U.S. patent application number 16/634539 was filed with the patent office on 2021-03-25 for multi-layered graft for tissue engineering applications.
The applicant listed for this patent is Ri.MED Foundation, University of Pittsburgh - Of the Commonwealth System of Higher Education. Invention is credited to Antonio D'Amore, Matteo Solazzo, William R. Wagner.
Application Number | 20210085834 16/634539 |
Document ID | / |
Family ID | 1000005301826 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210085834 |
Kind Code |
A1 |
D'Amore; Antonio ; et
al. |
March 25, 2021 |
Multi-Layered Graft for Tissue Engineering Applications
Abstract
A multi-layer device is provided that is useful in tissue
regeneration, for example, for vascular regeneration, e.g., for use
in treatment of a coronary vascular disease, such as for treatment
of myocardial infarction. A method of making the device also is
provided.
Inventors: |
D'Amore; Antonio;
(Pittsburgh, PA) ; Solazzo; Matteo; (Dublin,
IE) ; Wagner; William R.; (Gibsonia, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Pittsburgh - Of the Commonwealth System of Higher
Education
Ri.MED Foundation |
Pittsburgh
Palermo |
PA |
US
IT |
|
|
Family ID: |
1000005301826 |
Appl. No.: |
16/634539 |
Filed: |
July 26, 2018 |
PCT Filed: |
July 26, 2018 |
PCT NO: |
PCT/US18/43889 |
371 Date: |
January 27, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62537143 |
Jul 26, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 31/125 20130101;
A61L 2430/40 20130101; A61L 2430/22 20130101; A61L 31/146 20130101;
A61L 31/16 20130101; A61L 33/0005 20130101; A61L 31/047 20130101;
A61L 31/148 20130101 |
International
Class: |
A61L 31/04 20060101
A61L031/04; A61L 33/00 20060101 A61L033/00; A61L 31/12 20060101
A61L031/12; A61L 31/16 20060101 A61L031/16; A61L 31/14 20060101
A61L031/14 |
Claims
1. A method of making a synthetic tubular graft device, comprising:
depositing an ECM gel layer over a first tubular, porous,
biodegradable polymer matrix; and depositing a second tubular,
porous, biodegradable polymer matrix over the ECM gel to produce a
tubular structure.
2. The method of claim 1, wherein the first tubular, porous,
biodegradable polymer matrix is a dry-electrospun matrix.
3. The method of claim 1, wherein the ECM gel is prepared from
vascular tissue.
4. The method of claim 1, wherein the second tubular, porous,
biodegradable polymer matrix is prepared by phase separation.
5. The method of claim 1, wherein the first tubular, porous,
biodegradable polymer matrix and/or the second tubular, porous,
biodegradable polymer matrix comprises one or more of: poly(lactic
acid) (PLA); poly(trimethylene carbonate) (PTMC);
poly(caprolactone) (PCL); poly(glycolic acid) (PGA);
poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(-lactide-co-dl-lactide); a polymer comprising monomers derived
from esters including polyhydroxybutyrate, polyhydroxyvalerate,
polydioxanone, and/or polyglactin; a polymer comprising monomers
derived from lactones; or a polymer comprising monomers derived
from carbonates including polycarbonate, polyglyconate,
poly(glycolide-co-trimethylene carbonate), or
poly(glycolide-co-trimethylene carbonate-co-dioxanone).
6. The method of claim 1, comprising: dry electrospinning a
poly(ester urethane) urea onto a mandrel to form the first tubular,
porous, biodegradable polymer matrix; placing the mandrel
comprising the first tubular, porous, biodegradable polymer matrix
within a cylindrical mold having an inside diameter greater than an
outside diameter of the first tubular, porous, biodegradable
polymer matrix; depositing an ECM pre-gel about the first tubular,
porous, biodegradable polymer matrix; gelling the ECM pre-gel about
the first tubular, porous, biodegradable polymer matrix; and
inserting the ECM gel-coated first tubular, porous, biodegradable
polymer matrix into a tube of a porous poly(ester urethane) urea
matrix.
7. The method of claim 1, wherein: the first tubular, porous,
biodegradable polymer matrix has an inner diameter of from 1 mm to
2 mm; the device has a wall thickness of from 200 .mu.m to 1 mm;
the thickness of the combined layers of the first tubular, porous,
biodegradable polymer matrix plus the ECM gel ranges from 100 .mu.m
to 500 .mu.m; or the thickness of the second tubular, porous,
biodegradable polymer matrix plus the ECM gel ranges from 50 .mu.m
to 250 .mu.m.
8. The method of claim 1, wherein either or both of the first
tubular, porous, biodegradable polymer matrix and the second
tubular, porous, biodegradable polymer matrix comprises an
anti-thrombogenic polymer composition.
9. A multi-layer synthetic graft device comprising: a first porous,
biodegradable polymer matrix; an ECM gel layer over the first
porous, biodegradable polymer matrix; and a second porous,
biodegradable polymer matrix over the ECM gel.
10. The device of claim 9, comprising: a first tubular, porous,
biodegradable polymer matrix; an ECM gel layer disposed
circumferentially about the first tubular, porous, biodegradable
polymer matrix; and a second tubular, porous, biodegradable polymer
matrix disposed circumferentially about the ECM gel, wherein the
first tubular, porous, biodegradable polymer matrix is optionally a
dry-electrospun matrix.
11. The device of claim 9, wherein the ECM gel is prepared from
vascular tissue.
12. The device of claim 9, wherein the second tubular, porous,
biodegradable polymer matrix is prepared by thermally induced phase
separation.
13. The device of claim 9, wherein the first tubular, porous,
biodegradable polymer matrix, and/or the second tubular, porous,
biodegradable polymer matrix comprises one or more of: poly(lactic
acid) (PLA); poly(trimethylene carbonate) (PTMC);
poly(caprolactone) (PCL); poly(glycolic acid) (PGA);
poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones; or a polymer comprising
monomers derived from carbonates including polycarbonate,
polyglyconate, poly(glycolide-co-trimethylene carbonate), or
poly(glycolide-co-trimethylene carbonate-co-dioxanone).
