U.S. patent application number 12/984165 was filed with the patent office on 2011-04-28 for flexible drug delivery chip, its fabrication method and uses thereof.
This patent application is currently assigned to NATIONAL CHIAO TUNG UNIVERSITY. Invention is credited to San-Yuan Chen, Wei-Chen Huang, Dean-Mo Liu.
Application Number | 20110094885 12/984165 |
Document ID | / |
Family ID | 43647955 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094885 |
Kind Code |
A1 |
Chen; San-Yuan ; et
al. |
April 28, 2011 |
Flexible Drug Delivery Chip, its Fabrication Method and Uses
Thereof
Abstract
Nanodevice and method for in vivo monitoring and release of
drugs are provided. The disclosed nanodevice is characterized in
having a drug-loaded nanosphere that is capable of releasing the
encapsulated drugs upon magnetically stimulation. The nanodevice
may also be used as a contrast agent for in vivo imaging and
monitoring the concentration and distribution of the released drugs
and/or active compounds injected separately into a target site of a
subject.
Inventors: |
Chen; San-Yuan; (Hsinchu
City, TW) ; Huang; Wei-Chen; (Jhongli City, TW)
; Liu; Dean-Mo; (Jhubei City, TW) |
Assignee: |
NATIONAL CHIAO TUNG
UNIVERSITY
Hsinchu
TW
|
Family ID: |
43647955 |
Appl. No.: |
12/984165 |
Filed: |
January 4, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12554935 |
Sep 7, 2009 |
|
|
|
12984165 |
|
|
|
|
Current U.S.
Class: |
204/486 |
Current CPC
Class: |
A61K 9/0009 20130101;
C25D 13/04 20130101; C25D 13/14 20130101; A61K 31/4015 20130101;
A61M 37/00 20130101; A61K 9/0024 20130101; A61P 25/08 20180101 |
Class at
Publication: |
204/486 |
International
Class: |
C25D 15/00 20060101
C25D015/00 |
Claims
1. A method of fabricating a drug-containing cell, comprising:
providing a flexible substrate; constructing a drug-containing
reservoir by forming a plurality of side walls on the flexible
substrate to define a drug-containing volume thereon, wherein at
least one side of the drug-containing volume is not sealed by the
plurality of side walls; electrophoretically depositing a first
layer of drug-containing nanoparticles on the flexible substrate in
the drug-containing volume, forming a layer of metal on the first
layer of drug-containing nanoparticles by sputter deposition; and
electrophoretically depositing a second layer of drug-containing
nanoparticles on the metal layer.
2. The method of claim 1, wherein the electrophoretic deposition is
performed by steps of: providing an electrophoretic deposition
cell, which comprises: a colloidal suspension containing about
0.01-30% by weight of drug-containing nanoparticles; and a pair of
electrodes; immersing the flexible substrate having constructed
thereon the drug-containing reservoir in the colloidal suspension
in the electrophoretic deposition cell; and applying a voltage of
about 1-50 V to the pair of electrodes for a period of about 1-30
min or until the layer of drug-containing nanoparticles has a
thickness of at least 0.1 .mu.m.
3. The method of claim 2, wherein the colloidal suspension is
prepared by suspending the drug-containing nanoparticles in a
diluting medium selected from the group consisting of water, a
C.sub.1-6 alcohol, glycol, glycerin, dimethyl sulfoxide and a
combination thereof.
4. The method of claim 1, wherein a gap of about 0.5 cm to about 5
cm is formed between the pair of electrodes.
5. The method of claim 1, wherein the electrophoretic deposition is
carried out at a temperature ranges from about -10.degree. C. to
about 70.degree. C.
6. The method of claim 1, wherein the metal is selected form the
group consisting of Au, Ag, Pt, and Ta.
7. The method of claim 1, wherein the plurality of side walls are
made of a biocompatible material that is selected from the group
consisting of collagen, polyvinylchloride (PVC), polylactide,
polyethylene glycol, polycaprolactone (PCL), polycolide,
polydioxanone, and derivatives and copolymers thereof.
8. The method of claim 1, wherein the flexible substrate is made of
a material selected from the group consisting of polyethylene
terephthalate (PET), polyethylene, ethylene-vinyl acetate,
polyimides, polyamides, polyethylene naphthalate (PEN), polyimide
(PI) and polyaryletheretherketone (PEEK).
9. The method of claim 1, wherein each of the drug-containing
nanoparticles comprises a magnetic iron oxide-containing core and a
silicon dioxide shell, and a drug is encapsulated within the
magnetic iron oxide-containing core.
10. The method of claim 9, wherein the drug is ethosuximide.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional of U.S. application
Ser. No. 12/554,935, filed on Sep. 7, 2009, the full disclosure of
which is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] This disclosure is generally in the field of implantable
drug delivery devices, and more particularly in the field of
devices for the controlled release of a drug from a device
implantable in a body lumen or cavity, the method for fabricating
such device and uses thereof.
[0004] 2. Description of Related Art
[0005] Medication can be delivered to a patient through a variety
of methods, including oral ingestion, inhalation, transdermal
diffusion, subcutaneous and intramuscular injection, parenteral
administration and implants. Oral drug delivery remains the most
preferred way of administration of a medication. However, many
current drug delivery products such as oral capsules and tablets
possess drawbacks such as limited effectiveness on controlled drug
delivery that results in too rapid and incomplete absorption of the
drug, irritation of the gastrointestinal tract and other side
effects. Further, they may not provide localized therapy, and/or
real time monitoring of the distribution of the released drug.
Accordingly, a variety of devices and methods have been developed
to deliver drug in a more targeted manner.
