 5). All available
DNA and siRNA molecules were bound to the cationic particle surface
at particle-to-nucleic acid ratios of 10-100 (FIG. 5B). Noteworthy,
the high binding efficacy of MSNP was accompanied by protection of
DNA to DNase I degradation (FIG. 5C). By contrast,
phosphonate-coated particles did not show effective DNA
binding.
Plasmid DNA and siRNA Transfection with the Use of MSNP-PEI
[0249] Plasmid DNA (pDNA) containing a GFP insert was used to
transfect HEPA-1 cells cultured either in Nunc chamber slides for
performance of confocal microscopy or in 48-well plates for
assessment by flow cytometry. Cells were plated at a density of
2.times.10.sup.4 cells per well in 0.4 ml medium. pDNA/MSNP
complexes were prepared by mixing 100 ng/ml DNA with 25 .mu.g/ml
MSNP for 30 min prior to cellular incubation for 24 hr. Cells were
fixed for confocal microscopy as described above. Harvested cells
were used to conduct flow cytometry on FL-1 channel.
[0250] In the next set of experiments the efficacy of DNA delivery
was assessed by transfecting a GFP plasmid into HEPA-1 cells. While
plasmid delivery by the 10 and 25 KD PEI-coated particles resulted
in abundant cellular fluorescence, only faint fluorescence was
observed when the carrier particle was coated with a shorter length
polymer (FIG. 7). The transfection efficiency with the longer
length polymers compares favorably to the results with
Lipofectamine 2000. Moreover, while this commercial agent only
transduced a fraction of the cells in the population, MSNP-PEI-10
KD transfected >70% cells in the population (FIG. 7B). This was
confirmed by the magnitude of the MFI increase with the particles
versus Lipofectamine (FIG. 7A). Although also efficient for DNA
delivery, MSNP-PEI-25 KD did result in toxicity as explained
previously. This may not constitute a problem when stable
transfections are being performed because one selects for viable
and proliferating cells containing the expressed gene.
[0251] To perform siRNA experiments, HEPA-1 cells were prior
transfected with a GFP plasmid and then sorted in the FL-1 channel
to select stable GFP expressing cells. The sorted cells were plated
at a density of 5.times.10.sup.4 cells per well containing 0.4 ml
culture medium in chamber slides for performance of confocal
microscopy and in 48-well plates for performance of flow cytometry.
MSNP/siRNA complexes were prepared by incubating 500 ng/ml siRNA
with 25 .mu.g/ml of MSNP-PEI for 30 min in serum-free DMEM. Cells
were then exposed to the complexes for 3 hr. DMEM+10% FCS was then
added to bring the final volume to 400 .mu.l for 48 hr. Cells were
fixed and prepared for confocal microscopy as described above. For
flow cytometry cells were harvested and analyzed for fold decrease
in GFP expression (FL-1 channel).
[0252] To test whether siRNA delivery to its GFP-expressing HEPA-1
cells could provide knockdown of the expression of this fluorescent
protein, 100 ng GFP-siRNA was complexed with MSNP-PEI and incubated
with the cells for 48 hr. Comparison of the MFI of transfected
versus control cells showed that particles coated with 10 and 25 KD
polymers were capable of knocking down GFP expression by 55% and
60%, respectively (FIG. 6A). This was comparable to the
transfection efficiency of commercially available transfection
agent, Lipofectamine 2000. By contrast, scrambled siRNA delivery
did not have a GFP knockdown effect (FIG. 6A). Moreover, siRNA
delivery by 0.6, 1.2 and 1.8 KD PEI-coated particles did not exert
an effect on GFP expression. GFP knockdown was confirmed by
confocal microscopy (FIG. 6B) and immunoblotting for GFP protein
expression (FIG. 15). Please notice that although the toxicity of
the 25 KD polymer may contribute to decreased GFP expression, the
10 KD polymers is not toxic at this dose (FIG. 4). Scrambled siRNA
delivery had no effect on GFP expression (FIG. 6B). Confocal
studies using Texas Red-labeled siRNA was performed to track the
intracellular fate of the particles (FIG. 6B). This confirmed that
the particles coated with longer polymers were taken up in larger
numbers than the shorter range polymers in HEPA-1 cells (FIG. 6B,
15B).
Example 5
Paclitaxel Delivery
Cationic MSNP Efficiency in Delivering Paclitaxel to Pancreatic
Cancer Cells
[0253] MSNP are capable of delivering water-insoluble drugs to
cancer cells (Liong et al., ACS Nano, vol. 2, pp. 889-896, 2008).
In light of the high cellular uptake of PEI-coated particles, it
was logical to ask whether in the traditional use of the MSNP, the
polymer attachment still allows effective delivery of the
hydrophobic cancer drug, paclitaxel, to PANC-1 and BxPC3 cells.
Drug Loading of Paclitaxel
[0254] Paclitaxel was loaded into MSNP-PEI-1.2 KD and -25 KD in
DMSO, followed by washing in an aqueous buffer to entrap the
hydrophobic drug in the particle pores. Briefly, the modified
materials were loaded with paclitaxel by incubating 10 mg of the
nanoparticles in a solution of 1 mg of paclitaxel and 0.25 ml of
DMSO for 6 hours. After the drug-laden nanoparticles were removed
from the suspension by centrifugation and the supernatant removed
completely, the materials were dried under vacuum. The drug-laden
nanoparticles were washed and sonicated with PBS.
[0255] In order to determine the amount of paclitaxel that
partitioned to the MSNP, the aqueous particle suspension were
incubated for 6 hours at 4.degree. C. before centrifugation.
Methanol was used to release paclitaxel from MSNP to determine the
loading capacity. The drug-laden MSNP pellet was resuspended and
sonicated in methanol on three occasions and the supernatants were
combined to measure the release of the drug by UV absorption at 230
nm. 50 .mu.g/ml particles contained about 1 .mu.M of paclitaxel.
Release of the drug from the pores by using methanol confirmed that
equal amounts of paclitaxel were loaded into MSNP irrespective of
the polymer MW (FIG. 16).
Paclitaxel Delivery by MSNP-PEI
[0256] PANC-1 and BxPC3 cells were plated at 2.times.10.sup.4 cells
per well in a 96 well plate. MSNP particles, loaded with
paclitaxel, were incubated with the cells at doses of 10-50
.mu.g/ml for 48-72 hrs. Free paclitaxel corresponding to the amount
loaded into MSNP particles was suspended or dissolved in PBS and
DMSO to serve as controls. MTS assays were performed after 48 hours
to determine the cell viability after treatment.
[0257] Subsequent assessment of the impact of paclitaxel on the
viability of PANC-1 and BxPC3 cells showed the efficacy of
PEI-coated MSNP in drug delivery (FIG. 8). Thus, paclitaxel
delivery by MSNP-PEI-1.2 KD induced a rate of cytotoxicity that is
superior to the drug delivery by an aqueous suspension of
paclitaxel and as efficient as the drug suspended in a DMSO carrier
(FIG. 8). While MSNP-PEI-25 KD showed intrinsic particle-related
toxicity at doses >25 .mu.g/ml, the effect was comparable to
MSNP-PEI-1.2 KD (FIG. 8). These data demonstrate that the enhanced
cellular uptake of non-toxic cationic MSNP is capable of enhancing
the delivery of hydrophobic cancer drugs. This is also a novel
demonstration for the delivery function of MSNP.
Example 6
In Vivo Toxicity Test of MSNP
[0258] Animal experiment protocols were reviewed and approved by
the The Chancellor's Animal Research Committee (ARC) at UCLA.
Animal experiments were performed in accordance with UCLA
guidelines for care and treatment of laboratory animals and the NIH
Guide for the Care and Use of Laboratory Animals in Research
(DHEW78-23). The mice were randomly divided into three groups:
MSNP-phosphonate, MSNP-PEI 25 KD and the control group. Six mice
were used per group, since this number has enough statistical power
to discern differences in the toxic responses. Forty mg/kg
particles were used for i.v. injection through tail vein once a
week for two weeks. Animal weight was monitored after particle
injections. Animals were sacrificed later to obtain blood and
organs.
Biochemical Assay of Serum
[0259] The serum was obtained by centrifugation of the whole blood
at 3000 rpm for 15 min. The biochemical parameters were assayed by
UCLA Division of Laboratory Animal Medicine (DLAM) diagnostic
laboratory services.
Histology of Major Organs
[0260] A small piece of liver, kidney, spleen, lung, heart, and
brain was fixed by 10% formalin and then embedded into paraffin,
sectioned for 5 .mu.m thick, and mounted on the glass microscope
slides by UCLA Division of Laboratory Animal Medicine (DLAM)
diagnostic laboratory services. The sections were stained with
hematoxylin-eosin and examined by light microscopy.
Results
[0261] To use MSNP for nucleic acid and drug delivery, it is
necessary to first make sure the particle is safe in animals. And
for drug carriers, i.v. injection is the most used route. In vivo
toxicity test of MSNP were conducted in mice by i.v. injection of
20 mg/kg nanoparticles once a week for two weeks. Before the
injection, the particle size was characterized in saline, which is
commonly used in in vivo assays. However, the average size of
MSNP-phosphonate and MSNP-PEI 25 KD is 984 and 842 nm in saline,
respectively. Recent research showed that protein corona, the
protein coating on the particle surface, can stabilize nanoparticle
suspension and serum is high in proteins that can be used as a
dispersing agent for nanoparticles. 2% mouse serum was added to
saline and used to suspend the MSNP. The serum-containing saline
substantially decreased the average size of MSNP-phosphonate and
MSNP-PEI 25 KD to 249 and 278 nm, respectively.
[0262] After two weeks, animals were sacrificed. Blood and major
organs such as liver, kidney, spleen, lung, heart, and brain were
collected to do serum biochemistry assays and histology,
respectively. The serum chemistry tests showed no significant
changes in all the tested parameters between MSNP-treated and
control mice (Table 2).
TABLE-US-00002 TABLE 2 Serum biochemistry tests (Avg .+-. SD, n =
6) Control (Saline) MSNP-Phos MSNP-PEI 25 KD CHOL 162.5 .+-. 8.5
153.8 .+-. 15.4 144.4 .+-. 6.8 (mg/dL) CK (U/L) 3000.3 .+-. 2285.3
2690.5 .+-. 1129.3 3280.9 .+-. 1512.7 ALT (U/L) 59.5 .+-. 6.4 55.7
.+-. 8.4 46.1 .+-. 22.6 AST (U/L) 184.2 .+-. 70.2 182.2 .+-. 21.1
217.2 .+-. 65.6 ALP (U/L) 105.2 .+-. 8.6 102.1 .+-. 17.5 88.6 .+-.
48.9 TBILI 0.7 .+-. 0.1 0.9 .+-. 0.3 0.6 .+-. 0.1 (mg/dL) TPROT 6.2
.+-. 0.2 6.0 .+-. 0.4 5.9 .+-. 0.3 (mg/dL) GLU 140.8 .+-. 16.5
141.2 .+-. 29.2 140.8 .+-. 34.6 (mg/dL) PHOS 8.4 .+-. 0.7 7.4 .+-.
1.0 8.3 .+-. 0.6 (mg/dL) CA (mg/dL) 8.9 .+-. 1.7 9.2 .+-. 0.4 9.4
.+-. 0.2 CO2_LC 10.1 .+-. 2.2 13.3 .+-. 3.8 11.3 .+-. 1.1 (mEq/L)
BUN 20.8 .+-. 2.1 22.3 .+-. 9.3 22.6 .+-. 2.6 (mg/dL) CREAT 0.3
.+-. 0.0 0.3 .+-. 0.1 0.3 .+-. 0.0 (mg/dL) DBILI 0.9 .+-. 0.2 1.0
.+-. 0.5 0.7 .+-. 0.2 (mg/dL) ALB (g/dL) 3.3 .+-. 0.1 3.2 .+-. 0.2
3.2 .+-. 0.2 AGR (N/A) 1.2 .+-. 0.1 1.2 .+-. 0.1 1.1 .+-. 0.1
B_CREA 75.3 .+-. 16.2 79.2 .+-. 30.0 82.0 .+-. 12.4 (mg/dl) AMYL
1252.2 .+-. 215.1 1266.0 .+-. 189.5 1139.4 .+-. 122.0 (U/L) LDH
(U/L) 681.5 .+-. 152.8 638.8 .+-. 133.3 611.0 .+-. 141.6 MG (mg/dL)
2.0 .+-. 0.5 2.2 .+-. 0.2 2.3 .+-. 0.2 TRIG 201.2 .+-. 43.8 178.2
.+-. 65.3 156.0 .+-. 28.5 (mg/dL) Biochemical parameters includes
Cholesterol (CHOL), Creatine Kinase (CK), alanine aminotransferase
(ALT), aspartate aminotransferase (AST), Alkaline phosphatase
(ALP), total bilirubin (TBILI), total protein (TPROT), Glucose
(GLU), Inorganic phosphorus (PHOS), Calcium (CA), Carbon Dioxide
(CO2_LC), Blood Urea Nitrogen (BUN), Creatinine (CREAT), Direct
bilirubin (DBILI), Albumin (ALB), Albumin-globulin ratio (AGR),
Blood Creatinine (B_CREA), Amylase (AMYL), Lactate dehydrogenase
(LDH), Magnesium (MG), Triglycerides (TRIG).
[0263] Histology of major organs also showed no major changes among
the groups (representative liver, spleen and kidney sections were
shown in FIG. 17. These results show MSNP-phosphonate and MSNP-PEI
25 KD do not have acute toxicity to major organs or systems in
mice.
Example 7
Dual Deliverity siRNA and Anticancer Compound
Materials
[0264] Tetraethylorthosilicate (TOES, 98%), cetyltrimethylammonium
bromide (CTAB, 95%), fluorescein isothiocyanate (FITC, 90%),
doxorubicin hydrochloride (Dox, >98%), camptothecin (CPT, 95%),
vinblastine, polyethylenimine (PEI, branched, MW 25 kD),
bafilomycin A (.gtoreq.95%), ammonium chloride, .beta.-actin
antibody, and bovine serum albumin (BSA) were from Sigma (St.
Louis, Mo.). Polyethylenimine (branched, MW 1.8 and 10 kD) was
purchased from Alfa Aesar. 3-trihydroxysilylpropyl
methylphosphonate, cyanoethyltriethoxysilane, and
aminopropyltriethoxysilane were purchased from Gelest. Dulbecco's
Modified Eagle's medium (DMEM), penicillin/streptomycin, and
L-glutamine were purchased from Invitrogen (Carlsbad, Calif.).
Fetal calf serum (FCS) was from Atlanta Biologicals, Inc
(Lawrenceville, Ga.). LAMP-1 antibody was obtained from Abcam
(Cambridge, Mass.). siRNA for Pgp knockdown was purchased from IDT
Technologies (Coralville, Iowa). Tariquidar (>97%) was purchased
from MedKoo Biosciences, Inc. For all experiments and analyses,
water was de-ionized and filtered with a 0.45 .mu.m pore size
polycarbonate syringe filter (Millipore, Billerica, Mass.). All
chemicals were reagent grade and used without further purification
or modification.
Cell Lines
[0265] KB-31 and KB-V1 cells lines were confirmed as Dox-sensitive
and Dox-resistant cell lines, with IC.sub.50 values of 0.21 and
53.0 .mu.g/ml, respectively (FIG. 23). Immunoblotting analysis
confirmed that the Pgp expression in KB-V1 was >1,000 times that
of KB-31 cells (FIG. 23B).
