U.S. patent application number 13/453886 was filed with the patent office on 2012-08-16 for bioerodible matrix for tissue involvement.
This patent application is currently assigned to ALLERGAN, INC.. Invention is credited to Thomas E. Powell, Dennis E. Van Epps.
Application Number | 20120207837 13/453886 |
Document ID | / |
Family ID | 42561305 |
Filed Date | 2012-08-16 |
United States Patent
Application |
20120207837 |
Kind Code |
A1 |
Powell; Thomas E. ; et
al. |
August 16, 2012 |
BIOERODIBLE MATRIX FOR TISSUE INVOLVEMENT
Abstract
Disclosed herein are polyurethane polymer matrices with a
porosity of from about 20 microns to about 90 microns that are
useful in promoting closure and protection of incision sites;
supporting the lower pole position of breast implants; and
providing a partial or complete covering of breast implants to
provide a beneficial interface with host tissue and to reduce the
potential for malpositioning or capsular contracture. The disclosed
matrices can be seeded with mammalian cells.
Inventors: |
Powell; Thomas E.; (Santa
Barbara, CA) ; Van Epps; Dennis E.; (Goleta,
CA) |
Assignee: |
ALLERGAN, INC.
Irvine
CA
|
Family ID: |
42561305 |
Appl. No.: |
13/453886 |
Filed: |
April 23, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12705177 |
Feb 12, 2010 |
|
|
|
13453886 |
|
|
|
|
61164344 |
Mar 27, 2009 |
|
|
|
Current U.S.
Class: |
424/486 ;
424/93.7 |
Current CPC
Class: |
A61L 27/56 20130101;
A61L 27/18 20130101; A61L 27/3804 20130101; A61F 2/12 20130101;
A61L 27/3834 20130101; C08L 75/04 20130101; A61L 27/34 20130101;
C08L 67/04 20130101; A61P 17/00 20180101; A61L 2430/04 20130101;
A61L 2420/06 20130101; A61L 27/3886 20130101; A61L 27/58 20130101;
A61L 27/18 20130101; A61L 27/3604 20130101; A61L 27/18
20130101 |
Class at
Publication: |
424/486 ;
424/93.7 |
International
Class: |
A61K 35/12 20060101
A61K035/12; A61K 9/00 20060101 A61K009/00; A61P 17/00 20060101
A61P017/00 |
Claims
1. A medical implant for promoting tissue generation in a patient,
the medical implant comprising a matrix including a resorbable or
bioerodible polymer component and a cellular component.
2. The medical implant of claim 1 wherein the polymer component
comprises silk.
3. The medical implant of claim 1 wherein the polymer component is
a polyurethane polymer.
4. The medical implant of claim 1 wherein the polymer component
comprises a porous polyurethane polymer.
5. The medical implant of claim 1 wherein the polymer component
comprises a porous polyurethane polymer having a porosity of from
about 20 microns to about 350 microns.
6. The medical implant of claim 1 wherein the polymer component
comprises polycarolactone soft segments.
7. The medical implant of claim 1 wherein the cellular component
comprises stem cells.
8. The medical implant of claim 1 wherein the cellular component
comprises adipose cells.
9. The medical implant of claim 1 wherein the cellular component
comprises stem cells and adipose cells.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/705,177, filed Feb. 12, 2010, which claims priority to
U.S. Provisional Patent Application No. 61/164,344, filed Mar. 27,
2009, the entire disclosures of which are incorporated herein by
this reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to medical implants
for reconstruction, augmentation and/or wound healing and more
specifically relates to such implants including a polymer component
and a cellular component.
BACKGROUND OF THE INVENTION
[0003] Often following damage such as a surgical incision, skin can
benefit from additional support to promote wound healing. This is
in part because spontaneous recovery can require a long period of
time and pain can continue throughout the repair process.
[0004] Repair of soft tissue defects also is critical following
reconstructive and augmentative surgeries. For example, more than
250,000 reconstructive procedures are performed on the breast each
year. Women afflicted with breast cancer, congenital defects or
damage resulting from trauma have very few alternatives to
reconstruction. Surgery of the breast can also be cosmetic.
Cosmetic surgeries include augmentation, for example, using
implants; reduction; and reconstruction.
[0005] Mesh or matrix materials are generally used to provide
strength to fascia and soft tissue weakened by surgery or to
provide lift to soft tissue for reconstructive or cosmetic
purposes. There are basically two types of mesh or matrix materials
used surgically for these purposes, synthetic fiber meshes and
natural or modified organic or animal derived matrix materials. In
the synthetic fiber category, polypropylene, polyester and
polytetrafluoroethylene have been the primary materials used and
are sold by a number of different companies with variations in pore
size and weight. Current versions of the synthetic materials have
incorporated coatings or modifications of the fibers to enhance
biocompatibility. These current materials used to promote wound
healing or for soft tissue reconstruction or augmentation, however,
still suffer from shortcomings such as suboptimal volume retention,
donor site morbidity, and in some instances, continued poor
biocompatibility.
[0006] Accordingly, it is desirable to promote wound healing and
soft tissue reconstruction or augmentation by providing a suitable
matrix material for these purposes.
SUMMARY OF THE INVENTION
[0007] The present invention is generally directed to bioresorbable
or bioerodible polymer implants useful in reconstructive surgical
procedures, augmentation surgical procedures, promotion of wound
healing, and closure and protection of incision sites, without
limitation thereto.