[0006] The microdevices for local drug delivery are developed in
response to such need and they may address many of the problems
associated with systemic drug delivery. Activation of the drug
release may be passively or actively controlled. Examples of
controlled drug delivery devices are disclosed in U.S. Pat. No.
6,808,522 and U.S. Pat. No. 6,875,208. Implantable device is
particularly useful for the treatment of some maladies that are
difficult to treat with currently available therapies and/or
require administration of drugs to anatomical regions to which
access is difficult to achieve. One example is cancer, where large
dose of highly toxic chemotherapeutic agents such as rapamycin,
irinotecan (CPT-11) are typically administered to the patient
intravenously, which may result in numerous undesired side effects
outside the targeted area.
[0007] Thus, there is an increasing need of an improved implantable
drug delivery system and/or device with improved in vivo
adaptability and may deliver medication to targeted area with high
efficiently and fewer side effects.
[0008] This invention designs, manufactures, and employs a novel
implantable drug delivery chip that can be actively and remotely
released by proper stimulation at a desired body portion of a
subject without inducing any undesired side effects.
SUMMARY
[0009] This disclosure relates to a flexible drug delivery chip, a
method for fabricating the same and uses thereof. The flexible drug
delivery chip is fabricated by using electrophoretic deposition of
drug-loaded magnetic core-shell (i.e., Fe.sub.3O.sub.4@SiO.sub.2)
nanoparticles onto an electrically conductive flexible substrate.
The flexible drug delivery chip is suitable for in vivo
implantation into a body portion of a subject and being
magnetically activated to release drug from the magnetic core-shell
nanoparticles in a controlled manner in accordance with the
strength and/or duration of an external applied magnetic field. The
flexible chip offers advantages over conventional drug delivery
devices by improving dosing precision, ease of operation, wider
versatility of elution pattern and better compliance.
[0010] It is therefore a first aspect of this disclosure to provide
a drug-containing cell, which is a building block for constructing
the flexible drug delivery chip. The drug-containing cell includes
a flexible substrate and a drug-containing reservoir. The
drug-containing reservoir is formed on the flexible substrate and
further includes a plurality of side walls defining a
drug-containing volume, wherein at least one side of the
drug-containing volume is not sealed by the plurality of side
walls; a first layer of drug-containing nanoparticles deposited on
the flexible substrate in the drug-containing volume; a layer of
metal deposited on the first layer of drug-containing
nanoparticles; and a second layer of drug-containing nanoparticles
deposited on the metal layer. In one embodiment, the
drug-containing cell comprises two metal layers with each metal
layer being sandwiched between two layers of drug-containing
nanoparticles.
[0011] In one example, the plurality of side walls are made of a
biocompatible material selected from the group consisting of
polyvinylchloride (PVC), polylactide, polyethylene, ethylene-vinyl
acetate, polyimides, polyamides, polyethylene glycol,
polycaprolactone (PCL), polycolide, polydioxanone, and derivatives
and copolymers thereof. The flexible substrate is made of a
material selected from the group consisting of polyethylene
terephthalate (PET), poly (vinyl chloride) (PVC), polyethylene
naphthalate (PEN), polyimide (PI) and polyaryletheretherketone
(PEEK). Each of the drug-containing nanoparticles comprises a
magnetic iron oxide-containing core and a silicon dioxide shell,
and the drug is encapsulated within the magnetic iron
oxide-containing core. In one example, the drug is an antieleptic
agent. The metal is selected form the group consisting of Au, Ag,
Pt, and Ta. In one example, the metal is Au.
[0012] In a second aspect of this disclosure, there provides a
method of fabricating a drug-containing cell. The method includes
steps of: providing a flexible substrate; constructing a
drug-containing reservoir by forming a plurality of side walls on
the flexible substrate to define a drug-containing volume, wherein
at least one side of the drug-containing volume is not sealed by
the plurality of side walls; electrophoretically depositing a first
layer of drug-containing nanoparticles on the flexible substrate in
the drug-containing volume, forming a layer of metal on the first
layer of drug-containing nanoparticles by sputter deposition; and
electrophoretically depositing a second layer of drug-containing
nanoparticles on the metal layer.
[0013] In one example, electrophoretic deposition is performed by
steps of: (1) providing an electrophoretic deposition cell, which
comprises: a colloidal suspension containing about 0.01-30% by
weight of drug-containing nanoparticles; and a pair of electrodes;
(2) immersing the flexible substrate having constructed thereon the
drug-containing reservoir in the colloidal suspension in the
electrophoretic deposition cell; and (3) applying a voltage of
about 1-50 V to the pair of electrodes for a period of about 1-30
min or until the layer of drug-containing nanoparticles has a
thickness of at least 0.1 .mu.m. The colloidal suspension is
prepared by suspending the drug-containing nanoparticles in a
diluting medium selected from the group consisting of water, a
C.sub.1-6 alcohol, glycol, glycerin, dimethyl sulfoxide and a
combination thereof. Each electrode of the pair of electrodes in
the electrophoretic deposition cell is spaced apart from each other
for a distance of about 0.5 cm to about 5 cm. The electrophoretic
deposition is carried out at a temperature ranges from about
-10.degree. C. to about 70.degree. C.
[0014] In another example, the sputter deposition is any of
ion-beam sputtering, reactive sputtering, ion-assisted deposition,
high power impulse magnetron sputtering (HIPIMS) or gas flow
sputtering. The metal is selected form the group consisting of Au,
Ag, Pt, and Ta. In one example, the metal is Au.
