U.S. patent application number 14/680710 was filed with the patent office on 2017-03-02 for novel droplet-embedded microfibers, and methods and devices for preparing and using same.
The applicant listed for this patent is THE TRUSTEES OF PRINCETON UNIVERSITY. Invention is credited to Janine K. NUNES, Tamara PICO, Howard A. STONE, Eujin UM.
Application Number | 20170056331 14/680710 |
Document ID | / |
Family ID | 58103349 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170056331 |
Kind Code |
A1 |
STONE; Howard A. ; et
al. |
March 2, 2017 |
NOVEL DROPLET-EMBEDDED MICROFIBERS, AND METHODS AND DEVICES FOR
PREPARING AND USING SAME
Abstract
The invention includes microfluidic methods and devices that
allow for the continuous production of microfibers with embedded
droplets aligned along the length of the fiber at specific
positions. The invention allows for formation of single or multiple
emulsions within a fiber. The various phases comprised within the
fiber can vary in terms of in terms of hydrophobic/hydrophilic
character, solid/fluid, or gel crosslink density, which allows for
the introduction of heterogeneous microenvironments within the
fiber, each of which with distinct solubility characteristics,
permeability, and mechanical properties. Various compounds and
materials can be encapsulated in the different microcompartments of
the fiber for storage and delivery applications, as well as to
provide multifunctionality to the fiber structure. The disclosed
structures have a broad range of potential applications, for
example as engineered substrates with controlled release profiles
of multiple compounds for tissue engineering (such as a tissue
scaffold, for example) and bioengineering applications.
Inventors: |
STONE; Howard A.;
(Princeton, NJ) ; NUNES; Janine K.; (Plainsboro,
NJ) ; UM; Eujin; (Ulsan, KR) ; PICO;
Tamara; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE TRUSTEES OF PRINCETON UNIVERSITY |
Princeton |
NJ |
US |
|
|
Family ID: |
58103349 |
Appl. No.: |
14/680710 |
Filed: |
April 7, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61976599 |
Apr 8, 2014 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61K 49/0093 20130101;
A61K 9/0092 20130101; A61L 2300/62 20130101; A61K 49/0043 20130101;
A61L 27/50 20130101; A61K 9/5026 20130101; A61L 27/58 20130101;
A61L 27/54 20130101; A61K 31/085 20130101 |
International
Class: |
A61K 9/70 20060101
A61K009/70; A61K 47/36 20060101 A61K047/36; A61K 31/085 20060101
A61K031/085; A61K 49/00 20060101 A61K049/00; A61K 35/33 20060101
A61K035/33; A61K 35/74 20060101 A61K035/74 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was made with government support under grant
number FA9550-12-1-0368 awarded by the Air Force Office of
Scientific Research (AFOSR). The government has certain rights in
the invention.
Claims
1. A microfiber comprising a matrix material; wherein the
microfiber further comprises a plurality of droplets embedded in
the matrix material along a length thereof; wherein each one of the
plurality of droplets independently comprises a single fluid;
wherein each one of the plurality of droplets is insoluble in the
matrix material of the microfiber; and wherein, if the matrix
material of the microfiber is hydrophilic, the matrix material is
prepared from a precursor using at least one method selected from
the group consisting of polymerization, solvent extraction and
covalent crosslinking.
2. The microfiber of claim 1, wherein the matrix material has a
composition that does not vary substantially along a length of the
microfiber.
3. The microfiber of claim 1, wherein the matrix material has a
composition that varies along a length of the microfiber.
4. The microfiber of claim 1, wherein each one of the plurality of
the droplets has a like composition.
5. The microfiber of claim 1, wherein at least one of the plurality
of droplets has a first composition, and at least one other of the
plurality of droplets has a second composition, the first
composition being different from the second composition.
6. The microfiber of claim 1, wherein the matrix material further
comprises at least one agent selected from the group consisting of
a cell, tissue, filler, therapeutic drug, chemoattractant, biocide,
ion, peptide, protein, nucleic acid, magnetic compound, and
detectable probe.
7. The microfiber of claim 1, wherein at least one of the plurality
of droplets further comprises at least one agent selected from the
group consisting of a cell, tissue, filler, therapeutic drug,
chemoattractant, biocide, ion, peptide, protein, nucleic acid,
magnetic compound, and detectable probe.
8. The microfiber of claim 1, wherein at least one selected from
the group consisting of the matrix material and at least one of the
plurality of droplets comprises a magnetic compound.
9. The microfiber of claim 1, wherein the matrix material of the
microfiber is hydrophobic and the single fluid of the droplet is
hydrophilic.
10. The microfiber of claim 1, wherein the matrix material of the
microfiber is hydrophilic and the single fluid of the droplet is
hydrophobic.
11. The microfiber of claim 1, wherein the matrix material
comprises a first agent and at least one of the plurality of
droplets comprises a second agent, the second agent having distinct
solubility or distinct chemical compatibility from the first
agent.
12. The microfiber of claim 1, wherein the matrix material of the
microfiber is biodegradable.
13. A microfiber comprising a matrix material; wherein the
microfiber further comprises a plurality of droplets embedded in
the matrix material along the length thereof; wherein each one of
the plurality of droplets independently comprises an emulsion
comprising a first droplet phase within a second droplet phase; and
wherein the matrix material of the microfiber is insoluble in the
second droplet phase of each one of the plurality of droplets.
14. The microfiber of claim 13, wherein the matrix material has a
composition that does not vary substantially along a length of the
microfiber.
15. The microfiber of claim 13, wherein the matrix material has a
composition that varies along a length of the microfiber.
16. The microfiber of claim 13, wherein each one of the plurality
of the droplets has a like composition.
17. The microfiber of claim 13, wherein at least one of the
plurality of droplets has a first composition, and at least one
other of the plurality of droplets has a second composition, the
first composition being different from the second composition.
18. The microfiber of claim 13, wherein the matrix material further
comprises at least one agent selected from the group consisting of
a cell, tissue, filler, therapeutic drug, chemoattractant, biocide,
ion, peptide, protein, nucleic acid, magnetic compound, and
detectable probe.
19. The microfiber of claim 13, wherein at least one of the
plurality of droplets further comprises at least one agent selected
from the group consisting of a cell, tissue, filler, therapeutic
drug, chemoattractant, biocide, ion, peptide, protein, nucleic
acid, magnetic compound, and detectable probe.
20. The microfiber of claim 13, wherein at least one selected from
the group consisting of the matrix material and at least one of the
plurality of droplets comprises a magnetic compound.
21. The microfiber of claim 13, wherein the matrix material of the
microfiber is hydrophilic and the second droplet phase of each one
of the plurality of droplets is hydrophobic.
22. The microfiber of claim 13, wherein the matrix material of the
microfiber is hydrophobic and the second droplet phase of each one
of the plurality of droplets is hydrophilic.
23. The microfiber of claim 13, wherein the first droplet phase of
at least one of the plurality of droplets comprises a solid.
24. The microfiber of claim 13, wherein within at least one of the
plurality of droplets the first droplet phase comprises a first
agent and the second droplet phase comprises a second agent, the
second agent having at least one property selected from the group
consisting of solubility and chemical compatibility that is
distinct from that of the first agent.
25. The microfiber of claim 13, wherein the matrix material of the
microfiber is biodegradable.
26. A microfiber comprising an outer matrix material and an inner
matrix material; wherein the outer matrix material and the inner
matrix material span the length of the microfiber; wherein the
inner matrix material is embedded in the outer matrix material;
wherein the microfiber further comprises a plurality of droplets
embedded in the inner matrix material along the length thereof; and
wherein the inner matrix material of the microfiber is insoluble in
each one of the plurality of droplets and in the outer matrix
material.
27. The microfiber of claim 26, wherein the outer and inner matrix
materials are coaxially aligned within the microfiber.
28. The microfiber of claim 26, wherein the radius of the inner
matrix material is substantially constant along a length of the
microfiber.
29. The microfiber of claim 26, wherein the radius of the outer
matrix material is substantially constant along a length of the
microfiber.
30. The microfiber of claim 26, wherein each one of the plurality
of the droplets has a like composition.
31. The microfiber of claim 26, wherein at least one of the
plurality of droplets has a first composition, and at least one
other of the plurality of droplets has a second composition, the
first composition being different from the second composition.
32. The microfiber of claim 26, wherein at least one selected from
the group consisting of the outer matrix material and the inner
matrix material further comprises at least one agent selected from
the group consisting of a cell, tissue, filler, therapeutic drug,
chemoattractant, biocide, ion, peptide, protein, nucleic acid,
magnetic compound, and detectable probe.
33. The microfiber of claim 26, wherein at least one of the
plurality of droplets further comprises at least one agent selected
from the group consisting of a cell, tissue, filler, therapeutic
drug, chemoattractant, biocide, ion, peptide, protein, nucleic
acid, magnetic compound, and detectable probe.
34. The microfiber of claim 26, wherein the outer matrix material
is hydrophilic, the inner matrix material is hydrophobic, and each
one of the plurality of droplets is hydrophilic.
35. The microfiber of claim 26, wherein the outer matrix material
is hydrophobic, the inner matrix material is hydrophilic, and each
one of the plurality of droplets is hydrophobic.
36. A microfluidic device comprising: a first microfluidic duct for
delivering a first fluid; a second microfluidic duct for delivering
a second fluid, the second fluid being immiscible with the first
fluid, wherein the first microfluidic duct opens into the second
microfluidic duct and forms a first fluidic junction therewith; a
third microfluidic duct that is in fluid communication with the
first fluidic junction and is wettable by the second fluid; a
fourth microfluidic duct for delivering a third fluid, wherein the
third microfluidic duct opens into the fourth microfluidic duct and
forms a second fluidic junction therewith; and an outlet that is in
fluid communication with the second fluidic junction.
37. The microfluidic device of claim 36, wherein the first fluidic
junction is selected from the group consisting of a flow-focusing
junction and a t- junction.
38. The microfluidic device of claim 36, wherein the second fluidic
junction is a flow-focusing junction.
39. The microfluidic device of claim 36, wherein the third
microfluidic duct is at least partially coated with a polymer that
is wettable by the second fluid.
40. A microfluidic device comprising: a first microfluidic duct for
delivering a first fluid; a second microfluidic duct for delivering
a second fluid, the second fluid being immiscible with the first
fluid, wherein the first microfluidic duct opens into the second
microfluidic duct and forms a first fluidic junction therewith; a
third microfluidic duct that is in fluid communication with the
first fluidic junction and is wettable by the second fluid; a
fourth microfluidic duct for delivering a third fluid, wherein the
third microfluidic duct opens into the fourth microfluidic duct and
forms a second fluidic junction therewith, a fifth microfluidic
duct that originates from the second fluidic junction and is
wettable by the third fluid; a sixth microfluidic duct for
delivering a fourth fluid, wherein the fifth microfluidic duct
opens into the sixth microfluidic duct and forms a third fluidic
junction therewith; and an outlet that is in fluid communication
with the third fluidic junction.
41. The microfluidic device of claim 40, wherein the first and
second fluidic junctions are independently selected from the group
consisting of a flow- focusing junction and a t-junction.
42. The microfluidic device of claim 40, wherein the third fluidic
junction is a flow-focusing junction.
43. The microfluidic device of claim 40, wherein the third
microfluidic duct is at least partially coated with a polymer that
is wettable by the second fluid.
44. The microfluidic device of claim 40, wherein the fifth
microfluidic duct is at least partially coated with a polymer that
is wettable by the third fluid.
45. A method of preparing a microfiber, the method comprising the
steps of: providing the microfluidic device of claim 36; delivering
a first fluid to the first microfluidic duct and a second fluid to
the second microfluidic duct, whereby a first emulsion comprising
the first fluid into the second fluid is formed within or in the
proximity of the first fluidic junction; and delivering a third
fluid to the fourth microfluidic duct, whereby a mixture of the
third fluid and the first emulsion is formed within or in the
proximity of the second fluidic junction; and allowing the
microfiber to form within or in the proximity of the outlet of the
second fluidic junction.
46. A method of preparing a microfiber, the method comprising the
steps of: providing the microfluidic device of claim 40; delivering
a first fluid to the first microfluidic duct and a second fluid to
the second microfluidic duct, whereby a first emulsion comprising
the first fluid within the second fluid is formed within or in the
proximity of the first fluidic junction; delivering a third fluid
to the fourth microfluidic duct, whereby a second emulsion
comprising the first emulsion within the third fluid is formed
within or in the proximity of the second fluidic junction;
delivering a fourth fluid to the sixth microfluidic duct, whereby a
mixture of the fourth fluid and the second emulsion is formed; and
allowing the microfiber to form within or in the proximity of the
outlet of the third fluidic junction.