[0266] KB-31 and KB-V1 cells were plated at 1.times.10.sup.4 cells
per well in 96 well plate. The cells were treated with free Dox in
solution in doses ranging from 0.05-3.2 .mu.g/ml (KB-31) and 0.1-64
.mu.g/ml (KB-V1) for 72 hrs. The cell viability was determined by
the MTS assay. The treated cells were incubated with MTS working
solution for 2-3 hrs before measurement. The mean absorbance of
non-exposed cells served as the reference value for calculating
100% cellular viability. To view Pgp expression, the cells were
washed in PBS and the pellets lysed in a buffer containing Triton
X-100 and protease inhibitors after centrifugation. The protein
content of the supernatants was determined by the Bradford method.
100 .mu.g total protein was electrophoresed by 10% SDS-PAGE and
transferred to a PVDF membrane. After blocking, the membranes were
incubated with 1:1000 dilution of primary monoclonal antibody to
MDR1 (anti-Pgp C219, Abcam). The membranes were overlayed with goat
anti-mouse secondary antibody (1:1000 dilution) before the addition
of the HRP-conjugated streptavidin-biotin complex. The proteins
were detected using ECL reagent according to the manufacturer's
instructions.
Statistical Analysis
[0267] Data represent the mean.+-.SD for duplicate or triplicate
measurements in each experiment, which was repeated at least 3
times. Differences between the mean values were analyzed by
two-sided Student's t test or one way ANVOA and results were
considered statistically significant at p<0.05.
PEI Coated MSNP
[0268] An important consideration in the use of PEI is its
potential cytotoxicity (Xia et al., ACS Nano, vol. 3, pp.
3273-3286, 2009). In this regard, the polymer size plays an
important role in the cytotoxicity that results from proton
sequestration by unsaturated PEI amines in the lysosomal
compartment (Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
Thus, before the performance of Dox-induced cytotoxicity, it was
necessary to compare the cytotoxic potential of MSNP coated with
different PEI polymer lengths as shown in the FIG. 26. In brief,
the findings were that MSNP coated with the 25 kD polymer showed
considerable toxicity in the MTS assay when the particle
concentration is >25 .mu.g/ml. By contrast, particles coated
with 10 kD PEI have no toxic effects if the concentration is kept
<100 .mu.g/ml and the exposure time limited to .ltoreq.24 hr
(FIG. 26). Consequently, MSNP was used at doses <100 .mu.g/ml
and for exposure time periods <24 hrs in the drug delivery
studies to avoid effects on cell viability. Although no
cytotoxicity was seen with the 1.8 kD PEI polymer (FIG. 26A), this
particle is relatively ineffective for siRNA delivery and Pgp
knockdown (FIGS. 19B, 19C and 19D).
[0269] Because of the potential toxicity of PEI, it was necessary
to assess the cell viability of KB-V1 cells incubated with MSNP
coated with different PEI polymers. Briefly, 1.times.10.sup.4 cells
were plated onto 96 multi-well plates (Costar; Corning, N.Y.).
After incubation with the indicated amounts of the various PEI
coated MSNP for 24 hrs, the MTS assay was performed as described in
materials and methods section. MSNP coated with the 10 kD polymer
was examined for time periods ranging from 1-48 hrs, aiming to
chose an optimized time period for treatment that avoids PEI
toxicity. The cells were treated with 100 .mu.g/ml PEI-MSNP for 1,
4, 8, 16, 24, and 48 hrs, and the old medium was replenished by
fresh medium for another 71, 68, 56, 48, and 24 hrs culture. The
cytotoxicity assay was checked at 72 hrs after particle
treatment.
Particle Synthesis, PEI Coating and Interior Surface
Functionalization
[0270] The MSNPs were synthesized according to previously published
sol-gel procedure (Xia et al., ACS Nano, vol. 3, pp. 3273-3286,
2009; Jie et al., Small, vol. 3, pp. 1341-1346, 2007). Briefly, for
the synthesis of unmodified MSNP (OH-MSNP), 100 mg of CTAB was
dissolved in a solution of 48 mL water and 0.35 mL sodium hydroxide
(2 M) and heated to 80.degree. C. One half mL of TEOS was added
into the aqueous solution containing CTAB surfactants. For the
phosphonate modification, 3-trihydroxysilylpropyl methylphosphonate
was added to the mixture 15 minutes after the addition of TEOS. The
CTAB surfactants were then removed from the pores by heating the
particles in acidic ethanol. To perform PEI coating, 5 mg of
phosphonate-modified MSNP were dispersed in a solution containing
2.5 mg PEI (1.8 kD, 10 kD, 25 kD) in 1 ml absolute ethanol. After
sonication and stirring for 30 min the PEI coated particles were
washed with PBS. The amount of polymer coated onto the particle
surface was approximately 5 weight percentage.
[0271] Because Dox is positively charged under physiological pH, it
was necessary to demonstrate that phosphonate or other anionic
surface groups are effective for drug binding, including in
particles that have been coated with PEI. To demonstrate this
principle, particle surfaces were decorated with carboxylate (COOH)
and amine groups in addition to phosphonate and silanol (OH
groups). The surface functionalization was achieved by mixing
organoalkoxysilanes (made up in ethanol) with TEOS before adding
the mixture into the CTAB solution (Lim et al., J. Am. Chem. Soc.,
vol. 119, pp. 4090-4091, 1997). For carboxylate modification, 50
.mu.L cyanoethyltriethoxysilane was mixed with 500 .mu.L ethanol
and 500 .mu.L TEOS, then added into the surfactant solution. After
the surfactant removal process, the particles were further heated
in a solution of 50% sulfuric acid to hydrolyze the cyanide groups
into carboxylic groups. For amine modification, 50 .mu.L of
aminopropyltriethoxysilane was first mixed with 500 .mu.L ethanol
and 500 .mu.L TEOS before adding to the surfactant solution. After
2 hrs, the solution was cooled to room temperature and the
materials were washed with methanol before the surfactant removal
process.
Physicochemical Characterization of MSNP
[0272] PEI-coated phosphonate MSNP were characterized for size,
zeta potential, and shape, respectively. The shape and porous
structure were characterized using transmission electron microscopy
(JEOL JEM 2010, JEOL USA, Inc., Peabody, Mass.). Microfilms for TEM
imaging were made by placing a drop of the respective MSNP
suspensions onto a 200-mesh copper TEM grid (Electron Microscopy
Sciences, Washington, Pa.) and then drying at room-temperature
overnight. A minimum of 5 images for each sample was captured and
representative images included in FIG. 18. Particle size and zeta
potential in pure water, after stabilization with 1 mg/mL BSA in
water, or in cell culture medium were measured by ZetaSizer Nano
(Malvern Instruments Ltd., Worcestershire, UK). All the
measurements were performed in 40 .mu.g/ml MSNP suspensions in
filtered water or filtered complete cell culture media at pH 7.4.
The analysis was also studied on Dox loaded particles. Similar
analysis was also performed on cargo (Dox and siRNA) loaded
PEI-MSNP samples.
[0273] In order to determine if Pgp overexpression in KB-V1 cells
is impacted by Pgp siRNA delivery, PEI polymers in the size range
1.8-25 kD were electrostatically bound to the phosphonate-MSNP
surface. Polymer binding to 100-120 nm size MSNP, exhibiting
uniform pore sizes of 2-2.5 nm was confirmed by TEM (FIG. 18A,
left). The TEM image of the particles decorated with the 10 kD
polymer shows that the surface coating (arrows) did not occupy the
porous interior (FIG. 18A, right). To optimize the particle
dispersal for biological experimentation, the PEI-coated particles
were further treated with 1 mg/ml BSA before transfer to the
complete cell culture medium. BSA coating significantly improves
particle dispersal in water as well as salt-containing complete
DMEM (FIG. 18B). While the PEI-coated particles exhibit a high
positive zeta potential value in water, this value changes to
slightly negative upon dispersal in complete DMEM containing FCS
(FIG. 18B). Note that similar analysis was also performed on the
Dox loaded PEI-MSNP samples with or without siRNA binding, and that
no significant changes were found with or without cargo loading
(Table 3).
TABLE-US-00003 TABLE 3 Comparison of particle size and zeta
potential of PEI 10 kD MSNP before or after cargo loading. Size and
zeta potential remain the same with or without cargo loading. Zeta
Potential in Size in H.sub.2O/ Size in Size in BSA DMEM CDMEM
Particle H.sub.2O (nm) (nm) (nm) (mV) PEI 10 kD-MSNP 758 241 261
+34.1/-3.8 PEI 10 kD-Dox-MSNP 711 198 225 +28.1/-5.2 siRNA-PEI 832
234 278 +25.4/-7.3 10 kD-Dox-MSNP PEI-MSNP coating with Pgp siRNA
and use of agarose gel electrophoresis to determine N/P ratios
[0274] An agarose gel retardation assay was used to determine the
siRNA binding to PEI-MSNP. 0.1 .mu.g siRNA was mixed with 0.4-6.4
.mu.g amount PEI-MSNP in aqueous solution to obtain particle/nuclei
acid (N/P) ratios of 4-64. 10 .mu.L of the polyplex solution was
mixed with 2 .mu.L of 6.times. loading buffer and electrophoresed
in a 1.5% agarose gel containing 0.5 .mu.g/ml ethidium bromide (EB)
at 100 V for 30 minutes in Tris-boric acid (TBE) running buffer
(pH=8). Nucleic acid bands were detected by UV light (254 nm) and
the photos were captured in a Bio-Rad imaging system (Hercules,
Calif.). The results were used to calculate the threshold N/P
ratios for subsequent experiments. The threshold is defined as the
lowest N/P ratio value that prevents free siRNA from entering the
gel. To determine the influence of Dox loading, the gel
electrophoresis assay was also performed.
[0275] In order to determine the optimal N/P ratios for Pgp siRNA
delivery, agarose gel electrophoresis was used to evaluate binding
of various amounts of siRNA to MSNP coated with the different
polymer lengths as shown in FIG. 19A. This demonstrated that
binding capacity increases with increasing size of PEI polymers,
indicating that all siRNA was bound at a N/P ratio >16 (PEI 1.8
kD), >16 (PEI 10 kD) and >8 (PEI 25 kD). Based on this
result, N/P ratios of 80, 80 and 10 were used for polymer lengths
of 1.8, 10 or 25 kD, respectively for siRNA knockdown experiments.
It is worth mentioning that Dox trapped in the pores of MSNP does
not influence siRNA binding to the particle surface (FIG. 24) and
also that siRNA binding does not significant change the zeta
potential of MSNP (Table 3).
Cell Culture
[0276] All cell cultures were maintained in 25 cm.sup.2 or 75
cm.sup.2 cell culture flasks in which the cells were passaged at
70-80% confluency every 2-4 days. The drug-sensitive KB-31 line was
cultured in Dulbecco's Modified Eagle Medium (DMEM) (Carlsbad,
Calif.) containing 10% fetal calf serum (FCS), 100 U/ml penicillin,
100 .mu.g/ml streptomycin, and 2 mM L-glutamine (complete DMEM
medium). The MDR cell line, KB-V1 (kindly provided by Dr. Michael
M. Gottesman from National Cancer Institute, NIH, Bethesda, Md.),
was maintained in 1 .mu.g/ml of vinblastine (made up from 10 mg/ml
stock in DMSO) in complete DMEM (Ludwig et al., Cancer Res., vol.
66, pp. 4808-4815, 2006). While the doubling time of the parental
line was approximately 14-18 hrs, the resistant cell line doubled
every 25-30 hrs.
Assessment of Cellular Uptake of Dual Fluorescent Labeled
siRNA-PEI-MSNP by Confocal Microscopy
[0277] 200 .mu.g FITC-labeled PEI coated MSNP were incubated with
2.5 .mu.g Texas red-labeled Pgp siRNA for 30 minutes to yield a N/P
ratio of 80. Cellular uptake of MSNP was performed by adding 20
.mu.g/ml of the dual-labeled particles to 8-well chamber slides.
Each well contained 5.times.10.sup.4 cells in 0.4 ml culture
medium. Cell membranes were co-stained with 5 .mu.g/ml Alexa Fluor
633-conjugated wheat germ agglutinin (WGA) in PBS for 30 min.
Slides were mounted with Hoechst 33342 and visualized under a
confocal microscope (Leica Confocal 1P/FCS) in the UCLA/CNSI
Advanced Light Microscopy/Spectroscopy Shared Facility. High
magnification images were obtained with the 100.times. objective.
The signal intensity of the red channel, reflecting siRNA
abundance, was calculated by Image J software (version 1.37c,
NIH).
[0278] Subsequent performance of confocal microscopy utilizing
dual-labeled particles (Texas red-labeled-siRNA adsorbed to
FITC-labeled MSNP) demonstrated a high rate of cellular uptake in
KB-V1 cells in accordance with polymer length (FIG. 19B). Image J
analysis confirmed a significant increase in siRNA uptake for
particles coated with the 10 and 25 compared to the 1.8 kD polymer
(FIG. 19C). The reason for this high uptake is due to the
positively charged amines, which facilitates strong PEI binding to
and wrapping by the surface membrane (Xia et al., ACS Nano, vol. 3,
pp. 3273-3286, 2009). Please notice that the Pgp siRNA (red) and
FITC-MSNP (green) co-localize (yellow, merged) in the cell,
demonstrating that the nucleic acid is stably attached to the
PEI-coated particle surface (FIG. 19B). It has previously been
demonstrated that nucleic acids bound to the PEI-MSNP surface are
resistant to enzymatic cleavage (Xia et al., ACS Nano, vol. 3, pp.
3273-3286, 2009).
siRNA-PEI-MSNP Exposure and Assessment of PGP Expression
[0279] Pgp siRNA-PEI-MSNP complexes were freshly prepared as
described above. The siRNA duplex consists of
5'-r(CGGAAGGCCUAAUGCCGAA) dTdT (sense) and
5'-r(UUCGGCAUUAGGCCUUCCG) dTdG (antisense) strands. First, 5 .mu.l
of 250 ng/.mu.l Pgp siRNA or scrambled siRNA was added to 100 .mu.g
PEI 1.8 kD-MSNP (N/P ratio=80), 100 .mu.g PEI 10 kD-MSNP (N/P
ratio=80), or 12.5 .mu.g PEI 25 kD-MSNP (N/P ratio=10), in 5 .mu.l
aqueous solution. After incubation at room temperature for 30 min,
the complexes were stabilized by 1 mg/mL BSA and then transferred
into 1 ml complete DMEM. KB-V1 cells were plated at
2.times.10.sup.5 cells per well, then exposed to the complexes for
16 hrs. Sixteen hours later, the medium was replaced with fresh
DMEM containing 10% FCS and cultured for a further 56 hrs. Cells
then were harvested for immunoblotting.
[0280] Briefly, KB-31 and KB-V1 cells were plated at
1.times.10.sup.4 cells per well in 96 well plate. The cells were
treated with free Dox in solution in doses ranging from 0.05-3.2
.mu.g/ml (KB-31) and 0.1-64 .mu.g/ml (KB-V1) for 72 hrs. The cell
viability was determined by the MTS assay. The treated cells were
incubated with MTS working solution for 2-3 hrs before measurement.