[0008] Advantageously, the present implants are structured to be
useful in conjunction with traditional breast implants, for
example, for supporting the lower pole position of breast implants.
Further, the present implants may be used to provide a partial or
complete covering of breast implants, for example, traditional or
conventional breast implants. In this case, the present implants
may be effective in providing a beneficial interface with host
tissue thereby reducing the potential for malpositioning or
capsular contracture.
[0009] More specifically, the present implants comprise a polymer
component, for example, an resorbable or erodible material in the
form of a matrix (hereinafter, sometimes, "bioerodible or
bioresorbable matrix") comprising, for example, a polyurethane
formulation. The matrix may comprise polycarolactone, for example,
soft segments of polycarolactone, or another suitable material. In
specific embodiments, the matrices are at least one or more of the
following: biocompatible, resistant to loads experienced during
surgical implant; pliable, porous, sterilizable, remoldable, for
example, by invading tissue, and erodible or resorbable as new
tissue is formed.
[0010] The matrices may be porous. For example, in some
embodiments, the matrices have a porosity of between about 20
microns and about 350 microns. The porous matrices can be seeded
with stem cells or progenitor cells prior to or during implantation
in the body. When seeded with cells, the matrices may have an
enhanced effectiveness in replacement thereof with the patient's
own viable tissue.
[0011] There are many potential particular uses of the disclosed
matrices. The disclosed matrices can promote wound healing and soft
tissue reconstruction or augmentation by providing strength and
covering for incisions and/or by providing support and a substrate
for tissue in-growth and for growth of cells seeded on the matrix.
Particularly, the disclosed matrices can comprise interconnecting
cells or a fibrous network with enough strength to provide closure
and protection of incision sites. The matrices can also support the
lower pole position of breast implants or be used for mastopexy.
Additionally the matrices can be used as a partial or complete
covering of breast implants to provide a beneficial interface with
host tissue and to reduce the potential for malpositioning or
capsular contracture.
[0012] Following implantation, the disclosed matrices can be
absorbed into the body over time. This absorption can coincide as
infiltrating tissue replaces the matrix material. Thus, the matrix
can provide temporary scaffolding and well-defined structure during
wound healing and soft tissue reconstruction or augmentation. The
methods may further comprise the step of seeding the matrix with
viable cellular material prior to or during implantation.
[0013] Also provided are methods of promoting wound healing or
wound closure, for example, at an incision site. The methods
generally comprise implanting a matrix, for example a bioerodible
or bioresorbable polymer matrix as described elsewhere herein, at
the wound or incision site and allowing the wound or incision to
heal while the implant is eroded or absorbed in the body and is
replaced with the patient's own viable tissue. The methods may
further comprise the step of seeding the matrix with viable
cellular material prior to or during implantation.
[0014] Methods of augmenting or reconstructing the breast of a
human being are also provided. For example, a method is provided
for enhancing support of a conventional breast implant, for
example, enhancing support of the lower pole position of a breast
implant. For example, the method generally comprises the steps of
implanting a matrix, for example a bioerodible or bioresorbable
polymer matrix as described elsewhere herein, near or in proximity
to a breast implant, for example, a conventional breast implant,
and seeding the matrix with viable cellular material prior to or
during implantation.
[0015] The matrices can also be involved in a method of providing a
beneficial interface between host tissue and a prostheses, for
example, a breast implant. In some embodiments, the matrices are
structured to be effective to reduce the potential for
malpositioning or capsular contracture of breast implants. For
example, methods are provided for augmenting or reconstructing a
human breast, the methods generally comprising: providing a partial
or complete covering of breast implants wherein the partial or
complete covering comprises a matrix comprising a polymer, for
example, a porous polymer as described elsewhere herein, and the
porous polymer being seeded with viable cellular material. In some
embodiments, the matrix is a wrap-like configuration on a
conventional silicone or saline filled conventional breast implant.
The methods may further comprise the step of seeding the matrix
with viable cellular material prior to or during implantation.
[0016] The matrix material may comprise a woven or non-woven fabric
material, for example, a fiber spun, unwoven fabric such as felt,
or a foam material. As mentioned elsewhere herein, the matrix may
be porous.
[0017] In some embodiments, the matrices can comprise a
polyurethane polymer with a porosity of from about 20 microns to
about 350 microns In some embodiments, the matrix is a resorbable
polyurethane polymer. In some embodiments, the matrices are
polycarolactone soft segments appropriately shaped for implantation
at a surgical incision site.
[0018] In some embodiments of the invention, implants are provided
which comprise a polymer component, for example, such as the
bioerodible or bioresorbable polymer matrices described elsewhere
herein, and a cellular component, for example, viable stem cells
and adipose cells.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Following damage, such as that caused by a surgical
incision, skin can benefit from additional support to promote wound
healing. Mesh or matrix materials are generally used to provide
strength to fascia and soft tissue weakened by surgery or to
provide lift to soft tissue for reconstructive or cosmetic purposes
including breast reconstruction or mastopexy. Two types of mesh or
matrix materials are commonly used surgically for these purposes:
synthetic fiber meshes and natural or modified organic or animal
derived matrix materials. These currently-used materials, however,
still suffer from shortcomings such as suboptimal volume retention,
donor site morbidity, and in some instances, continued poor
biocompatibility.