47. A system comprising a microfluidic device and first, second and
third fluid reservoirs, wherein the microfluidic device comprises
first, second, third and fourth microfluidic ducts and an outlet,
wherein the first fluid reservoir comprises a first fluid and is in
fluid communication with the first microfluidic duct, wherein the
second fluid reservoir comprises a second fluid and is in fluid
communication with the second microfluidic duct, the second fluid
being immiscible with the first fluid, wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith; wherein the third microfluidic
duct is in fluid communication with the first fluidic junction and
is wettable by the second fluid; wherein the third fluid reservoir
comprises a third fluid and is in fluid communication with the
fourth microfluidic duct, wherein the third microfluidic duct opens
into the fourth microfluidic duct and forms a second fluidic
junction therewith; and wherein the outlet is in fluid
communication with the second fluidic junction.
48. A system comprising a microfluidic device and first, second,
third and fourth fluid reservoirs, wherein the microfluidic devices
comprises first, second, third, fourth, fifth and sixth
microfluidic ducts and an outlet, wherein the first fluid reservoir
comprises a first fluid and is in fluid communication with the
first microfluidic duct, wherein the second fluid reservoir
comprises a second fluid and is in fluid communication with the
second microfluidic duct, the second fluid being immiscible with
the first fluid, wherein the first microfluidic duct opens into the
second microfluidic duct and forms a first fluidic junction
therewith; wherein the third microfluidic duct is in fluid
communication with the first fluidic junction and is wettable by
the second fluid; wherein the third fluid reservoir comprises a
third fluid and is in fluid communication with the fourth
microfluidic duct, wherein the third microfluidic duct opens into
the fourth microfluidic duct and forms a second fluidic junction
therewith; wherein the fifth microfluidic duct originates from the
second fluidic junction and is wettable by the third fluid; wherein
the fourth fluid reservoir comprises a fourth fluid and is in fluid
communication with the sixth microfluidic duct; wherein the fifth
microfluidic duct opens into the sixth microfluidic duct and forms
a third fluidic junction therewith; and wherein the outlet is in
fluid communication with the third fluidic junction.
49. A method of physically displacing a microfiber, the method
comprising applying a magnetic field to a microfiber, wherein the
microfiber is at least one selected from the group consisting of:
(a) a microfiber comprising a matrix material; wherein the
microfiber further comprises a plurality of droplets embedded in
the matrix material along the length thereof; wherein each one of
the plurality of droplets independently comprises a single fluid;
wherein the matrix material of the microfiber is insoluble in each
one of the plurality of droplets; and wherein at least one selected
from the group consisting of the matrix material and at least one
of the plurality of droplets comprises a magnetic compound; (b) a
microfiber comprising a matrix material; wherein the microfiber
further comprises a plurality of droplets embedded in the matrix
material along the length thereof; wherein each one of the
plurality of droplets independently comprises an emulsion
comprising a first droplet phase within a second droplet phase;
wherein the matrix material of the microfiber is insoluble in the
second droplet phase of each one of the plurality of droplets; and
wherein at least one selected from the group consisting of the
matrix material and at least one of the plurality of droplets
comprises a magnetic compound; (c) a microfiber comprising an outer
matrix material and an inner matrix material, wherein the outer
matrix material and the inner matrix material span the length of
the microfiber; wherein the inner matrix material is embedded in
the outer matrix material; wherein the microfiber further comprises
a plurality of droplets embedded in the inner matrix material along
the length thereof; wherein the inner matrix material of the
microfiber is insoluble in each one of the plurality of droplets
and in the outer matrix material; and wherein at least one selected
from the group consisting of the matrix material and at least one
of the plurality of droplets comprises a magnetic compound; whereby
the microfiber is physically displaced.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/976,599,
filed Apr. 8, 2014, which is incorporated herein by reference in
its entirety.
BACKGROUND
[0003] One-dimensional, high aspect ratio flexible structures, such
as micro- and nanofibers, offer various advantages. In one aspect,
the properties, geometry and composition of micro- and nanofibers
can be controlled at the micron and sub-micron length scales (Jun,
et al., 2014, Lab Chip 14:2145; Li & Xia, 2004, Adv. Mater.
16:1151). In another aspect, these fibers can be used at larger
length scales to create complex assemblies and three-dimensional
architectures, such as meshes and textiles (Burger, et al., 2006,
Annu Rev. Mater. Res. 36:333; Onoe, et al., 2013, Nat. Mater.
12:584).
[0004] Approaches that add versatility and functionality to micro-
and nanofibers would allow for the creation of `smart` materials
useful within life science and materials science applications. The
utilization of composite structures is a common approach to add
such multifunctionality. Composite fiber structures with tailored
volume fractions of components, precise spatial control, and
controlled chemistry and loading of cargo are appealing for many
applications, such as scaffolds for the spatial control of cellular
microenvironments in tissue engineering (Yamada, et al., 2012, Soft
Matter 8:3122; Yamada, et al., 2012, Biomaterials 33:8304), local
delivery of therapeutics for wound healing applications (Zahedi, et
al., 2010, Polymer. Adv. Tech. 21:77; Zilberman, et al., 2009, J.
Biomed. Mater. Res. A 89A:654), immobilization and protection of
bacteria in bioreactors (Nardi, et al., 2012, J. Environ. Prot.
3:164), self-healing composite materials for load bearing
applications (Sinha-Ray, et al., 2012, J. Mater. Chem. 22:9138),
and food science (Arecchi, et al., 2010, J. Food Sci. 75:N80;
Sultana, et al., Int. J. Food Microbiol. 62:47).
[0005] An exemplary approach for generating composite fibers is to
use an emulsion as the pre-fiber solution (Arecchi, et al., 2010,
J. Food Sci. 75:N80; Sultana, et al., Int. J. Food Microbiol.
62:47; Dong, et al., 2009, Small 5:1508; Sanders, et al., 2003,
Macromolecules 36:3803; Sy, et al., 2009, Adv. Mater. 21:1814;
Korehei & Kadla, 2013, J. Appl. Microbiol. 114:1425; Kriegel,
et al., 2009, Langmuir 25:1154). Using this process, cargos such as
proteins, antimicrobial compounds, and self-healing compounds have
been incorporated into electrospun nanofibers. To avoid the
mechanical stresses associated with bulk emulsification techniques
on fragile cargo, as are results of use of homogenizers and
ultrasonication, other techniques have been developed, such as
compound jet electrospinning, coaxial electrospinning, thermally
induced in-fiber emulsification of an extruded core-shell fiber,
coaxial microfluidics, microfluidics incorporating stratified flows
for mosaicked fibers, and valve-based microfluidics for coded
fibers. These techniques can generate micro/nanofibers containing
various cargos, including cells, drugs, and proteins.
[0006] Some methods for producing composite fibers, such as using
bulk emulsification, are relatively simple to execute, but lack the
spatial control desired for advanced applications. Others, while
efficient at fabricating fibers with complex morphologies and a
high level of spatial control, rely on complex device designs and
externally controlled actuation.
[0007] There is a need in the art for novel methods and devices for
preparing multi-compartment nano- and microfibers comprising
embedded droplets along the length of the fibers. In certain
aspects, such methods and devices should allow for control over the
spacing of the embedded droplets along the length of the fiber. In
other aspects, such methods and devices should allow for
encapsulation of components in distinct microcompartments. This
provides controlled storage, dissolution and/or delivery of the
components. The present invention meets this need.
BRIEF SUMMARY
[0008] The invention provides microfibers comprising a matrix
material, and microfibers comprising an outer matrix material and
an inner matrix material. The invention further provides
microfluidic devices, and methods of preparing microfibers using
same. The invention further provides systems comprising a
microfluidic device and one or more fluid reservoirs. The invention
further provides methods of physically displacing a microfiber in
accordance with the present invention.
[0009] In certain embodiments, the microfiber further comprises a
plurality of droplets embedded in the matrix material along a
length thereof; wherein each one of the plurality of droplets
independently comprises a single fluid; wherein each one of the
plurality of droplets is insoluble in the matrix material of the
microfiber; and wherein, if the matrix material of the microfiber
is hydrophilic, the matrix material is prepared from a precursor
using at least one method selected from the group consisting of
polymerization, solvent extraction and covalent crosslinking.
[0010] In certain embodiments, the microfiber further comprises a
plurality of droplets embedded in the matrix material along the
length thereof; wherein each one of the plurality of droplets
independently comprises an emulsion comprising a first droplet
phase within a second droplet phase; and wherein the matrix
material of the microfiber is insoluble in the second droplet phase
of each one of the plurality of droplets.
[0011] In certain embodiments, the outer matrix material and the
inner matrix material span the length of the microfiber; wherein
the inner matrix material is embedded in the outer matrix material;
wherein the microfiber further comprises a plurality of droplets
embedded in the inner matrix material along the length thereof; and
wherein the inner matrix material of the microfiber is insoluble in
each one of the plurality of droplets and in the outer matrix
material.
[0012] In certain embodiments, the matrix material has a
composition that does not vary substantially along a length of the
microfiber. In other embodiments, the matrix material has a
composition that varies along a length of the microfiber. In yet
other embodiments, each one of the plurality of the droplets has a
like composition. In yet other embodiments, at least one of the
plurality of droplets has a first composition, and at least one
other of the plurality of droplets has a second composition, the
first composition being different from the second composition.
[0013] In certain embodiments, the matrix material further
comprises at least one agent selected from the group consisting of
a cell, tissue, filler, therapeutic drug, chemoattractant, biocide,
ion, peptide, protein, nucleic acid, magnetic compound, and
detectable probe. In other embodiments, at least one of the
plurality of droplets further comprises at least one agent selected
from the group consisting of a cell, tissue, filler, therapeutic
drug, chemoattractant, biocide, ion, peptide, protein, nucleic
acid, magnetic compound, and detectable probe. In yet other
embodiments, at least one selected from the group consisting of the
matrix material and at least one of the plurality of droplets
comprises a magnetic compound.
[0014] In certain embodiments, the matrix material of the
microfiber is hydrophobic and the single fluid of the droplet is
hydrophilic. In other embodiments, the matrix material of the
microfiber is hydrophilic and the single fluid of the droplet is
hydrophobic. In yet other embodiments, the matrix material of the
microfiber is hydrophilic and the second droplet phase of each one
of the plurality of droplets is hydrophobic. In yet other
embodiments, the matrix material of the microfiber is hydrophobic
and the second droplet phase of each one of the plurality of
droplets is hydrophilic. In yet other embodiments, the first
droplet phase of at least one of the plurality of droplets
comprises a solid.
[0015] In certain embodiments, the matrix material comprises a
first agent and at least one of the plurality of droplets comprises
a second agent, the second agent having distinct solubility or
distinct chemical compatibility from the first agent. In other
embodiments, within at least one of the plurality of droplets the
first droplet phase comprises a first agent and the second droplet
phase comprises a second agent, the second agent having at least
one property selected from the group consisting of solubility and
chemical compatibility that is distinct from that of the first
agent. In yet other embodiments, the matrix material of the
microfiber is biodegradable.
[0016] In certain embodiments, the outer and inner matrix materials
are coaxially aligned within the microfiber. In other embodiments,
the radius of the inner matrix material is substantially constant
along a length of the microfiber. In yet other embodiments, the
radius of the outer matrix material is substantially constant along
a length of the microfiber. In yet other embodiments, at least one
selected from the group consisting of the outer matrix material and
the inner matrix material further comprises at least one agent
selected from the group consisting of a cell, tissue, filler,
therapeutic drug, chemoattractant, biocide, ion, peptide, protein,
nucleic acid, magnetic compound, and detectable probe.
[0017] In certain embodiments, the outer matrix material is
hydrophilic, the inner matrix material is hydrophobic, and each one
of the plurality of droplets is hydrophilic. In other embodiments,
the outer matrix material is hydrophobic, the inner matrix material
is hydrophilic, and each one of the plurality of droplets is
hydrophobic.
[0018] In certain embodiments, the microfluidic device comprises a
first microfluidic duct for delivering a first fluid; a second
microfluidic duct for delivering a second fluid, the second fluid
being immiscible with the first fluid; wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith; a third microfluidic duct that
is in fluid communication with the first fluidic junction and is
wettable by the second fluid; a fourth microfluidic duct for
delivering a third fluid; wherein the third microfluidic duct opens
into the fourth microfluidic duct and forms a second fluidic
junction therewith; and an outlet that is in fluid communication
with the second fluidic junction.