14. The device of claim 9, wherein: the first tubular, porous,
biodegradable polymer matrix has an inner diameter ranging from 1
mm to 2 mm; the device has a wall thickness of from 200 .mu.m to 1
mm; the thickness of the combined layers of the first tubular,
porous, biodegradable polymer matrix plus the ECM gel ranges from
100 .mu.m to 500 .mu.m; or the thickness of the second tubular,
porous, biodegradable polymer matrix plus the ECM gel ranges from
50 .mu.m to 250 .mu.m.
15. The device of claim 9, wherein either or both of the first
tubular, porous, biodegradable polymer matrix and the second
tubular, porous, biodegradable polymer matrix comprises an
anti-thrombogenic polymer composition.
16. A method of producing, repairing or replacing a tissue in a
patient, comprising implanting in the patient the device of claim 9
in the patient.
17. The method of claim 16, wherein the device is tubular and/or is
anastamosed to a blood vessel of the patient.
18-19. (canceled)
20. The method of claim 16, wherein the patient is suffering from
an ischemic event.
21. The method of claim 20, wherein the ischemic event is a
coronary artery disease, and the device is anastamosed to a
coronary artery.
22. A kit comprising the device according to claim 9 in suitable
packaging, such as a foil and/or plastic pouch or container, such
as a Mylar package.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/537,143 filed Jul. 26, 2017, which is
incorporated herein by reference in its entirety.
[0002] Coronary Heart Disease (CHD) affects 2-6% of the general
population currently representing the most common cause of death in
the developed countries with a total of 660 k/year coronary attacks
and 400 k deaths/year in the USA only. The speed in restoring
physiological perfusion conditions compromised by vessels stenosis
is a major factor regardless of the different therapeutic
intervention approaches currently available. Early stage critical
lesions are typically treated with angioplasty (with/without stent
support). Whereas, golden standard to treat more severe conditions
involves coronary artery bypass graft via autologous vessels such
as the saphenous vein, the internal thoracic artery, the radial
artery or the gastroepiploic artery.
[0003] Yet, due to limited tissue availability, relatively
inadequate performance and substantial donor-site morbidity the
native vessel transplants remain sub-optimal therapies. These
limitations have stressed the importance to continue efforts in
searching for alternative vascular grafts with improved incremental
outcomes. While being characterized by an extended half-life,
non-degradable materials such as PET (Dacron.RTM.) and ePTFE
(Teflon.RTM.) require daily anticoagulation therapy and generally
induce mechanical mismatch at the prosthesis--tissue interface.
Biological tissue (e.g., dECM, UBM, SIS) based graft has introduced
a number of advantages when compared to PET and ePTFE conduits.
However, control over device structure and function was partial due
to the substantial dependence on the tissue source and
decellularization protocol. Most importantly, thrombogenicity and
intimal hyperplasia still remain a relatively frequent failure
mechanism.
[0004] Tissue engineered vascular graft (TEVG), based on the notion
of endogenous tissue growth, represents a promising solution. The
vast majority of the in vivo studies available within the TEVG
literature involve non-degradable/degradable devices prepared
mainly via electrospinning, TIPS or particulate leaching. While
this approach has represented a substantial improvement in terms of
capacity to tune graft morphology, bioactivity of the processed
synthetic materials is limited when compared to biologic material
based grafts.
[0005] N. L'Heureux et al. (Human Tissue Engineered Blood Vessel
For Adult Arterial Revascularization, Nature Medicine, 2006 March;
12(3):361-5) proposed a three-layered structure fabricated by cell
sheets apposition, however the scaffold required high cost and a 28
weeks processing time. TEVG presented by Zhang et al. (Fabrication
of three-dimensional poly(.epsilon.-caprolactone) scaffolds with
hierarchical pore structure for tissue engineering, Materials
Science and Engineering: C 33(4) (2013) 2094-2103) showed a
three-layered structure, but suffered the major limitation of
reduced host cell infiltration due to its nondegradable and
non-porous nature. Similarly, Liu et al. (A bio-inspired high
strength three-layer nanofiber vascular graft with structure guided
cell growth, Journal of Materials Chemistry B 5(20) (2017)
3758-3764) introduced a PLA/PCL three-layered design mimicking
native structure. Yet, the small pore sizes and the lack of a
bioactive component make this prototype not suitable for the
acellular host-cell recruitment paradigm. Zhang et al. (In vivo
biocompatibility and hemocompatibility of a polytetrafluoroethylene
small diameter vascular graft modified with sulfonated silk
fibroin, Am. J. Surg. 213(1) (2017) 87-93) developed a
three-layered design combining electrospinning and braiding of silk
fibroin and poly(L-lactide-co-.epsilon.-caprolactone).
Unfortunately, graft mechanical compliance was underphysiological
with the artificial vessel being generally stiffer than the native
one.
[0006] There is a need for a processing technique and associated
devices for use in preparation of vascular grafts that provide
industrial scalability. There is also a need for graft structures
that duplicate native tissue functional heterogeneity.
SUMMARY OF THE INVENTION
[0007] Provided herein are methods and systems that overcome the
aforementioned limitations by combining the merits and benefits of
both synthetic (e.g., improved control on structure and function)
and biologic tissue derived scaffolds (e.g., bioactivity). To mimic
the structure and function of native blood vessels, the biohybrid,
three-layered graft design presented herein is based on native
tissue functional heterogeneity (e.g., presence of anatomically
distinct components specialized to fulfill a specific
function).
[0008] In one aspect, a method of making a synthetic tubular graft
device is provided. The method comprises depositing an ECM gel
layer over a first tubular, porous, biodegradable polymer matrix;
and depositing a second tubular, porous, biodegradable polymer
matrix over the ECM gel to produce a tubular structure.