[0020] Provided are resorbable matrices to provide strength and
covering for incisions and soft tissue reconstruction or
augmentation. The disclosed matrices can provide immediate strength
to an incision site or soft tissue reconstruction or augmentation
site and also provide a substrate for tissue in-growth. In certain
embodiments, the disclosed matrix can comprise interconnecting
cells or a fibrous network with enough strength to provide closure
and protection of incision sites. The disclosed matrices can also
support the lower pole position of breast implants or can be used
as a partial or complete covering of breast implants to provide a
beneficial interface with host tissue and to reduce the potential
for malpositioning or capsular contracture. Ultimately the
non-biologic resorbable material can be absorbed and the
infiltrating tissue can replace the matrix. Thus, the matrix can
provide temporary scaffolding and well-defined structure until it
is no longer needed.
[0021] In one embodiment of the disclosed matrices, the matrices
can comprise a bioerodible polyurethane formulation using
polycarolactone soft segments or another erodible material. In the
case of polyurethane matrices, this porosity should be between
about 20 microns and about 350 microns. Disclosed matrices can also
be seeded with stem cells or progenitor cells to enhance the
replacement of the matrices with viable tissue. In disclosed
embodiments the porosity of the material can be adjusted to achieve
optimal tissue interaction and viability.
[0022] In some embodiments of the invention, the matrix comprises a
biocompatible, bioerodible material which possess sufficient
mechanical properties to resist loads experienced during
implantation into the patient. The material is pliable and porous
to allow cell invasion or growth and is absorbed or degraded as new
tissue is formed.
[0023] The present matrices in some embodiments comprise
bioerodible biopolymers. As used herein, the term "biopolymer" is
understood to encompass naturally occurring polymers, as well as
synthetic modifications or derivatives thereof. Such biopolymers
include, without limitation, hyaluronic acid, collagen, recombinant
collagen, cellulose, elastin, alginates, chondroitin sulfate,
chitosan, chitin, keratin, silk, small intestine submucosa (SIS),
and blends thereof. These biopolymers can be further modified to
enhance their mechanical or degradation properties by introducing
cross-linking agents or changing the hydrophobicity of the side
residues. Other suitable biocompatible, bioerodible polymers
include, without limitation, aliphatic polyesters, polyalkylene
oxalates, polyamides, polycarbonates, polyorthoesters,
polyoxaesters, polyamidoesters, polyanhydrides, polyphosphazenes
and polyurethanes. Any suitable aromatic or aliphatic diisocyanates
can be used and are considered to be included within the scope of
the present invention.
[0024] Polyurethane materials are generally synthesized by reacting
polyisocyanates with polyols. In general, examples of polyols used
include polyether polyols such as poly(ethylene oxide) and
poly(propylene oxide), modified polyether polyols,
polytetramethylene glycol, condensation polyester polyols produced
by reacting dicarboxylic acids with diols, lactone-type polyester
polyols produced by ring opening polymerization of
.epsilon.-caprolactone or the like, and polycarbonate polyols.
[0025] When no additional protective agents are used in a
polyurethane polymer, the effect of moisture causes the pure
polyester polyurethanes having the polyol component based on adipic
acid and glycol to be hydrolytically degraded. The polyester
component in the soft segment is saponified by water, and the
polyurethane chains split into shorter units. This degradation
occurs even under mild conditions, i.e., at temperatures and at an
atmospheric humidity.
[0026] In one embodiment, a polyurethane polymer with beneficial
characteristics is obtained by reacting about 100 parts by weight
of a polyol mixture with 1,6-hexamethylene diisocyanate, isophorone
diisocyanate or dicyclohexylmethane 4,4'-diisocyanate and
diol-chain-lengthening means. The NCO coefficient, formulated from
the quotients of the equivalency ratios of isocyanate groups
multiplied by 100 and of the sum of the hydroxyl groups from the
polyol mixture and the chain-lengthening means, is from to about 97
to about 99. The polyol mixture consists of about 70 to about 90
parts by weight of polyester polyol having a molecular weight of
about 2000, based on adipic acid with ethane diol, butane diol,
hexane diol, diethylene glycol or neopentyl glycol, as well as of
about 10 to about 30 parts by weight of polyether polyol on the
basis of polyethylene glycol having a molecular weight of about 800
to about 4000. The chain lengthening means can be 1,4-butane diol
and/or 1,6-hexane diol. The 1,6-hexamethylene diisocyanate,
isophorone diisocyanate or dicyclohexylmethane 4,4'-diisocyanate
can be present in an equivalency ratio to the polyol mixture of
about 2.8:1.0 to about 12.0:1.0. The chain lengthening means can be
present in an equivalency ratio to the polyol mixture of about
1.75:1.0 to about 11.3:1.0.
[0027] The polyol mixture for preparing polyurethane polymers used
in the disclosed matrices can contain, on the one hand, about 70 to
about 90 parts by weight of polyester polyol having a molecular
weight of about 2000, on the basis of adipic acid with ethane diol
or with butane diol, hexane diol, diethylene glycol or neopentyl
glycol. On the other hand, the polyol mixture can contain about 10
to about 30 parts by weight of polyether polyol on the basis of
polyethylene glycol having a molecular weight of about 800 to about
4000.