[0019] In certain embodiments, the microfluidic device comprises a
first microfluidic duct for delivering a first fluid; a second
microfluidic duct for delivering a second fluid, the second fluid
being immiscible with the first fluid; wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith; a third microfluidic duct that
is in fluid communication with the first fluidic junction and is
wettable by the second fluid; a fourth microfluidic duct for
delivering a third fluid; wherein the third microfluidic duct opens
into the fourth microfluidic duct and forms a second fluidic
junction therewith, a fifth microfluidic duct that originates from
the second fluidic junction and is wettable by the third fluid; a
sixth microfluidic duct for delivering a fourth fluid; wherein the
fifth microfluidic duct opens into the sixth microfluidic duct and
forms a third fluidic junction therewith; and an outlet that is in
fluid communication with the third fluidic junction.
[0020] In certain embodiments, the first fluidic junction is
selected from the group consisting of a flow-focusing junction and
a t-junction. In other embodiments, the second fluidic junction is
a flow-focusing junction. In yet other embodiments, the third
microfluidic duct is at least partially coated with a polymer that
is wettable by the second fluid. In yet other embodiments, the
first and second fluidic junctions are independently selected from
the group consisting of a flow-focusing junction and a t-junction.
In yet other embodiments, the third fluidic junction is a
flow-focusing junction. In yet other embodiments, the third
microfluidic duct is at least partially coated with a polymer that
is wettable by the second fluid. In yet other embodiments, the
fifth microfluidic duct is at least partially coated with a polymer
that is wettable by the third fluid.
[0021] In certain embodiments, the method of preparing a microfiber
comprises the steps of: providing a microfluidic device in
accordance with the present invention; delivering a first fluid to
the first microfluidic duct and a second fluid to the second
microfluidic duct, whereby a first emulsion comprising the first
fluid into the second fluid is formed within or in the proximity of
the first fluidic junction; and delivering a third fluid to the
fourth microfluidic duct, whereby a mixture of the third fluid and
the first emulsion is formed within or in the proximity of the
second fluidic junction; and allowing the microfiber to form within
or in the proximity of the outlet of the second fluidic
junction.
[0022] In certain embodiments, the method of preparing a microfiber
comprises the steps of: providing a microfluidic device in
accordance with the present invention; delivering a first fluid to
the first microfluidic duct and a second fluid to the second
microfluidic duct, whereby a first emulsion comprising the first
fluid within the second fluid is formed within or in the proximity
of the first fluidic junction; delivering a third fluid to the
fourth microfluidic duct, whereby a second emulsion comprising the
first emulsion within the third fluid is formed within or in the
proximity of the second fluidic junction; delivering a fourth fluid
to the sixth microfluidic duct, whereby a mixture of the fourth
fluid and the second emulsion is formed; and allowing the
microfiber to form within or in the proximity of the outlet of the
third fluidic junction.
[0023] In certain embodiments, the system comprises a microfluidic
device and first, second and third fluid reservoirs; wherein the
microfluidic device comprises first, second, third and fourth
microfluidic ducts and an outlet; wherein the first fluid reservoir
comprises a first fluid and is in fluid communication with the
first microfluidic duct; wherein the second fluid reservoir
comprises a second fluid and is in fluid communication with the
second microfluidic duct, the second fluid being immiscible with
the first fluid; wherein the first microfluidic duct opens into the
second microfluidic duct and forms a first fluidic junction
therewith; wherein the third microfluidic duct is in fluid
communication with the first fluidic junction and is wettable by
the second fluid; wherein the third fluid reservoir comprises a
third fluid and is in fluid communication with the fourth
microfluidic duct; wherein the third microfluidic duct opens into
the fourth microfluidic duct and forms a second fluidic junction
therewith; and the outlet is in fluid communication with the second
fluidic junction.
[0024] In certain embodiments, the system comprises a microfluidic
device and first, second, third and fourth fluid reservoirs,
wherein the microfluidic devices comprises first, second, third,
fourth, fifth and sixth microfluidic ducts and an outlet, wherein
the first fluid reservoir comprises a first fluid and is in fluid
communication with the first microfluidic duct, wherein the second
fluid reservoir comprises a second fluid and is in fluid
communication with the second microfluidic duct, the second fluid
being immiscible with the first fluid, wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith; wherein the third microfluidic
duct is in fluid communication with the first fluidic junction and
is wettable by the second fluid; wherein the third fluid reservoir
comprises a third fluid and is in fluid communication with the
fourth microfluidic duct, wherein the third microfluidic duct opens
into the fourth microfluidic duct and forms a second fluidic
junction therewith; wherein the fifth microfluidic duct originates
from the second fluidic junction and is wettable by the third
fluid; wherein the fourth fluid reservoir comprises a fourth fluid
and is in fluid communication with the sixth microfluidic duct;
wherein the fifth microfluidic duct opens into the sixth
microfluidic duct and forms a third fluidic junction therewith; and
wherein the outlet is in fluid communication with the third fluidic
junction.
[0025] In certain embodiments, the method of physically displacing
a microfiber comprises applying a magnetic field to a microfiber in
accordance with the present invention, wherein the microfiber
comprises a magnetic compound, whereby the microfiber is physically
displaced.
[0026] In certain embodiments, the microfiber comprises a matrix
material; wherein the microfiber further comprises a plurality of
droplets embedded in the matrix material along the length thereof;
wherein each one of the plurality of droplets independently
comprises a single fluid; wherein the matrix material of the
microfiber is insoluble in each one of the plurality of droplets;
and wherein at least one selected from the group consisting of the
matrix material and at least one of the plurality of droplets
comprises a magnetic compound.
[0027] In certain embodiments, the microfiber comprises a matrix
material; wherein the microfiber further comprises a plurality of
droplets embedded in the matrix material along the length thereof;
wherein each one of the plurality of droplets independently
comprises an emulsion comprising a first droplet phase within a
second droplet phase; wherein the matrix material of the microfiber
is insoluble in the second droplet phase of each one of the
plurality of droplets; and wherein at least one selected from the
group consisting of the matrix material and at least one of the
plurality of droplets comprises a magnetic compound.
[0028] In certain embodiments, the microfiber comprises an outer
matrix material and an inner matrix material, wherein the outer
matrix material and the inner matrix material span the length of
the microfiber; wherein the inner matrix material is embedded in
the outer matrix material; wherein the microfiber further comprises
a plurality of droplets embedded in the inner matrix material along
the length thereof; wherein the inner matrix material of the
microfiber is insoluble in each one of the plurality of droplets
and in the outer matrix material; and wherein at least one selected
from the group consisting of the matrix material and at least one
of the plurality of droplets comprises a magnetic compound.
BRIEF DESCRIPTION OF THE FIGURES
[0029] For the purpose of illustrating the invention, there are
depicted in the drawings certain embodiments in accordance with the
present invention. However, the invention is not limited to the
precise arrangements and instrumentalities of the embodiments
depicted in the drawings.
[0030] FIG. 1 is a non-limiting illustration of microfluidic
devices and compositions in accordance with the present invention.
Panel (a) illustrates a non-limiting microfluidic device geometry
designed for generating alginate particle-in-oil compartments
encapsulated in an alginate fiber. The enlarged part of the channel
shows each step of the in situ fabrication of the multicompartment
fibers, with the hydrophilic region of the channel indicated in
dark grey (red). All the inlets for each solution used in
generating multicompartment fibers are indicated in the schematic
device. Panels (b)-(d) illustrate microscope images showing each
step of the multicompartment fiber fabrication including: panel
(b)--inner alginate particle generation in an oil phase; panel
(c)--alginate-in-oil double emulsion formation in the region
grafted with hydrophilic polymer; panel (d)--formation of the
complete composite alginate fiber containing double emulsion
droplets and sheathed by an aqueous solution of calcium chloride in
the main channel. Panels (e)-(f) illustrate resulting fibers
collected from the outlet containing double emulsions that consist
of (panel (e)) a single alginate particle per oil compartment, and
(panel (f)) multiple alginate particles per oil compartment. Scale
bars=200 .mu.m.
[0031] FIG. 2 illustrates non-limiting examples of encapsulation in
the multicompartment fibers. Panel (a) illustrates bright-field and
fluorescence images of alginate-in-oil-in-alginate fibers where
fluorescent nanoparticles are encapsulated in the inner alginate
particles of the fibers. The fibers were freely suspended in
calcium chloride solution. Scale bars=200 .mu.m. Panel (b)
illustrates bright-field images of an alginate-in-oil-in-alginate
fiber where the alginate core particles contain magnetic
microparticles, allowing the fiber to be attracted to a magnet (at
right), as indicated by the arrow. Scale bars=500 .mu.m. Panels
(c)-(d) illustrate encapsulation of live cells in
alginate-in-oil-in-alginate fibers. Panel (c) illustrates
fibroblast cells growing in the alginate fiber compartment with
ferrofluid inside the oil-droplet compartment, 3 days after the
initial encapsulation. Live/dead assay was performed using
calcein-AM (green fluorescence) and ethidium homodimer-1 (red
fluorescence). Panel (d) illustrates E. coli cells encapsulated in
the oil-in-alginate fibers suspended in Luria-Bertani (LB) growth
medium after 3 hours. Scale bars=100 .mu.m.
[0032] FIG. 3 illustrates a study of the antibacterial effect of
eugenol oil on E. coli cells within exemplary multicompartment
fibers. As illustrated in panel (a), for the alginate fibers
containing up to 10% (v/v) eugenol droplets inside, the
GFP-expressing E. coli cells grew around the oil droplets and
covered most of the fibers completely after 15 hours. As
illustrated in panel (b), in 20% (v/v) eugenol droplets-in-alginate
fibers, the growth of E. coli already slowed down around the oil
droplets after 3 hours, and no growth was observed around the rim
of the droplets even after 15 hours.
[0033] FIG. 4 illustrates the stability and dissolution studies of
exemplary multicompartment fibers in (panels (a)-(b)) a solution of
sodium citrate and (panel (c)) a solution of ethanol in water.
Panel (a) illustrates bright-field images of
alginate-in-oil-in-alginate fibers suspended in a solution of
sodium citrate showing the dissolution of the alginate hydrogel,
which leaves behind the oil droplets. Panel (b) illustrates
bright-field images of alginate-in-ferrofluid oil-in-alginate
fibers suspended in a solution of sodium citrate, showing the
partial dissolution of an inner alginate particle in an oil droplet
(indicated by the red arrow), where the oil droplet was released
from the dissolving alginate fiber, and then the inner alginate
particle broke open. After relatively long times, the broken inner
alginate particle dissolved completely leaving only oil droplets.
Panel (c) illustrates comparison of green NP alginate-in-Nile red
oil-in-alginate fibers left for 18 hours in DI water (left) and
water/ethanol solution (right), showing the loss of the oil
solution containing Nile red dye, in the case of the ethanol but
not in the case of pure water. The fluorescent nanoparticles in the
inner alginate particles remained intact in the presence of
ethanol. Scale bars=200 .mu.m.
[0034] FIG. 5 illustrates bright-field images of exemplary oil
droplets-in-fiber structure (panel (a)) generated inside a main
channel, (panel (b)) freely suspended in an aqueous solution, and
(panel (c)) spun using a motor. The fibers were stretched and
therefore the shapes of inner oil compartments were elongated as
well. Panel (d) illustrates resulting fibers after some of the oil
droplets had escaped.
[0035] FIG. 6 is a table illustrating exemplary flow rate
conditions of the inner alginate solution and the number of the
inner alginate particles per oil drop at each flow rate of the oil
phase. The flow rates of calcium chloride solution and the alginate
solution for fibers were kept at 6 mLhr.sup.-1 and 0.6 mLhr.sup.-1,
respectively.
[0036] FIG. 7 illustrates non-limiting examples of exemplary
microfluidic devices. Panel (a) illustrates the channel geometry of
two different dimensions to fabricate the multicompartment fibers,
Design 1 and Design 2. Panels (b)-(e) illustrate dimensions of the
multicompartment fibers as a function of the oil phase flow rate
are shown, while the flow rates of calcium chloride solution and
the alginate solution for fibers were fixed to be 6 mLhr.sup.-1 and
0.6 mLhr.sup.-1, respectively. The overall distance between oil
droplets in the fiber in Design 1 (panel (b)) was shorter than in
Design 2 (panel (c)). The diameter of oil droplets and the width of
alginate stream in Design 1 (panel (d)) and Design 2 (panel (e))
are also shown. Overall, the increase in the widths w1 and w2
(Design 2) compared to the Design 1 resulted in the larger
diameters of oil droplets and the longer distance between the
droplet compartments in the fiber.