[0009] In another aspect, a multi-layer synthetic graft device is
provided. The device comprises a first porous, biodegradable
polymer matrix; an ECM gel layer over the first porous,
biodegradable polymer matrix; and a second porous, biodegradable
polymer matrix over the ECM gel.
[0010] In yet another aspect, a method of producing, repairing or
replacing a tissue in a patient is provided. The method comprises
implanting in the patient a multi-layer synthetic graft device in
the patient. The device comprises a first porous, biodegradable
polymer matrix; an ECM gel layer over the first porous,
biodegradable polymer matrix; and a second porous, biodegradable
polymer matrix over the ECM gel.
[0011] In another aspect, a kit is provided. The kit comprises a
multi-layer synthetic graft device in suitable packaging, such as a
foil and/or plastic pouch or container, such as a Mylar package.
The device comprises a first porous, biodegradable polymer matrix;
an ECM gel layer over the first porous, biodegradable polymer
matrix; and a second porous, biodegradable polymer matrix over the
ECM gel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1A is a schematic diagram of a graft device according
to one aspect of the present invention. FIG. 1B is a cross-section
of the device shown in FIG. 1A on a plane perpendicular to the
longitudinal axis L.
[0013] FIG. 2: Schematic of the 3 layer scaffold fabrication
process. LAYERS 1-3. A) The electrospun layer is positioned on a
steel rod and secured with sutures at the edges. B) The sample is
inserted into a custom-made mold and maintained coaxial with the
mold cavity. D) ECM gel solution is injected into the mold. D) The
mold is closed and rests overnight in an incubator at 37.degree. C.
so that the ECM solution can transition to the gel state. E) the
second graft layer made of ECM gel is then formed. F) TIPS outer
layer is gently slipped on the gel layer so that the three-layered
structure is obtained.
[0014] FIG. 3: Schematic of the electrospinning setup. LAYER 1
formation. A) Processing variables utilized for layer one
fabrication (Tunica Intima). B) Electrospinning deposition at t=0,
C) t=10 min, and D) t=20 min. Electrospun layers with 3 different
thicknesses: E) 100 .mu.m, F) 200 .mu.m, and G) 300 .mu.m.
[0015] FIG. 4: LAYERS 2-3 formation. A) TIPS mold: metal rod 3.8
mm, thickness PTFE tubing 0.8 mm, glass tube ID 6 mm. B) PEUU TIPS
layer for tunica adventitia with ID 3.5 mm. C) gel layer formed
around the electrospun layer on the mold. D) Detail of the ECM gel
layer. E) Three-layered small-diameter vascular graft (layer 1:
electrospun, layer 2 ECM gel, layer 3 TIPS).
[0016] FIG. 5: H&E cross-sections, histological comparison of
native vs. engineered graft. A) representative porcine coronary
artery cross-section and C) longitudinal section B) engineered
graft cross section and D) longitudinal section. Asterisk indicates
the lumen side.
[0017] FIG. 6: SEM cross sections native coronary artery vs.
engineered graft comparison. A, E) Porcine native vessel with
distinct tunica adventitia and tunica media-intima. Capacity to
control/modulate vessel global compliance by changing the ES layer:
three-layered vascular graft with 3 different ES layer thicknesses
including B, F) 100 .mu.m; C, G) 200 .mu.m; D, H) 300 .mu.m. I-L)
Detailed view of ES layer morphology and of M-N) TIPS layer
morphology.
[0018] FIG. 7: Macroscopic morphology comparison. Porcine native
coronary arteries (n=3) vs. three-layered scaffold (with ES layer
measuring 100 .mu.m). Functional heterogeneity has been duplicated
in the engineered vascular graft in terms of layers thickness.
Results were presented as mean.+-.st. deviation.
[0019] FIGS. 8A-8D: Global mechanical compliance. Pressure--volume
test results for porcine coronary arteries. FIG. 8A) Right coronary
arteries (RCA, n=3).
[0020] FIG. 8B) Left Circumflex coronary arteries (LCx, n=3). FIG.
8C) Left Anterior Descending coronary arteries (LAD, n=2). FIG. 8D)
Cumulative average for the coronary arteries (n=8).
[0021] FIGS. 9A-9E: Global mechanical compliance. Pressure--volume
test results for engineered graft with 3 different ES layer
thickness values (data presented as mean.+-.st. deviation)
including: FIG. 9A) 100 .mu.m (n=4), FIG. 9B) 200 .mu.m (n=4), FIG.
9C) 300 .mu.m (n=3). FIG. 9D) Native vs. engineered graft
comparison. FIG. 9E) global mechanical compliance comparison,
showing physiologically relevant compliance values.
[0022] FIGS. 10A-10D: Suture retention test. Impact of ES layer
thickness, suture retention characteristics for grafts fabricated
with increasing ES thickness including: FIG. 10A) ES=100 .mu.m
(n=3), FIG. 10B) 200 .mu.m (n=3), FIG. 10C) 300 .mu.m (n=3). FIG.
10D) native vs. engineered vessel comparison. Results were
presented as mean.+-.st. deviation and showed 1) comparable values
of retention force, 2) capacity to tune the retention force by
increasing ES thickness.
DETAILED DESCRIPTION
[0023] Other than in the operating examples, or where otherwise
indicated, the use of numerical values in the various ranges
specified in this application are stated as approximations as
though the minimum and maximum values within the stated ranges are
both preceded by the word "about". In this manner, slight
variations above and below the stated ranges can be used to achieve
substantially the same results as values within the ranges. Also,
unless indicated otherwise, the disclosure of ranges is intended as
a continuous range including every value between the minimum and
maximum values. As used herein "a" and "an" refer to one or
more.