The mean absorbance of non-exposed cells served as the reference
value for calculating 100% cellular viability. To view Pgp
expression, the cells were washed in PBS and the pellets lysed in a
buffer containing Triton X-100 and protease inhibitors after
centrifugation. The protein content of the supernatants was
determined by the Bradford method. 100 .mu.g total protein was
electrophoresed by 10% SDS-PAGE and transferred to a PVDF membrane.
After blocking, the membranes were incubated with 1:1000 dilution
of primary monoclonal antibody to MDR1 (anti-Pgp C219, Abcam). The
membranes were overlayed with goat anti-mouse secondary antibody
(1:1000 dilution) before the addition of the HRP-conjugated
streptavidin-biotin complex. The proteins were detected using ECL
reagent according to the manufacturer's instructions.
[0281] A commercially available cationic liposomal transfection
agent (Lipofectamine 2000) was used as a positive control. Protein
abundance was quantified by densitometric scanning using a laser
Personal Densitometer SI and Image Quant software (Amersham
Biosciences).
[0282] To assess the efficacy of Pgp siRNA delivered by PEI-coated
MSNP, Pgp expression was followed by western blotting (FIG. 19D).
This demonstrated 80 or 90% reduction, in MDR-1 expression in cells
treated with MSNP coated particles that contain the 10 and 25 kD
polymers, respectively. This efficacy was maintained in Dox-loaded
MSNP (FIG. 25). Scrambled siRNA-PEI-MSNP (marked as "X" in FIG.
19D) was used as a negative control to rule out any impact by the
siRNA delivery method. No Pgp knockdown was seen in the scrambled
siRNA-MSNP group. The PEI-coated particles were also more effective
than the commercially available transfection agent, Lipofectamine
2000, which is widely used in molecular biology.
Optimizing Dox Loading and Release Via a Proton-Sensitive Mechanism
In Vitro
[0283] Based on its cationic charge at pH 7.4, it was uncertain
whether Dox (pKa=8.2) would bind to the negatively charged porous
interior, including under circumstances where the exterior surface
was occupied by PEI. 10 mg of MSNP functionalized by OH, COOH or
phosphonate attachments were mixed with 1 mg of Dox in 0.25 mL
water for 12 hrs. As control, positively charged amine-MSNP was
used. Subsequently, the particles were collected by centrifugation
and washed with water. To corroborate the electrostatic binding
hypothesis, the cationic fluorescent dye, Hoechst 33342 (pKa=11.9)
was used as model cargo in the same particles. This procedure was
repeated in phosphonate MSNP that were coated with 10 and 25 kD PEI
polymers. In order to compare the loading yields of above
particles, 1 mg Dox-loaded MSNP pellet was resuspended and
sonicated in 1 mL of a heated HCl solution (pH=5.0) for 15 minutes.
After centrifugation, another 1 mL fresh HCl aqueous solution was
added. All the supernatants were combined until the MSNP became
colorless. At this point the pH was readjusted to 7.0 by 1 M NaOH
and the fluorescence spectrum of Dox measured at excitation and
emission wavelength of 485/550 nm in a microplate reader
(SpectraMax M5 Microplate Reader, Molecular Device, USA). The
procedure was also repeated to determine Dox loading in MSNP coated
with 10 kD and 25 kD PEI polymers.
[0284] The effects of acidification and ethanol extraction of
Dox-loaded phosphonate MSNP were assessed. 1 mg Dox-loaded MSNP was
suspended into 3 ml phenol red-free DMEM medium acidified to pH 5.0
or replenished with 10% (v/v) ethanol at 37.degree. C. The
supernatants were collected at various time points and cleared by
centrifugation for measurement of Dox fluorescence. Similar
experiments were carried out in siRNA bound phosphonate-MSNP coated
with PEI polymers. To see if the release profile will be influenced
by siRNA binding, release after 12 hrs was studied using
siRNA-PEI-Dox-MSNP.
[0285] MSNP are capable of loading and releasing water-insoluble
drugs (paclitaxel and camptothecin) by a phase transfer mechanism
that can be reversed by ethanol washing of the particles to
demonstrate the role of hydrophobicity in MSNP drug entrapment (Xia
et al., ACS Nano, vol. 3, pp. 3273-3286, 2009; Jie et al., Small,
vol. 3, pp. 1341-1346, 2007). A key question was whether similar
effective packaging of water-soluble Dox, is possible at
physiological pH, where the drug (pKa=8.2) carries a positive
charge. One conceivable approach is electrostatic attachment to the
negatively charged MSNP surface. To test this possibility, Dox was
loaded in MSNP decorated with OH, COOH or phosphonate groups. These
particles were also compared to positively charged particles
decorated with amine groups. After washing of the drug-bound
particles and quantification of Dox release by HCl, the loading
capacities of OH--, COOH-- and phosphonate-MSNP were 1.2%, 4.2% and
8.4% (w/w), respectively (FIG. 20A). By contrast, amine-decorated
particles showed low (<0.1%, w/w) Dox binding capacity (FIG.
20A). The principle of electrostatic binding to a negatively
charged particle surface was also demonstrated through the use of a
cationic dye, Hoechst 33342, which bound to negative but not a
positive MSNP surface (FIG. 27). Importantly, electrostatic binding
of Dox to the phosphonate surface was not negated by when the
particles were also coated with 10 or 25 kD PEI polymers; these
particles demonstrated equivalent loading capacity to the uncoated
phosphonate particles (FIG. 20B).
[0286] Importantly, Dox could be released in a time-dependent
manner from the phosphonate-MSNP or PEI-phosphonate-MSNP surface by
lowering of the solution pH (FIGS. 20C and 20D). The Dox release
profile was not be affected by siRNA binding to PEI on exterior
surface of the particle (FIG. 28). This establishes the possibility
that intracellular drug release should be possible if the particles
are capable of gaining entrance to acidifying cellular
compartments.
[0287] To illustrate the drug loading/release mechanism is
different between water soluble drug and water insoluble drug, the
effect of surface charge on binding and release of the hydrophobic
chemotherapeutic agent, CPT was evaluated. 10 mg of
surfactant-extracted particles was mixed in a solution of 1 mg of
CPT and 0.25 mL DMSO for 12 hrs. The CPT-loaded particles were
collected by centrifugation, dried under vacuum, and washed with
water. The loading yield, release profile was studied based on the
fluorescent readout of CPT (.lamda..sub.ex/em=370/429 nm) in a
microplate reader (FIG. 32).
Confocal Microscopy to Determine MSNP Lodging in an Acidifying
Cellular Compartment, Including the Effects of Inhibiting Lysosomal
Acidification on Dox Release
[0288] KB-V1 cells grown on chamber slides were fixed,
permeabilized, and labeled with standard immunocytochemistry
protocol (Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
LAMP-1 staining was performed by using a 1:500 dilution of
mouse-anti-human mAb (H4A3, Abcam, USA) for 16 hrs at 4.degree. C.
This was followed by a 1:500 diluted TRITC-conjugated
goat-anti-mouse secondary antibody (Santa Cruz, USA) for 1 hr at
room temperature. Cell membranes and nuclei were stained with WGA
633 and Hoechst 33342, respectively. Slides were visualized under a
confocal microscope (Leica Confocal 1P/FCS). Since the Dox release
is a proton-sensitive process, the effect of neutralizing the
lysosomal pH with NH.sub.4Cl was also investigated in KB-31 cells.
These cells were initially treated with 40 .mu.g/ml FITC-labeled
MSNP that were simultaneously coated with the 10 kD PEI polymer
with or without the addition of 20 mM NH.sub.4Cl. All the images of
the particles and fluorescent Dox release were captured by the same
confocal microscopy applying same parameter setting over a 72 hour
time period.
[0289] In order to determine whether this is possible in KB-V1
cells, the intracellular localization of FITC-labeled MSNP was
measured in relation to lysosomal co-staining by fluorescent
labeled anti-LAMP-1 antibody. Indeed, confocal microscopy confirmed
>55% co-localization of the green-labeled particles with the
red-labeled lysosomes (FIG. 20E). Moreover, in a subsequent
confocal study released Dox from PEI-coated particles after
entrance into the lysosome could reach the nucleus, which was
brightly stained by the fluorescent drug (FIG. 20F, upper panel).
Some of the drug was retained in particles localized in the
peri-nuclear region. This visual image changed completely when
cells were treated with NH.sub.4Cl; most Dox remained confined to
the lysosomal compartment with little or no nuclear staining (FIG.
20F, lower panel). This suggests that the interference in lysosomal
acidification by NH.sub.4Cl prevents effective Dox release to KB-V1
nuclei.
Determination of Intracellular Dox Concentration
[0290] Dox uptake in KB-V1 cells was quantitatively evaluated in a
microplate reader at 72 hrs. 5.times.10.sup.4 cells were placed
into a 96 wells plate and treated with 2 .mu.g/ml free Dox or the
equivalent amount of drug loaded into MSNP before or after PEI
coating, with or without attachment of Pgp siRNA. Following the
washing of the cells in cold PBS, the intracellular Dox
fluorescence was detected at excitation and emission wavelength of
485/550 nm in a microplate reader (SpectraMax M5 Microplate Reader,
Molecular Device, USA). Moreover, confocal images were captured at
the end of experiment. Image J software (version 1.37c, NIH) was
used to analyze the nuclear fluorescence.
[0291] The relative inefficiency of free Dox to induce KB-V1
cytotoxicity may be a result of the rapid rate by which the drug
was being exported by the overexpressed Pgp. Intracellular Dox
concentration can be determined by measuring cellular Dox
fluorescence intensity in a microplate reader (FIG. 21A). The
comparatively low drug uptake after treatment with free Dox was
slightly improved by delivering the drug via the phosphonate-MSNP.
While the total amount of intracellular drug increased when being
delivered by particles coated with the 10 kD PEI polymer (FIG.
21A), little of the drug reached the nucleus as determined by
confocal imaging (FIG. 21B). Interestingly, the intracellular Dox
concentration increased significantly in the presence of siRNA
(FIG. 21A) so that there was also a significant increase in nuclear
Dox staining by 72 hr (FIG. 21B). This contrasts with most of the
Dox being confined to the endosomal compartment in cells not
receiving siRNA, suggesting that although PEI-MSNP may take more
Dox into to cells, any released drug is rapidly extruded from the
cell before reaching the nucleus (FIG. 21B). This suggests that
knocking down Pgp expression (FIG. 25) allows a sufficient quantity
of the drug being slowly released from the particle to enter the
nucleus where it induces cytotoxicity. A quantitative measurement
of Dox release to the nucleus through the use of Image J software
confirmed a statistically significant increase of the drug in KB-V1
nuclei after delivery by siRNA-PEI-Dox-MSNP as compared to free Dox
or Dox loaded into the particles without siRNA (FIG. 21C). Dox
delivered by PEI-MSNP in the presence of siRNA significantly
enhance intranuclear Dox concentration when compared to free Dox or
Dox delivered by MSNP or PEI-MSNP without siRNA.
Assessment of Cytotoxicity and Apoptosis in KB-V1 Cells Treated
with Dox-Loaded Particles in the Absence and Presence of Pgp
siRNA
[0292] To measure cytotoxicity of the different Dox formulations,
KB-V1 cells were treated with free Dox, Dox-MSNP, PEI-Dox-MSNP and
siRNA-PEI-Dox-MSNP, respectively. For the latter two particle
types, incubation time was for 16 hrs before replenishment of the
old medium with fresh complete DMEM and performance of a MTS assay
at 72 hrs. Based on the absorption readout at 490 nm, the IC.sub.50
of free and Dox-loaded MSNP were calculated. The induction of
apoptosis at 72 hours was assessed through the use of Annexin
V-SYTOX Blue. Briefly, 5.times.10.sup.5 cells were harvested and
stained by FITC-Annexin V-SYTOX Blue working solution (Annexin V,
Trevigen; SYTOX Blue, Invitrogen) at room temperature for 15 min.
The cells were washed in binding buffer before performance of flow
cytometry (Becton Dickinson, Mountain View, Calif.). Date analysis
was performed by BD CellQuest. To confirm the flow data in which
there may be a minor overlap of Dox with FITC-Annexin V, a TUNEL
detection kit was used according to the manufacturer's instructions
to confirm the induction of apoptosis. Briefly, 72 hrs following
treatment with free Dox or Dox loaded particles, cells were washed,
fixed, and permeabilized before TUNEL staining. The number of
TUNEL-positive cells was assessed under a fluorescent microscope
(200.times.). At least 3 fields were counted by the same
investigator to calculate the percentage of TUNEL positive
cells.
[0293] In order to reconcile these findings with improved cell
killing, the MTS assay was used to compare KB-V1 cytotoxicity under
incremental Dox concentrations (FIG. 22A). Based on the calculated
IC.sub.50 values of the various formulations, it was possible to
rank the killing efficiency as follows:
siRNA-PEI-Dox-MSNP>PEI-Dox-MSNP.apprxeq.Dox-MSNP>free Dox.
Moreover, the IC.sub.50 value of the siRNA-delivering MSNP was
approximately 2.5 times lower than the IC.sub.50 of free Dox or
other Dox-loaded particles. This suggests an additive effect
between the drug and the siRNA that are being delivered by MSNP.
Although it was not possible to restore drug sensitivity to the
level seen in KB-31 cells, a much higher percentage of apoptotic
KB-V1 cells were observed after treatment with Dox-loaded MSNP that
co-delivers siRNA as compared to free Dox or Dox delivered by
non-siRNA delivering particles (FIG. 22B). Flow cytometry data was
confirmed through the use of another apoptosis assay using TUNEL
staining (FIG. 29), which showed an identical trend. Failure to
fully restore drug sensitivity could be due to extremely high
levels of Pgp expression and/or additional drug resistant pathways
in KB-V1 that were not targeted in the current research. Because of
the duration of time it takes for the siRNA to exert its effect,
cell viability was analyzed after longer treatment periods (e.g. 96
hrs) but did not observe any improvement in cytotoxicity (FIG. 30).
In addition, KB-V1 cells were treated by co-administration of Dox
and Tariquidar, which is a potent and effective Pgp inhibitor in
human clinical trial, to see if KB-V1 sensitivity can be restored
to that seen in KB-31 cells. While this combination significantly
improves cell killing capability in KB-V1 cells, it is incapable of
completely restoring Dox sensitivity to the level seen in KB-31
cells (FIG. 31).
Example 8
Small Particle Size and Surface Modification
[0294] A key challenge for improving the efficacy of passive drug
delivery to tumor sites by a nanocarrier is to limit
reticuloendothelial system (RES) uptake and to maximize the
enhanced permeability and retention (EPR) effect. Size reduction
and surface functionalization of mesoporous silica nanoparticles
(MSNP) reduces particle opsonization while enhancing the passive
delivery of monodispersed, 50 nm doxorubicin-laden MSNP to a human
squamous carcinoma xenograft in nude mice after intravenous
injection. Using near infrared (NIR) fluorescence imaging and
elemental Si analysis, passive accumulation of .about.12% of the
injected particle load was demonstrated at the tumor site, where
there is effective cellular uptake and the delivery of doxorubicin
to KB-31 cells. This was accompanied by the induction of apoptosis
and an enhanced rate of tumor shrinking compared to free
doxorubicin. The improved drug delivery was accompanied by a
significant reduction in systemic side effects such as animal
weight loss as well as reduced liver and renal injury. These
results demonstrate that it is possible to achieve effective
passive tumor targeting by MSNP size reduction as well as
introducing steric hindrance and electrostatic repulsion through
coating with a co-polymer. Further endowment of this
multifunctional drug delivery platform with targeting ligands and
nanovalves may further enhance cell-specific targeting and
on-demand release.