[0037] FIG. 8 illustrates exemplary non-limiting compositions in
accordance with the present invention. Panel (a) illustrates
bright-field and fluorescence images of alginate-in-oil-in-alginate
fibers where fluorescent nanoparticles are encapsulated in the
inner alginate particles of the fiber. The fibers were spun using a
motor. Scale bars=200 .mu.m. Panel (b) illustrates encapsulation of
FITC conjugated BSA in the inner alginate particles in the
alginate-in-oil-in-alginate fiber composite structure stored in DI
water for 20 hours. Scale bars=100 .mu.m. Panel (c) illustrates
alginate-in-oil-in-alginate fiber, where the oil compartment
contained a ferrofluid, flowing out of the outlet tubing of the
microfluidic device. Inset bright field image shows the structure
of the magnetic multicompartment fiber. Scale bar=200 .mu.m. As
illustrated in panel (d), the fiber was deflected in the direction
of a magnet, as indicated by the arrow. Panel (e) illustrates
fibroblast cells after 6 days of growing inside the fiber with
ferrofluid-oil droplets, forming the cell spheroids. Panel (f)
illustrates the finding that cell-encapsulated fibers, spun on the
needles using a motor, formed a thin cell-sheet of alginate
hydrogel embedded with ferrofluid-oil droplets. Scale bars=200
.mu.m.
[0038] FIG. 9 illustrates growth of GFP-expressing E. Coli around
the oil compartment of 2 wt % Span80 (also known as sorbitane
monooleate, or sorbitan oleate) in mineral oil in the alginate
fiber. Black arrows indicate where the oil droplets were inside the
fiber. Scale bars=200 .mu.m.
[0039] FIG. 10 illustrates non-limiting examples of
alginate-in-oil-in alginate fibers. Panel (a) illustrates overlaid
bright-field and fluorescence images of alginate-in-Nile Red
oil-in-alginate fibers suspended in water showing the long-term
stability of the multicomponent fibers. Scale bars=200 .mu.m. Panel
(b) illustrates that the oil compartment dissolved and shrank in
volume in water when more soluble oil, such as eugenol, was used as
the oil compartment instead of mineral oil. Scale bars=100 .mu.m.
Panel (c) illustrates bright-field and fluorescence images of
alginate-in-Nile Red oil-in-alginate fibers in a water/ethanol
solution, where the presence of ethanol caused the contents of the
oil compartment to escape the fiber as shown by the loss of dye
from the oil compartments. Scale bars=200 .mu.m.
[0040] FIG. 11 is a non-limiting diagrammatic illustration of an
exemplary composition of droplets-in-fiber with core droplets in
the form of (panel A) single emulsions and (panel B) double
emulsions.
[0041] FIG. 12 is a non-limiting diagrammatic illustration of an
exemplary microfluidic device for making droplets-in-fiber (single
emulsion).
[0042] FIG. 13 is a non-limiting diagrammatic illustration of an
exemplary microfluidic device for making droplets-in-fiber (double
emulsion).
[0043] FIG. 14 is a non-limiting diagrammatic illustration of
selective grafting of the channel region (hatched) with hydrophilic
polymer for robust oil droplet generation in a hydrophobic
channel.
[0044] FIG. 15 is a set of non-limiting examples of drops-in-fiber
structures generated using a microfluidic method in accordance with
the present invention: (panel A) mineral oil-in-alginate
microfibers, (panel B) aligned alginate-in-mineral oil-in-alginate
microfibers, where the core alginate regions contained polystyrene
nanoparticles, (panel C) alginate-in-mineral oil-in-alginate
microfibers, where the outer alginate fiber contained fibroblast
cells, and (panel D) alginate-in-ferrofluid-in-alginate microfiber.
As illustrated in panel E, the fiber fell vertically when collected
but, as illustrated in panel F, the fiber was deflected in the
presence of a magnet.
[0045] FIG. 16 illustrates the formation of core-shell
droplet-in-fiber fibers. Panel a illustrates bright-field
microscopy image of microfluidic device during the production of
the core-shell droplet-in-fiber fibers, where water droplets were
flowed into a polymerizable hydrophobic monomer solution, which was
then flowed into a polymerizable hydrophilic monomer solution. The
monomer solutions were polymerized when exposed to UV light in the
main channel. Panel b illustrates bright-field microscopy image of
a core-shell droplet-in-fiber structure showing three compartments.
Panel c illustrates higher magnification view of the fiber
structure.
[0046] FIG. 17 illustrates fluorescence microscopy images of
droplet-in-fibers, where the aqueous droplets contain rhodamine
labeled dextran. As illustrated in panel a, the fibers were swollen
in 1 wt % tween 80 solution, where the concentration of dextran was
measured to be 2.4 wt %, then (panel b) the solution was changed to
20 wt % PEG.sub.8000 where the aqueous compartments shrunk over 21
hours and the concentration of dextran was measured to be 3.6 wt %.
As illustrated in panel c, the solution was again changed to 1 wt %
tween 80, where the aqueous compartments were swollen to recover
almost the same concentration as in panel a, after approximately 27
hours, 2.6 wt % dextran. The concentration of dextran in the fibers
was measured from the calibrated fluorescence intensity. The fibers
produced in this figure were prepared by pulsed UV light, so that
they were of short uniform length. Scale bars=500 .mu.m.
[0047] FIG. 18 illustrates hydrophobic droplet-in-fibers wrapped
around needles immersed in water. On the left, the fiber precursor
solution contained 76 vol % PEG.sub.250DA, 20 vol % PEG.sub.700DA
and 4 vol % photoinitiator. On the right, the fiber precursor
solution contained 96 vol % PEG.sub.250DA and 4 vol %
photoinitiator. Both fibers contained aqueous droplets with 1 wt %
erioglaucine (blue dye). The presence of the higher molecular
weight monomer allowed the blue dye to diffuse out of the fiber.
The inset image shows a higher magnification view of the fibers
containing only PEG.sub.250DA. Scale bar=1 cm.
DETAILED DESCRIPTION OF THE INVENTION
[0048] The present invention provides novel methods and devices for
preparing multi-compartment microfibers comprising droplets
embedded along the length of the fiber. The present invention
further provides microfibers prepared using the methods and/or
devices recited herein. Fibers in accordance with the present
invention can be used, for example, for the efficient storage and
release of multiple cargos. Such fibers can also, for example,
comprise magnetic materials, allowing for external actuation.
[0049] In certain embodiments, the present invention provides a
passive microfluidic process that comprises a droplet generation
step and a fiber formation step. In other embodiments, the
inventive microfluidic methods and devices allow for the in situ
fabrication of novel composite fibers based on the droplet-in-fiber
structure.
[0050] The present disclosure recites a passive microfluidic
approach to the fabrication of multicompartment fibers that exhibit
a droplet-in-fiber structure. The inventive methods and devices
allow for embedding double emulsion droplets in fibers, which may
be hydrophobic or hydrophilic, (comprising, in a non-limiting
example, alginate and polyethylene glycol di-acrylate (PEG-DA), and
allow for encapsulation of various materials, both
hydrophilic/hydrophobic, solid/liquid, and biological/inorganic.
For example, the inventive methods and devices allow for preparing
encapsulating fibers with a magnetic property, or for preparing a
cell scaffold, so that cell behaviors in response to certain
chemicals compartmentalized within the fiber can be studied.
[0051] The hierarchical structure of the inventive fibers allows
for more choices on the materials to be encapsulated in the fiber
itself, and on the solvents used to release the material. Unlike a
method that employs solvent evaporation of the oil droplets for
incorporating polymer spheres in a fiber, the inventive methods
allow for encapsulating double emulsions inside the fiber, and for
creating hydrogel particles inside the fiber. These embedded double
emulsion droplets arranged along the length of the fiber provide a
heterogeneous microenvironment where distinct microcompartments
have alternating hydrophilic or hydrophobic characteristics, as
well as contrasting physical states (for example, solid versus
liquid).
[0052] The alternating properties of the microcompartments, where
there are repeating regions with alternating hydrogel-oil-hydrogel
environments, can be used for the co-encapsulation of both
lipophilic and hydrophilic compounds. Such fiber structures can be
used, for example, for the co-encapsulation and co-delivery of
compounds with incompatible solubilities, selective dissolution,
and multifunctionality.
[0053] In certain embodiments, the microfluidic methods of the
present invention are modular, and the devices of the present
invention comprise distinct regions for sequential generation of
each of the components that makes up the final fiber structure.
This modular approach makes it possible to add various droplet
operations, such as alternating droplet flow for introducing
distinct chemistries, or modules to control the length and shape of
the fibers, which can be used to generate more advanced fiber
structures with greater composition and geometry control for
diverse applications.
[0054] It is difficult to stably deliver drugs to the specific site
using microcapsules or microparticles, because those usually show
high initial burst release rates. In contrast, the core-droplet
generation in the fiber is a robust method of compartmentalization
at the microscale. Further, the droplets-in-fiber of the present
invention enables more spatiotemporal control in the release
profile, and also allows for either simultaneous or sequential
delivery of multiple materials. The compartmentalization within the
fibers of the present invention allow for compounds not commonly
combined within one construct, possibly due to incompatible
solubilities or the need for very different release profiles, to be
combined within the same structure, stored within their preferred
microenvironment, and co-delivered to the desired target.
[0055] In certain embodiments, the methods of the present invention
allow for the fabrication of composite fiber structures that
exhibit a high level of spatial control within the fiber structure.
In other embodiments, the methods of the present invention allow
for embedding droplets at regularly spaced positions along the
length of the fiber. In yet other embodiments, the methods of the
present invention allow for embedding droplets at preselected
positions, within experimental error, along the length of the
fiber.
[0056] In certain embodiments, the droplets-in-fiber structure is a
one-dimensional array of stored droplets, and thus temporal order
of droplet production is preserved within the fiber structure. When
generating only droplets or particles via a sequential process such
as a microfluidic process, the information of each particle, such
as temporal order of production and the sequence of multiple and
varying chemistries, is lost when collected in the outlet. Current
technology needs a method to incorporate an index in each particle
to save the information. The present invention saves the
spatiotemporal information of droplet generation by keeping the
droplets in order inside the fiber as they are produced.
[0057] In certain embodiments, the present invention has an
advantage over typical methods of dispersing functional
microparticles in polymer because it produces ordered composites as
opposed to a random dispersion of the particles in bulk polymer.
The in situ production of droplets-in-fiber controls the dispersity
of the particles and the spatial alignment of different
materials.
[0058] The encapsulation capabilities of the fiber structures of
the present invention were demonstrated by testing the ease of
loading various cargos within each type of microcompartment in the
fiber, where the cargo can be a model drug or a component that adds
functionality to the fiber, such as magnetic properties. In a
non-limiting example, the fiber of the present invention can be
used as a cell scaffold, allowing for loading of distinct chemicals
in the droplet. In certain embodiments, cells can be easily
encapsulated in the fiber through the microchannel along with the
double emulsion droplets, and the cells dispersed in the fiber can
eventually grow for several days into densely packed aggregates. In
another non-limiting example, the distinct microcompartments
present in the fibers of the present invention, including the outer
fiber body and each of the droplet compartments, can be selectively
dissolved or removed by exposure to solvents of suitable
polarity.
[0059] The microfibers of the present invention may be utilized in
a novel delivery system for therapeutics, such as wound dressing
with encapsulated functional drugs or antibiotics. Another
exemplary use of the microfibers of the present invention is in
tissue engineering as a tissue scaffold, where biodegradable and
biocompatible compounds are used in the fiber composition. Cells
can be grown within or on the composite fiber and their positions
can be controlled depending on the cells' affinity for the
compartments in the fiber. Furthermore, one of the compartments can
be utilized to physically manipulate the fibers, such as
encapsulation of magnetic particles to move the fiber under
magnetic force, while other compartments retain their
functionality.
DEFINITIONS
[0060] As used herein, each of the following terms has the meaning
associated with it in this section.
[0061] As used herein, unless defined otherwise, all technical and
scientific terms generally have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. Generally, the nomenclature used herein and the
laboratory procedures in surface chemistry are those well-known and
commonly employed in the art.
[0062] As used herein, the articles "a" and "an" refer to one or to
more than one (i.e. to at least one) of the grammatical object of
the article. By way of example, "an element" means one element or
more than one element.
[0063] As used herein, the term "about" will be understood by
persons of ordinary skill in the art and will vary to some extent
on the context in which it is used. As used herein, "about" when
referring to a measurable value such as an amount, a temporal
duration, and the like, is meant to encompass variations of .+-.20%
or .+-.10%, more preferably .+-.5%, even more preferably .+-.1%,
and still more preferably .+-.0.1% from the specified value, as
such variations are appropriate to perform the disclosed
methods.
[0064] As used herein, the term "fluid" refers to a homogeneous or
heterogeneous phase that is capable of demonstrating fluidic
(flowing) behavior under the experimental conditions under
consideration. In certain embodiments, a fluid comprises a liquid
or a gas. In other embodiments, the fluid consists essentially of a
liquid or a gas. In yet other embodiments, the fluid consists of a
liquid or a gas.