[0024] As used herein, the term "comprising" is open-ended and may
be synonymous with "including", "containing", or "characterized
by". The term "consisting essentially of" limits the scope of a
claim to the specified materials or steps and those that do not
materially affect the basic and novel characteristic(s) of the
claimed invention. The term "consisting of" excludes any element,
step, or ingredient not specified in the claim. As used herein,
embodiments "comprising" one or more stated elements or steps also
include, but are not limited to embodiments "consisting essentially
of" and "consisting of" these stated elements or steps. For
definitions provided herein, those definitions refer to word forms,
cognates and grammatical variants of those words or phrases.
[0025] As used herein, the term "patient" or "subject" refers to
members of the animal kingdom including but not limited to human
beings and "mammal" refers to all mammals, including, but not
limited to human beings.
[0026] As used herein, "treatment" or "treating" of a wound or
defect means administration to a patient by any suitable dosage
regimen, procedure and/or administration route of a composition,
device or structure with the object of achieving a desirable
clinical/medical end-point including attracting progenitor cells,
healing a wound, correcting a defect, etc.
[0027] As used herein, the terms "cell" and "cells" refer to any
types of cells from any animal, such as, without limitation, rat,
mice, monkey, and human. For example and without limitation, cells
can be progenitor cells, such as stem cells, or differentiated
cells, such as endothelial cells and smooth muscle cells. In
certain aspects, cells for medical procedures can be obtained from
the patient for autologous procedures, or from other donors for
allogeneic procedures.
[0028] As used herein, the term "polymer composition" is a
composition comprising one or more polymers. As a class, "polymers"
includes, for example and without limitation, homopolymers,
heteropolymers, copolymers, block co-polymers and can be both
natural and synthetic. Homopolymers contain one type of building
block, or monomer, whereas copolymers contain more than one type of
monomer.
[0029] A polymer "comprises" or is "derived from" a stated monomer
if that monomer is incorporated into the polymer. Thus, the
incorporated monomer that the polymer comprises is not the same as
the monomer prior to incorporation into the polymer, in that at the
very least, during incorporation of the monomer, certain groups,
e.g., terminal groups, that are modified during polymerization are
changed, removed, and/or relocated, and certain bonds may be added,
removed, and/or modified. An incorporated monomer is referred to as
a "residue" of that monomer. A polymer is said to comprise a
specific type of linkage if that linkage is present in the polymer,
thus, a polyester comprises a plurality of ester linkages, a
polyurethane comprises a plurality of urethane (carbamate)
linkages, and a poly(ester urethane) urea comprises ester,
urethane, and urea linkages. Unless otherwise specified, molecular
weight for polymer compositions refers to weight average molecular
weight (Mw). A "moiety" is a portion of a molecule, compound or
composition, and includes a residue or group of residues within a
larger polymer.
[0030] A bioerodible polymer is a polymer that degrades in vivo
over a time period, which can be tailored to erode over a time
period ranging from days to months, and up to two years, for
example, a polymeric structure, when placed in vivo, will fully
degrade within a time period of up to two years. By "bioerodible,"
it is meant that a polymer, once implanted and placed in contact
with bodily fluids and/or tissues, will degrade either partially or
completely through chemical, biochemical and/or enzymatic
processes. Non-limiting examples of such chemical reactions include
acid/base reactions, hydrolysis reactions, and enzymatic cleavage.
In certain non-limiting embodiments, the biodegradable polymers may
comprise homopolymers, copolymers, and/or polymeric blends
comprising, without limitation, one or more of the following
monomers: glycolide, lactide, caprolactone, dioxanone, and
trimethylene carbonate. In other non-limiting embodiments, the
polymer(s) comprise labile chemical moieties, non-limiting examples
of which include esters, anhydrides, or polyanhydrides, which can
be useful in, for example and without limitation, controlling the
degradation rate of the scaffold or particles and/or the release
rate of therapeutic agents, such as the conditioned medium, from
the scaffold or particles.
[0031] By "biocompatible," it is meant that a polymer composition
and its normal degradation in vivo products are cytocompatible and
are substantially non-toxic and non-carcinogenic in a patient
within useful, practical and/or acceptable tolerances. By
"cytocompatible," it is meant that the polymer can sustain a
population of cells and/or the polymer composition, device, and
degradation products thereof are not cytotoxic and/or carcinogenic
within useful, practical, and/or acceptable tolerances. For
example, the polymer when placed in a human epithelial cell culture
does not adversely affect the viability, growth, adhesion, and
number of cells. In one non-limiting embodiment, the compositions
and/or devices are "biocompatible" to the extent they are
acceptable for use in a human or veterinary patient according to
applicable regulatory standards in a given jurisdiction. In another
example, the biocompatible polymer, when implanted in a patient,
does not cause a substantial adverse reaction or substantial harm
to cells and tissues in the body, for instance, the polymer
composition or device does not cause unacceptable inflammation,
necrosis, or an infection resulting in harm to tissues from the
implanted scaffold. A "patient" is a human or non-human animal.
[0032] Non-limiting examples of a bioreodible polymer useful for
tissue or vascular growth scaffolds or the described particles
described herein include: a polyester, a polyester-containing
copolymer, a polyanhydride, a polyanhydride-containing copolymer, a
polyorthoester, and a polyorthoester-containing copolymer. In one
aspect, the polyester or polyester-containing copolymer is a
poly(lactic-co-glycolic) acid (PLGA) copolymer. In another
embodiment, the bioerodible polymer is selected from the group
consisting of poly(lactic acid) (PLA); poly(trimethylene carbonate)
(PTMC); poly(caprolactone) (PCL); poly(glycolic acid) (PGA);
poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; and polyphosphazenes. Additional
bioerodible, biocompatible polymers include: a poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones including
polycaprolactone; or a polymer comprising monomers derived from
carbonates including polycarbonate, polyglyconate,
poly(glycolide-co-trimethylene carbonate), or poly(glycolide-co-tri
methylene carbonate-co-dioxanone).
[0033] Non-erodable polymers either do not erode substantially in
vivo or erode over a time period of greater than two years.