[0028] In an equivalency ratio of about 2.8:1.0 to about 12.0:1.0
to the polyol mixture, the polyurethane compound contains, in
addition, 1,6-hexamethylene diisocyanate, isophorone diisocyanate
or dicyclohexylmethane 4,4'-diisocyanate.
[0029] Serving as chain lengtheners can be 1,4-butane diol or
1,6-hexane diol, alternately or in combination, in an equivalency
ratio to the polyol mixture of about 1.75:1.0 to about 11.3:1.0.
The NCO coefficient, formulated from the quotients of the
equivalency ratios of isocyanate groups multiplied by 100 and the
sum of the hydroxyl groups from the polyol combination and the
chain lengthener can amount to about 97 to about 99.
[0030] When aliphatic polyesters are used in making the disclosed
matrices, the aliphatic polyesters can be homopolymers or
copolymers (random, block, segmented, tapered blocks, graft,
triblock, etc.) having a linear, branched or star structure.
Suitable monomers for making aliphatic homopolymers and copolymers
include, but are not limited to, lactic acid, lactide (including
L-, D-, meso and L,D mixtures), glycolic acid, glycolide,
.epsilon.-caprolactone, p-dioxanone, trimethylene carbonate,
.DELTA.-valerolactone, .beta.-butyrolactone, .epsilon.-decalactone,
2,5-diketomorpholine, pivalolactone,
.alpha.,.alpha.-diethylpropiolactone, ethylene carbonate, ethylene
oxalate, 3-methyl-1,4-dioxane-2,5-dione,
3,3-diethyl-1,4-dioxan-2,5-dione, .gamma.-butyrolactone,
1,4-dioxepan-2-one, 1,5-dioxepan-2-one, 6,6-dimethyl-dioxepan-2-one
and 6,8-dioxabicycloctane-7-one.
[0031] Elastomeric copolymers also are appropriate for use in
making the disclosed matrices. Suitable elastomeric polymers
include those with an inherent viscosity in the range of about 1.2
dL/g to about 4 dL/g, in the range of about 1.2 dL/g to about 2
dL/g and in the range of about 1.4 dL/g to about 2 dL/g, as
determined at 25.degree. C. in a 0.1 gram per deciliter (g/dL)
solution of polymer in hexafluoroisopropanol (HFIP). Further,
suitable elastomers exhibit a high percent elongation and a low
modulus, while possessing good tensile strength and good recovery
characteristics. In particular disclosed embodiments, the elastomer
from which the matrix is formed exhibits a percent elongation
greater than about 200 percent or greater than about 500 percent.
In addition to these elongation and modulus properties, suitable
elastomers also should have a tensile strength greater than about
500 psi or greater than about 1,000 psi, and a tear strength of
greater than about 50 lbs/inch or greater than about 80
lbs/inch.
[0032] Exemplary bioerodible, biocompatible elastomers include, but
are not limited to, elastomeric copolymers of
.epsilon.-caprolactone and glycolide with a mole ratio of
.epsilon.-caprolactone to glycolide of from about 35/65 to about
65/35 or from about 35/65 to about 45/55; elastomeric copolymers of
.epsilon.-caprolactone and lactide where the mole ratio of
.epsilon.-caprolactone to lactide is from about 35/65 to about
65/35 or from about 35/65 to about 45/55; elastomeric copolymers of
lactide and glycolide where the mole ratio of lactide to glycolide
is from about 95/5 to about 85/15; elastomeric copolymers of
p-dioxanone and lactide where the mole ratio of p-dioxanone to
lactide is from about 40/60 to about 60/40; elastomeric copolymers
of .epsilon.-caprolactone and p-dioxanone where the mole ratio of
.epsilon.-caprolactone to p-dioxanone is from about 30/70 to about
70/30; elastomeric copolymers of p-dioxanone and trimethylene
carbonate where the mole ratio of p-dioxanone to trimethylene
carbonate is from about 30/70 to about 70/30; elastomeric
copolymers of trimethylene carbonate and glycolide where the mole
ratio of trimethylene carbonate to glycolide is from about 30/70 to
about 70/30; elastomeric copolymers of trimethylene carbonate and
lactide where the mole ratio of trimethylene carbonate to lactide
is from about 30/70 to about 70/30, or blends thereof.
[0033] Hydrogel polymers are hydrophilic, three-dimensional
networks that absorb or adsorb large amounts of water or biological
fluids, while maintaining their distinct three-dimensional
structure. Hydrogel polymers such as alginate, coral, agarose,
fibrin, collagen, cartilage, hydroxyapatite, calcium phosphate,
polylactic acid (PLA), polyglycolic acid (PGA) or their copolymer
(PLGA), chitosan, and polyethylene glycol-based polymers (peg-based
polymers) such as polyethylene glycol diacrylate, polyethylene
glycol dimethacrylate and mixtures thereof are also appropriate for
use. A polyethylene glycol diacrylate or dimethacrylate monomer can
have a molecular weight of about 1000 to about 100,000 daltons and
about 2000 to about 5000 daltons.
[0034] Polyethylene glycol-based hydrogel polymers have certain
advantages for tissue engineering applications because of their
biocompatibility and their demonstrated capacity to support growth
and differentiation of stem cells into multiple lineages. In one
embodiment, a matrix can be formed by polymerization of
polyethylene glycol diacrylate monomer [MW 3400; Shearwater
Polymers, Huntsville, Ala.]. In another embodiment, aliphatic
polyesters are synthesized in a ring-opening polymerization. The
monomers generally are polymerized in the presence of an
organometallic catalyst and an initiator at elevated temperatures.