[0065] As used herein, the term "instructional material" includes a
publication, a recording, a diagram, or any other medium of
expression that may be used to communicate the usefulness of the
compositions, devices and/or methods of the present invention. In
certain embodiments, the instructional material may be part of a
kit useful for generating compositions of the present invention.
The instructional material of the kit may, for example, be affixed
to a container that contains compositions and/or devices of the
present invention or be shipped together with a container that
contains compositions and/or devices of the present invention.
Alternatively, the instructional material may be shipped separately
from the container with the intention that the recipient uses the
instructional material and compositions, methods and/or devices
cooperatively. For example, the instructional material is for use
of a kit; or instructions for use of the compositions, methods
and/or devices of the present invention.
[0066] As used herein, the term "microdevice" refers to a device
that has at least one component with at least one spatial dimension
less than 1 millimeter.
[0067] As used herein, the term ".mu.m" is the abbreviation for
"micron" or "micrometer", and it is understood that 1 .mu.m=0.001
mm=10.sup.-6 m=1 millionth of a meter.
[0068] As used herein, the term "nanodevice" refers to a device
that has at least one component with at least one spatial dimension
less than 1 micron.
[0069] As used herein, the term "nm" is the abbreviation for
"nanometer" and it is understood that 1 nm=1 nanometer=10.sup.-9
m=1 billionth of a meter.
[0070] As used herein, the term "soluble" as applied to two or more
phases refers to the fact that the two or more phases can mix and
stay as a resulting homogenous phase without significant phase
separation over time. In a non-limiting example, water and
hydrophobic liquids (such as oils and liquid waxes) are not
substantially soluble in each other.
[0071] As used herein, the term "tween 80" refers to a polyethylene
sorbitol ester also known as Polysorbate 80, PEG (80) sorbitan
monooleate, or polyoxyethylenesorbitan monooleate.
[0072] As used herein, the term "wettable by a fluid" as applied to
a material refers to the fact that the material has similar
polarity, chemical composition and/or physical composition to the
fluid and the material have favorable molecular interactions. In
certain embodiments, a hydrophilic fluid has a lower contact angle
than a hydrophobic fluid when interacting with a hydrophilic
material. In other embodiments, a hydrophobic fluid has a lower
contact angle than a hydrophilic fluid when interacting with a
hydrophobic material. In yet other embodiments, a hydrophilic fluid
has a higher spreading coefficient than a hydrophobic fluid when
interacting with a hydrophilic material. In other embodiments, a
hydrophobic fluid has a higher spreading coefficient than a
hydrophilic fluid when interacting with a hydrophobic material.
[0073] Throughout this disclosure, various aspects of the present
invention may be presented in a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the present invention.
Accordingly, the description of a range should be considered to
have specifically disclosed all the possible sub-ranges as well as
individual numerical values within that range and, when
appropriate, partial integers of the numerical values within
ranges. For example, description of a range such as from 1 to 6
should be considered to have specifically disclosed sub-ranges such
as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6,
from 3 to 6, and so on, as well as individual numbers within that
range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This applies
regardless of the breadth of the range.
DISCLOSURE
[0074] In certain embodiments, the methods and devices of the
present invention allow for the preparation of a fiber comprising
core-droplets arranged along the length of the fiber at regularly
spaced and/or specific locations. The core-droplets can be either
single emulsions (FIG. 11, panel A) or multiple emulsions, such as
double emulsions (FIG. 11, panel B).
[0075] A wide range of materials, which are in liquid state prior
to solidification, can be used to prepare the fibers of the present
invention. For example, fibers can be synthesized from precursor
solutions using polymerization (for example, photochemical
polymerization or thermal polymerization), solvent extraction (or
phase inversion), covalent crosslinking (for example, covalently
crosslinking a protein or any other amine-containing polymer with
glutaraldehyde or any other oligo- or polyaldehyde) and/or ionic
crosslinking (for example, alginate and a polyvalent ion such as
Ca.sup.2+). For example, biodegradable hydrophobic polyester fibers
can be synthesized from polymer solutions using solvent extraction
to achieve solidification.
[0076] The composition of the core-droplets, which is immiscible
with the continuous phase in which it forms, can also be widely
varying. In certain embodiments, a drops-in-fiber configuration has
adjacent phases in the fiber structure alternating with respect to
their hydrophobic/hydrophilic properties. In other embodiments, in
the case of drops-in-fiber structures generated from aqueous two
phase systems (ATPS), all compartments in the fiber may be
hydrophilic. Each of the phases--the outer fiber body and each of
the layers in the core-droplets--may also contain materials that
are dissolved or dispersed in the precursor solutions prior to
fiber generation and become encapsulated within that phase of the
fiber.
[0077] In certain embodiments, the core droplets are solid, thus
ensuring that the droplets do not escape the fiber body. Such
embodiments may be beneficial, for example, when the inner water
droplets in water-in-oil-in-alginate fibers are unstable and tend
to escape the middle oil phase to merge with the outer fiber phase.
The core droplets may be solidified using polymerizable materials,
such as alginate and others. Alternatively, liquid core droplets
may be stabilized with various surfactant and nanoparticle
stabilizers, such as in Pickering emulsions.
[0078] In certain embodiments, the process of generating
droplets-in-fiber structures uses passive microfluidic devices that
rely on droplet breakup and hydrodynamic focusing mechanisms. One
such device comprises, for example, a sequence of modular device
operations, such as a flow-focusing junction or t-junction, where
each module adds to the complexity of the fiber structure and
composition. This modular approach makes it possible to add
distinct droplet operations, such as alternating droplet flow for
alternating chemistries, into the overall device geometry for added
complexity in the fiber structure. The specific methods for
producing single emulsion and double emulsion droplets-in-fiber
structures are illustrated herein in non-limiting embodiments.
[0079] In non-limiting embodiments, the method of generating
droplets-in-fiber (single emulsion) includes the following steps.
Step 1: generation of core-droplets in continuous phase 1. Step 2:
fiber formation from continuous phase 1 in continuous phase 2.
[0080] Continuous phase 1 templates the final solid fiber
structure. Continuous phase 2 is a sheath flow that focuses the
stream of continuous phase 1, and may contain chemicals that
trigger solidification of the stream of continuous phase 1. The
composition of the solution of the core-droplets is selected so
that it is immiscible with continuous phase 1, allowing for the
formation of droplets. In non-limiting examples, the core-droplets
are oil immiscible with an aqueous alginate solution of continuous
phase 1, and continuous phase 2 is an aqueous stream with dissolved
calcium chloride. In that particular case, the calcium ions
crosslink the alginate stream to form the fiber with encapsulated
oil droplets. Alternatively, in non-limiting examples, the
core-droplets are oil immiscible with an aqueous polyamine solution
of continuous phase 1, and continuous phase 2 is an aqueous stream
with dissolved glutaraldehyde or another polyaldehyde; or the
core-droplets are oil immiscible with an aqueous
acrylamide/bisacrylamide solution of continuous phase 1, and
continuous phase 2 is an aqueous stream with dissolved ammonium
persulfate or another soluble oxidant, and so on.
[0081] In certain embodiments, the device for making
droplets-in-fiber (single emulsion) includes modules for generating
core-droplets in continuous phase 1, and forming fibers from
continuous phase 1 in continuous phase 2. For step 1, the channel
module can be in the form of a focusing channel or t-junction. For
step 2, the channel module can be in the form of a focusing channel
(FIG. 12)
[0082] In non-limiting embodiments, the method for generating
droplets-in-fiber (double emulsion) includes the following steps.
Step 1: generation of core-droplets in continuous phase 1. Step 2:
generation of double-emulsions (core-droplets in continuous phase
1) in continuous phase 2. Step 3: fiber formation from continuous
phase 2 in continuous phase 3.
[0083] Continuous phase 1 is the outer layer of the double emulsion
droplets. Continuous phase 2 becomes the outer fiber structure.
Continuous phase 3 is a sheath flow which focuses the stream of
continuous phase 2 to form the fiber, and may contain chemicals
that trigger solidification of the fiber. In certain embodiments,
the core-droplets comprise an alginate solution, and continuous
phase 1 comprises an oil phase immiscible with the alginate
solution. In other embodiments, continuous phase 2 comprises an
alginate solution, and continuous phase 3 comprises calcium
chloride solution; or continuous phase 2 comprises a polyamine
solution, and continuous phase 3 comprises a solution comprising
glutaraldehyde or another polyaldehyde; or continuous phase 2
comprises an aqueous acrylamide/bisacrylamide solution, and
continuous phase 3 comprises ammonium persulfate or another aqueous
oxidant.
[0084] In certain embodiments, the device for making
droplets-in-fiber (double-emulsion) comprises modules for
generating core-droplets in continuous phase 1, generating double
emulsions (core-droplets in continuous phase 1) in continuous phase
2, and forming fibers from continuous phase 2 in continuous phase
3. For step 1 and step 2, the channel module can be in the form of
a focusing channel or t-junction. For step 3, the channel module
can be in the form of a focusing channel (FIG. 13)
[0085] Microfluidic devices can be fabricated from any material
that can form a channel structure, such as polydimethylsiloxane
(PDMS), glass, silicon, polycarbonate, thiolene based resins
(Norland Optical Adhesive), and/or polymethylmethacrylate. The mold
of the microchannel can be fabricated using, for example, a
conventional photolithography technique, etching, milling, 3D
printing, and pulled glass capillaries. The channel structures can
be bonded to form a closed channel with openings for inlets and
outlets.
[0086] In certain embodiments, the surface wetting characteristics
of the microchannel walls are of interest when forming multiple
emulsions. In other embodiments, the continuous phase has to
appropriately wet the walls in the region of the microchannel, so
that stable droplets of the non-wetting phase are formed therein.
For example, in order to generate aqueous phase core-droplets in a
continuous oil phase, the channel walls should be hydrophobic. For
the inverse emulsion, oil/hydrophobic droplets in an aqueous
stream, the channel walls must be hydrophilic. To vary the wetting
properties of the channel walls, graft hydrophilic polymer can be
selectively grafted in desired regions of a hydrophobic channel. In
non-limiting examples, in a hydrophobic microfluidic channel the
region of oil droplet generation in aqueous phase is selectively
grafted with hydrophilic polymer for example, poly(acrylic acid)
(FIG. 14). Other methods can be used to selectively functionalize
PDMS, for example, layer-by-layer deposition of polyelectrolytes
(Bauer, et al., 2010 Lab Chip 10:1814) and photoreactive sol-gel
coatings (Abate, et al., 2008 Lab Chip 8:2157).
Compositions
[0087] The invention provides microfibers, which are exemplified in
a non-limiting manner herein. The invention should not be construed
to be limited to the description herein, and contemplates any
combination(s) of the embodiments recited herein.
[0088] In one aspect, the invention provides a microfiber
comprising a matrix material, wherein the microfiber further
comprises a plurality of droplets embedded in the matrix material
along the length thereof. Each one of the plurality of droplets
independently comprises a single fluid, and is insoluble in the
matrix material of the microfiber.
[0089] In another aspect, the invention provides a microfiber
comprising a matrix material, wherein the microfiber further
comprises a plurality of droplets embedded in the matrix material
along the length thereof. Each one of the plurality of droplets
independently comprises an emulsion comprising a first droplet
phase within a second droplet phase. Further, the matrix material
of the microfiber is insoluble in the second droplet phase of each
one of the plurality of droplets.
[0090] In yet another aspect, the invention provides a microfiber
comprising an outer matrix material and an inner matrix material;
wherein the outer matrix material and the inner matrix material
span the length of the microfiber; and wherein the inner matrix
material is embedded in the outer matrix material. The microfiber
further comprises a plurality of droplets embedded in the inner
matrix material along the length thereof. Further, the inner matrix
material of the microfiber is insoluble in each one of the
plurality of droplets and in the outer matrix material.
[0091] In certain embodiments, the matrix material is hydrophilic.
In other embodiments, the matrix material is hydrophobic.
[0092] In certain embodiments, the matrix material is prepared from
a precursor using at least one method selected from the group
consisting of polymerization, solvent extraction, ionic
crosslinking and covalent crosslinking. In other embodiments, the
matrix material is prepared from a precursor using at least one
method selected from the group consisting of polymerization,
solvent extraction, and covalent crosslinking. In yet other
embodiments, the matrix material is not prepared from a precursor
using ionic crosslinking. In yet other embodiments, the matrix
material is not prepared from a precursor using polymerization. In
yet other embodiments, the matrix material is not prepared from a
precursor using solvent extraction. In yet other embodiments, the
matrix material is not prepared from a precursor using ionic
crosslinking. In yet other embodiments, the matrix material is not
prepared from a precursor using covalent crosslinking.