Compositions such as, for example and without limitation, PTFE,
poly(ethylene-co-vinyl acetate), poly(n-butyl methacrylate),
poly(styrene-b-isobutylene-b-styrene) and polyethylene
terephthalate are considered to be non-erodable polymers. Other
suitable non-erodable polymer compositions are broadly known in the
art, for example, in stent coating and transdermal reservoir
technologies. The growth scaffolds described herein may comprise a
non-erodible polymer composition.
[0034] In some examples, one or more layers of the device may be
formed from a biodegradable and biocompatible scaffold material,
such as a synthetic polymeric composition comprising
poly(ester-urethane)urea (PEUU). PEUU can be synthesized using
putrescine as a chain extender and a two-step solvent synthesis
method. For example, a poly(ester urethane) urea elastomer (PEUU)
may be made from polycaprolactonediol (MW 2,000) and
1,4-diisocyanatobutane, with a diamine, such as putrescine as the
chain extender. A suitable PEUU polymer may be made by a two-step
polymerization process whereby polycaprolactone diol (Mw 2,000),
1,4-diisocyanatobutane, and putrescine are combined in a 1:2:1
molar ratio, though virtually any molar feed ratio may suffice so
long as the molar ratio of each monomer component is >0. In one
embodiment, the molar feed ratio of polycaprolactone diol plus
putrescine is equal to that of diisocyanatobutane. In the first
polymerization step, a 15 wt % solution of 1,4-diisocyanatobutane
in DMSO is stirred continuously with a 25 wt % solution of diol in
DMSO. In the second step, stannous octoate is added and the mixture
is allowed to react at 75.degree. C. for 3 hours, with the addition
of triethylamine to aid dissolution. A poly(ether ester urethane)
urea elastomer (PEEUU) may be made by reacting
polycaprolactone-b-polyethylene glycol-b-polycaprolactone triblock
copolymers with 1,4-diisocyanatobutane and putrescine. In a
preferred embodiment, PEEUU is obtained by a two-step reaction
using a 2:1:1 reactant stoichiometry of
1,4-diisocyanatobutane:triblock copolymer:putrescine. In the first
polymerization step, a 15 wt % solution of 1,4-diisocyanatobutane
in DMSO is stirred continuously with a 25 wt % solution of triblock
compolymer diol in DMSO. In the second step, stannous octoate is
added and the mixture is allowed to react at 75.degree. C. for 3
hours. The reaction mixture is then cooled to room temperature and
allowed to continue for 18 h. The PEEUU polymer solution is then
precipitated with distilled water and the wet polymer is immersed
in isopropanol for 3 days to remove unreacted monomer and dried
under vacuum.
[0035] In another aspects, one or more layers of the device is
formed from a poly(ester carbonate urethane)urea (PECUU) or
poly(carbonate)urethane urea (PCUU) material. PECUU and PCUU are
described, for example, in Hong et al. (Tailoring the degradation
kinetics of poly(ester carbonate urethane)urea thermoplastic
elastomers for tissue engineering scaffolds Biomaterials,
doi:10.1016/j.biomaterials.2010.02.005). PECUU is synthesized, for
example, using a blended soft segment of polycaprolactone (PCL) and
poly(1,6-hexamethylene carbonate) (PHC) and a hard segment of
1,4-diisocyanatobutane (BDI) with chain extension by putrescine.
Different molar ratios of PCL and PHC can be used to achieve
different physical characteristics. Putrescine is used as a chain
extender by a two-step solvent synthesis method. In one example,
the (PCL+PHC):BDI:putrescine molar ratio is defined as 1:2:1.
Variable molar ratios of PCL and PHC (e.g., PCUPHC ratios of 100/0
(yielding a PEUU), 75/25, 50/50, 25/75 and 0/100 (yielding a PCUU))
are completely dissolved in DMSO in a 3-neck flask with argon
protection and then BDI is added to the solution, following 4 drops
of Sn(Oct)2. The flask is placed in an oil bath at 70.degree. C.
After 3 h, the prepolymer solution is cooled at room temperature
and then a putrescine/DMSO solution is added dropwise into the
agitated solution. The final polymer solution concentration is
controlled to be approximately 4% (w/v). Then the flask is than
placed in an oil bath and kept at 70.degree. C. overnight. The
polymer is precipitated in an excess volume of cool deionized water
and then dried in a vacuum at 60.degree. C. for 3 days. The
polyurethane ureas synthesized from the different PCL/PHC molar
ratios defined above are referred to as PEUU, PECUU 75/25, PECUU
50/50, PECUU 25/75 and PCUU, respectively. In practice, the yields
of all final products using this method is approximately 95%.
[0036] In aspects, a polymer composition may be anti-thrombogenic,
meaning the polymer includes a moiety that resists formation of a
thrombus. Anti-thrombogenic polymer compositions are known in the
medical arts. In one aspect, a polymer composition, such as a
polyanhydride, a polyester, a polyurethane, PCUU, PECUU, PEUU,
PEEUU, and polyacrylates are modified with a zwitterion moiety,
either incorporated into the backbone of the polymer or pendant
therefrom. In one example, an antithrombogenic polymer comprises a
pendant phosphorylcholine, such as in a polymer composition
comprising 2-methacryloyloxyethyl phosphorylcholine (MPC) (see,
e.g., Goda, T., et al., Critical update on 2-methacryloyloxyethyl
phosphorylcholine (MPC) polymer science. J. Appl. Polym. Sci. 2015,
DOI: 10.1002/APP.41766). In another example, a sulfobetaine moiety
is incorporated into a polymer composition, as in Ye, S. et al.
(Nonthrombogenic, Biodegradable Elastomeric Polyurethanes with
Variable Sulfobetaine Content. ACS Appl. Mater. Interfaces, 2014, 6
(24), pp 22796-22806). Additional sulfobetaine- or
phosphorocholine-containing polymer compositions are described in
Ye, S., et al. (Hollow Fiber Membrane Modification with Functional
Zwitterionic Macromolecules for Improved Thromboresistance in
Artificial Lungs Langmuir 2015 31 (8), 2463-2471) and in Malkin, A.