[0015] In a third aspect of this disclosure, there provides a
flexible drug delivery chip, which is composed of two
drug-containing cells of this disclosure arranged in a head-to-head
configuration so as to form a drug-releasing chamber. Each of the
two drug-containing cells is characterized in having one metal
layer sandwiched between two layers of drug-containing
nanoparticles. The drug-releasing chamber is characterized in
having one side of the chamber being exposed to the surrounding
environment thereby providing an outlet for drug elution. In one
example, the drug encapsulated within each of the nanoparticles is
controlled released from the drug-releasing chamber by applying an
external magnetic field with a power from about 0.05 kA/m to 2.5
kA/m for a period of about 10 sec to 180 sec. The flexible drug
delivery chip has a thickness of no more than 0.5 mm.
[0016] These and other features, aspects, and advantages of the
present invention will become better understood with reference to
the following description and appended claims.
[0017] It is to be understood that both the foregoing general
description and the following detailed description directed to the
uses and application of such nanodevice are not strictly limited to
the ranges described in those examples, and are intended to provide
further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The file of this patent contains at least one drawing
executed in color. Copies of this patent with color drawing(s) will
be provided by the Patent and Trademark Office upon request and
payment of the necessary fee.
[0019] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0020] FIG. 1(a) is a schematic diagram of a drug-containing cell
in accordance with one example of this disclosure;
[0021] FIG. 1(b) is the schematic cross-sectional view of the
drug-containing cell of FIG. 1(a);
[0022] FIG. 2 is a flow chart detailing steps for forming the
drug-containing cell of FIG. 1 in accordance with one particular
embodiment of this disclosure;
[0023] FIG. 3(a) is a schematic diagram illustrating the
drug-delivery chip constructed from two drug-containing cells of
FIG. 1 in accordance with one particular embodiment of this
disclosure;
[0024] FIG. 3(b) illustrates the mechanical flexibility exhibited
by the drug-delivery chip of FIG. 3(a);
[0025] FIG. 4 illustrates high resolution transmission electron
microscopy (HRTEM) photographs of Fe.sub.3O.sub.4@SiO.sub.2
nanoparticles prepared in accordance with one embodiment of this
disclosure;
[0026] FIG. 5 illustrates Fourier Transform Infrared Spectroscopy
spectra of Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles, ESM, and
ESM-loaded nanoparticles in accordance with one embodiment of this
disclosure;
[0027] FIG. 6 illustrates drug release profiles for the ESM-loaded
nanoparticles in accordance with one embodiment of this
disclosure;
[0028] FIG. 7 is SEM image at higher magnification reveals a
structurally uniform and nonporous morphology of the coating on the
substrate in accordance with one embodiment of this disclosure;
[0029] FIG. 8 illustrates ESM release profiles of the flexible chip
of Example 2 under continuous stimulation of different magnetic
field strengths in accordance with one embodiment of this
disclosure;
[0030] FIG. 9 illustrates drug release profiles of the flexible
chip of Example 2 under the various conditions of magnetic
induction in accordance with one embodiment of this disclosure;
[0031] FIG. 10 illustrate representative examples of spontaneous
SWDs under intraperitoneal administration of saline, ethosuximide
(ESM) (28 mg/kg, i.p.), ESM with the ESM-loaded nanoparticles
(ESM-Fe.sub.3O.sub.4@SiO.sub.2) (40 mg/kg, i.p.), and ESM
containing chip (ESM-chip) (ca. 40 mg/kg, intraperitoneal
implantation) in accordance with one embodiment of this disclosure;
and
[0032] FIG. 11 illustrates comparison of SWD number and total SWD
duration with saline and 3 different forms of ESM in Long-Evans
rats with spontaneous SWDs (n=8), in which (A) illustrates ESM (0.5
ml, 28 mg/kg, i.p.) significantly decreased SWD number and total
SWD duration, (B) illustrates ESM loaded nanoparticles
(ESM-Fe.sub.3O.sub.4@SiO.sub.2) (40 mg/kg, i.p.) significantly
reduced SWD number and total SWD duration, and (C) illustrates
ESM-Chip (ca. 40 mg/kg, intraperitoneal implantation) significantly
reduced SWD number and total SWD duration. * P<0.01; **
P<0.001.
DETAIL DESCRIPTION OF THE DISCLOSURE
[0033] Reference will now be made in detail to the present
embodiments of the invention, examples of which are illustrated in
the accompanying drawings.
[0034] Described below is a flexible drug delivery chip for in vivo
magnetically controlled drug release, its fabrication method and
uses thereof. The novel flexible drug delivery chip may be
implanted into a desired body portion of a subject and may be
actively and remotely controlled to release encapsulated drug to
the implant site, such as the arm or any other suitable body
portion of a subject, such as a human.
The Fabrication of a Drug-Containing Cell
[0035] Referring to FIG. 1a, which is a schematic diagram of a
drug-containing cell 100. The drug-containing cell 100 is a
building block for constructing a flexible drug delivery chip of
this disclosure. The drug-containing cell 100 is characterized in
having a ".cndot." shape drug-containing reservoir 110 defined by a
plurality of side walls 120 formed on three sides of a flexible
substrate 130 and thereby further defining a drug-containing volume
140 characterized in having at least one side not sealed by the
plurality of side walls 120. Referring to FIG. 1(b), which is a
front cross-sectional view of the drug-containing reservoir 110 of
FIG. 1(a), multiple layers are deposited in sequence within the
drug-containing volume 140, including from bottom to top: a first
layer of drug-containing nanoparticles 150, a metal layer 160, and
a second layer of drug-containing nanoparticles 150.
[0036] In an alternative embodiment, the drug-containing reservoir
110 may have two sides, instead of one side, not sealed by the
plurality of side walls 120 and thereby is characterized in having
an "L" shape or other suitable shape. In the case when the
drug-containing reservoir 110 is in "L" shape, two adjacent sides
of the reservoir 110 remain exposed to the surrounding environment,
thereby forming two outlets for drugs to be released from two
directions that are orthogonal to each other.