In one embodiment, the organometallic catalyst is tin based, e.g.,
stannous octoate, and is present in the monomer mixture at a molar
ratio of monomer to catalyst ranging from about 10,000/1 to about
100,000/1. The initiator is typically an alkanol (including diols
and polyols), a glycol, a hydroxyacid, or an amine, and is present
in the monomer mixture at a molar ratio of monomer to initiator
ranging from about 100/1 to about 5000/1. The polymerization
typically is carried out at a temperature range from about
80.degree. C. to about 240.degree. C., or from about 100.degree. C.
to about 220.degree. C., until the desired molecular weight and
viscosity are achieved.
[0035] One of ordinary skill in the art will appreciate that the
selection of a suitable polymer or copolymer for forming the
disclosed matrices depends on several factors. The more relevant
factors in the selection of the appropriate polymer(s) that is used
to form the matrix include biodegradation kinetics; in vivo
mechanical performance; cell response to the material in terms of
cell attachment, proliferation, migration and differentiation; and
biocompatibility. Other relevant factors that, to some extent,
dictate the in vitro and in vivo behavior of the polymer include
the chemical composition, spatial distribution of the constituents,
the molecular weight of the polymer and the degree of
crystallinity.
[0036] The ability of the material substrate to resorb in a timely
fashion in the body environment is critical. But the differences in
the degradation time under in vivo conditions also can be the basis
for combining two different copolymers. For example, a copolymer of
35/65 .epsilon.-caprolactone and glycolide (a relatively fast
degrading polymer) is blended with 40/60 .epsilon.-caprolactone and
lactide copolymer (a relatively slow degrading polymer) to form the
matrix. In one embodiment, the rate of resorption of the matrix by
the body approximates the rate of replacement of the matrix by
tissue. That is to say, the rate of resorption of the matrix
relative to the rate of replacement of the matrix by tissue must be
such that the structural integrity required of the matrix is
maintained for the required period of time. Thus, the disclosed
matrices advantageously balance the properties of bioerodibility,
resorption and structural integrity over time and the ability to
facilitate tissue in-growth, each of which is desirable, useful or
necessary in tissue healing and soft tissue reconstruction or
augmentation.
[0037] In another embodiment, it can be desirable to use polymer
blends to form structures which transition from one composition to
another composition in a gradient-like architecture. Matrices
having this gradient-like architecture are particularly
advantageous in tissue healing and soft tissue reconstruction or
augmentation.
[0038] In one embodiment, the matrix can be made by a
polymer-solvent phase separation technique, such as lyophilization.
Generally, however, a polymer solution can be separated into two
phases by any one of four techniques: (a) thermally induced
gelation/crystallization; (b) non-solvent induced separation of
solvent and polymer phases; (c) chemically induced phase
separation, and (d) thermally induced spinodal decomposition. The
polymer solution is separated in a controlled manner into either
two distinct phases or two bicontinuous phases. Subsequent removal
of the solvent phase usually leaves a porous matrix having a
density less than that of the bulk polymer and pores in the
micrometer ranges.
[0039] The steps involved in the preparation of these matrices can
include choosing the appropriate solvents for the polymers to be
lyophilized and preparing a homogeneous solution of the polymer in
the solution. The polymer solution then can be subjected to a
freezing and a vacuum drying cycle. The freezing step
phase-separates the polymer solution and the vacuum drying step
removes the solvent by sublimation and/or drying, thus leaving a
porous, polymer matrix, or an interconnected, open-cell, porous
matrix.
[0040] Suitable solvents that can be used in the preparation of the
disclosed matrices include, but are not limited to,
hexafluoroisopropanol (HFIP), cyclic ethers (e.g., tetrahydrofuran
(THF) and dimethylene fluoride (DMF)), acetone, methylethyl ketone
(MEK), 1,4-dioxane, dimethlycarbonate, benzene, toluene, N-methyl
pyrrolidone, dimethylformamide, chloroform, and mixtures thereof. A
homogeneous solution of the polymer in the solvent is prepared
using standard techniques.
[0041] The applicable polymer concentration or amount of solvent
that can be utilized can vary with each system. Generally, the
amount of polymer in the solution can vary from about 0.01% to
about 90% by weight or from about 0.1% to about 30% by weight,
depending on factors such as the solubility of the polymer in a
given solvent and the final properties desired in the particular
matrix.
[0042] In one embodiment, solids can be added to the
polymer-solvent system to modify the composition of the resulting
matrix surfaces. As the added particles settle out of solution to
the bottom surface, regions can be created that can have the
composition of the added solids, not the matrix polymeric material.
Alternatively, the added solids can be more concentrated in desired
regions (i.e., near the top, sides, or bottom) of the resulting
matrix, thus causing compositional changes in all such regions.
[0043] A variety of types of solids can be added to the
polymer-solvent system. In one embodiment, the solids are of a type
that will not react with the polymer or the solvent. Generally, the
added solids can have an average diameter of less than about 1 mm
and in certain embodiments can have an average diameter of about 50
to about 500 microns. In particular embodiments, the solids can be
present in an amount such that they constitute from about 1 to
about 50 volume percent of the total volume of the particle and
polymer-solvent mixture (wherein the total volume percent equals
100 volume percent).