[0093] The composition of any of the matrix materials contemplated
may vary, or not vary, along the length of the microfiber.
Likewise, each one of the plurality of the droplets has a like
composition, or the compositions of the plurality of the droplet
are not identical among themselves. The fibers may comprise at
least one agent selected from the group consisting of a cell,
tissue, filler, therapeutic drug, chemoattractant, biocide, ion,
peptide, protein, nucleic acid, magnetic compound, and detectable
probe. Such agent may be embedded in the matrix material or in at
least one of the plurality of droplets. In the case that such agent
is magnetic compound (such as, but not limited to, iron, nickel,
cobalt, oxides thereof, and the like), the fiber can interact with
magnetic fields and may be manipulated physically by exposure to a
magnetic field (such as the magnetic field of a magnet).
[0094] In certain embodiments, the fluid comprising a droplet and
the matrix material in which the droplet is embedded have distinct
polarity and solubility profiles, so that they cannot dissolve in
each other. For example, one may be hydrophobic and the other may
be hydrophilic, and vice versa.
[0095] In certain embodiments, the fiber comprises an outer matrix
material and an inner matrix material, both materials spanning the
length of the fiber. In other embodiments, those materials may be
coaxially aligned with each other. In yet other embodiments, those
materials may be located so that they do not share the same
longitudinal axis. In yet other embodiments, the radius of at least
one selected from the group consisting of the outer matrix material
and inner matrix material is substantially constant along the
length of the microfiber.
[0096] In certain embodiments, the fibers have an average width
selected from the group consisting of: from about 10 .mu.m to about
1 mm, from about 10 .mu.m to about 900 .mu.m, from about 10 .mu.m
to about 800 .mu.m, from about 10 .mu.m to about 700 .mu.m, from
about 10 .mu.m to about 600 .mu.m, from about 10 .mu.m to about 500
.mu.m, from about 10 .mu.m to about 400 .mu.m, from about 10 .mu.m
to about 300 .mu.m, from about 10 .mu.m to about 200 .mu.m, from
about 10 .mu.m to about 100 .mu.m, from about 100 .mu.m to about 1
mm, from about 100 .mu.m to about 900 .mu.m, from about 100 .mu.m
to about 800 .mu.m, from about 100 .mu.m to about 700 .mu.m, from
about 100 .mu.m to about 600 .mu.m, from about 100 .mu.m to about
500 .mu.m, from about 100 .mu.m to about 400 .mu.m, from about 100
.mu.m to about 300 .mu.m, from about 100 .mu.m to about 200 .mu.m,
and any fractions or multiples thereof.
[0097] In certain embodiments, the fibers have an average length
that is equal to or greater than a value selected from the group
consisting of: about 100 .mu.m, about 200 .mu.m, about 300 .mu.m,
about 400 .mu.m, about 500 .mu.m, about 600 .mu.m, about 700 .mu.m,
about 800 .mu.m, about 900 .mu.m, about 1 mm, about 2 mm, about 5
mm, about 10 nm, about 20 mm, about 40 mm, about 60 mm, about 80
mm, about 100 mm, about 200 mm, about 400 mm, about 600 mm, about
800 mm, about 1 m, or any fractions or multiples thereof.
[0098] In certain embodiments, the droplets embedded in the fibers
have an average diameter selected from the group consisting of:
about 10 .mu.m, about 20 .mu.m, about 30 .mu.m, about 40 .mu.m,
about 50 .mu.m, about 60 .mu.m, about 70 .mu.m, about 80 .mu.m,
about 90 .mu.m, about 100 .mu.m, about 200 .mu.m, about 300 .mu.m,
about 400 .mu.m, about 500 .mu.m, and any fractions or multiples
thereof.
[0099] In certain embodiments, the linear distance between two
consecutive droplets embedded in a fiber is independently selected
from the group consisting of: about 100 .mu.m, about 200 .mu.m,
about 300 .mu.m, about 400 .mu.m, about 500 .mu.m, about 600 .mu.m,
about 700 .mu.m, about 800 .mu.m, about 900 .mu.m, about 1 mm,
about 2 mm, about 5 mm, about 10 nm, about 20 nm, about 40 nm,
about 60 nm, about 80 nm, about 100 nm, or any fractions or
multiples thereof.
Devices and Systems
[0100] The present invention provides devices for preparing
microfibers, which are exemplified in a non-limiting manner herein.
The invention should not be construed to be limited to the
description herein, and contemplates any combination(s) of the
embodiments recited herein.
[0101] The present invention provides a microfluidic device such
as, but not limited to, the device illustrated in FIG. 12. The
device comprises a first microfluidic duct for delivering a first
fluid ("core-droplet materials"); a second microfluidic duct for
delivering a second fluid ("continuous phase 1"), the second fluid
being immiscible with the first fluid, wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith ("channel junction for step 1").
The device further comprises a third microfluidic duct that is in
fluid communication with the first fluidic junction and is wettable
by the second fluid; a fourth microfluidic duct for delivering a
third fluid ("continuous phase 2"), wherein the third microfluidic
duct opens into the fourth microfluidic duct and forms a second
fluidic junction therewith ("channel junction for step 2"). The
device further comprises an outlet that is in fluid communication
with the second fluidic junction.
[0102] The present invention further provides a microfluidic device
such as, but not limited to, the device illustrated in FIG. 13. The
device comprises a first microfluidic duct for delivering a first
fluid ("core-droplet materials"); a second microfluidic duct for
delivering a second fluid ("continuous phase 1"), the second fluid
being immiscible with the first fluid, wherein the first
microfluidic duct opens into the second microfluidic duct and forms
a first fluidic junction therewith ("channel junction for step 1").
The device further comprises a third microfluidic duct that is in
fluid communication with the first fluidic junction and is wettable
by the second fluid; a fourth microfluidic duct for delivering a
third fluid ("continuous phase 2"), wherein the third microfluidic
duct opens into the fourth microfluidic duct and forms a second
fluidic junction therewith ("channel junction for step 2"). The
device further comprises a fifth microfluidic duct that originates
from the second fluidic junction and is wettable by the third
fluid; a sixth microfluidic duct for delivering a fourth fluid
("continuous phase 3"), wherein the fifth microfluidic duct opens
into the sixth microfluidic duct and forms a third fluidic junction
therewith ("channel junction for step 3"). The device further
provides an outlet that is in fluid communication with the third
fluidic junction.
[0103] The present invention further provides a system comprising a
microfluidic device and first, second and third fluid reservoirs.
The microfluidic device comprises first, second, third and fourth
microfluidic ducts and an outlet. The first fluid reservoir
comprises a first fluid and is in fluid communication with the
first microfluidic duct. The second fluid reservoir comprises a
second fluid and is in fluid communication with the second
microfluidic duct, the second fluid being immiscible with the first
fluid. The first microfluidic duct opens into the second
microfluidic duct and forms a first fluidic junction therewith. The
third microfluidic duct is in fluid communication with the first
fluidic junction and is wettable by the second fluid. The third
fluid reservoir comprises a third fluid and is in fluid
communication with the fourth microfluidic duct. The third
microfluidic duct opens into the fourth microfluidic duct and forms
a second fluidic junction therewith. The outlet is in fluid
communication with the second fluidic junction.
[0104] The present invention provides a system comprising a
microfluidic device and first, second, third and fourth fluid
reservoirs. The microfluidic devices comprises first, second,
third, fourth, fifth and sixth microfluidic ducts and an outlet.
The first fluid reservoir comprises a first fluid and is in fluid
communication with the first microfluidic duct. The second fluid
reservoir comprises a second fluid and is in fluid communication
with the second microfluidic duct, the second fluid being
immiscible with the first fluid. The first microfluidic duct opens
into the second microfluidic duct and forms a first fluidic
junction therewith. The third microfluidic duct is in fluid
communication with the first fluidic junction and is wettable by
the second fluid. The third fluid reservoir comprises a third fluid
and is in fluid communication with the fourth microfluidic duct.
The third microfluidic duct opens into the fourth microfluidic duct
and forms a second fluidic junction therewith. The fifth
microfluidic duct originates from the second fluidic junction and
is wettable by the third fluid. The fourth fluid reservoir
comprises a fourth fluid and is in fluid communication with the
sixth microfluidic duct. The fifth microfluidic duct opens into the
sixth microfluidic duct and forms a third fluidic junction
therewith. The outlet is in fluid communication with the third
fluidic junction.
[0105] The invention contemplates any type of fluidic junction
known in the art. In certain embodiments, each fluidic junction is
independently selected from the group consisting of a flow-focusing
junction and a t-junction. In other embodiments, at least one
fluidic junction is a flow-focusing junction. In yet other
embodiments, one or more additional microfluidic ducts open into
one or more of the microfluidic ducts recited herein, allowing for
the introduction of one or more additional fluids at any stage of
preparation of the microfiber.
[0106] In certain embodiments, one or more of the microfluidic duct
is at least partially coated with a polymer that is wettable by at
least one of the fluids being flowed through the one or more of the
microfluidic ducts, thus allowing formation of the appropriate
emulsion therein.
Methods
[0107] The invention provides methods of preparing microfibers,
which are exemplified in a non-limiting manner herein. The
invention further provides methods of physically displacing
microfibers, which are exemplified in a non-limiting manner herein.
The invention should not be construed to be limited to the
description herein, and contemplates any combination(s) of the
embodiments recited herein.
[0108] The invention provides a method of preparing a microfiber
using a device such as, but not limited to, the device illustrated
in FIG. 12. According to this procedure, the first fluid
("core-droplet materials") is delivered to the first microfluidic
duct and a second fluid ("continuous phase 1") is delivered to the
second microfluidic duct, whereby a first emulsion comprising the
first fluid into the second fluid is formed within or in the
proximity of the first fluidic junction ("channel junction for step
1"). Then, a third fluid ("continuous phase 2") is delivered to the
fourth microfluidic duct, whereby a mixture of the third fluid and
the first emulsion is formed within or in the proximity of the
second fluidic junction ("channel junction for step 1"). The
microfiber is then allowed to form within or in the proximity of
the outlet of the second fluidic junction.
[0109] The invention also provides a method of preparing a
microfiber using a device such as, but not limited to, the device
illustrated in FIG. 13. According to this procedure, the first
fluid ("core-droplet materials") is delivered to the first
microfluidic duct and a second fluid ("continuous phase 1") is
delivered to the second microfluidic duct, whereby a first emulsion
comprising the first fluid within the second fluid is formed within
or in the proximity of the first fluidic junction ("channel
junction for step 1"). Then, a third fluid ("continuous phase 2")
is delivered to the fourth microfluidic duct, whereby a second
emulsion comprising the first emulsion within the third fluid is
formed within or in the proximity of the second fluidic junction
("channel junction for step 2"). Then, a fourth fluid is delivered
to a sixth microfluidic duct, whereby a mixture of the fourth fluid
and the second emulsion is formed ("channel junction for step 3").
The microfiber is then allowed to form within or in the proximity
of the outlet of the third fluidic junction.
[0110] It should be noted that the system of the invention is
modular and thus the same inlets, ducts and/or fluidic junctions
need not be used throughout the preparation of the microfiber. The
invention contemplates, for example, using one or more first
fluids, one or more second fluids, and so forth during the
preparation of a microfiber of the present invention. Further, the
invention contemplates using one or more first microfluidic ducts,
one or more second microfluidic ducts, and so forth during the
preparation of a microfiber of the present invention. Further, the
invention contemplates using one or more first fluidic junctions,
one or more second fluidic junctions and so forth during the
preparation of a microfiber of the present invention. Such changes
in inlets, ducts and/or junctions may take place at any time during
the preparation of the microfiber; they may take place by
physically replacing any one of the inlets, ducts and/or fluidic
junctions with another one, or by directing the
microfiber-in-preparation to a new set of inlets, ducts and/or
fluidic junctions by virtue of a physical barrier or a physical
connection.
[0111] The invention further provides a method of physically
displacing a microfiber. The method comprises applying a magnetic
field to an inventive microfiber that comprises a magnetic
compound. In certain embodiments, the microfiber is repelled by the
magnetic field. In other embodiments, the microfiber is attracted
by the magnetic field.
[0112] Every formulation or combination of components described or
exemplified can be used to practice the invention, unless otherwise
stated. Specific names of compounds are intended to be exemplary,
as it is known that one of ordinary skill in the art can name the
same compounds differently. When a compound is described herein
such that a particular isomer or enantiomer of the compound is not
specified, for example, in a formula or in a chemical name, that
description is intended to include each isomers and enantiomer of
the compound described individual or in any combination. Although
the description herein contains many embodiments, these should not
be construed as limiting the scope of the present invention but as
merely providing illustrations of some of the presently preferred
embodiments of the present invention.