[0037] The flexible substrate for use in this disclosure is
generally made of a material selected from the group consisting of
polyethylene terephthalate (PET), poly (vinyl chloride) (PVC),
polyethylene naphthalate (PEN), polyimide (PI) and
polyaryletheretherketone (PEEK). In one example, the flexible
substrate 14 is made of PET. The plurality of side walls 120 are
typically formed from a biocompatible material, which includes, but
is not limited to, polyvinylchloride (PVC), polylactide,
polyethylene, ethylene-vinyl acetate, polyimides, polyamides,
polyethylene glycol, polycaprolactone (PCL), polycolide,
polydioxanone, and derivatives and/or copolymers thereof. In one
example, the plurality of side walls 16 is made of PVC.
[0038] Each of the drug-containing nanoparticles is characterized
in having a magnetic iron oxide-containing core and a silicon
dioxide shell (e.g., Fe.sub.3O.sub.4@SiO.sub.2), with the drug
being encapsulated within the magnetic iron oxide-containing core.
The drug-containing Fe.sub.3O.sub.4@SiO.sub.2nanoparticles may be
prepared by a method described previously (Hu et al., J. Nanosci.
Nanotechnol (2009) 9(2):866-870). In general, each of the
nanoparticles has an average diameter of about 10 nm to 100 nm,
such as about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40,
50, 60, 70, 80, 90 or 100 nm.
[0039] The term "drug" or "biologically active substance" may be
used interchangeably herein, and refers to a compound or
composition useful for the treatment and/or prevention of
conditions in a variety of therapeutic areas and can be
administered to a living organism, especially animals such as
mammals, particularly humans. The drug useful herein includes, but
is not limited to, nucleic acids such as DNA or small interference
RNA (siRNA); peptides; proteins such as bovine serum albumin,
glycoproteins or collagens; antibiotics; antioxidants such as
vitamin E or vitamin C (i.e., ascorbic acid); immunogenic
preparations such as a vaccine preparation; an anti-epileptic
agent, such as acetazolamide, carbamazepine, clobazam, clonazepam,
diazepam, ethosuximide (ESM), ethotoin, felbamate, fosphenytoin,
gabapentin, lamotrigine, levetiracetam, mephenytoin, metharbital,
methsuximide, methazolamide, oxcarbazepine, phenobarbital,
phenytoin, phensuximide, pregabalin, primidone, sodium valproate,
stiripentol, tiagabine, topiramate, trimethadione, valproic acid,
vigabatrin or zonisamide; an anti-tumor agent such as rapamycin,
taxol, camptothecin (CPT), topotecan (TPT) or irinotecan (CPT-11);
an anti-bacterial agent such as zinc oxide or quaternary ammonium
compounds; an anti-viral agent such as acyclovir, ribavirin,
zanamivir, oseltamivir, zidovudine or lamivudine; an
anti-proliferative agent such as actinomycin, doxorubicin,
daunorubicin, valrubicine, idarubicin, epirubicin, bleomycin,
plicamycin or mitomycin; an anti-inflammatory agent such as
orticosteroids, ibuprofen, methotrexate, aspirin, salicyclic acid,
diphenyhydramine, naproxen, phenylbutazone, indomethacin or
ketoprofen; an anti-diabetic agent, which includes sulfonylureas
such as tolbutamide, acetohexamide, tolazamide, chlorpropamide,
glipizide, glyburide, glimepiride or gliclazide; meglitinides such
as repaglinide or nateglinide; biguanides such as metformin,
phenformin, or buformin; thiazolidinediones such as rosiglitazone,
pioglitazone or troglitazone; alpha-glucosidase inhibitors such as
miglitol or acarbose; peptide analogs such as exenatide,
liraglutide, taspoglatide, vildagliptin, sitagliptin or
pramlintide; and a hormone such as insulin, epidermal growth factor
(EGF), and steroids such as progesterone, estrogen, corticosteroids
and androgens. In one example, the drug is an antieleptic agent,
such as ethosuximide (ESM). Suitable amount of drug that may be
encapsulated with the magnetic iron oxide-containing core must be
determined empirically. According to one embodiment of this
disclosure, the amount of drug in each nanoparticle ranges from
about 0.01% to 80% (wt %), such as 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2,
5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45,
48, 50, 52, 55, 58, 60, 62, 65, 68, 70, 72, 75, 78 or 80%.
[0040] The metal layer 170 usually comprises a metal that is
selected form the group consisting of Au, Ag, Pt, and Ta. In one
example, the metal is Au.
[0041] Referring to FIG. 2, which is a flow chart detailing steps
for forming the drug-containing cell 100 of FIG. 1 in according to
one particular embodiment of this disclosure. The method begins
with the step 201, in which a polyethylene terephthalate (PET)
substrate is cut into suitable dimension, such as 20 mm.times.50
mm.times.0.02 mm. In step 202, several strips of PVC film are
adhered onto the PET substrate to form a ".cndot." shape reservoir,
which is characterized in having one side of the reservoir not
sealed by the PVC strips. In steps 203 to 205, multiple layers are
deposited in sequence within the reservoir, including a first layer
of drug-containing nanoparticles (step 203), a metal layer (step
204) and a second layer of drug-containing nanoparticles (step
205). The layer of drug-containing nanoparticles in step 203 or 205
is formed by electrophoretic deposition (EPD), and the metal layer
in step 204 is formed by sputter deposition (SD).