[0295] A preliminary study using MSNP with a .about.100 nm primary
particle size has shown that these particles could be taken up and
accumulate in a human breast cancer (MCF-7) xenograft in nude mouse
(Lu, et al., Small, vol. 6, pp. 1794-1805, 2010). However, the EPR
effect was not calculated in this study and it has been realized
that the original synthesis method yields particles that
agglomerate extensively in biological media. This could make those
particles ineffective from an EPR perspective insofar as the
preferred particle size is generally considered to be in the 50-100
nm size range (Perrault et al., Nano Lett., vol. 9, pp. 1909-1915,
2009; Lee et al., Mol. Pharm., vol. 7, pp. 1195-1208, 2010; Cho et
al., Clin. Cancer Res., vol. 14, pp. 1310-1316, 2008). Thus, size
reduction might be helpful to increase the passive targeting
effects of MSNP but even if the size was shrunken, the ionic
conditions and proteins present in biological fluids could
contribute to agglomeration and that may require additional design
features (Perrault et al., Nano Lett., vol. 9, pp. 1909-1915,
2009).
[0296] In this study a dynamic design strategy was used to improve
the biodistribution and the EPR effect of the first generation MSNP
to improve doxorubicin delivery to a human squamous carcinoma
xenograft in nude mice. A dramatic improvement of the EPR effect
was produced by reducing the primary particle size to .about.50 nm
(Davis et al., Nat. Rev. Drug Discov., vol. 7, pp. 771-782, 2008)
as well as by decorating the particle surface with a cationic
co-polymer. These design features in combination with the
electrostatic binding of doxorubicin to phosphonate groups in the
particle pore allow efficient doxorubicin delivery, some due to
intracellular release, at the cancer site (Meng et al., ACS Nano,
vol. 4, pp. 4539-4550, 2010). Not only are these design features
superior to induce tumor shrinkage and apoptosis compared to the
free drug, but also dramatically improves the safety profile of
systemic doxorubicin delivery.
Synthesis and Physicochemical Characterization of MSNP
[0297] Materials: Cetyl trimethylammonium bromide (CTAB, 95%),
Pluronic F127, tetraorthoethylsilicate (TEOS, 98%)
3-(trihydroxysilyl)propyl methylphosphonate (42% in H.sub.2O),
polyethyleneimine (PEI, 1.2 kD), 4-(dimethylamino)pyridine (99%),
N,N'-disuccinimidyl carbonate (95%), poly(ethylene glycol) methyl
ether (m-PEG, MW 5 kD), phthalic anhydride (99%) and polybrene were
purchased from Sigma (St. Louis, Mo.).
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (NAPTS) was
purchased from Gelest (Morrisville, Pa.). Amine-reactive near
infrared fluor DyLight 680 NHS ester was purchased from Thermo
Scientific (Rockford, Ill.). D-Luciferin was purchased from Xenogen
(Alameda, Calif.). Apoptosis TUNEL detection kit (Click-iT TUNEL
kit), bovine serum albumin (BSA), DPBS solution, L-glutamine,
penicillin, streptomycin, and DMEM medium were obtained from
Invitrogen. Fetal bovine serum (FBS) was purchased from Atlanta
Biologicals. Anti-CD31 antibody was purchased from BD Bioscience.
All reagents were used without further purification.
[0298] Synthesis of NP1. Established procedures were followed to
synthesize the classically designed or first-generation MSNP (NP-1)
(Liong et al., ACS Nano, vol. 2, pp. 889-896, 2008; Meng et al.,
ACS Nano, vol. 4, pp. 4539-4550, 2010; Meng et al., J. Am. Chem.
Soc., vol. 132, pp. 12690-12697, 2010; Lu et al., Small, vol. 6,
pp. 17949-1805, 2010). Briefly, 250 mg of CTAB was dissolved in 120
mL of water, followed by the addition of 875 .mu.L of 2M NaOH
aqueous solution. The solution was heated to and kept at 80.degree.
C. for 30 minutes before 1.25 mL of TEOS was added. The solution
went from clear to opaque, which is indicative of a hydrolysis
process. After 15 minutes, 315 .mu.L of trihydroxysilylpropyl
methylphosphonate was added. The reaction was kept at 80.degree. C.
for another 2 h. The resulting nanoparticles were centrifuged and
washed with methanol. In order to remove the CTAB, the
as-synthesized particles were suspended in 60 mL of methanol and
2.3 mL of 12 M hydrochloride acid. The solution was refluxed for 10
h and the MSNP designated NP1 were collected for centrifugation and
further washing with methanol.
[0299] Synthesis of NP2. 200 mg of Pluronic F127 was mixed with 250
mg of CTAB and 120 mL of H.sub.2O. The solution was heated to
80.degree. C. and kept for 30 min. 1 mL of TEOS was mixed with 200
.mu.L of NAPTS in 1 mL of ethanol and then added drop-wise into the
CTAB solution. 300 .mu.L of trihydroxysilylpropyl methylphosphonate
was added 20 min later. The solution was filtered through a 0.22
.mu.m polycarbonate syringe filter (Millipore, Billerica, Mass.)
and to remove the CTAB, the filtrate was mixed with 120 mL methanol
and 0.8 g of NH.sub.4NO.sub.3. The solution was heated to
70.degree. C. for 30 min. The particles were collected by
centrifugation and washed with methanol. To conduct PEG coating,
m-PEG was used because this polymer contains only a single reactive
hydroxyl group that can be used for PEI attachment; regular PEG has
two reactive ends that may cause particle cross-linking. For the
attachment to PEI, the hydroxyl group on m-PEG was replaced with a
NHS-ester (referred as activated m-PEG) that is capable of reacting
with the PEI amine residues. 10 mg of the as-synthesized MSNP was
suspended in 1.5 mL of DMF and mixed with 50 mg of activated m-PEG
(Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009). The solution
was stirred for a further 24 h and the particles were collected,
sequentially washed with DMF and ethanol and eventually
re-suspended in water.
[0300] Synthesis of NP3. The reduced size silica core was
synthesized as described above. To perform PEI coating, 10 mg of
as-synthesized small MSNP was suspended in 1 mL of 2.5 mg/mL PEI
ethanolic solution. The solution was sonicated and stirred for 30
min. This process was repeated twice to substitute the F127 coating
that was previously achieved by attaching PEI to the NP3 surface.
The particles were further washed in ethanol to remove excess PEI
and trace amount of F127 residue. The PEI-coated particle was
subsequently transferred into 1.5 mL of DMF, mixed with 50 mg of
activated m-PEG, and stirred for 24 h. The nanoparticles were
washed with DMF, ethanol and re-suspended in water.
[0301] Physicochemical characterization. All MSNPs were
characterized for size distribution, shape, and surface charge. The
shape and structure were characterized using a transmission
electron microscope (JEOL JEM 2010, JEOL USA, Inc., Peabody,
Mass.). TEM samples were prepared by placing a drop of the
nanoparticle saline suspension at a concentration of 100 .mu.g/mL
onto a 200-mesh copper grid (Electron Microscopy Sciences,
Washington, Pa.) and then drying at room temperature overnight.
Primary particle size was measured by random sampling of at least
10 particles that were imaged on a TEM grid. Image J software was
used to determine the average MSNP diameter. Particle size and zeta
potential in solution were measured by ZetaSizer Nano (Malvern
Instruments Ltd., Worcestershire, UK). All of the measurements were
performed with the nanoparticles suspended in filtered water or
saline at 100 .mu.g/mL nanoparticle concentration. Similar analysis
was also performed on the doxorubicin-loaded particles.
[0302] Three generations of particles (designated NP1-NP3) were
developed (FIG. 33). NP1 denotes the first generation of a
phosphonate-coated MSNP with a primary size of .about.100 nm and
exhibiting a negative zeta-potential (Table 4). These particles are
useful for the electrostatic attachment and proton-dependent
doxorubicin release in acidifying endosomal compartments in cancer
cells (Liong et al., ACS Nano, vol. 2, pp. 889-896, 2008; Meng et
al., ACS Nano, vol. 4, pp. 4539-4550, 2010; Meng et al., J. Am.
Chem. Soc., vol. 132, pp. 12690-12697, 2010; Xia et al., ACS Nano,
vol. 3, pp. 3273-3286, 2009). NP1 is also capable of delivering
camptothecin to a human breast cancer (MCF-7) xenograft (Lu et al.,
Small, vol. 6, pp. 1794-1805, 2010). However, because of this
particle's relatively large primary size and high rate of
agglomeration in saline (Table 4 and FIG. 34B) and other biological
media (e.g., 306 nm in DMEM medium; 867 nm in BEGM medium) (Xia et
al., ACS Nano, vol. 3, pp. 3273-3286, 2009), it was necessary to
consider reducing its size as well as changing its surface
characteristics to improve the EPR effect. The first approach was
synthesis of NP2 (FIG. 33), which exhibits a primary size of 50 nm
(as determined by TEM analysis) before undergoing PEGylation.
Following its coating with a 5 kD PEG polymer, NP2 exhibits a
hydrodynamic diameter of a .about.70 nm as determined by DLS (FIGS.
33 and 34). However, while this particle exhibits a negative zeta
potential and a hydrodynamic size of 70 nm in water (Table 4), it
undergoes considerable agglomeration in saline with potential
interference in extravasation at the tumor site. It was therefore
necessary to construct a 50 nm primary particle (FIG. 33) coated
with a PEI-PEG co-polymer to take advantage of the stronger
electrostatic repulsion of a cationic particle surface. This
yielded a particle with a positive zeta-potential, hydrodynamic
diameter of .about.77 nm in water and the size of 110 nm in saline
(Table 4). The improved dispersal of NP3 was confirmed by TEM,
showing that NP3 is essentially monodispersed in saline while NP2
and NP1 form incrementally larger agglomerates (FIG. 34B). To
further illustrate the dispersal characteristics of the
saline-suspended particles, photographic images were obtained and
showed optical transparency of the NP3 suspension while the
previous particle generations resulted in turbid suspensions (FIG.
34C).
TABLE-US-00004 TABLE 4 Comparison of particle sizes. Zeta Primary
size Size in H.sub.2O Size in Potential in Particle type (nm) (nm)
Saline (nm) H.sub.2O/(mV) NP1 100 260 520 -25.30 NP2 50 70 597
-20.5 NP3 50 77 110 +46.7
[0303] Drug loading and loading yield measurement. 10 mg of various
particles were suspended in 0.5 mL of 5 mg/mL doxorubicin aqueous
suspension. The solution was stirred for 24 h and the nanoparticles
were collected through centrifugation and carefully washed with
H.sub.2O. To measure the loading yields of the various particles, 1
mg of doxorubicin-loaded MSNP was resuspended and sonicated in 1 mL
heated 0.1 M HCl for 15 min. After centrifugation, another 1 mL of
fresh HCl aqueous solution was added. This process was repeated at
least for 5 times. The pH of supernatant was readjusted to 7.0 by 1
M NaOH and the fluorescence spectrum of doxorubicin was measured at
excitation and emission wavelength of 485/550 nm in a microplate
reader (SpectraMax M5Microplate Reader, Molecular Device, USA).
[0304] NIR fluorescent labeling. The NIR fluorescent dye, DyLight
680 NHS ester, was used for particle labeling. For NP1, 10 mg of
all the particles was suspended in 1 mL of ethanol and mixed with
0.1 mg of the DyLight 680 and 0.5 .mu.L of NAPTS. The reaction was
kept under inert atmosphere and stirred at room temperature for 12
h. The resulting particles were centrifuged and washed with
H.sub.2O. For NP2 and NP3, 10 mg each were suspended in 1 mL of DMF
and mixed with 0.1 mg of DyLight 680. After 12 h, the particles
were washed with H.sub.2O.
[0305] Cell culture and luciferase transfection. KB-31 cancer cells
were maintained in 25 cm.sup.2 or 75 cm.sup.2 cell culture flasks
in which the cells were passaged at 70-80% confluency every 3 days.
The cells were cultured in Dulbecco's Modified Eagle Medium (DMEM)
(Carlsbad, Calif.) containing 10% FBS, 100 U/mL penicillin, 100
.mu.g/mL streptomycin, and 2 mM L-glutamine (complete medium). To
generate a stable cell line constitutively expressing luciferase,
1.5.times.10.sup.4 KB-31 cells in 40 .mu.L complete DMEM
(supplemented with 10% FBS, 100 U/mL penicillin, 100 .mu.g/mL
streptomycin, 2 mM L-glutamine, and 8 .mu.L/mL polybrene) was
transduced with 10 .mu.L of a lentivirus (Cignal Finder Lenti
Pathway Reporter Qiagen/SA Biosciences; 1.4.times.10.sup.7 TU/mL)
in 96 well tissue culture plates. Spinoculation (centrifugal
inoculation) was performed at 1,200 g for 60 minutes. The viral
containing media was removed after 16 h and the cultures
replenished with fresh DMEM media. Cells were allowed to
proliferate to a population size of 1.2.times.10.sup.6 cells. A
heterogeneous pool of transduced cells was selected by using 1
.mu.g/mL puromycin for at least 14 days prior to tumor
implantation.
[0306] Establishment of the KB-31-luc tumor xenograft model.
Athymic BALB/c nu/nu female mice (6 weeks) were purchased from the
Charles River Laboratory, and maintained under pathogen-free
conditions. All animal experiments were performed using protocols
approved by the UCLA Animal Research Committee. The tumor cell
suspension (0.1 ml, 5.times.10.sup.6 cells/mL) was injected
subcutaneously into the mice. To perform imaging, the tumor-bearing
animals were used 2.5 weeks after tumor implantation. In the tumor
growth inhibition experiments, the nude mice were randomly divided
into 4 groups and received the listed range of treatments, which
commenced 1 week after tumor implantation.
[0307] Determining MSNP biodistribution. The tumor-bearing mice
were randomly divided into three groups (n=3). To visualize the
tumor, anesthetized mice were i.p. injected with 75 mg/kg
D-Luciferin. Eight minutes after injection, bioluminescence images
were acquired using an IVIS Imaging System (Xenogen). Acquisition
time was 10 s. Subsequently, the mice were intravenously
administered with NIR dye-labeled NP1, NP2, or NP3 at doses of 50
mg/kg (.about.1 mg nanoparticles per mouse), and the fluorescence
images were taken at indicated time points. 72 h after injection,
the tumor tissue together with major organs (heart, lung, spleen,
liver, kidney, brain and cardiac muscle) were collected and used
for ex vivo image. Around 100-200 mg tissue for each organ was
accurately weighed out, washed, homogenated, and the fluorescence
intensities per unitary amount of each organ were measured by a
microplate reader (Molecular Device, M5e).
[0308] Immunohistochemical staining to determine CD31 expression in
the tumor tissue. The tumor-bearing mice were randomly divided into
three groups (n=3) and intravenously administered with the
doxorubicin loaded NP1, NP2, or NP3 at doses of 50 mg/kg (.about.1
mg nanoparticles per mouse). The tumor tissues were rapidly
collected after 72 h, frozen and OCT embedded before sectioning to
provide 4 .mu.m thick slices. The slices were washed three times in
PBS, fixed in cold acetone for 15 min and the slide subsequently
blocked using 1% normal goat serum at room temperature for 10 min.