[0044] Exemplary solids include, but are not limited to, leachable
solids for pore creation and particles of bioerodible polymers not
soluble in the solvent system that are effective as reinforcing
materials or to create pores as they are degraded, non-bioerodible
materials, and biologically-derived bioerodible materials.
[0045] Suitable leachable solids include, without limitation,
nontoxic leachable materials such as salts (e.g., sodium chloride,
potassium chloride, calcium chloride, sodium tartrate, sodium
citrate, and the like), biocompatible mono and disaccharides (e.g.,
glucose, fructose, dextrose, maltose, lactose and sucrose),
polysaccharides (e.g., starch, alginate, chitosan) and water
soluble proteins (e.g., gelatin and agarose). The leachable
materials can be removed by immersing the matrix with the leachable
material in a solvent in which the particle is soluble for a
sufficient amount of time to allow leaching of substantially all of
the particles, but which does not dissolve or detrimentally alter
the matrix. In one embodiment, the matrix can be dried after the
leaching process is complete at a low temperature and/or vacuum to
minimize hydrolysis of the matrix unless accelerated degradation of
the matrix is desired.
[0046] In certain embodiments, mammalian cells can be seeded or
cultured with the disclosed matrices prior to implantation. Cells
that can be seeded or cultured on the matrices include, but are not
limited to, bone marrow cells, stem cells, mesenchymal stem cells,
synovial derived stem cells, embryonic stem cells, umbilical cord
blood cells, umbilical Wharton's jelly cells, precursor cells
derived from adipose tissue, bone marrow derived progenitor cells,
peripheral blood progenitor cells, stem cells isolated from adult
tissue and genetically transformed cells or combinations of the
above cells. The cells can be seeded on the matrices for a short
period of time (<1 day) just prior to implantation, or cultured
for a longer (>1 day) period to allow for cell proliferation and
extracellular matrix synthesis within the seeded matrix prior to
implantation.
[0047] In one embodiment, stem cells are seeded or cultured on the
disclosed matrices. De novo synthesis of soft tissue prepared from
stem cells within a matrix provides constructs for repair,
augmentation or reconstruction of soft tissue. Adult stem cells are
capable of differentiating into all connective tissue-forming cell
lineages including adipose tissue. Stem cells can be obtained with
minimally invasive procedures from bone marrow or other sources in
the body, are highly expandable in culture, and can be readily
induced to differentiate into adipose tissue-forming cells after
exposure to a well-established adipogenic inducing supplement
(Pittenger et al., Caplan, 2003).
[0048] In one embodiment stem cells are derived from bone marrow
cells. In addition, adipose tissue is an especially rich source of
stem cells. In both human and animal studies, processed
lipoaspirate (PLA) contains stem cells at a frequency of at least
0.1%, and more typically greater than 0.5%. In some instances, PLA
can be obtained which contains between about 2-12% stem cells. The
amount of stem cells obtained from PLA can be substantially greater
than the published frequency of 1 in 100,000 (0.001%) from marrow.
Furthermore, collection of adipose tissue is associated with lower
morbidity than collection of a similar volume of marrow. In
addition, adipose tissue contains endothelial precursor cells,
which are capable of providing therapy to patients.
[0049] When utilized as a source of stem cells, adipose tissue can
be obtained by any method known to a person of ordinary skill in
the art. For example, adipose tissue can be removed from a patient
by suction-assisted lipoplasty, ultrasound-assisted lipoplasty, and
excisional lipectomy. In addition, the procedures can include a
combination of such procedures. Suction assisted lipoplasty can be
desirable to remove the adipose tissue from a patient as it
provides a minimally invasive method of collecting tissue with
minimal potential for stem cell damage that can be associated with
other techniques, such as ultrasound assisted lipoplasty. The
adipose tissue should be collected in a manner that preserves the
viability of the cellular component and that minimizes the
likelihood of contamination of the tissue with potentially
infectious organisms, such as bacteria and/or viruses.
[0050] For some applications preparation of the active cell
population can require depletion of the mature fat-laden adipocyte
component of adipose tissue. This is typically achieved by a series
of washing and disaggregation steps in which the tissue is first
rinsed to reduce the presence of free lipids (released from
ruptured adipocytes) and peripheral blood elements (released from
blood vessels severed during tissue harvest), and then
disaggregated to free intact adipocytes and other cell populations
from the connective tissue matrix.
[0051] Disaggregation can be achieved using any conventional
techniques or methods, including mechanical force (mincing or shear
forces), enzymatic digestion with single or combinatorial
proteolytic enzymes, such as collagenase, trypsin, lipase, liberase
H1 and pepsin, or a combination of mechanical and enzymatic
methods. For example, the cellular component of the intact tissue
fragments can be disaggregated by methods using
collagenase-mediated dissociation of adipose tissue, similar to the
methods for collecting microvascular endothelial cells in adipose
tissue, as known to those of skill in the art. Additional methods
using collagenase that can be used are also known to those of skill
in the art. Furthermore, methods can employ a combination of
enzymes, such as a combination of collagenase and trypsin or a
combination of an enzyme, such as trypsin, and mechanical
dissociation.