[0042] Electrophoretic deposition is typically carried out by steps
of: (1) providing an electrophoretic deposition cell, which
comprises: a colloidal suspension containing about 0.01-30% by
weight of drug-containing nanoparticles; and a pair of electrodes;
(2) immersing a flexible substrate (e.g., the PET substrate) having
constructed thereon the drug-containing reservoir in the colloidal
suspension in the electrophoretic deposition cell; and (3) applying
a voltage of about 1-50 V to the pair of electrodes for a period of
about 1-30 min or until the layer of drug-containing nanoparticles
has a thickness of at least 0.1 .mu.M. The colloidal suspension is
prepared by suspending the drug-containing nanoparticles in a
diluting medium selected from the group consisting of water, a
C.sub.1-6 alcohol, glycol, glycerin, dimethyl sulfoxide and a
combination thereof. The C.sub.1-6 alcohol may be selected from the
group consisting of methanol, ethanol, propanol, isopropanol,
butanol, isobutanol, sec-butanol, pentanol, isopentanol, hexanol
and the like. In one example, the diluting medium is water. In
another example, the diluting medium is methanol. The two
electrodes in the electrophoretic deposition cell are usually
spaced apart from each other for a distance of about 0.5 cm to
about 5 cm. In one example, a gap of about 2 cm is formed between
the pair of electrodes in the electrophoretic deposition cell. The
electrophoretic deposition is carried out at a temperature ranges
from about -10.degree. C. to about 70.degree. C.
[0043] Sputter deposition is a physical vapor deposition technique
for depositing thin film by sputtering, that is, by ejecting
material from a source target (e.g., a metal) and then deposited
the ejected material onto a substrate (e.g., the PET substrate).
Suitable sputter deposition technique for depositing the metal
layer in this disclosure may be chosen from any of ion-beam
sputtering, reactive sputtering, ion-assisted deposition, high
power impulse magnetron sputtering (HIPIMS) or gas flow sputtering.
In this example, plasma sputtering is used to sputter deposited a
metal layer of Au. The thickness of the metal layer is typically in
a range of about 5 to 10 .mu.m. In one example, Au layer has a
thickness of about 6.5 .mu.m.
[0044] The electrophoretic deposition and the sputter deposition
may be respectively repeated for several times, such as 2, 3 or 4
times, depends on the desired volume of the drug-containing
reservoir in the drug-containing cell. In one example, the
electrophoretic deposition is performed twice, whereas the sputter
deposition is performed just once. In other example, the
electrophoretic deposition and the sputter deposition may be
repeated for the same number of times, such as 2, 3 or 4 times.
The Construction of a Drug-Delivery Chip for In Vivo Magnetically
Controlled Drug Release
[0045] In order to construct a drug-delivery chip 300, two
drug-containing cells 100 fabricated in accordance with the steps
described above are arranged in a head-to-head configuration, as
illustrated in FIG. 3(a). Specifically, one drug-containing cell
100 is inverted and placed on top of the other drug-containing cell
100, so as to join the two drug-containing reservoirs 110 by
aligning the plurality of side walls 120 of each reservoir 110 and
connecting the two drug-containing volumes 140 and thereby forming
a drug-releasing chamber 310. The drug-releasing chamber 310 is
characterized in having one side of the chamber being exposed to
the surrounding environment and thus provides an outlet for drug
elution. The side of the chamber remained exposed to surrounding
environment is typically result from connecting the sides of the
two drug-containing reservoirs 110 that are not sealed by the
plurality of side walls 120. Alternatively, the drug-releasing
chamber 310 may provide two outlets, instead of one outlet, for
drug elution, if the drug-containing cell 100 having two sides not
sealed by the plurality of side walls 120 is used as a building
block for constructing the drug-delivery chip 300. The flexible
drug delivery chip 300 thus constructed typically has a thickness
of no more than 0.5 mm.
[0046] The constructed drug-delivery chip 300 may be implanted into
a suitable body portion of a subject, such as an arm area, a brain
area or the peritoneal lumen or cavity of a human, depends on the
disease, condition or disorder that requires medical treatments.
The rug-delivery chip 300 of this disclosure also exhibits good
mechanical flexibility and therefore is more adaptable to the
surrounding environment after implantation. Suitable subject that
may benefit from the drug-delivery chip 300 of this disclosure
includes, but is not limited to, human or non-human animal. Such
non-human animals include all domesticated and feral vertebrates,
e.g., mammals, such as primates, dogs, rodents (e.g., mouse or
rat), cats, sheep, horses or pigs; and non-mammals, such as birds,
amphibians, reptiles and etc. In one example, subjects for whom
implantation of the drug-delivery chip 300 may be beneficial
include subjects with epilepsy.
[0047] The drug encapsulated within each nanoparticle in the layer
of drug-containing nanoparticles 150 may be controlled released
from the drug-releasing chamber 310 by the application of an
external magnetic field (MF) with a power from about 0.05 kA/m to
2.5 kA/m, such as about 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,
2.1, 2.2, 2.3, 2.4 or 2.5 kA/m. The duration of the applied MF may
last for a period of about 10 to 180 sec, such as about 10, 20, 30,
40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170 or
180 sec. Since one side of the drug-releasing chamber 310 remained
open to the surrounding environment, hence gradual drug release
form the chamber, despite negligible as compared to the
magnetically induced drug release, may still be seen in some
examples. However, in general, the amount of the drug (e.g., ESM)
that is released from the chamber increases as the power of the
applied magnetic field increases. In one example, the magnetically
induced drug release with a power of 2.5 kA/m is at least 10 folds
higher than the amount of gradual drug release. In another example,
stepwise drug release profile may be achieved by repeatedly turning
on and/or off the applied MF at suitable internals. For example,
turn the MF on for about 1 min, then shut it off for 10 min, and
repeat the on/off action for at least 2, 3, 4 or 5 times, or until
the accumulated amount of the released drug has reached a
pre-determined level. Therefore, the effective amount of the drugs
in the body portion may be controlled by the strength and/or
duration of the MF applied. In other words, the drugs encapsulated
within the nanoparticles in the delivery chip may be released in a
controlled manner by proper adjusting the strength and/or duration
of the applied MF on the body portion of the subject.