[0113] Those skilled in the art will recognize, or be able to
ascertain using no more than routine experimentation, numerous
equivalents to the specific procedures, embodiments, claims, and
examples described herein. Such equivalents were considered to be
within the scope of this invention and covered by the claims
appended hereto. For example, it should be understood, that
modifications in reaction conditions, including but not limited to
reaction times, reaction size/volume, and experimental reagents,
such as solvents, catalysts, pressures, atmospheric conditions,
e.g., nitrogen atmosphere, and reducing/oxidizing agents, with
art-recognized alternatives and using no more than routine
experimentation, are within the scope of the present application.
In general the terms and phrases used herein have their
art-recognized meaning, which can be found by reference to standard
texts, journal references and contexts known to those skilled in
the art. Any preceding definitions are provided to clarify their
specific use in the context of the present invention.
[0114] The following examples further illustrate aspects of the
present invention. However, they are in no way a limitation of the
teachings or disclosure of the present invention as set forth
herein.
EXAMPLES
[0115] The invention is now described with reference to the
following Examples. These Examples are provided for the purpose of
illustration only, and the invention is not limited to these
Examples, but rather encompasses all variations that are evident as
a result of the teachings provided herein.
Materials and Methods
Channel Fabrication:
[0116] The microfluidic device for making multicompartment
microfibers was fabricated from polydimethylsiloxane (PDMS) by soft
lithography. The mold of the microchannel, including a sequence of
flow-focusing channels, was fabricated by standard photolithography
from photoresist (SU-8 2010 and SU-8 2025, MicroChem) on a silicon
wafer. The mold of the top layer of the channel was fabricated on
the silicon wafer using two-step lithography of 30 .mu.m and 90
.mu.m in height, and the bottom layer was fabricated to be 80 .mu.m
in height. Channel dimensions are shown in FIG. 7.
[0117] A degassed 10:1 mixture of PDMS prepolymer and curing agent
(Sylgard 184, Dow Corning) was poured on the channel mold and
released after 2 hours of curing at 65.degree. C. The closed
channel structure with openings for inlets and outlets was formed
by bonding top and bottom layers of PDMS with plasma treatment. The
devices were heated at 95.degree. C. for a day to recover
hydrophobicity of the PDMS channels, and stored in vacuum
overnight, before localized grafting of the hydrophilic polymer,
poly(acrylic acid) (PAA). (Schneider, et al., 2011, Langmuir
27:1232). The channel was masked with black electrical tape leaving
only the region for oil droplet generation transparent. The channel
was filled with 10% w/v benzophenone (photoinitiator) in acetone
for 70-90 seconds, and flushed with air. Then the channel was
filled with 10 wt % acrylic acid in DI water and exposed under a
335 nm-610 nm Bandpass color filter to UV light for 90-150 seconds.
In this time range, the time of treatment with benzophenone and
acrylic acid was increased if the oil solution wet the PAA grafted
region when forming a droplet, and decreased if the alginate stream
started to adhere to the channel wall upon contact with calcium
chloride solution. The channel was washed with ethanol, pH 10
water, and DI water respectively, before fiber fabrication.
Chemical Sample Preparation:
[0118] For the sheath flow of the fiber formation, 1.5-2% (w/v) of
calcium chloride solution in DI water was used.
[0119] For the alginate fiber, 0.5-1 wt % sodium alginate (from
brown algae) with 0.1-0.25 wt % poly(vinyl alcohol) (PVA; Molecular
weight, 31,000-50,000) dissolved in DI water or PBS was used. PVA
is a biocompatible polymer. Also, after collecting the fibers, they
were rinsed with DI water or PBS, and stored in DI water to allow
any water-soluble components in the fiber to be removed. Then
UV-Vis spectroscopy was used to determine the presence of PVA,
which shows a maximum absorbance around 216 nm. No absorbance peaks
were observed in the wavelength range 210-240 nm from the sample
solution over 24 hours. For cell encapsulation, the alginate-PVA
solution was filtered through 0.22 .mu.m pore-sized filter prior to
mixing with cells. The mammalian cells, NIH/3T3 mouse fibroblast
cells (ATCC), were cultured in Dulbecco's modified Eagle medium
(DMEM; ATCC) supplemented with 10% (v/v) calf bovine serum and 1%
(v/v) penicillin. The cells were prepared to be 1-2.times.10.sup.5
cellsmL.sup.-1 in the final alginate solution. For encapsulating
mammalian cells in the alginate fiber, a solution of 0.5 wt %
alginate with 0.1 wt % PVA dissolved in PBS was used. The bacterial
cells were Escherichia coli (E. Coli, S17-1.lamda.pir) that express
green fluorescent protein (GFP) from a plasmid, induced by
isopropyl .beta.-D-1-thiogalactopyranoside (IPTG). More details on
the cells, including plasmid construction, is recited in Drescher,
et al., 2014, Curr. Biol. 24:50. The E. coli cells were prepared in
the alginate solution to be 4-5.times.10.sup.6 cellsmL.sup.-1. For
encapsulating bacterial cells, a solution of 1 wt % alginate with
0.25 wt % PVA dissolved in PBS was used.
[0120] For the oil droplet compartment, mineral oil with 2 wt %
Span 80 was used in general. For solidifying inner alginate
droplets to prevent them from escaping the oil compartment, 5%
(v/v) of calcium chloride-saturated undecanol was mixed with the
oil solution. The concentrations of the cargos to be carried in the
oil compartment were 0.3 mgmL.sup.-1 for Nile red, 0.8% (v/v) for
magnetic particles in oil-phase (EMG 909, FerroTec), and 10 and 20%
(v/v) for eugenol. To demonstrate the antibacterial effect of the
oil compartment to the bacterial cells encapsulated in the fiber,
eugenol was first mixed with undecanol and added to the final
concentration of 10 and 20% (v/v) in the oil compartment of 2 wt %
Span 80 in mineral oil. The final concentration of undecanol in the
oil solution was 5% (v/v). In the case of using just eugenol for
the oil compartment, 2 wt % Span 80 was added to eugenol to form
stable droplets.
[0121] The concentration of alginate-PVA solution in the inner
alginate compartment was kept the same as the alginate fiber. As
for the cargos, 0.5% (v/v) 200 nm orange fluorescent particles
(FluoSpheres, Invitrogen), 1% (w/v) FITC conjugated BSA, or 0.04%
(v/v) of 190 nm Dragon Green fluorescent particles (Uniform Dyed
Microspheres, Bangs Laboratories, Inc.) were mixed with the
alginate solution. For water-based magnetic particles, 2% (v/v) of
1 .mu.m-magnetic polystyrene particles were mixed in the alginate
solution. Chemicals not indicated with vendors were purchased from
Sigma-Aldrich.
Fiber Collection and Treatment:
[0122] Multicompartment fibers were collected as suspensions in DI
water or wound between two rotating needles controlled by a motor
(Barnant Motor Mixer, Model No. 700-5412). Fibers encapsulating the
fibroblast cells were collected in DMEM supplemented with 10% calf
bovine serum and 1% penicillin, and stored in the 5%
CO.sub.2-humidified incubator at 37.degree. C. To test the cell
viability inside the multicompartment fibers, 2 .mu.M of calcein AM
and 4 .mu.M of ethidium-homodimer-1 (EthD-1) from LIVE/DEAD
Viability/Cytotoxicity kit for mammalian cells (Molecular Probes)
were applied in the DMEM 1 hour prior to the observation under a
fluorescent microscope. The cell viability was analyzed with the
green (calcein AM) and red (EthD-1) fluorescence images using image
analysis software, ImageJ (NIH). E. coli-encapsulated fibers were
either collected in LB media containing 1 mM IPTG and 100
.mu.gmL.sup.-1 Kanamycin (kanamycin sulfate; Fisher). For selective
dissolution of the cargos from the oil compartment of the fibers,
ethanol (Reagent alcohol, BDH) was added to the fiber suspensions.
The de-cross-linking agent, 160 mM sodium citrate
(Na.sub.3C.sub.6H.sub.5O.sub.7, Sigma-Aldrich) in DI water was used
as calcium chelator to degrade the alginate fiber or inner alginate
particles.
Example 1
[0123] For the work described herein, the base composition of the
fiber was exemplified with calcium alginate, but the microfluidic
method of the present invention can be adapted to other
solidification methods such as photochemistry and solvent
extraction. Alginate is a biopolymer that can undergo a mild but
rapid gelation in the presence of divalent cations to form a
hydrogel. Thus, the fundamental structure of the fiber consisted of
an alginate-in-oil-in-alginate configuration.
[0124] A schematic of the channel configuration and the
multicompartment fiber is illustrated in FIG. 1, panel a. Oil
droplets were encapsulated in the fiber (FIG. 5), or water-in-oil
double emulsion droplets were encapsulated in the fiber (FIG. 1).
The hydrophobic walls of the polydimethylsiloxane (PDMS)
microchannel allow for making aqueous droplets in the oil
continuous phase and prevent adhesion during the production of the
hydrogel fibers. In order to make oil droplets in an aqueous
stream, the PDMS walls were chemically modified to become
hydrophilic in that region of the microchannel. To achieve the
hierarchical structuring, the microfluidic device comprises a
sequence of flow-focusing junctions. At the first junction,
droplets of alginate solution are generated in the oil phase, and
the alginate droplets are gelled by the calcium ions in the oil
phase (FIG. 1, panel b). In certain embodiments, the inner aqueous
phase may be gelled because the alginate particles are more stable
than aqueous droplets in the final fiber structure. At the second
junction, oil droplets containing alginate particles are formed in
alginate solution (FIG. 1, panel c). At the third junction, the
alginate fiber with embedded alginate particle-in-oil droplets is
formed as the alginate stream is focused by an outermost aqueous
sheath solution containing calcium ions, which triggers
solidification of the alginate stream (FIG. 1, panel d).
[0125] One advantage of using microfluidics for droplet generation
is the ease of customization of the size and density of the droplet
and particle microcompartments within the fiber structure. Selected
studies on the dimension and the stability of droplets in the
fibers are summarized in FIGS. 6-7. The methods of the present
invention allow for preparation of fibers with one alginate
particle per oil droplet (FIG. 1, panel e) or multiple alginate
particles per oil droplet (FIG. 1, panel f) according to the flow
rates described in FIG. 6. Without wishing to be limited by any
theory, the flow rate of the oil phase contributes to the stability
of the fiber because, at high flow rates, the oil solution may wet
the channel wall. In certain embodiments, the ratio of the flow
rates of the inner alginate phase to the oil phase were set at less
than 0.4, so that the inner alginate phase formed stable droplets
inside the oil phase. Also, the distance between the oil droplet
compartments in the fiber can be controlled by the dimension of the
channel and the flow rates (FIG. 7). Overall, the distance between
the droplets is inversely proportional to the droplet generation
frequency, which can increase with the flow rate of the oil phase
and decrease with an increase in channel dimension (by producing
larger volumes of the droplets). In the presently exemplified work,
the distance between the droplet compartments ranged from 750 .mu.m
to 16 mm, while the diameters of the droplet compartments ranged
from 113 .mu.m to 187 .mu.m. The width of the alginate stream
ranged from 80 .mu.m to 128 .mu.m, where there were no droplets.
The region surrounding the droplets were 10-20 .mu.m thicker. The
uniformity of the fiber width can be improved, for example, by
incorporating oil droplets with smaller diameters compared to the
width of the fiber, and also by increasing the strength of the
fiber using a higher concentration of alginate in the solution.
TABLE-US-00001 TABLE 1 Summary of multicompartment fiber
encapsulation. Fiber compartment Cargo FIG. (panel) Inner alginate
particle Fluorescent nanoparticles 2 (a); 8 (a); 4 (c)
FITC-conjugated BSA 8 (b) Magnetic microparticles 2 (b) Middle oil
droplet Fluorescent dye (Nile red) 4 (c); 10 (a) & (c)
Ferrofluid 2 (c); 8 (c)-(f) Eugenol (antimicrobial) 3; 10 (b)
Alginate fiber NIH/3T3 fibroblast cells 2 (c); 8 (e)-(f)
Escherichia coli 2 (d); 3; 9
Example 2
[0126] A wide variety of cargos can be added to the different
compartments of the microfiber. Table 1, FIG. 2 and FIG. 8
illustrate the encapsulation of various materials in the three
different microcompartments of the composite fiber. As
calcium-crosslinked alginate is hydrophilic and has pore sizes on
the order of 10 nm, the heterogeneous composite structure of the
fiber is more suitable for storing materials with various sizes and
chemistries. Thus, encapsulation of small molecule, macromolecule,
and micro- and nano-particulate cargo was investigated, some of
which are hydrophobic and others hydrophilic.