D., et al. (Development of Zwitterionic Sulfobetaine Block
Copolymer Conjugation Strategies for Reduced Platelet Deposition in
Respiratory Assist Devices J Biomed Mater Res B Appl Biomater. 2018
Feb. 9. doi: 10.1002/jbm.b.34085).
[0037] Methods of preparation of the polymeric compositions
described herein are broadly-known. For example, diamines and diols
are useful building blocks for preparing the described polymer
compositions. Diamines as described above have the structure
H.sub.2N--R--NH.sub.2 where "R" is an aliphatic or aromatic
hydrocarbon or a hydrocarbon comprising aromatic and aliphatic
regions. The hydrocarbon may be linear or branched. Examples of
useful diamines are putrescine (R=butylene) and cadaverine
(R=pentylene). Useful diols include polycaprolactone (e.g., Mw
1000-5000), multi-block copolymers, such as polycaprolactone-PEG
copolymers, including polycaprolactone-b-polyethylene
glycol-b-polycaprolactone triblock copolymers of varying sizes.
Other building blocks for useful diols include, without limitation
glycolides (e.g., polyglycolic acid (PGA)), lactides, dioxanones,
and trimethylene carbonates. Diisocyanates have the general
structure OCN--R--NCO, where "R" is an aliphatic or aromatic
hydrocarbon or a hydrocarbon comprising aromatic and aliphatic
regions. The hydrocarbon may be linear or branched.
[0038] As used herein, the terms "extracellular matrix" and "ECM"
refer to a natural scaffolding for cell growth. ECM is a complex
mixture of structural and non-structural biomolecules, including,
but not limited to, collagens, elastins, laminins,
glycosaminoglycans, proteoglycans, antimicrobials,
chemoattractants, cytokines, and growth factors. In mammals, ECM
often comprises about 90% collagen in its various forms. The
composition and structure of ECMs vary depending on the source of
the tissue. For example, small intestine submucosa (SIS), urinary
bladder matrix (UBM), liver stroma ECM, and dermal ECM each differ
in their overall structure and composition due to the unique
cellular niche needed for each tissue.
[0039] As used herein, the term "derive" and any other word forms
or cognates thereof, such as, without limitation, "derived" and
"derives", refers to a component or components obtained from any
stated source by any useful method. For example and without
limitation, generically, an ECM-derived gel refers to a gel
comprised of components of ECM obtained from any tissue by any
number of methods known in the art for isolating ECM. In another
example, mammalian tissue-derived ECM refers to ECM comprised of
components of a particular mammalian tissue obtained from a mammal
by any useful method.
[0040] The methods described herein involve preparation of ECM or
an ECM gel. The ECM gel is reverse gelling, or can be said to
exhibit reverse thermal gelation, in that it forms a gel upon an
increase in temperature. As the temperature rises above a certain
temperature in a reverse gel, a hydrogel is formed. The general
concept of reverse gelation of polymers is broadly known in the
chemical arts (see, e.g., U.S. Pat. Nos. 8,361,503 and 8,691,276,
U.S. Patent Application Publication Nos. 20150010510 and
20170173217, and International Patent Application No.
PCT/US2017/013355, each of which is incorporated herein by
reference for its technical disclosure). International Patent
Application No. PCT/US2017/013355 discloses and describes ECM gel
prepared from vascular sources. The ECM compositions described
herein are prepared, for example, from decellularized or
devitalized, intact tissue as described below. An ECM gel is
prepared by digestion of the ECM material with an acid protease,
neutralization of the material to form a pre-gel, and then raising
the temperature of the pre-gel above a gelation temperature, for
example, the lower critical solution temperature (LCST) of the
pre-gel, to cause the pre-gel to gel. As used herein, the term
"gel" includes hydrogels. The transition temperature for
acid-protease-digested from solution to gel is typically within the
range of from 10.degree. C. to 40.degree. C. and any increments or
ranges therebetween, for example, from 20.degree. C. to 35.degree.
C. For example, the pre-gel can be warmed to 37.degree. C. to form
a hydrogel.
[0041] Tissue for preparation of ECM, ECM-derived pre-gel
solutions, and gels as described herein may be harvested in any
useful manner. According to various aspects, the ECM materials
described herein are prepared from vascular tissue, such as
vascular adventitia (tunica adventitia), vascular media (tunica
media), and/or intima (tunica intima) tissue, such as arterial or
venous tissue, such as aortic tissue. For example and without
limitation, in one aspect, the ECM material is prepared from
harvested porcine aorta, and in another, from human aorta. If a
portion of the blood vessel is used, such as one or two of the
vascular adventitia, media, or tunica, the portion is dissected
from the harvested tissue, and is optionally frozen. Arterial or
venous, e.g., aorta tissue, is obtained by any suitable method, for
example, by manually isolating from the surrounding tissue. In one
aspect, the ECM gel is prepared from vascular tunica media. In
another aspect, the ECM gel is prepared from vasculature including
intima, media, and/or adventitia layers, e.g., an intact blood
vessel including intima, media, and adventitia layers.
[0042] Decellularized or devitalized tissue can be dried, either
lyophilized (freeze-dried) or air dried. The ECM composition is
optionally comminuted at some point, for example, prior to acid
protease digestion in preparation of an ECM gel, for example, prior
to or after drying. The comminuted ECM can also be further
processed into a powdered form by methods, for example and without
limitation, such as grinding or milling in a frozen or freeze-dried
state. As used herein, the term "comminute" and any other word
forms or cognates thereof, such as, without limitation,
"comminution" and "comminuting", refers to the process of reducing
larger particles, e.g., of dried ECM, into smaller particles,
including, without limitation, by tearing, grinding, blending,
shredding, slicing, milling, cutting, shredding, shearing, and
pulverizing. ECM can be comminuted while in any form, including,
but not limited to, hydrated forms, frozen, air-dried, lyophilized,
powdered, sheet-form.