[0048] Reference will now be made in detail to the embodiments of
the invention, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference
numbers are used in the drawings and the description to refer to
the same or like parts.
EXAMPLES
[0049] The following Examples are provided to illustrate certain
aspects of the present invention and to aid those of skilled in the
art in practicing this invention. These Examples are in no way to
be considered to limit the scope of the invention in any
manner.
Example 1
Preparation of Drug-Loaded Nanoparticles
1.1 Preparation of Core-Shell Fe.sub.3O.sub.4@SiO.sub.2
Nanoparticles
[0050] Core-shell Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles were
synthesized via conventional microemulsion and sol-gel technology
as previously described (Hu et al., J. Nanosci. Nanotechnol. (2008)
8:1-5; Santra et al., Adv. Mat. (2005) 17:2165-2169). Briefly, the
monodispersed superparamagnetic iron oxide nanoparticles
(Fe.sub.3O.sub.4) were synthesized by a high temperature
decomposition of Fe(acac).sub.3. Two key steps were employed in
forming monodispersed nanoparticles. First, growing nuclei at
200.degree. C. and then raising the reaction temperature to
300.degree. C. to permit the iron oxide nanoparticles to grow to
uniform size. The iron oxide nanoparticles have an average diameter
of 5 nm. To design the core-shell structure, a small amount, 0.5
ml, of the Fe.sub.3O.sub.4 suspension was added to 7.7 ml
cyclohexane to create the oil phase, while the aqueous phase was
composed of 1.6 ml hexanol and 0.34 ml H.sub.2O. Next, these two
phases were mixed following the addition of 2 g octyl phenol
ethoxylate as the surfactant to form a water-in-oil phase. After
adding 2 g of TEOS and aging the mixture for 6 hours, the
core-shell Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles was synthesized
successfully by microemulsion and sol-gel process. This permitted
hydrolysis and condensation reactions to occur, thereby allowing
nanoparticles to be formed through gelation. The synthesized
nanoparticles were then examined under a transmission electron
microscope (TEM, JEM-2100, Japan) and were characterized using
electrophoretic light scattering (ELS) for zeta potential
determination.
[0051] FIGS. 3(a) to 3(c) are high resolution transmission electron
microscopy (HRTEM) photographs of the prepared nanoparticles.
Results from FIGS. 3(a) to 3(c) confirm that each nanoparticle has
a spherical geometry with a mean diameter of about 300 nm, and
nanometric magnetic particles were embedded and distributed
randomly within the core. Each of the nanoparticles possesses a
Fe.sub.3O.sub.4 crystallographic ferrite core and a silica shell.
The shell has a thickness of about 5-10 nm. Images presented in
FIG. 4 illustrate that the silica shell exhibits a relatively
compact structure, where no appreciable pores are detectable under
high microscopic resolution.
1.2 Drug Encapsulation and Characterization of the Drug-Loaded
Nanoparticles
[0052] In order to incorporate the hydrophilic anticonvulsant drug,
ethosuximide (ESM), into the core-shell nanoparticles, the drug was
first dissolved completely in aqueous solution, with a
concentration of 5 wt %. The drug was incorporated using an
emulsification process described previously for the synthesis of
Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles (Hu et al., (2009) supra).
After encapsulation of the drug in the core phase of the
nanoparticle, a subsequent SiO.sub.2 layer deposition was applied
to form a thin outer shell phase, acting as a barrier to regulate
the drug release profile.
[0053] The ESM encapsulated within the Fe.sub.3O.sub.4@SiO.sub.2
nanoparticle was confirmed using Fourier Transform Infrared
Spectroscopy (FTIR) analysis, as shown in FIG. 5 where the
characteristic peak at the position of 1714 nm.sup.-1 designates
the C.dbd.O bond in ESM for the ESM-containing nanoparticles. The
amount of ESM associated with the nanoparticles was determined by
applying a magnetic field to allow the complete release of the drug
into the environment within a short magnetic induction period, as
demonstrated in an earlier study (See Santra et al., (2005) supra).
FIG. 6 illustrates the drug release profiles for the
Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles with and without magnetic
induction. The full strength of the magnetic field is 2.5 kA/m.
Under the full magnetic strength of the field, aliquot amounts of
the buffer solutions were withdrawn at 10-second intervals, the
concentration of ESM released was measured via HPLC, and the
cumulative amount of drug release was determined using Equation
(1):
Cumulative released ( % ) = R t L .times. 100 % ( 1 )
##EQU00001##
where L and R.sub.t represent the initial amount of drug loaded and
the cumulative amount of drug released at time t, respectively.
[0054] There is little or no release detectable in the absence of
the magnetic field. Although a small amount of drug (about 4-5%),
which reaches a relatively constant level after only 20 seconds of
immersion, was measured. It is believed that this represents the
washing off of surface residue remaining from nanoparticle
preparation. Nonetheless, the vast majority of ESM is released
(-100%) with a relatively short induction period (30-40 seconds).
This indicates a burst release profile that can be easily managed.
This test not only reveals an encapsulation efficiency of about
10%, but the resulting release profiles also suggest the
fast-response behavior of the Fe.sub.3O.sub.4@SiO.sub.2
nanoparticles to magnetic induction.