The sections were overlayed with rat-anti-mouse CD31 monoclonal
antibody (1:500) at 4.degree. C. overnight. After removal of the
primary antibody and washing in PBS for 3 times, FITC-labeled
goat-anti-rat IgG (1:500) was added and incubated for 1 h at room
temperature. The slides were visualized under a fluorescence
microscope (Zeiss, Germany).
[0309] Nude mouse studies to determine the effect of
doxorubicin-loaded NP3 on tumor shrinkage. One week after tumor
implantation, the KB-31 tumor-bearing mice were randomly divided
into four groups of five animals each. These groups were used for
comparing the effects of saline, empty nanoparticles, free
doxorubicin, and doxorubicin-loaded NP3, respectively. The latter
group received intravenous administration of 120 mg/kg (.about.2.4
mg per animal) NP3, which is equivalent to a doxorubicin dose of 4
mg/kg (.about.0.08 mg per animal), weekly for 3 weeks. The free
doxorubicin group received the same drug dose weekly for 3 weeks,
while the group receiving empty NP3 was treated with 120 mg/kg on a
weekly basis. The fourth group was treated with saline as control.
The body weight and tumor size were accurately recorded twice per
week. Tumor weight was calculated according to the formula: Tumor
weight (mg)=(length in mm).times.(width in mm).sup.2/2 (Meng et
al., ACS Nano I, vol. 4, pp. 2773-2783, 2010).
[0310] TUNEL staining of the tumor tissue. A section of the tumor
from each animal was used for TUNEL staining. The slides containing
the tumor section were washed, fixed, and permeabilized before
performance of TUNEL staining according to the manufacturer's
instructions (Invitrogen, Carlsbad, Calif.). Nuclei were stained by
Hoechst 33342 dye. The number of TUNEL positive cells (green
staining) was assessed under a fluorescent microscope (200.times.).
The same sections were also used for recording of the red
fluorescent images of the doxorubicin that was present in the
particles or the tissues. At least three fields were counted by the
same investigator to calculate the percentage of TUNEL positive
cells.
[0311] Blood biochemistry to assess possible toxicity. Following
the animal experiments described above, the mice were sacrificed on
21.sup.st day and serum collected by centrifuging the whole blood
at 5,000 rpm for 15 min. The biochemical parameters, including
cholesterol (CHOL), triglycerides (TRG), alanine aminotransferase
(ALT), aspartate aminotransferase (AST), total bilirubin (TBILI),
glucose (GLU), inorganic phosphorus (PHOS), total protein (TPR),
calcium (CAL), blood urea nitrogen (BUN), creatinine (CRE), and
albumin (ALB) were assayed by UCLA Division of Laboratory Animal
Medicine (DLAM) diagnostic laboratory services.
[0312] Tumor and major organ histology. Appropriate size sections
of the tumor, liver, kidney, spleen, lung, heart, and brain were
fixed in 10% formalin and then embedded into paraffin. Tissue
sections of 4 .mu.m thickness were mounted on glass slides by the
UCLA Division of Laboratory Animal Medicine (DLAM) diagnostic
laboratory services. The sections were stained with
hematoxylin-eosin (H&E) and examined by light microscopy. The
slides were read by an experienced veterinary pathologist.
[0313] Drug loading and loading yield measurement. 10 mg of various
particles were suspended in 0.5 mL of 5 mg/mL doxorubicin aqueous
suspension. The solution was stirred for 24 h and the nanoparticles
were collected through centrifugation and carefully washed with
H.sub.2O. To measure the loading yields of the various particles, 1
mg of doxorubicin-loaded MSNP was resuspended and sonicated in 1 mL
heated 0.1 M HCl for 15 min. After centrifugation, another 1 mL of
fresh HCl aqueous solution was added. This process was repeated at
least for 5 times. The pH of supernatant was readjusted to 7.0 by 1
M NaOH and the fluorescence spectrum of doxorubicin was measured at
excitation and emission wavelength of 485/550 nm in a microplate
reader (SpectraMax M5Microplate Reader, Molecular Device, USA).
Comparison of the Biodistribution of Labeled and Drug Laden NP1-NP3
In Vivo
[0314] In order to determine whether the redesign of particle size
and surface coating improve the biodistribution of the various MSNP
types, imaging studies were performed in a nude mouse model used
for subcutaneous growth of a human tumor xenograft. To visualize
the tumor growth in a doxorubicin-sensitive HeLa squamous carcinoma
cell line, KB-31 cells were used for stable transfection with a
luciferase vector and then used that for obtaining bioluminescence
images in the mice following intraperitoneal (i.p.) injection of
D-Luciferin (FIG. 35A, 1.sup.st row). To also visualize the
particles in vivo, the MSNP were designed to incorporate a
near-infrared (NIR) dye that exhibits high photon penetration in
the animal tissue (Frangioni et al., Curr. Opin. Chem., vol. 7, pp.
626-634, 2003; Farist et al., Clin. Phys. Phgsiol. Meas., vol. 12,
pp. 353-358, 1991). In order to quantitatively compare the
biodistribution of NP1-NP3, the data show that the particles had
similar labeling efficiency per unit mass (FIG. 40). Initial
reference images were obtained prior to particle injection to show
a very low NIR background in the tumor-bearing animals (FIG. 35A,
2.sup.rd row). These animals were then injected with 50 mg/kg of
each NIR dye-labeled particle types via the tail vein and
fluorescence images captured at the indicated time points (FIG.
35A, 3.sup.rd-5.sup.th row). The supine images indicate that the
majority of NP1 were captured by the liver and spleen within 24 h
and this profiling was maintained for at least 72 h. By contrast,
NP2 showed less prominent liver uptake with a sustained systemic
distribution (longer circulation time), indicating the ability of
PEG coating to decrease particle opsonization and removal by the
RES. Interestingly, a barely visible tumor signal could only be
obtained in one of three animals (FIG. 35A, middle panel). A
similar reduction in RES uptake and increased circulation time were
obtained for NP3, which showed prominent particle uptake in the
tumor tissue at 24 h, suggestive of a strong EPR effect (FIG. 35A,
right panel). Moreover, the fluorescence intensity at the tumor
site increased gradually, peaking at 48 h and was then sustained
for at least 72 h.
[0315] In order to obtain more quantitative data that can be used
for calculating the EPR effect, the same animals were sacrificed at
72 h post-injection and ex vivo fluorescence intensity images were
obtained for the tumor tissue as well as major organs such as
liver, spleen, lung, kidney, brain, muscle and heart (FIG. 35B).
Consistent with the in vivo images, NP3 showed the highest
fluorescence intensity in the tumor tissue compared to other
particle types (FIG. 35B). However, NP3 showed abundant
distribution to the liver and spleen as well as relatively high
fluorescence intensity in the lung compared to the other particle
types. The collected organs were accurately weighed and used for
the quantitative analysis of particle distribution by expressing
the fluorescence intensity per unit mass of tissue (FIG. 35C). This
readout demonstrated the highest particle concentration at the
tumor site in animals treated with NP3 (FIG. 35C). When expressed
as a percentage of the total mass of the particles administered,
.about.1%, .about.3% and .about.12% of NP1, NP2 and NP3 load,
respectively could be seen to biodistribute to the tumor tissue at
72 h (FIG. 35D). To further confirm the EPR calculation based on
fluorescence intensity, inductively coupled plasma mass
spectrometry (ICP-MS) was used to quantify the Si abundance in the
major target organs (tumor, liver, kidney and spleen) of saline-
and NP3-treated animals (FIG. 41). Consistent with the fluorescence
data, .about.10% of the total administered elemental Si dose could
be demonstrated in the NP3 treated tumor tissue (FIG. 41). While
slightly lower than the estimation of the EPR effect by using
fluorescence intensity, it has to be considered that some degree of
heterogeneity in tumor vascularity can influence fluorescent
imaging intensity to explain this small difference (Bettio et al.,
J. Nucl. Med., vol. 2006, pp. 1153-1160, 2006). All considered, the
estimated EPR of .about.12% in the KB-31 model is exceptionally
good compared to other polymer/co-polymer based drug and siRNA
nanocarrier delivery platforms, where a passive targeting rate of
3.5-10% has been reported for different particle types (de Wolf et
al., Int. J. Pharm., vol. 331, pp. 167-175, 2007; Kaul et al., J.
Drug Target., vol. 12, pp. 585-591, 2004; Verbaan et al., J. Gene
Med., vol. 6, pp. 64-75, 2004; Fenske et al., Curr. Opin. Mol.
Ther., vol. 3, pp. 153-158, 2001).
[0316] In order to determine whether drug loading exerts an effect
on particle biodistribution, doxorubicin was loaded into NP1, NP2
and NP3 at w/w ratios of 3.3%, 2.5% and 3%, respectively. The red
fluorescence properties of doxorubicin allowed us to make
semi-quantitative visual comparisons of the amount of drug in the
tumor tissue. In order to facilitate this interpretation the tumor
blood vessels were visualized by CD31 immunohistochemistry (FIG.
36). This allowed us to visually compare the relative abundance of
the drug fluorescence signal in relation to its intratumoral
distribution. This analysis showed that doxorubicin delivery by NP3
was the most effective for this type of tumor and this particle
generation was chosen for subsequent studies to perform intravenous
drug delivery in the xenograft model as well as for safety
assessment compared to treatment with free doxorubicin.
Doxorubicin Delivery and Release by NP3 at the Tumor Site Leads to
Efficient Apoptosis and Tumor Shrinkage
[0317] Since NP3 exhibits the best EPR effect and is responsible
for the highest doxorubicin accumulation in the tumor site, it was
asked how drug-laden particles compared to free doxorubicin or
empty particles in terms of their ability to induce apoptosis and
inhibit tumor growth in the KB-31 tumor model. Tumor-bearing
animals were injected intravenously on a weekly basis for 3 weeks
with a NP3 dose of 120 mg/kg. This is equivalent to the
administration of 4 mg/kg doxorubicin per injection and was
compared to delivering the same dose of free doxorubicin, injected
weekly for 3 weeks. A saline-treated control was included as well
as a group of animals treated with empty particles. When comparing
the effect on tumor size, doxorubicin loaded NP3 showed a
significantly higher rate of tumor shrinkage than the free drug
(FIGS. 37A and 42). No tumor inhibition was found with saline
treatment or the use of empty particles (FIGS. 37A and 42).
Following sacrifice of the animals, the tumor tissues were
collected for accurate weighing (FIGS. 37B and 42). This
demonstrated 85% tumor inhibition by doxorubicin-loaded NP3
compared to 70% inhibition by the free drug (FIG. 37B). This
difference is statistically significant (p<0.05).
[0318] Since doxorubicin inhibits cancer cell growth through
induction of apoptosis (Gamen et al., Exp. Cell Res., vol. 258, pp.
223-235, 2000), TUNEL staining was used to compare the abundance
and localization of TUNEL-positive cells (green fluorescence) in
relation to the doxorubicin fluorescence (FIG. 38A). This analysis
also allowed us to detect the drug-laden particles in relation to
the cells undergoing apoptosis. By merging the red and green
fluorescent images, the yellow composites show that there is indeed
an overlap between the drug and apoptotic cells (FIG. 38A, bottom
panel). By contrast, the tissues from animals treated with free
doxorubicin showed significantly less drug signal, fewer apoptotic
cells and lesser fluorescence overlap (FIG. 38A, left panel).
Quantification of the number of TUNEL-positive cells was
significantly higher during NP3 delivery of doxorubicin
(.about.38%) compared to mice treated with free drug alone
(.about.13%) (FIG. 38B). Additional nuclear staining with Hoechst
dye as well as image enlargement of regions "I" and "II" in FIG.
38A further demonstrated that the doxorubicin-laden particles could
be visualized as red fluorescent specks or dots, frequently
appearing in a perinuclear arrangement (FIG. 38C, lower panel).
This is in favor of cellular entrance of the particles, with
presumably some of the drug release taking place in the acidifying
endosomal compartment as previously demonstrated by us in KB-31
cells (Meng et al., J. Am. Chem. Soc., vol. 132, pp. 12690-12697,
2010). This stands in contrast to the dull homogeneous background
in cancer cells of the mice treated with the free drug (FIG. 38C,
upper panel).
Doxorubicin Delivery by NP3 Reduces Systemic, Hepatic and Renal
Toxicity Compared to Free Drug
[0319] The safety of MSNP drug delivery is of key importance in the
assessment of this delivery platform. This includes the inherent
safety of the delivery vehicle as well as any potential benefits
that may accrue from encapsulated drug delivery. Accordingly,
safety profiling was performed by comparing the effects of saline,
free doxorubicin, empty NP3 and doxorubicin-laden NP3. The safety
profiling included assessment of total body weight, blood
chemistry, histological examination of major organs as well as
performance of a red blood cell lysis assay. Compared to saline
treated tumor-bearing mice, no significant body weight changes were
observed during the administration of either empty NP3 or
nanoparticles loaded with doxorubicin (FIG. 39A). In contrast,
animals receiving free doxorubicin administration showed a cyclical
decrease in body weight following each of the weekly drug
administrations (FIG. 39A). Moreover, these animals also showed
significant elevations of the liver function enzymes, alanine
aminotransferase (ALT) and aspartate aminotransferase (AST), as
well as an increased total bilirubin (TBIL) value compared to the
saline control (Table 5). In addition, the doxorubicin treated
animals showed a mild increase in inorganic phosphate (PHOS) levels
(Table 5). In contrast, when doxorubicin was delivered by NP3, the
ALT, PHOS and TBIL levels stayed normal with only a smaller but
significant increase in the AST level (Table 5). In mice treated
with the empty NP3 carrier, biochemical analysis did not show any
significant changes in liver function, kidney function (blood urea
nitrogen, BUN; creatinine, CRE), cholesterol (CHOL), triglycerides
(TRG), glucose (GLU), PHOS, total protein (TPR), calcium (CAL) and
albumin (ALB) (Table 5).
TABLE-US-00005 TABLE 5 Serum biochemistry profiles. Biochemical
parameters.sup.a Saline Unloaded NP3 free Dox Dox-NP3 CHOL (mg/dL)
110.0 .+-. 18.2 118.0 .+-. 18.4 97.8 .+-. 12.8 122.3 .+-. 8.5 TRG
(mg/dL) 79.0 .+-. 36.5 110.3 .+-. 22.5 91.5 .+-. 21.2 96.0 .+-.
24.9 ALT (u/L) 23.3 .+-. 6.8 26.7 .+-. 4.0 36.8 .+-. 8.0* 27.3 .+-.
2.1.sup.# AST (u/L) 132.0 .+-. 23.4 183.3 .+-. 23.2 347.8 .+-.