[0052] The active cell population (processed lipoaspirate) can then
be obtained from the disaggregated tissue fragments by reducing the
presence of mature adipocytes. Separation of the cells can be
achieved by buoyant density sedimentation, centrifugation,
elutriation, differential adherence to and elution from solid phase
moieties, antibody-mediated selection, differences in electrical
charge; immunomagnetic beads, fluorescence activated cell sorting
(FACS), or other means.
[0053] In one embodiment, solutions contain collagenase at
concentrations from about 10 .mu.g/ml to about 50 .mu.g/ml and are
incubated at from about 30.degree. C. to about 38.degree. C. for
from about 20 minutes to about 60 minutes. A particular
concentration, time and temperature is 20 .mu.g/ml collagenase
(Blendzyme 1, Roche) incubated for 45 minutes, at about 37.degree.
C.
[0054] Following disaggregation the active cell population can be
washed/rinsed to remove additives and/or by-products of the
disaggregation process (e.g., collagenase and newly-released free
lipid). The active cell population could then be concentrated by
centrifugation. In one embodiment, the cells are concentrated and
the collagenase removed by passing the cell population through a
continuous flow spinning membrane system or the like, such as, for
example, the system disclosed in U.S. Pat. No. 5,034,135; and
5,234,608, which are incorporated by reference herein.
[0055] In addition to the foregoing, there are many post-wash
methods that can be applied for further purifying the active cell
population. These include both positive selection (selecting the
target cells), negative selection (selective removal of unwanted
cells), or combinations thereof. In another embodiment the cell
pellet could be resuspended, layered over (or under) a fluid
material formed into a continuous or discontinuous density gradient
and placed in a centrifuge for separation of cell populations on
the basis of cell density. In a similar embodiment continuous flow
approaches such as apheresis and elutriation (with or without
counter-current) could be used. Adherence to plastic followed by a
short period of cell expansion has also been applied in bone
marrow-derived adult stem cell populations. This approach uses
culture conditions to preferentially expand one population while
other populations are either maintained (and thereby reduced by
dilution with the growing selected cells) or lost due to absence of
required growth conditions. The active cells that have been
concentrated, cultured and/or expanded can be incorporated into
disclosed matrices.
[0056] In one embodiment, stem cells are harvested, the harvested
cells are contacted with an adipogenic medium for a time sufficient
to induce differentiation into adipocytes, and the adipocytes are
loaded onto a biocompatible matrix which is implanted. In
additional embodiments, at least some of the stem cells can be
differentiated into adipocytes so that a mixture of both cell types
is initially present that changes over time to substantially only
adipocytes, with stem cells being present in small to undetectable
quantities. Adipose tissue is fabricated in vivo by the stem cells
or prepared ex vivo by the stem cells.
[0057] Cells can be integrated with the disclosed matrices using a
variety of methods. For example, the matrices can be submersed in
an appropriate growth medium for the cells of interest, and then
directly exposed to the cells. The cells are allowed to proliferate
on the surface and interstices of the matrix. The matrix is then
removed from the growth medium, washed if necessary, and implanted.
Alternatively, the cells can be placed in a suitable buffer or
liquid growth medium and drawn through the matrix by using vacuum
filtration.
[0058] Cells can also be admixed with a precursor of the matrix,
and the matrix can then be constructed around the cells, capturing
at least some of the cells within the matrix network. In another
embodiment, the cells of interest are dissolved into an appropriate
solution (e.g., a growth medium or buffer) and then sprayed onto a
matrix while the matrix is being formed by electrospinning. This
method is particularly suitable when a highly cellularized matrix
is desired. Cells can also be electrosprayed onto the matrix during
electrospinning. As presently described, electrospraying involves
subjecting a cell-containing solution with an appropriate viscosity
and concentration to an electric field sufficient to produce a
spray of small charged droplets of solution that contain cells.
[0059] In one embodiment, the matrix is a biocompatible, resorbable
polyurethane polymer matrix with a pore size of about 20 microns to
about 350 microns that includes stem cells derived from bone marrow
and/or adipose tissue. This embodiment can also include an
adipogenic agent dispersed within the matrix. The adipogenic agent
can be, without limitation, proglitazone, growth factors of the
.beta.-family, prostaglandins, ciglitazone, dexamethasone or
combinations thereof.
[0060] Furthermore, the disclosed matrices can be used as a
therapeutic agent, or drug, release depot. The variety of different
therapeutic agents that can be used in conjunction with the
disclosed matrices is vast. In general, therapeutic agents that can
be administered via the disclosed matrices include, without
limitation: anti-rejection agents, analgesics, anti-oxidants,
anti-apoptotic agents such as erythropoietin, anti-inflammatory
agents such as anti-tumor necrosis factor .alpha., and combinations
thereof.
[0061] To form such a release depot, the polymer could be mixed
with a therapeutic agent prior to forming the matrix.
Alternatively, a therapeutic agent could be coated onto the
polymer, in one embodiment with a pharmaceutically acceptable
carrier. Any pharmaceutical carrier can be used that does not
dissolve the polymer. The therapeutic agent can be present as a
liquid, a finely divided solid, or any other appropriate physical
form. Typically, but optionally, the depot can include one or more
additives, such as diluents, carriers, excipients, stabilizers or
the like.