[0127] As a model particle cargo, 200 nm fluorescent nanoparticles
were added to the inner alginate particle to produce fluorescent
core microfibers (FIG. 2, panel a, and FIG. 8, panel a). The
nanoparticles were clearly encapsulated in the inner particles of
the fiber, and were not found elsewhere in the fiber structure.
Encapsulation of proteins was demonstrated by adding fluorescein
isothiocyanate (FITC) conjugated bovine serum albumin (BSA;
molecular weight: 66 kDa) to the alginate particles.
FITC-conjugated BSA encapsulated in the inner alginate particle was
also protected by the oil layer of the outer droplet compartment,
and the fluorescence was observed for at least 20 hours (FIG. 8,
panel b).
[0128] Similarly, magnetic microparticles of 1 .mu.m diameter were
added to the inner alginate particle. The magnetic alginate
particles allowed the fiber to respond to an external magnetic
field (FIG. 2, panel b), where the multicompartment fiber,
suspended in calcium chloride solution, was drawn towards a magnet.
The fibers can also exhibit magnetic properties by adding magnetic
material to the oil phase. To illustrate this feature, an oil-based
ferrofluid, containing 10 nm diameter iron oxide nanoparticles, was
incorporated in the oil droplets of the fiber to produce
magnetically responsive fibers (FIG. 8, panels c and d).
Example 3
[0129] A hydrogel fiber can be used to study three-dimensional cell
growth and as a scaffold for tissue engineering. The methods and
devices of the present invention allow for incorporating magnetic
properties in hydrogels, without having to disperse the magnetic
particles in the hydrogel precursors. With that objective,
oil-based ferrofluid was added in the oil compartment of the fibers
and mammalian cells were grown inside the alginate fiber (FIG. 2,
panel c; FIG. 8, panels e and f). The cells, which were randomly
dispersed throughout the outer alginate regions of the fiber
initially, grew and formed aggregates. Those aggregates continued
to increase in size to form large spherical aggregates over the
incubation period (FIG. 8, panel e). A live/dead assay showed high
viability (94% viability) of the cells after growing for 6 days
inside fibers that were freely suspended in cell medium. Since the
oil-based ferrofluid was localized only in the oil compartment,
very high concentrations of ferrofluid were encapsulated for strong
magnetic attraction without affecting the cells in the fiber.
Fibers spun with a motor formed a sheet of cells embedded with
ferrofluid droplets (FIG. 8, panel f). After 6 days, 84% of the
cells grown in the sheet were viable, showing more death of the
cells in the middle of the sheet possibly due to a deficiency of
oxygen and nutrient transport.
[0130] With respect to the use of magnetic particles in the
distinct compartments, the fibers can be retrieved and separated
from solution using a magnet, which subjects the fibers to less
mechanical stress than many other separation methods. So for
multistep procedures where the fibers need to be moved to different
solutions, such as multiple washing steps, magnetic separation is
convenient. Furthermore, the added magnetic functionality suggests
that the multicompartment fibers can be utilized in bioseparations
and assembly.
Example 4
[0131] The growth of bacterial cells, Escherichia coli (E. coli),
in the oil droplet-in-alginate fibers (FIG. 2, panel d) was also
tested. The E. coli cells encapsulated in the fibers were suspended
in the LB medium for 21 hours, and grew well inside the fibers
where they completely surrounded the oil droplets (FIG. 9). The oil
microcompartments of the fiber can be used to encapsulate
hydrophobic drugs or antibacterial chemicals to test their effects
on the cells. For example, eugenol is an antibacterial compound
found in clove oil. Eugenol was dissolved in the oil compartment,
in a solution comprising mineral oil with 5% (v/v) undecanol and 2
wt % Span 80. The undecanol was used to aid the mixing of eugenol
oil with the mineral oil. Qualitatively, a reduction in the overall
growth rate of E. coli was observed in the presence of the
eugenol-oil droplets inside the fiber, at eugenol concentrations up
to 10% (v/v). However, no significant difference in the cell growth
was around the eugenol droplets (FIG. 3, panel a), compared with
the cells around oil droplets with no eugenol (FIG. 9). At 20%
(v/v) eugenol-oil droplets, a significant decrease in the cell
population around the oil droplets was observed (FIG. 3, panel b).
Thus, multicompartment fibers carrying either oil or water-based
droplets can be used to study the effect of drugs on cells, even
with chemicals of low solubility in water. Also, the encapsulated
droplets provide another method to localize and pattern multiple
cell types inside the fiber according to the attractive or
repulsive characteristics of the cells towards the contents of the
droplets.
Example 5
[0132] The multicompartment fibers of the present invention
exhibited long-term stability when stored in water.
Alginate-in-oil-in-alginate fibers were prepared, and stored in
deionized (DI) water. The fibers were monitored periodically over a
30 days period, and no significant changes in the fiber structure
were observed during this time (FIG. 10, panel a). The fiber
compartments--inner alginate particles, oil droplets, and the
alginate fiber itself--remained intact during a month of storage in
DI water, showing no evidence of droplet coalescence. Thus, the
multicompartment fibers can be used as a stable storage system of
the alginate particles or oil droplets.
[0133] The previously described experiments were conducted with
mineral oil as the oil phase. However, when oil with higher
miscibility in water, such as eugenol, was used (solubility in
water, 2.46 mgmL.sup.-1), the fiber structure change over time.
Eugenol droplets (100% eugenol) embedded in the fiber dissolve in
water, shrinking from 120 .mu.m to 50 .mu.m in diameter over a
period of 2 hours (FIG. 10, panel b). Depending on properties such
as size and hydrophilic/hydrophobic affinity, the materials to be
encapsulated in the droplet compartment can be stably stored or
released over time from the fiber.
[0134] Upon demand, the droplet compartment stored inside the fiber
can also be released and recovered. Calcium alginate gels can be
dissolved using chelating agents, such as sodium citrate, where the
citrate anions remove the calcium cations from the alginate gel,
thereby uncrosslinking the gel. In order to demonstrate the release
of the oil compartments, an aqueous solution of sodium citrate was
added to a suspension of the multicompartment fibers of the present
invention in DI water. The alginate gel that composes the main body
of the fibers began to dissolve, releasing the oil droplets, which
then floated to the surface of the solution (FIG. 4, panel a). In
the early stages of dissolution, the inner alginate particles in
the oil droplets remained intact and were visible in the released
oil droplets. The inner alginate particles did eventually dissolve
leaving only oil droplets in solution. Without wishing to be
limited by any theory, there was an intermediate step in the
dissolution of some of the inner alginate particles (FIG. 4, panel
b); upon release of the oil droplets from the fiber, the intact
inner alginate particles, which appeared to have shell structures,
first ruptured and broke into pieces, and then eventually dissolved
completely.
[0135] To study the effect of the hydrophobic chemical on the
cells, a lipophilic compound such as eugenol, which has slight
solubility in water, was used. If the miscibility of the compounds
in the oil droplets is too low to cause passive release in pure
water, a suitable solvent, such as dimethylsulfoxide (DMSO), may be
added at low concentrations to aid in the removal of the contents
of the oil microcompartments of the fibers. For non-biological
applications, stronger organic solvents may be used.
[0136] As a non-limiting example, ethanol was used to affect oil
phase removal. The oil phase, which was a solution of mineral oil,
5% (v/v) undecanol, and 2 wt % Span 80 surfactant, was slightly
miscible with ethanol, and thus was able to slowly escape the oil
microcompartments in the fiber in the presence of ethanol.
Alginate-in-oil-in-alginate fibers were prepared with 0.3
mgmL.sup.-1 of a lipophilic fluorescent dye, Nile Red, in the oil
droplets, and green fluorescent nanoparticles of 190 nm diameter in
the inner alginate particles; one fiber sample was immersed in
water, and the second fiber sample was immersed in an ethanol/water
solution. The red fluorescence of the Nile Red dye in the oil
microcompartments was observed in the fiber immersed over 18 hours
in water (FIG. 4, panel c, left). However, upon addition of
ethanol, the red fluorescence in the oil droplets of the fibers
became less intense and appeared more diffuse over time (FIG. 10,
panel c). After a longer time, no further red fluorescence was
observed in the fibers, which indicates that the lipophilic dye
partitioned from the oil microcompartments into the suspending
solution because of the presence of ethanol. In addition, the oil
microcompartments lost their spherical shape as their contents were
removed (FIG. 4, panel c, right). Green fluorescence from the
nanoparticles encapsulated in the inner alginate particles of the
fibers was still observed, indicating that the core structures were
unaffected by the presence of ethanol. Without wishing to be
limited by any theory, materials that are already encapsulated
inside the inner alginate particles remain inside as long as the
material has lower affinity towards the solvents. Depending on the
solvents suitable for the specific application, materials may be
encapsulated either in the aqueous phase or the oil phase; as there
is a broad range available for material selection. This highlights
the fact that the multicompartment fibers of the present invention
can be applied towards various biological and non-biological
applications.
Example 6
[0137] The present invention includes fiber microstructures such as
a core-shell droplet-in-fiber structure. In such structure, there
are three microcompartments, wherein the middle hydrophobic
compartment is a continuous core that spans the length of the
fiber. In certain embodiments, higher loading capacities are
achieved due to the larger hydrophobic compartment of the fiber
core, as opposed to the hydrophobic droplet phase of the
double-emulsion-in-fiber structure.
[0138] Water droplets in a hydrophobic monomer solution, composed
of 60 vol % trimethylolpropane triacrylate (TMPTA), 20 vol %
eugenol and 20 vol % Darocur 1173 photoinitiator, were generated at
the first flow-focusing junction. The TMPTA solution, containing
water droplets, was flowed into a hydrophilic monomer solution,
composed of 54 vol % poly(ethylene glycol diacrylate) (PEG-DA;
MW=575 g/mol), 42 vol % water and 4 vol % photoinitiator at the
second flow-focusing junction. Because the interfacial tension
between the TMPTA and PEG monomer solutions was very low, the TMPTA
jet remained as a stable stream within the PEG solution, without
significant breaks. The three phases (water, TMPTA and PEG) were
flowed into a non-reactive oil solution, composed of hexadecane
with 4 vol % Span 80, at the third junction. Again, as the
interfacial tension between the oil and PEG phases was very low,
the streams did not fragment into droplets. FIG. 16, panel a,
illustrates various solutions flowing in the microfluidic device.
Once in the main channel, the solutions were exposed to UV light,
and converted to a solid fiber, composed of a hydrophilic shell
with a continuous hydrophobic core containing water droplets (FIG.
16, panels b-c).
Example 7
[0139] Hydrophobic droplet-in-fibers were prepared according to the
methods of the present invention. Water droplets were embedded in a
UV-polymerized hydrophobic fiber using the microfluidic method of
the present invention, using two flow-focusing junctions. Aqueous
droplets were first formed in a hydrophobic monomer solution of
poly(ethylene glycol) diacrylate (PEG-DA, MW=250 g/mol) with 4 vol
% photoinitiator at the first junction, then the water-PEG phases
were sheathed by a non-reactive oil phase, composed of hexadecane
with 10 vol % Span 80 at the second flow-focusing junction. The
PEG-DA jet was crosslinked when exposed to UV light in the main
channel. Hydrophobic fibers containing aqueous droplets were thus
produced. Various compounds were dissolved into the aqueous
droplets, including a food grade dye, erioglaucine, rhodamine
labeled dextran and the protein, xylanase. The dissolved compounds
remained within the aqueous compartments. However, water and other
small molecules diffused in and out of the microcompartments
depending on the composition of the suspending medium. For example,
as shown in FIG. 17, when the fibers are suspended in an aqueous
solution containing 1 wt % Tween 80, the aqueous compartments
appeared swollen due to influx of water, but appear deflated when
suspended in a 20 wt % solution of poly(ethylene glycol) (MW=8000
g/mol). This indicates that the concentration of the dissolved
compound can be changed within the fiber. The ability of varying
the osmotic property of the aqueous compartment may be used in
applications that require controlled concentration changes, such as
protein crystallization, as well as in sensing applications and
controlled release applications.
[0140] Further, if the composition of the fiber precursor solution
was change, for example, by adding a small amount of longer chain
PEG-DA monomer, the permeability of the fiber is varied, allowing
for the release of the dissolved compounds from the fiber (FIG.
18).
[0141] The disclosures of each and every patent, patent
application, and publication cited herein are hereby incorporated
herein by reference in their entirety.
[0142] While the invention has been disclosed with reference to
specific embodiments, it is apparent that other embodiments and
variations of this invention may be devised by others skilled in
the art without departing from the true spirit and scope of the
present invention. The appended claims are intended to be construed
to include all such embodiments and equivalent variations.
* * * * *