[0043] In order to prepare solubilized ECM tissue, ECM, for
example, comminuted ECM, is digested with an acid protease in an
acidic solution to form a digest solution. As used herein, the term
"acid protease" refers to an enzyme that cleaves peptide bonds,
wherein the enzyme has increased activity of cleaving peptide bonds
in an acidic pH. A non-limiting example of a suitable acid protease
is pepsin.
[0044] As an example, the digest solution of ECM is kept at a
constant stir for a certain amount of time at room temperature. In
one aspect, the pH is maintained at less than pH 4.0 or at pH
2.0.+-.0.3 during acid protease digestion of the decellularized
aortic adventitial tissue as described herein. The ECM digest can
be used immediately or can be stored at -20.degree. C. or frozen
at, for example and without limitation, -20.degree. C. or
-80.degree. C. In certain aspects, the ECM digest is snap frozen in
liquid nitrogen. To form a "pre-gel solution", the pH of the digest
solution is raised to a pH between 6.8 and 7.8. The pH can be
raised by adding one or more of a base or a buffer, such as an
isotonic buffered solution, for example and without limitation,
NaOH or PBS at pH 7.4. The method optionally does not include a
dialysis step prior to gelation, yielding a more-complete ECM-like
matrix that typically gels at 37.degree. C. more slowly than
comparable collagen or dialyzed ECM preparations. The gel therefore
retains more of the qualities of native ECM due to retention of
many native soluble factors, such as, without limitation,
cytokines. These factors contribute to chemoattraction of cells and
proper rearrangement of tissue at the site of injury, rather than a
fibrotic response that leads to unwanted scarring. In other
embodiments, the ECM is dialyzed prior to gelation to remove
certain soluble components.
[0045] As used herein, the term "isotonic buffered solution" refers
to a solution that is buffered to a pH between 6.8 and 7.8, e.g.,
pH 7.4, and that has a balanced concentration of salts to promote
an isotonic environment. As used herein, the term "base" refers to
any compound or a solution of a compound with a pH greater than 7.
For example and without limitation, the base is an alkaline
hydroxide or an aqueous solution of an alkaline hydroxide. In
certain aspects, the base is NaOH, or NaOH in PBS. This "pre-gel"
solution can, at that point be incubated at a suitably warm
temperature, for example and without limitation, at about
37.degree. C. to gel.
[0046] In the method of preparing an ECM gel, the ECM may be
partially or completely digested with the acid protease, such as
pepsin. The degree of digestion of the ECM can be determined by
comparison on a gel, or by ascertaining the degree of degradation
of hyaluronic acid, for example, by Western blot (anti-hyaluronic
acid antibodies are commercially-available from multiple sources)
or chromatographic methods, as are broadly known. For example, in a
partial digestion, hyaluronic acid is digested less than 50%, 40%,
30%, 25%, 20%, or 10%. As indicated above, the digested ECM is
neutralized to a pH of 6.8-7.8, e.g., 7.2-7.6, or 7.4 to produce a
pre-gel solution, and the pre-gel solution is gelled by incubation
at a temperature at which the material gels, e.g., at a temperature
above 20.degree., 25.degree., 30.degree., or 35.degree. C., such as
at 37.degree. C.
[0047] In one aspect, a multi-layer device is provided, such as a
tubular device that is, for example, suitable for replacement of a
blood vessel. The device can be characterized as a tissue growth
matrix or scaffold in that it is supportive of cell infiltration,
cell growth, and/or cell differentiation. In another aspect, the
device is formed as a sheet. In yet another aspect, the device is
formed in a three-dimensional structure, such as a tube. Layers of
the device are porous, in that liquids can pass into, and through
the layers. Porosity of the layers can vary, and typically pores
(openings) comprise from 10% to 95% of the volume of the layer,
such as 10%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 75%, 80%, 90%,
or 95%. The porosity, shapes, and interconnectivity of the pores
can vary from layer-to-layer of the multi-layered device, and
depend on the method used to make the respective layer.
[0048] Layers can be formed by any useful method, as are
broadly-known in the technical field of the invention. For example
and without limitation, by phase separation, e.g., by Thermally
Induced Phase Separation (TIPS), Non-solvent Induced Phase
Separation (NIPS), or Diffusion Induced Phase Separation (DIPS),
which are broadly-known processes and may be used independently to
prepare one or more layers of the described devices.
High-resolution 3D printing technologies can deposit materials with
microscale resolution, permitting highly-organized structures, and
also may be employed to prepare one or more of the described layers
of the device described herein. Porous layers also may be prepared
by particulate leaching, that is by dissolution, e.g., in water, of
dissolvable particles, such as salt or sugar particles embedded in
a polymer structure, for example, a cast or molded polymer
structure.
[0049] In further detail, TIPS takes advantage of the thermodynamic
instability of polymer solutions at certain temperatures. The TIPS
phase separation procedure requires the use of a solvent with a low
melting point that is easy to sublime. In TIPS, when a polymer is
dissolved in a solvent, it becomes thermodynamically unstable at
low temperatures and will spontaneously separate into two phases.
Once the polymer is dissolved in an appropriate solvent, phase
separation is induced through the addition of a small quantity of
water. This then results in a polymer-rich and a polymer-poor
phase. Following cooling below the solvent melting point and
vacuum-drying to sublime the solvent, a porous scaffold is
obtained. In NIPS, a polymer solution (that is, a polymer dissolved
in a solvent) is immersed in a non-solvent bath (coagulation bath),
typically water, where the exchange of solvent and non-solvent
takes place. Specifically, the solvent migrates from the polymer
solution to the coagulation bath, while the non-solvent follows the
reverse path, leading to the formation of the membrane.