[0062] The amount of therapeutic agent can depend on the particular
agent being employed and the particular goal of providing the
therapeutic agent. Typically, the amount of agent can represent
about 0.001 percent to about 70 percent, about 0.001 percent to
about 50 percent, or about 0.001 percent to about 20 percent by
weight of the depot. The quantity and type of polymer incorporated
into the therapeutic agent delivery depot can vary depending on the
release profile desired and the amount of agent employed.
[0063] In another embodiment, a disclosed cell-seeded matrix can
undergo gradual degradation (mainly through hydrolysis) with
concomitant release of the dispersed therapeutic agent for a
sustained or extended period. This can result in prolonged
delivery, e.g. over about 1 to about 5,000 hours or over about 2 to
about 800 hours, of effective amounts, e.g. from about 0.0001
mg/kg/hour to about 10 mg/kg/hour, of the therapeutic agent. This
dosage form can be administered as is necessary depending on the
particular situation at hand. Following this or similar procedures,
those skilled in the art will be able to prepare a variety of
formulations.
[0064] In one embodiment, the structure of the matrix should be
effective to facilitate tissue ingrowth. One tissue
ingrowth-promoting matrix includes pores of a sufficient size to
permit cell growth therein. An effective pore size is one in which
the pores have an average diameter in the range of from about 10 to
about 1,000 microns, or from about 20 to about 90 microns.
[0065] In another embodiment, the matrix is a biocompatible,
resorbable polyurethane polymer matrix with a pore size of about 20
microns to about 350 microns that includes stem cells derived from
bone marrow and/or adipose tissue, and an adipogenic agent, a
nutrient medium, optionally a growth factor, and at least one
antibiotic. Exemplary adipogenic agents, nutrients and antibiotics
include, without limitation, amphotericin B, ciglitazone, biotin,
dexamethasone, gentamicin, insulin, 3-isobutyl-1-methylxanthine,
L-thyroxine or combinations thereof.
[0066] In another embodiment, the matrix is biocompatible,
bioerodible polyurethane formulation that can incorporate
polycarolactone soft segments. In this embodiment, pores can range
in size from about 20 microns to about 350 microns. The matrix can
be seeded with one or more mammalian cell types and/or therapeutic
agents.
[0067] As stated, the disclosed matrices have many potential uses
including, without limitation, as promoting closure and protection
of incision sites; supporting the lower pole position of breast
implants; and providing a partial or complete covering of breast
implants, for example, textured breast implants, to provide a
beneficial interface with host tissue and to reduce the potential
for malpositioning or capsular contracture.
[0068] Unless otherwise indicated, all numbers expressing
quantities or properties and so forth used in the specification and
claims are to be understood as being modified in all instances by
the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the specification and
attached claims are approximations that can vary depending upon the
desired properties sought to be obtained. At the very least, and
not as an attempt to limit the application of the doctrine of
equivalents to the scope of the claims, each numerical parameter
should at least be construed in light of the number of reported
significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting
forth the broad scope of the invention are approximations, the
numerical values set forth in the specific examples are reported as
precisely as possible. Any numerical value, however, inherently
contains certain errors necessarily resulting from the standard
deviation found in their respective testing measurements.
[0069] The terms "a," "an," "the" and similar referents used in the
context of describing the invention (especially in the context of
the following claims) are to be construed to cover both the
singular and the plural, unless otherwise indicated herein or
clearly contradicted by context. Recitation of ranges of values
herein is merely intended to serve as a shorthand method of
referring individually to each separate value falling within the
range. Unless otherwise indicated herein, each individual value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein is intended
merely to better illuminate the invention and does not pose a
limitation on the scope of the invention otherwise claimed. No
language in the specification should be construed as indicating any
non-claimed element essential to the practice of the invention.
[0070] Groupings of alternative elements or embodiments of the
invention disclosed herein are not to be construed as limitations.
Each group member can be referred to and claimed individually or in
any combination with other members of the group or other elements
found herein. It is anticipated that one or more members of a group
can be included in, or deleted from, a group for reasons of
convenience and/or patentability. When any such inclusion or
deletion occurs, the specification is deemed to contain the group
as modified thus fulfilling the written description of all Markush
groups used in the appended claims.
[0071] Certain embodiments of this invention are described herein,
including the best mode known to the inventors for carrying out the
invention. Of course, variations on these described embodiments
will become apparent to those of ordinary skill in the art upon
reading the foregoing description. The inventor expects skilled
artisans to employ such variations as appropriate, and the
inventors intend for the invention to be practiced otherwise than
specifically described herein. Accordingly, this invention includes
all modifications and equivalents of the subject matter recited in
the claims appended hereto as permitted by applicable law.
Moreover, any combination of the above-described elements in all
possible variations thereof is encompassed by the invention unless
otherwise indicated herein or otherwise clearly contradicted by
context.
[0072] Furthermore, references have been made to patents and
printed publications throughout this specification. Each of the
above-cited references and printed publications are individually
incorporated herein by reference in their entirety.
[0073] In closing, it is to be understood that the embodiments of
the invention disclosed herein are illustrative of the principles
of the present invention. Other modifications that can be employed
are within the scope of the invention. Thus, by way of example, but
not of limitation, alternative configurations of the present
invention can be utilized in accordance with the teachings herein.
Accordingly, the present invention is not limited to that precisely
as shown and described.
* * * * *