[0055] Zeta potential analysis reveals that the isoelectric point
(IEP) of the nanoparticles is located in a highly-acidic region, as
given in Table 1. As such, the Fe.sub.3O.sub.4@SiO.sub.2
nanoparticles show an increasingly negative charge over a wide pH
range of .about.3 to .about.12. In comparison to the zeta potential
of pure SiO2 nanoparticles, it appears that the incorporation of
Fe.sub.3O.sub.4 could slightly neutralize the negative charging of
the silica shell. The highly negative charged
Fe.sub.3O.sub.4@SiO.sub.2 nanoparticles, after re-dispersing in
ethanol, showed a relatively stable suspension for at least 24
hours.
TABLE-US-00001 TABLE 1 Zeta potential analysis reveals the IEP of
the nanoparticles located over a wide range of pH from ~3 to ~12.
Zeta potential Zeta potential of of SiO.sub.2
SiO.sub.2@Fe.sub.3O.sub.4 pH value (mV) (mV) 2.85 -36 -11 5.48
-51.6 -41.3 9.06 -53.5 -42.9 11.82 -54.2 -47
Example 2
Fabrication of a Drug Delivery Chip
2.1 Fabrication of a Drug-Containing Cell
[0056] To set up an electrophoretic deposition cell, an ITO
(In-doped SnO.sub.2)-coated conducting flexible plate (PET
substrate, JoinWill Tech. Co., Ltd, Taiwan, having an electrical
resistance of sq/50.OMEGA.) with dimensions of 20 mm.times.50
mm.times.0.02 mm was used as an anode and was patterned by
lamination with PVC tape for three side walls of the substrate in
advance (See FIG. 1), leaving one side unsealed as the outlet for
drug elution. Final lamination of the substrate was performed at a
later stage of the assembly. The area of the PET substrate that can
be used for membrane deposition is pre-designed to be 1 cm.sup.2 (1
cm.times.1 cm). A stainless steel plate (316L) with dimensions of
20 mm.times.50 mm.times.0.02 mm (YEONG-SHIN Co., LTD, Taiwan) was
used as cathode and was carefully cleansed sequentially by
sonication in acetone, ethanol, and deionized water at room
temperature. After the cathode was cleaned and rinsed, it was then
dried by blowing with nitrogen gas. A pair of parallel electrodes
with 2 cm separation was set vertically in a glass beaker
containing the colloidal suspension with 5 wt % of the
ESM-containing nanoparticles of Example 1.2 under magnetic
agitation. A constant dc voltage (30 V) was applied between two
electrodes for 10 minutes. After deposition, the substrate was
carefully withdrawn from the glass beaker and dried at room
temperature for 1 hour. Under a constant electrical field of 30 V,
the ESM-containing nanoparticles of Example 1.2 deposited onto the
anodic substrate and reached a thickness of .about.22 um with a
deposition time of 10 minutes, corresponding to a deposition rate
of about 2.2 um/min. Scanning electron microscopy revealed that a
uniform and porous coating can be formed (FIG. 7), indicating that
the nanoparticles can be successfully assembled with an
orderly-arranged configuration, on the flexible substrate.
[0057] After the first deposition of the ESM-containing
nanoparticles of Example 1.2 (as the first layer), the flexible
substrate was subjected to further coating with a thin layer of
sputtered gold to cover the membrane. The purpose of the thin gold
coating is twofold; first, it prevents undesired detachment of the
deposited nanoparticles from the first layer, and the second, it
imparts conductivity for further deposition. Following the same
procedure, the second and third layers of the coatings were carried
out to form the final drug-containing cell. The second and third
layers of the nanoparticle-assembled membranes can be deposited
consecutively after a thin coating of Au is applied.
[0058] After ambient drying, a structural analysis showed that the
resulting multilayer membrane exhibits a thickness of about 70 um
and demonstrates excellent structural integrity. Additionally, no
considerable delaminated fragments were ever detected. Microscopic
examination also indicated a well packed configuration of the drug
nanocarriers, leaving nanometric inter-particle voids distributed
uniformly throughout the entire membrane. Such a well-packed
nanostructure is suggested to stem from strong inter-particle
repulsion occurring as a result of the nanoparticles substantial
negative charge. The zeta potential reaches a level of about -42 mV
at neutral conditions, which should energetically regulate the
assembly of the nanoparticles upon impact with the anodic
substrate. Despite this, estimates indicate that about 350
nanoparticles reach the substrate over a surface area of 1 um.sup.2
per minute.
2.2 Construction of a Drug Delivery Chip
[0059] A drug delivery chip was constructed by use of two
drug-containing cells of Example 2.1 arranged in a head-to-head
configuration or as the manner illustrated in FIG. 2. This resulted
in one side of the chip remaining exposed to the surrounding
environment thereby providing an outlet for drug elution. The
experimental setup is presented schematically in FIG. 2a. The
resulted chip-like device has a total thickness of less than 0.5 mm
and is mechanically flexible (FIG. 2b).
2.3 Characterization of the Drug Delivery Chip of Example 2.2
[0060] The drug delivery chip of Example 2.2 was subjected to in
vitro drug release test. Briefly, a magnetic field was generated,
using a home-made AC magnetic generator, with a constant frequency
of 70 kHz to trigger drug elution from the flexible drug-carrying
chip to examine the release capabilities of said chip. Drug
concentration before and after the release tests was assessed by
reverse phase high-performance liquid chromatography (RPHPLC)
(AGILENT TECHNOLOGIES Co., LTD, Taiwan). Drug solutions were
handled at a constant volume of 50 ul, which was injected into the
HPLC. The Diode Array Detector was set at 217 nm to detect the
anti-epileptic drug, ESM. The mobile phase consisted of 50% water,
as phase A, and 50% Methanol, as phase B, with a flow rate of 1.0
mL/min, a gradient elution profile of 5.0-50.0% B with a linear
ramp from 0-5 min, 50.0-5.0% B with a linear ramp from 5-10 min,
and finally, a 10-min washout period. Drug-free nanoparticle
suspensions were prepared as standard controls by immersing
Fe.sub.3O.sub.4@SiO.sub.2 particles in water at a concentration of
3% v/v. Test samples were prepared using the same procedure, where
3% v/v Fe.sub.3O.sub.4@SiO.sub.2 encapsulated with ESM was used for
drug release tests under various durations of magnetic induction.