73.9* 174.0 .+-. 38.2.sup.# TBIL (mg/dL) 0.2 .+-. 0.0 0.3 .+-. 0.0
0.4 .+-. 0.0* .sup. 0.2 .+-. 0.0.sup.# GLU (mg/dL) 111.3 .+-. 18.6
106.0 .+-. 20.4 102.5 .+-. 29.2 108.0 .+-. 9.4 PHOS (mg/dL) 8.6
.+-. 0.7 8.5 .+-. 0.2 9.5 .+-. 0.8* .sup. 7.5 .+-. 0.7.sup.# TPR
(g/dL) 4.8 .+-. 0.3 5.7 .+-. 0.2 5.0 .+-. 0.4 5.4 .+-. 0.2 CAL
(mg/dL) 9.4 .+-. 0.2 9.7 .+-. 0.2 9.0 .+-. 0.5 9.8 .+-. 0.1 BUN
(mg/dL) 16.0 .+-. 2.6 20.0 .+-. 4.4 17.3 .+-. 2.6 19.0 .+-. 4.1 CRE
(mg/dL) 0.3 .+-. 0.0 0.3 .+-. 0.0 0.3 .+-. 0.1 0.3 .+-. 0.0 ALB
(g/dL) 2.3 .+-. 0.2 2.8 .+-. 0.1 2.4 .+-. 0.2 2.6 .+-. 0.1
.sup.aBlood was collected from the sacrificed animals and the serum
obtained by centrifuging the whole blood at 5,000 rpm for 15 min.
The biochemical parameters were assayed by UCLA Division of
Laboratory Animal Medicine (DLAM) diagnostic laboratory services.
These parameters include cholesterol (CHOL), triglycerides (TRG),
alanine aminotransferase (ALT), aspartate aminotransferase (AST),
total bilirubin (TBILI), glucose (GLU), inorganic phosphorus
(PHOS), total protein (TPR), calcium (CAL), blood urea nitrogen
(BUN), creatinine (CRE), and albumin (ALB). *p < 0.05, compared
to saline; .sup.#p < 0.05, compared to free doxorubicin.
[0320] Histological examination of the liver showed prominent
hepatic steatosis in the animals treated with free doxorubicin
(FIG. 39B, upper panel) (Garg et al., J. Clin. Endocrinol. Metab.,
vol. 2002, pp. 87-3019-3022). Steatosis represents fatty
degeneration as a result of metabolic impairment of triglyceride
synthesis and elimination and is a frequent feature of toxic liver
injury, including during chemotherapy (Nomura et al., Am. J.
Roentgenol., vol. 189, pp. 1484-1488, 2007; Kandutsch et al., Eur.
J. Surg. Oncol., vol. 34, pp. 1231-1236, 2008). No steatosis was
observed in any of the other treatment groups (FIG. 43, upper
panel). Free doxorubicin delivery also resulted in nephrotoxicity,
which manifested as glomerular swelling (FIG. 39B, lower panel)
(Yagmurca et al., Clinica. Chimica. Acta., vol. 348, pp. 27-34,
2004). No significant abnormalities were found in the mice treated
by saline or empty particle (FIG. 43, lower panel). Since the NP3
also abundantly biodistributed in lung, histological examination of
the lung tissue was performed but did not show any gross pathology
resulting from empty or drug-loaded NP3 (FIG. 44). Interestingly,
histological examination of myocardial tissue did not show any
gross pathology in any of the experimental groups (FIG. 45). This
is probably due to the relatively low doxorubicin dose and short
treatment period (Arola et al., Cancer Res., vol. 60, pp.
1789-1792, 2000).
[0321] Because of the cationic (PEI) component the co-polymer
coating is potentially toxic to cell membranes, including the
ability to lyse red blood cells (RBC), a hemolysis assay was
performed using heparinized mouse RBC (Slowing et al., Small, vol.
5, pp. 57-62, 2009). The results did not show any hemoglobin
release in response to empty NP3 at concentrations as high as 2500
.mu.g/mL (FIG. 46). This is at least 10 times higher than the
therapeutic dose requirements. These results are in agreement
previous studies showing that coating of the MSNP surface with
shorter length (<10 KD) PEI polymers do not lead to significant
toxicity in a range of normal and tumor cells (Xia et al., ACS
Nano, vol. 3, pp. 3273-3286, 2009).
[0322] Attachment of polyethyleneimine-Polyethylene glycol
(PEI-PEG) copolymer on a 50 nm MSNP core has been shown to lead to
an increase in circulatory half-life as well as exceptionally good
EPR effects compared to other polymer/co-polymer based drug and
siRNA nanocarrier delivery platforms, where a passive targeting
rate of 3.5-10% has been reported for different particle types. Not
only are these design features superior for the induction of
apoptosis and tumor shrinkage compared to the free drug but also
improved the safety of doxorubicin delivery.
[0323] By using size tuning and decoration of the MSNP surface with
a PEI-PEG co-polymer, particle dispersal and biodistribution were
improved to achieve therapeutically useful doxorubicin delivery to
a tumor xenograft site in nude mice. Through the use of NIR
fluorescence imaging and elemental Si analysis, a 50 nm particle,
consisting of mesoporous silica core coated with the PEI-PEG
co-polymer was capable of achieving an excellent EPR effect
compared to non-coated larger particles (NP1) or a 50 nm particle
decorated with PEG only (NP2). In addition to passive particle
accumulation at the tumor site, NP3 was also capable of entering
KB-31 tumor cells to deliver a toxic dose of doxorubicin and
ability to induce a higher rate of apoptosis compared to the free
drug. The encapsulated drug was also associated with less systemic,
hepatic and renal toxicity compared to free doxorubicin. This is
the first demonstration of how the optimal design of the MSNP
platform can achieve passive drug delivery, which in combination
with intracellular uptake resulted in an efficacious antitumor
effect.
[0324] The integrated use of a series of design improvements to
achieve in vivo tumor shrinkage and EPR >10% has not been
described previously for MSNPs. The best recorded EPR effects with
a polymer or co-polymer based nanocarrier system with therapeutic
efficacy was in the range of 3.5 to 10% (de Wolf et al., Int. J.
Pharm., vol. 331, pp. 167-175, 2007); Kursa et al., Bioconjugate
Chem., vol. 14, pp. 222-231, 2002; Kircheis et al., Cancer Gene.
Ther., vol. 9, pp. 673-680, 2002). The ability to exceed this
delivery with this MSNP platform is highly significant since this
has been achieved without targeting ligands or the use of
sophisticated design features such as the attachment of nanovalves
(Lu et al., Small, vol. 3, pp. 1341-1346, 2007; Liong et al., ACS
Nano, vol. 2, pp. 889-896, 2008; Meng et al., J. Am. Chem. Soc.,
vol. 132, pp. 12690-12697, 2010). The first step was to construct a
50 nm mesoporous silica core to approach a carrier size more
conducive for slipping past the malformed blood vessel
fenestrations in the tumor. This feature was achieved by using a
co-templating agent method for particle synthesis. This involves
addition of an optimal amount of Pluronic F127 to cetyl
trimethylammonium bromide (CTAB), which is the standard surfactant
used for synthesis of the first-generation MSNP (Liong et al., ACS
Nano, vol. 2, pp. 889-896, 2008; Meng et al., ACS Nano, vol. 4, pp.
4539-4550, 2010; Meng et al., J. Am. Chem. Soc., vol. 132, pp.
12690-12697, 2010; Xia et al., ACS Nano, vol. 3, pp. 3273-3286,
2009). The Pluronic F127 changes the structure of the CTAB
micelles, which affects their micelle packing behavior and
therefore leading to a smaller particle size (Febvay et al., Nano
Lett., vol. 10, pp. 2211-2219, 2010). Pluronic F127 also improves
the dispersion of the hydrophobic silica precursor,
tetraorthoethylsilicate (TEOS), and also coats newly formed MSNPs,
helping to protect them from agglomeration and oligomerization.
[0325] The second key design feature is PEGylation of the MSNP
surface which results in reduced RES uptake, as demonstrated for
NP2 and NP3. This prolongs the particles' circulation time, which
has a direct bearing on the EPR effect. Similar to previous
findings, He et al. previously demonstrated that PEGylation of an
80 nm MSNP results in a longer blood-circulation lifetime compared
to naked particles in healthy ICR mice (He et al., Small, vol. 7,
pp. 271-280, 2011). However, PEGylation alone only achieved an EPR
effect of .about.3% for NP2, because the particles agglomerated to
.about.600 nm size, thereby preventing extravasation the tumor
site. Although PEG provides steric hindrance that could
theoretically interfere in nanoparticle aggregation in water, the
increased ionic strength of biological media compresses the
electric double layer on the particle surface (Petersen et al.,
Bioconjugate Chem., vol. 13, pp. 845-854, 2002; Tang et al.,
Biomaterials, vol. 24, pp. 2351-2362, 2003; Kunath et al., Pharm.
Res., vol. 19, pp. 810-817, 2002). This significantly weakens the
repulsion between particles. The introduction of cationic charge by
using a PEI co-polymer overcame this problem. It is also important
to mention that reduced particle opsonization after PEGylation may
also reduce immunogenic potential, thereby adding an additional
safe design feature (Xia et al., ACS Nano, vol. 3, pp. 3273-3286,
2009).
[0326] The attachment of the PEI-PEG co-polymer was undertaken with
a view of improving the MSNP dispersal and thereby reducing the
particle's hydrodynamic size to be as close as possible to the
primary particle size. The effectiveness of the strategy was
demonstrated by the acquisition of a positive zeta-potential on NP3
as well as achieving a monodisperse suspension with an average
hydrodynamic size .about.100 nm in saline. Similar use of a
co-polymer strategy to shrink particle size to improve dispersal
was previously demonstrated in the preparation of albumin
nanoparticles (Zhang et al., Biomaterials, vol. 31, pp. 952-963,
2010), PEI-PEG block co-polymer (Petersen et al., Bioconjugate
Chem., vol. 13, pp. 845-854, 2002; Tang et al., Biomaterials, vol.
24, pp. 2351-2362, 2003; Kunath et al., Pharm. Res., vol. 19, pp.
810-817, 2002), gold nanoparticles (Kawano et al., J. Controlled
Release, vol. 111, pp. 382-389, 2006), and silica particles
(Thierry et al., Langmuir, vol. 24, pp. 8143-8150, 2008). In
particular, the use of a PEI-PEG co-polymer resulted in the
smallest possible hydrodynamic size and the best state of dispersal
of these materials compared to coating with PEG only. To illustrate
the importance of the cationic charge in achieving these design
features, amine groups on the PEI in the co-polymer were
neutralized with phthalic anhydride and could demonstrate that the
less cationic NP3 underwent a dramatic size increase in saline
(FIG. 47). Consistent with research using trimethylammonium
modified MSNP with a primary size 50-100 nm capable of liver
accumulation (Lee et al., Adv. Funct. Mater., vol. 19, pp. 215-222,
2009), it would appear that the size reduction effect of the
PEI-PEG coating is the major reason for improving biodistribution
and therapeutic outcome. The placement of a positive charge on the
MSNP surface endows these particles with the ability to bind,
protect and deliver nucleic acids as described in Examples 1-7
above. PEI coating is useful for the delivery of a P-glycoprotein
(Pgp) siRNA that restores doxorubicin sensitivity in a
doxorubicin-resistant HeLa cell line (Meng et al., ACS Nano, vol.
4, pp. 4539-4550, 2010).
[0327] The EPR effect of therapeutic nanoparticles plays a key role
in their accumulation at the tumor site. Compared to nanoparticles
containing surface ligands that promote active targeting of tumor
cells or tumor tissue, the use of the EPR effect is considered to
be a passive targeting strategy (Maeda et al., H.; Kabanov, A.;
Kataoka, K.; Okano, T.; Fang, J.; Sawa, T.; Maeda, H., Factors and
Mechanism of "EPR" Effect and the Enhanced Antitumor Effects of
Macromolecular Drugs Including SMANCS. In Polymer Drugs in the
Clinical Stage, Springer US: 2004, 519, 29-49; Fang et al., Adv.
Drug Delivery Rev., vol. 63, pp. 136-151, 2011). Nonetheless, the
EPR effect is tunable and can be accomplished through redesign of
the nanocarrier or manipulating the tumor microenvironment.
Examples of the latter strategy include elevation of systemic blood
pressure by angiotensis II (Suzuki et al., J. Natl. Cancer Inst.,
vol. 67, pp. 663-669, 1981), using a vasodilator such as NO
releasing agents (Seki et al., Cancer Sci., vol. 100, pp.
2426-2430, 2009) or increasing vascular permeability with
biomolecules such as VEGF and iRGD peptide (Minko et al., Pharm.
Res., vol. 17, pp. 505-517, 2000; Sugahara et al., Science, vol.
328, pp. 1031-1035, 2010). However, all of these adjuvant
treatments pose some hazard and may not be useful for every
treatment consideration. Redesign of the nanomaterial could also
impact the EPR effect as reviewed above. It is important to mention
here that after their extravasation, the cellular attachment and
uptake of the nanoparticles are dependent on their diffusion and
that the diffusion constant is inversely correlated to nanoparticle
size (Lee et al., Mol. Pharm., vol. 7, pp. 1195-1208, 2010). In
this regard it has previously been shown that the size reduction of
block co-polymer micelles through a correct combination of polymers
could enhance this nanocarrier's uptake in a human breast cancer
xenograft (Lee et al., Mol. Pharm., vol. 7, pp. 1195-1208, 2010).
It is further worth noting that the EPR effect is highly dependent
on the cancer type, including the extent of neo-angiogenesis and
the vascularity of the tumor (Maeda et al., Bioconjugate Chem.,
vol. 21, pp. 797-802, 2010; Mao et al., Pharm. Res., vol. 22, pp,
2058-2068, 2005). While in a previous study MSNP was capable of
accumulating in a human breast carcinoma (MCF-7) xenograft (Lu et
al., Small, vol. 6, pp. 1794-1805, 2010), a satisfactory EPR effect
was not achieved with this material in the KB-31 model. However,
size reduction and coating the 50 nm particles with a PEI-PEG
co-polymer could increase particle uptake by an order of magnitude
in KB-31 tumor sites. Moreover, the passive enhancement of NP3
accumulation at these tumor sites is accompanied by intracellular
uptake without requiring the attachment of a ligand. The cationic
particle surface could play an active role in promoting this uptake
as previously demonstrated in a variety of cancer cell types in
vitro (Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
[0328] Key to any therapeutic intervention is the inherent safety
of the delivery system. The empty NP3 failed to elicit any adverse
effects after intravenous injection as determined by animal body
weight, blood biochemistry, and histological analysis of major
organs and tissues. Moreover, these particles did not damage red
cell membranes when using a hemolysis assay (FIG. 46). Another
design feature to consider from a safety perspective is particle
coating with a PEI polymer. While it is well known that PEI by
itself or coated onto particle surfaces could lead to toxicity,
demonstrated to be dependent on the polymer length and cationic
charge density (Xia et al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
Thus, while high molecular weight (.gtoreq.10 kD) PEI polymers can
induce considerable cellular toxicity in a variety of normal and
transformed cell types, there is no generation of cellular toxicity
by the 1.2 kD polymer (Xia et al., ACS Nano, vol. 3, pp. 3273-3286,
2009). This was confirmed by conducting cytotoxicity studies with
NP3 in cancer cell lines (not shown). The apparent reason is the
distribution and density of cationic charge on the longer length
versus the shorter length PEI polymers, allowing the longer length
polymers to induce membrane damage as well as the possibility of
inducing a so-called "proton sponge effect" that is associated with
lysosomal damage density (Xia et al., ACS Nano, vol. 3, pp.
3273-3286, 2009; Zhang et al., ACS Nano 2011, 10.1021/nn200328m).