Results were illustrated in FIG. 8.
[0061] FIG. 8 illustrates the release profiles of ESM from the
flexible chip under magnetic fields (MF) of varying strengths: 0
A/m (i.e., no MF), 1.0 k A/m, and 2.5 k A/m. The amount of ESM
released without magnetic induction was relatively low; about 9-10%
over a time span of 60 minutes. In comparison, under a stronger
magnetic field, 1.0 kA/m, 40% of ESM was released, and the
strongest magnetic field, 2.5 kA/m, produced 100% drug release
within the same 60 minute time period. These field-strength
specific release profiles strongly indicate that the applied
magnetic field effectively drives the release of the drug from the
deposited membrane.
[0062] A stepwise change in the drug eluting profile can be
detected at various time intervals upon repeated on-off magnetic
operation, as is seen in FIG. 9. In the presence of magnetic
induction, a rapid response in drug elution from the chip is
observed with the form of a burst-like profile. With no induction,
the drug eluting profile becomes relatively slow. From our
understanding, the slower release profile is essentially a
consecutive outward diffusion behavior of the drug from inside the
chip. This is a direct result of rapid removal from the
previous-stage induction, rather than a true release profile of the
chip. On this basis, a zero- or near zero-release profile can be
reasonably achieved, which provides another alternative drug
release mode for the chip.
Example 3
In Vivo Drug Release from the Drug Delivery Chip of Example 2
[0063] In this example, adult male Long-Evans (N=60) rats were
randomly divided into 4 treated groups (n=15 in each group). All
rats were kept in a sound-attenuated room under a 12:12 hour
light-dark cycle (07:00-19:00 lights on) with food and water
provided ad libitum. The experimental procedures were reviewed and
approved by the Institutional Animal Care and Use Committee.
Briefly, the recording electrodes were implanted under
pentobarbital anesthesia (60 mg/kg, i.p.). Subsequently, the rat
was placed in a standard stereotaxic apparatus. In total, six
stainless steel screws were driven bilaterally into the skull
overlying the frontal (A +2.0, L 2.0 with reference to the bregma)
and occipital (A -6.0, L 2.0) regions of the cortex to record
cortical field potentials. A ground electrode was implanted 2 mm
caudal to lambda. Dental cement was applied to fasten the
connection socket to the surface of the skull. Following suturing
to complete the surgery, animals were given an antibiotic
(chlortetracycline) and housed individually in cages for recovery.
Long-Evans rats are used because they often display spontaneous
SWDs, which have been demonstrated to be associated with absence
seizures in several aspects of evidence. In this preliminary animal
test, we compared effect among saline, ethosuximide (ESM),
ESM-loaded nanoparticles (ESM-Fe.sub.3O.sub.4@SiO.sub.2) and
ESM-containing chip (ESM-Chip) in spontaneous SWDs of Long-Evans
rats. The chip of Example 2.3 (5 mm.times.5 mm.times.0.02 mm) was
implanted into the peritoneum of the rats, while the other three
doses were subjecting to IP injection.
[0064] FIG. 10 depicts representative examples of spike-wave
discharges (SWDs) after the administration of saline, ESM,
ESM-Fe.sub.3O.sub.4@SiO.sub.2, and magnetically-induced ESM-Chip.
The SWDs showed no obvious difference. In this experiment, we
recorded 1-hour spontaneous brain activity before the treatment
(baseline) and another 1-hour spontaneous brain activity 30 minutes
after the treatment. The indexes were normalized by average of the
two 1-hour baselines. In the conditions of administering
ESM-Fe.sub.3O.sub.4@SiO.sub.2 and magnetically-triggered ESM-Chip,
rats were restrained in a plastic box then put into the center of a
coil following by magnetic stimulus (2.5 kA/m) as the one being
aforementioned in vitro to release ESM. Although it is hard to
quantify the amount of the ESM released into the rats, results
surely indicated that the amount of ESM released, from both
ESM-Fe.sub.3O.sub.4@SiO.sub.2 (FIG. 10B) and ESM-Chip (FIG. 10C),
demonstrated significant effect in reducing the number and total
duration of spontaneous SWDs, as compared to ESM alone (FIG. 10A).
Although a peritoneum implantation was employed, instead of brain
site, controlled ESM release from these in-vivo data, albeit
relatively preliminary, evidenced that the ESM loaded nanoparticles
as well as ESM-chip can be successfully eluted through an external
magnetic stimulus, as that observed in vitro. In the meantime, the
therapeutic efficacy of the ESM being eluted appeared to preserve
its effect in SWD suppression.
[0065] The foregoing description of various embodiments of the
invention has been presented for purpose of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise embodiments disclosed. Numerous
modifications or variations are possible in light of the above
teachings. The embodiments discussed were chosen and described to
provide the best illustration of the principles of the invention
and its practical application to thereby enable one of ordinary
skill in the art to utilize the invention in various embodiments
and with various modifications as are suited to the particular use
contemplated. All such modifications and variations are within the
scope of the invention as determined by the appended claims when
interpreted in accordance with the breadth to which they are
fairly, legally, and equitably entitled.
* * * * *