It is also worth mentioning that intravenous injection of the
equivalent of NP1 coated with a 25 kD PEI polymer in mice did not
elicit any significant toxicity in a previous study in mice (Xia et
al., ACS Nano, vol. 3, pp. 3273-3286, 2009).
[0329] Equally important is the demonstration of the improvement of
the high level of doxorubicin toxicity by encapsulating the drug in
NP3 (Portney et al., Anal. Bioanal. Chem., vol. 386, pp. 620-630,
2006; Vallet-Regi et al., Chem. Mater., vol. 13, pp. 308-311,
2000). Thus, compared to the free drug, doxorubicin encapsulation
did not exert an effect on total body weight or impacting liver and
kidney function (FIGS. 39C and 43). Interestingly, evidence of
histological damage to the myocardium was not observed in this
study, even with free doxorubicin (Hayek et al., N. Engl. J. Med.,
vol. 352, pp. 2456-2457, 2005). This may be due to the comparative
high sensitivity of KB-31 cancer cells to the effects of
doxorubicin (Meng et al., ACS Nano, vol. 4, pp. 4539-4550, 2010).
This reduction of systemic toxicity is likely due to the drug being
bound to the negatively charged phosphonate groups in the particle
pores, therefore not being released in the bloodstream. Doxorubicin
release from phosphonate-coated MSNP pores take place in acidifying
endosomal compartment in KB-31 cells (Meng et al., ACS Nano, vol.
4, pp. 4539-4550, 2010). While it is difficult to study endosomal
release at the intact animal level, fluorescence visualization data
demonstrate the presence of doxorubicin containing NP3 in a
perinuclear distribution in KB-31 cells undergoing apoptosis in
vivo (FIG. 38C). Thus, intracellular drug release may contribute to
the higher rate of KB-31 cell apoptosis in this study. This feature
may be enhanced by using a pH-dependent nanovalve that is capable
of opening intracellularly in KB-31 cells with the capability of
doxorubicin release to the nucleus (Meng et al., J. Am. Chem. Soc.,
vol. 132, pp. 12690-12697, 2010).
[0330] It is important to mention that similar to other
nanocarriers (Li et al., Mol. Pharm., vol. 5, pp. 496-504, 2008)
that the vast majority of systemically administered MSNPs are
sequestered by the RES irrespective of the design feature. The lack
of observable toxicity of the doxorubicin-laden particles in the
liver and spleen is an interesting finding that has not been
resolved as yet. Without wishing to be bound by theory, one
possibility is that the traditional biomarkers used for following
liver injury are ineffective in reflecting RES damage, but another
explanation is that the RES and organs like the liver are quite
resilient in dealing with doxorubicin toxicity when the drug is
encapsulated. This could involve protective features such as
hepatobiliary transfer, which has been shown to be quite prominent
in another MSNP study (Souris et al., Biomaterials, vol. 31, pp.
5564-5574, 2010). It is also possible that the relatively slow rate
of drug release from the particle pores could prevent acute
toxicity due to drug conjugation, inactivation or excretion (Maeda
et al., Eur. J. Pharm. Biopharm., vol. 71, pp. 409-419, 2009;
Torchilin et al., Adv. Drug Deliver. Rev., vol. 63, pp. 131-135,
2011). There is also a considerable capacity of mononuclear
macrophages to destroy or sequester particulate matter (Noguchi et
al., Cancer Sci., vol. 89, pp. 307-314, 1998). It is important to
mention that in a previous study tracking of elemental Si following
systemic MSNP administration could lead to the recovery of
.about.94% of the injected MSNP bolus in the urine and feces within
4 days (Lee et al., Angew. Chem. Int. Ed., vol. 49, pp. 8214-8219,
2010). This is in agreement with the demonstration by Souris et al.
of the rapid bioelimination of MSNP through hepatobiliary excretion
in murine experiments (Souris et al., Biomaterials, vol. 31, pp.
5564-5574, 2010). This constitutes another important safety feature
of a nanocarrier that could either be degraded in situ into
cellular subcomponents or could be excreted from the body once the
carrier has served its therapeutic purpose. The in vivo
biodegradability and bioelimination of MSNP is comparable to
abiotic studies, showing the gradual decomposition of MSNP in
simulated body fluids at 37.degree. C., including demonstrating a
breakdown of the MSNP architecture with a decrease in their BET
surface area (Cauda et al., Micropor. Mesopor. Mat., vol. 132, pp.
60-71, 2010).
[0331] Size tuning and decoration of the MSNP surface with a
PEI-PEG co-polymer constitutes an efficient doxorubicin delivery
strategy for a human squamous carcinoma xenograft in nude mice. In
vivo imaging and elemental analysis demonstrate that these design
modifications lead to an excellent EPR effect and sufficient
nanocarrier accumulation to achieve tumor cell killing that is more
effective than the free drug. This delivery may minimize the
chemotherapeutic side effects at the intact animal level as well as
susceptible organs. These results are encouraging from the
perspective of moving the MSNP platform into clinical trials as
well as introducing additional design features that will make it
possible to perform theranostics as well to obtain on-demand drug
release at the tumor site by a series of nanovalves that can be
controlled through pH, temperature, photon wavelength or a magnetic
field.
Example 9
MSNP with Increased Aspect Ratio
[0332] Experiment Reagents. Commercial reagents and analytical
materials used in this study include: tetraethoxysilane (TEOS, 98%,
Aldrich), cetyltrimethylammonium bromide (CTAB, 98%, Aldrich),
perfluorooctanoic acid (PFOA, 96%, Aldrich), methanol (99.9%,
Fisher), triethylamine (99.5%, Aldrich), ethanol (200 proof,
Pharmaco-AAPER), 3-aminopropyltriethoxysilane (APTES, 99%, Gelest),
rhodamine-B-isothiocyanate (RITC, Aldrich), fluorescein
isothiocynate (FITC, >90%, Aldrich), amiloride (Aldrich),
cytochalasin D (Aldrich), sodium azide (NaN.sub.3, Aldrich), and
2-deoxyglucose (2-DG, Aldrich), camptothecin (CPT, 99%, Aldrich),
Taxol (99%, Aldrich). RPMI 1640 cell culture medium,
penicillin/streptomycin, L-glutamine, Alexa 594-phalloidin, and
Hoechst 33342 were purchased from Invitrogen (Carlsbad, Calif.).
Fetal bovine serum (FBS) was from Atlanta Biologicals, Inc
(Lawrenceville, Ga.). Anti-LAMP-1 and anti-GTP-Rac1 antibody were
obtained from Abcam (Cambridge, Mass.) and Cell signaling (Danvers,
Mass.). Anti-total-Rac1, anti-clathrin and anti-caveolin antibodies
were purchased from Santa Cruz Biotechnology (Santa Cruz, Calif.).
Deionized H.sub.2O was obtained from a Millipore water purification
system. Toluene (99.5%) refluxed before use.
[0333] MSNP Synthesis. MSNPs were synthesized via a modified
procedure to yield rod-shaped structures..sup.19 MSNP with
different AR were chemically synthesized by a sol-gel approach
using a surfactant/co-structure direct agent (CSDA) mixture as
template. Different shaped MSNP and AR were synthesized by varying
the PFOA/CTAB molar ratio as follows: MSNP0=0; MSNP1=0.015;
MSNP2=0.03; MSNP3=0.06. The PFOA/CTAB mixture was stirred at 600
rpm for 1 h at room temperature before the addition of 2.1 mL 2 M
NaOH. Subsequently, the solution temperature was raised to
80.degree. C. before the addition of 4.1 mL of TEOS. This mixture
was stirred for an additional 2 h and the precipitate was carefully
collected by filtration. After washing 3 times with methanol and
deionized water, the solids were air dried overnight at room
temperature. The MSNP templates were removed by extracting the CTAB
with HCl containing methanol under nitrogen protection. The
resulting MSNP were collected by filtration, washed by methanol,
and dried overnight in air. Depending on the shape and AR, the
particles were designated MSNP0, MSNP1, MSNP2 and MSNP3 as
explained in Table 6. To visualize the particles under a confocal
microscope or perform flow cytometry, FITC- or RITC-labeled MSNP
were prepared by suspending 200 mg of MSNP in 10 mL of dry toluene
with 3 uL of APTES, followed by the attachment of FITC or RITC in
ethanol. The labeled MSNP were collected by centrifugation and
washed by methanol and water before use.
[0334] Physicochemical Characterization of MSNP. MSNP were
characterized for shape (aspect ratio), surface area, hydrodynamic
size, and zeta potential. The shape and morphology of the MSNP were
characterized by scanning electron microscopy (SEM, JSM-6700F) at
15 kV. The pore structure and aspect ratio were studied by using a
transmission electron microscope, JEM 1200-EX operated at 80 kV.
Microfilms for TEM imaging were obtained by placing a drop of the
respective MSNP suspensions onto a 200-mesh copper TEM grid and
drying at room-temperature overnight. The AR values were determined
by measuring the length and diameter of at least 30 randomly
selected particles. X-ray diffraction (XRD) patterns were recorded
on a Panalytical X'Pert Pro Powder Diffractometer with Ni-filtered
Cu K.alpha. radiation. UV-vis spectra were collected using a Cary
5000 UV-vis-NIR spectrophotometer. For surface area measurement,
N.sub.2 adsorption-desorption isotherms were obtained on a
Quadrasorb SI surface area analyzer and pore size analyzer
(Quantachrome instruments, Florida, USA). The BET model was applied
to evaluate the specific surface areas and the
Barret-Joyner-Halenda (BJH) method was used to calculate the pore
size. Particle hydrodynamic size and zeta potential were measured
in pure water or cell culture medium using a ZetaSizer Nano
(Malvern Instruments Ltd., Worcestershire, UK).
[0335] The morphology of the rods, in comparison to the spherical
particles, is shown in the SEM and TEM images in FIG. 48A. MSNP0
are spheres of .about.110 nm diameter, exhibiting uniform pore
sizes of 2.5 nm and an AR=1 (FIG. 1A). By increasing the
perfluorooctanoic acid (PFOA)/cetyltrimethylammonium bromide (CTAB)
doping ratio during the synthesis, it was possible to obtain
rod-shaped cylinders with dimensions of 110-130/60-80 nm (MSNP1),
160-190/60-90 nm (MSNP2), and 260-300/50-70 nm (MSNP3),
respectively (Table 6). These values were used to calculate the AR,
which varied from 1.5-1.7 (MSNP1), 2.1-2.5 (MSNP2) and 4-4.5
(MSNP3). In spite of differences in the AR, the pore structure and
pore sizes of the rods are similar (FIG. 48 and Table 6). However,
with an increase in the AR of the MSNP from 1 to 4.5, the surface
area of these particles decreased from 1077.9 m.sup.2/g to 760.2
m.sup.2/g (Table 6). Small angle powder XRD (FIG. 48B) analysis
showed 3 well-resolved peaks that can be indexed as the 100, 110
and 200 reflections and confirms the hexagonal symmetry (p6m) of
the pore structure..sup.20 The rod-shaped particles showed
periodical "fringes" along their length (indicated by arrows in
FIG. 48A), which represent the ordered helical hexagonal pore
arrangements as reported in the literature..sup.19, 21, 22
TABLE-US-00006 TABLE 6 Physicochemical characterization of MSNP
Samples MSNP0 MSNP1 MSNP2 MSNP3 Aspect ratio 1~1.2 1.5~1.7 2.1~2.5
4.0~4.5 d.sub.100 (nm) 4 4 4 4 Pore diameter (nm) 2.5 2.5 2.5 2.5
Surface area (m.sup.2/g) 1077.9 926.1 896.9 760.2 Size in H.sub.2O/
219/1036/ 207/723/ 198/902/ 185/1023/ RPMI/CRPMI (nm).sup.a 239 229
337 249 Zeta potential in 15.7/-5.7 17.1/-6.9 13.0/-5.7 13.5/-6.2
H.sub.2O/CRPMI (mV) .sup.aParticle size measurements were performed
using dilute suspensions (100 .mu.g/mL) in water or RPMI at pH 7.4
in a ZetaSizer Nano (Malvern Instruments Ltd., Worcestershire, UK).
To disperse the particles, the stock solutions in water (20 mg/mL)
were sonicated (Tekmar Sonic Disruptor probe) for 15 s before use.
In order to coat the surface of MSNP with FBS, 19 .mu.L of particle
suspension was mixed with 1 .mu.L FBS before addition to complete
medium and sonication for 15 s. RPMI denotes the particle size in
RPMI cell culture medium without serum; CRPMI reflects the size of
MSNP that pre-coated using FBS in complete RPMI containing 10%
FBS.
[0336] To optimize the particle dispersal for purposes of
biological experimentation, the MSNP were suspended in distilled
water containing 5% fetal bovine serum (FBS) and ultimately
transferred into complete RPMI containing 10% FBS..sup.13 Not only
does this sequence of particle suspension prevent agglomeration due
to culture medium ionic effects but also adjusts the particles'
zeta potentials from positive to negative as a result of protein
adsorption (Table 6).
[0337] MSNP Dispersion and Use to Perform Tissue Culture. All cell
cultures were maintained in 75 cm.sup.2 cell culture flasks in
which the cells were passaged at 70-80% confluency every 2-3 days.
The human cervical (Hela) and lung cancer (A549) cells were
cultured in RPMI 1640 containing 10% FBS, 100 U/mL penicillin, 100
.mu.g/mL streptomycin, and 2 mM L-glutamine (complete RPMI medium).
To disperse MSNP in cell culture medium, the water stock solution
was sonicated (Tekmar Sonic Disruptor probe) for 10 s before use.
In order to coat the surface of MSNP with FBS, 19 .mu.L MSNP
suspension was mixed with 1 .mu.L FBS. Complete cell culture media
was then added to the serum-coated MSNP suspension.
[0338] Assessment of cellular MSNP uptake by flow cytometry and
confocal microscopy. For the performance of flow cytometry,
aliquots of 1.times.10.sup.5 cells (Hela & A549 cells) were
cultured in 12-well plates in 1 mL medium. RITC-labeled spherical
MSNP were added to the above cultures at 20 .mu.g/mL for 1 h,
washed carefully in PBS and then incubated with different
FITC-labeled MSNP at 20 .mu.g/mL for 6 h. The purpose of prior
incubation with the RITC-labeled spheres is to demonstrate that
cells can distinguish between a spherical shape and a rod-shaped
particle. All cell types were trypsinized and washed in PBS for 3
times. Cells were analyzed in a SCAN flow cytometer using mean FL-2
and FL-1 to assess RITC and FITC fluorescence, respectively. Data
are reported as fold increase in mean fluorescence intensity (MFI),
using MSNP0 uptake as reference.
[0339] For the confocal studies, cellular uptake of the spheres and
different AR particles was performed by adding 20 .mu.g/mL
FITC-labeled particles to 8-well chamber slides. Each well
contained 5.times.10.sup.4 cells in 0.5 mL culture medium. Cell
membranes were co-stained with 5 .mu.g/mL Alexa Fluor
633-conjugated wheat germ agglutinin (WGA) in PBS for 30 min.
Slides were mounted with Hoechst 33342 and visualized under a
confocal microscope (Leica Confocal 1P/FCS) in the UCLA/CNSI
Advanced Light Microscopy/Spectroscopy Shared Facility. High
magnification images were obtained with the 100.times.
objective.
[0340] AR influences cellular uptake of MSNPs in Hela cells and
A549 cells. Previous publications have shown that a non-spherical
shape enhances the abundance and rate of cellular uptake of
nanoparticles..sup.1, 3, 6, 23 In order to assess cellular uptake
of FITC-labeled MSNP in Hela cells and A549 cell line, a
combination of flow cytometry and confocal microscopy was used. The
fluorescence labeling efficiency is similar for all particle
surfaces, allowing us to compare the uptake abundance directly
(FIG. 53). Compared to spherical particles (MSNP0), there was a
significant increase in the mean fluorescence intensity (MFI) of
cells exposed to rod-shaped particles (FIG. 49A). This amounted to
an 18-, 40- and 8-fold increase of the MFI for MSNP1, MSNP2 and
MSNP3, respectively. Interestingly, the cellular association of
MSNP2 was consistently increased compared to MSNP1 or MSNP3,
suggesting that the intermediary AR is preferred for cellular
uptake. The preference for a rod vs. a spherical shape was further
confirmed by comparing FITC-labeled materials with RITC-labeled
spheres (FIG. 49A). While all the cell populations internalized the
RITC-labeled spheres to the same degree, there was a definitive
increase in the uptake of the FITC-labeled rods in proportion to
the ratios cited above.
[0341] The flow data was confirmed by confocal images showing
higher uptake of FITC-labeled rods compared to the FITC-labeled
spheres (FIG. 49B). Moreover, among the rods, the particles with an
AR of 2.1-2.5 were endocytosed to greater abundance (FIG. 49B) and
at more rapid rate compared to MSNP1 and MSNP3 (FIG. 49C).
Moreover, MSNP2 appeared to localize predominantly in the
perinuclear region of Hela cells whereas MSNP1 and MSNP3 were more
randomly distributed (FIG. 49B).
[0342] To further confirm that the impact of AR is not unique to
Hela cells, the experiments were repeated in the A549 lung cancer
cell line (FIG. 54). Consistent with the Hela data, MSNP2 yielded
the highest cellular uptake compared to spheres or longer/shorter
rods (FIG. 54).
[0343] Transmission electron microscopy of MSNP treated cells. Hela
cells were treated with each of the MSNP variants at 20 .mu.g/mL
for 3 h. The cells were washed in PBS and immediately fixed with
2.5% glutaraldehyde in PBS. After secondary fixation in 1%
OsO.sub.4 in PBS, the cells were dehydrated in a graded ethanol
series, treated with propylene oxide, and embedded in resin.
Approximately 60-70 nm thick sections were cut on a Leica
ultramicrotome and picked up on formvar-coated copper grids. The
sections were examined in a CM120 electron microscope
(Philips).
[0344] Electron tomography. TEM grids were used for the tomography
imaging on an FEI Tecnai F20 microscope operated at 200 kV. Tilt
series were acquired by tilting the specimen from -70.degree. to
70.degree. at 1.degree. increments and with a TIETZ F415MP 16
megapixel CCD camera at a magnification of 26,600.times. and then
aligned using the ETOMO program in the IMOD package..sup.63 The
aligned tilt series were then further processed using the
reconstruction Inspect3D program from FEI, with the SIRT option, to
improve reconstruction accuracy and contrast. 3D movies of the
aligned tilt series were generated using both Inspect3d and Windows
movie maker. Visualization of 3D tomographic reconstructions were
performed using 3DMOD of IMOD.sup.63 and Amira
(http://www.amira.com/).
[0345] F-actin staining and filopodia counting. Hela cells were
seeded into 8-well chamber slides and incubated with or without
MSNP at a concentration of 20 .mu.g/mL for 6 h. Cells were washed 3
times in PBS, fixed with 3.7% formaldehyde for 30 min, and
permeabilized with 0.25% Triton X-100 for 10 min. For F-actin
staining, cells were incubated with Alex 594 phalloidin in the dark
for 30 min at room temperature. The slides were viewed using a
confocal microscope equipped with a 100.times. oil-immersion
objective. The average number of filopodia per cell as determined
by actin fiber staining was calculated by counting at least 20
randomly selected cells in each exposure category..sup.29 After
filopodia counting, two-sided Student's t test was performed to
determine whether there was a statistically significant
difference..sup.29
[0346] Drug and temperature inhibition studies. Hela cells were
seeded in a 12-wells plate at the density of 1.times.10.sup.5 per
well. The cells were pre-cultured in serum free RPMI 1640 medium
containing amiloride (75 .mu.M), Cyto D (2.5 .mu.g/mL), or 0.1%
NaN.sub.3/50 mM 2-DG for 3 h. Alternatively, cells were placed at
4.degree. C. After 3 h pretreatment, the media was exchanged into
fresh complete RPMI 1640 that contained 20 .mu.g/mL FITC-labeled
MSNP2, one of the chemical inhibitors (amiloride, Cyto D or
NaN.sub.3/2-DG), and 10% FBS. To observe a temperature effect, the
cellular incubation with particles was carried out at 4.degree. C.
for 6 h. Following a 6 h incubation period, the cells were washed
with PBS and then processed for flow cytometry as described above.
The filopodia counting was performed by confocal microscopy as
described above.
[0347] MSNP2 uptake requires cytoskeleton activation and filopodia
formation. Electron microscopy (EM) was used for ultrastructural
resolution of the route of MSNP uptake in Hela cells (FIG. 50).
Although Hela cells are capable of endocytosing nanoparticles by
various routes,.sup.1, 24 MSNPs were taken up by a process of
macropinocytosis as evidenced by the presence of filopodia and
formation of macropinocytotic vesicles (FIG. 50A)..sup.25
Noteworthy, the number of filopodia and extent of membrane ruffling
were dramatically enhanced in cells exposed to MSNP2 compared to
cells exposed to MSNP3 (FIG. 50A) or MSNP1 (not shown). More
detailed TEM images of MSNP2 macropinocytosis are shown in FIG. 55
together with electron tomography and 3D image reconstruction
(FIGS. 56 and 60). Electron tomography was powerful enough to
capture the porous structure of the particles inside the cells, an
ultrastructural feature that has not previously been accomplished
previously.
[0348] Since macropinocytosis and filopodia formation is dependent
on actin assembly at the surface membrane,.sup.26-28 Alexa
594-phalloidin staining was performed to visualize these
cytoskeletal changes. The confocal images demonstrate that compared
to spheres or shorter and longer rods, MSNP2 induced the most
prominent changes in actin polymerization in Hela cells (FIG. 50B).
Scoring of the number of filopodia by a technique previously
published in the literature.sup.29 (and explained in the legend of
FIG. 50C), demonstrated a 7-fold increase in filopodia number in
cells treated with MSNP2 compared to MSNP0, MSNP1 and MSNP3 (FIG.
50C). In addition, the actin assembly in response to MSNP2 was
sustained for at least 6 h compared to the transient effects seen
with stimuli such as epidermal growth factor..sup.26
[0349] Chemical inhibitors are widely used to confirm the
occurrence of macropinocytosis and as a means of distinguishing
this uptake mechanism from clathrin- and caveolae-mediated
uptake..sup.26, 30 Prior cellular treatment with amiloride.sup.26
as well as the cytoskeletal inhibitor cytochalasin D (Cyto
D).sup.1, 31 decreased MSNP2 uptake by >50% (FIG. 50D). These
agents also interfered in MSNP-induced filopodia formation (FIG.
50E). The energy dependence of the macropinocytosis pathway was
confirmed by culturing the cells at 4.degree. C..sup.32 or
pretreating them with sodium azide (NaN.sub.3)/2-deoxyglucose
(2-DG) for 3 h before the addition of the particles (FIG.
50D)..sup.1 All of the above inhibitors also decreased filopodia
formation and MSNP uptake by >60% (FIG. 50E).
[0350] To study the subcellular fate of endocytosed MSNP2, confocal
microscopy was used to localize FITC-labeled MSNP2 in relation to
clathrin-coated vesicles, caveolae and lysosomes in Hela cells
(FIG. 57)..sup.33 These endocytotic compartments were localized by
RITC-labeled secondary antibodies capable of binding to primary
antibodies recognizing clathrin, caveolin-1 and LAMP-1,
respectively. Image J software analysis to quantify FITC-labeled
MSNP2 colocalization with labeled compartments showed that while
<1% of these rods were localized in clathrin or caveolin-1
stained compartments (FIG. 57, upper panel), more MSNP2 entered a
LAMP-1 positive compartment (FIG. 57, lower panel). Thus, while
<5% of the particles entered the LAMP-1 positive compartment by
6 h, this fraction increased to 75% by 36 h. All considered, these
data indicate that MSNP2 are primarily taken up by macropinocytosis
and ultimately shuttled into an acidifying endosomes that
specialize in particle degradation. Interestingly, the MSNP-laden
lysosomes could be seen to change their localization from a random
to a clustered arrangement in the cell (FIG. 57, bottom right
panel). The significance of this redistribution is uncertain.
[0351] Assessment of cellular Rac1 activation. To study Rac1
activation, Hela cells were serum-starved for 4 h before
introduction of the particles that were dispersed in RPMI
containing 10% FBS. Cells were incubated with the particles for 30
min at a concentration of 20 .mu.g/mL. Because FBS may also
contribute to Rac1 activation due to the presence of growth
factors, it was necessary to include a control where serum starved
cells were exposed to complete RPMI for 30 min to allow adjustment
for any possible Rac1 activation due to the complete medium. After
fixation and permeabilization, cells were stained with antibodies
recognizing the activated, GTP-bound form of Rac1 or total Rac1
protein..sup.35-37 The primary antibodies were detected by
secondary antibodies conjugated to Alexa 594 or FITC, respectively.
Nuclei were stained by Hoechst 33342. The Alexa 594 fluorescence
intensity as a measure of Rac1 activation was determined by Image J
software. The fluorescence intensity of control cells incubated in
serum-containing medium for 30 min was chosen as reference with
fluorescent intensity=1. The fluorescence intensity of cells
treated with the various MSNPs was then expressed as the
fold-increase compared to this control value. The experiment was
repeated in presence of amiloride, Cyto D, NaN.sub.3/2-DG as well
as 4.degree. C. as described above.
[0352] MSNP2 promotes active macropinocytosis through Rac1
activation. Macropinocytosis is frequently initiated by external
stimuli, such as viruses.sup.25 or growth factors.sup.34 capable of
activating membrane-associated signaling cascades that play a role
in actin polymerization and plasma membrane ruffling..sup.26, 30
One of the signaling mechanisms involves the activation of the
GTP-binding protein, Rac1, which plays a role in membrane ruffling,
cytoskeletal changes and closure of macropinosome..sup.26, 30 In
order to see if Rac1 is activated during MSNP macropinocytosis, an
immunochemical technique was used that distinguishes activated,
GTP-bound Rac1 from total cellular Rac1 protein..sup.35-37 This was
accomplished by using a secondary Alexa 594-conjugated antibody
that recognizes anti-GTP-Rac1 as well as a FITC-labeled secondary
antibody that binds to a framework site in Rac1..sup.35-37 Use of
these antibody pairs for confocal studies in Hela cells showed more
intense Rac1 activation (red fluorescence) in cells treated with
MSNP2 compared to cells exposed to MSNP0, MSNP1 or MSNP3 (FIG. 51).
In contrast, the total Rac1 abundance (green fluorescence) remained
the same across the cell populations. Use of Image J software to
calculate the increase in Alexa 594 fluorescence demonstrated an
approximately 4-fold increase in abundance of activated Rac1
following MSNP2 treatment (FIG. 51B). Longer and shorter rods
induced less prominent Rac1 activation (FIG. 51B). These response
differences were sustained for at least 30 minutes. Noteworthy,
Rac1 activation was suppressed in MSNP2-exposed cells treated with
amiloride, NaN.sub.3/2-DG, or cultured at 4.degree. C. (FIG. 58).
In contrast, Cyto D, which functions downstream of Rac1, had no
significant effect (FIG. 58).
[0353] Drug loading and loading capacity measurement. Two
hydrophobic anticancer drugs, Taxol and camptothecin (CPT), were
loaded into different MSNP using 20 mg of each type of particles
suspended into a solution containing 0.5 mg of each drug in 1 mL
DMSO. After 24 h, the particles were collected by centrifugation,
and the trace amounts of DMSO were removed by drying under vacuum.
The drug-laden particles were washed and stored as an aqueous stock
solution at 20 mg/mL. To measure the loading capacity of the
particles, they were resuspended in methanol and thoroughly
sonicated to remove the drug from the pores. After centrifugation
and removal of the supernatant, the process was repeated 3 times to
elute all drug. The supernatants were combined and the amount of
free drug calculated using Taxol absorbance at 229 nm and the CPT
fluorescence at excitation and emission wavelengths of 370 and 448
nm, respectively, in a microplate reader (SpectraMax M5 Microplate
Reader, Molecular Device, USA).
[0354] Assessment of Hela cytotoxicity in response to treatment
with drug loaded particles. Hela cells were plated at
1.times.10.sup.4 cells per well in 96 well plates. MSNP, loaded
with CPT or Taxol, were incubated with the cells to deliver CPT
concentrations of 0.1-8.0 .mu.g/mL and Taxol concentrations of
0.1-2.0 .mu.g/mL for 36 h. The effect of the MSNP-bound drug was
compared to similar amounts of free drug delivered in PBS or
DMSO/PBS. A MTS assay was performed 36 h after drug and particle
exposure to assess cellular viability as previous described by
us..sup.13
[0355] Statistical analysis. Data represent the mean.+-.SD for
duplicate or triplicate measurements in each experiment.
Differences between the mean values were analyzed by two-sided
Student's t test or one way ANVOA. All experiments were repeated at
least twice.
[0356] Delivery of hydrophobic chemotherapeutic agents by long AR
particles. Due to the ordered porous structure and large surface
area capable of cargo loading, MSNPs have emerged as a
multifunctional drug delivery platform..sup.11-15, 38 In light of
the facilitated cellular uptake of MSNP2, the cytotoxic effects of
two hydrophobic chemotherapeutic agents, camptothecin (CPT) and
paclitaxel (Taxol) were compared, delivered by spherical and long
AR particles. The drugs were loaded into the particles by a phase
transition approach that was previously developed..sup.11-13
Particle-mediated drug delivery was compared against the free drugs
(dissolved in PBS alone or PBS supplemented with 0.1% DMSO), using
a MTS assay. Use of this assay to compare equivalent amounts of
drugs being delivered over a 36 h time period demonstrated that the
cytotoxic potential of drug-laden
MSNP2>MSNP1>MSNP3>MSNP0.apprxeq.drugs delivered by
PBS/DMSO>>drugs delivered by PBS (FIG. 52). Notice that the
particle themselves were devoid of toxicity as shown in FIG.
59.
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[0420] The embodiments illustrated and discussed in this
specification are intended only to teach those skilled in the art
the best way known to the inventors to make and use the invention.
Figures are not drawn to scale. In describing embodiments of the
invention, specific terminology is employed for the sake of
clarity. However, the invention is not intended to be limited to
the specific terminology so selected. The above-described
embodiments of the invention may be modified or varied, without
departing from the invention, as appreciated by those skilled in
the art in light of the above teachings. It is therefore to be
understood that, within the scope of the claims and their
equivalents, the invention may be practiced otherwise than as
specifically described.
* * * * *
References