[0050] Another useful method for producing the tissue structures
and/or controlled-release devices is electrodeposition. The
polymeric scaffold can be electrospun, e.g., on a mandrel in the
case of a tubular tissue scaffold, e.g., a vascular tissue.
Electrospinning permits fabrication of scaffolds that resemble the
scale and fibrous nature of the native extracellular matrix (ECM).
The ECM is composed of fibers, pores, and other surface features at
the sub-micron and nanometer size scale. Such features directly
impact cellular interactions with synthetic materials such as
migration and orientation. Electrospinning also permits fabrication
of oriented fibers to result in anisotropic scaffolds. These
aligned scaffolds can influence cellular growth, morphology and ECM
production.
[0051] Generally, the process of electrospinning involves placing a
polymer-containing fluid (e.g., a polymer solution, a polymer
suspension, or a polymer melt) in a reservoir equipped with a small
orifice, such as a needle or pipette tip and a metering pump. One
electrode of a high voltage source is also placed in electrical
contact with the polymer-containing fluid or orifice, while the
other electrode is placed in electrical contact with a target
(typically a collector screen or rotating mandrel). During
electrospinning, the polymer-containing fluid is charged by the
application of high voltage to the solution or orifice (e.g., about
3-15 kV) and then forced through the small orifice by the metering
pump that provides steady flow. While the polymer-containing fluid
at the orifice normally would have a hemispherical shape due to
surface tension, the application of the high voltage causes the
otherwise hemispherically shaped polymer-containing fluid at the
orifice to elongate to form a conical shape known as a Taylor cone.
With sufficiently high voltage applied to the polymer-containing
fluid and/or orifice, the repulsive electrostatic force of the
charged polymer-containing fluid overcomes the surface tension and
a charged jet of fluid is ejected from the tip of the Taylor cone
and accelerated towards the target, which typically is biased
between -2 to -10 kV. Optionally, a focusing ring with an applied
bias (e.g., 1-10 kV) can be used to direct the trajectory of the
charged jet of polymer-containing fluid. As the charged jet of
fluid travels towards the biased target, it undergoes a complicated
whipping and bending motion. If the fluid is a polymer solution or
suspension, the solvent typically evaporates during mid-flight,
leaving behind a polymer fiber on the biased target. If the fluid
is a polymer melt, the molten polymer cools and solidifies in
mid-flight and is collected as a polymer fiber on the biased
target. As the polymer fibers accumulate on the biased target, a
non-woven, porous mesh (matrix) is formed on the biased target.
[0052] The properties of the electrospun elastomeric matrices can
be tailored by varying the electrospinning conditions. For example,
when the biased target is relatively close to the orifice, the
resulting electrospun mesh tends to contain unevenly thick fibers,
such that some areas of the fiber have a "bead-like" appearance.
However, as the biased target is moved further away from the
orifice, the fibers of the non-woven mesh tend to be more uniform
in thickness. Moreover, the biased target can be moved relative to
the orifice. In certain embodiments, the biased target is moved
back and forth in a regular, periodic fashion, such that fibers of
the non-woven mesh are substantially parallel to each other. When
this is the case, the resulting non-woven mesh may be anisotropic,
e.g., having a higher resistance to strain in the direction
parallel to the fibers, compared to the direction perpendicular to
the fibers. In other embodiments, the biased target is moved
randomly relative to the orifice, so that the resistance to strain
in the plane of the non-woven mesh is isotropic. The target can
also be a rotating mandrel. In this case, the properties of the
non-woven mesh may be changed by varying the speed of rotation. The
properties of the electrospun elastomeric scaffold may also be
varied by changing the magnitude of the voltages applied to the
electrospinning system.
[0053] Electrospinning may be performed using two or more nozzles,
wherein each nozzle is a source of a different polymer solution.
The nozzles may be biased with different biases or the same bias in
order to tailor the physical and chemical properties of the
resulting non-woven polymeric mesh. Additionally, many different
targets may be used. In addition to a flat, plate-like target, a
mandrel may be used as a target.
[0054] When the electrospinning is to be performed using a polymer
suspension, the concentration of the polymeric component in the
suspension can also be varied to modify the physical properties of
the elastomeric scaffold. For example, when the polymeric component
is present at relatively low concentration, the resulting fibers of
the electrospun non-woven mesh have a smaller diameter than when
the polymeric component is present at relatively high
concentration. Without any intention to be limited by this theory,
it is believed that lower concentration solutions have a lower
viscosity, leading to faster flow through the orifice to produce
thinner fibers. One skilled in the art can adjust polymer
concentrations to obtain fibers of desired characteristics. Useful
ranges of concentrations for the polymer component include from
about 1% wt. to about 15% wt., from about 4% wt. to about 10% wt.
and from about 6% wt. to about 8% wt.
[0055] Thickness of the matrix can be controlled by either
adjusting the viscosity of the polymer composition to be deposited
and/or adjusting duration of the electrospinning. Use of more
viscous polymer composition may result in thicker fibers, requiring
less time to deposit a matrix of a desired thickness. Use of a less
viscous polymer composition may result in thinner fibers, requiring
increased deposition time to deposit a matrix of a desired
thickness. The thickness of the matrix and fibers within the matrix
affects the speed of bioerosion of the matrix. These parameters are
optimized, depending on the end-use of the matrix, to achieve a
desired or optimal physiological effect.
[0056] Dry electrospinning refers to electrodeposition of only a
polymer composition as described above. In contrast, wet
electrospinning employs concurrent electrodeposition, or deposition
of liquids during the electrodeposition of the polymer. Suitable
liquids include water, saline, PBS, cell culture medium, and any
other suitable ingredient, such as one or more therapeutic agents.
In practice, while cytocompatible and non toxic, dry-electrospun
layers are often marginally-supportive of cell infiltration, and,
as indicated below, can be used as a barrier layer to prevent or
retard stenosis of the nascent blood vessel due to intima
hyperplasia. In contrast, wet electrospun layers are typically more
supportive of cell infiltration.
[0057] According to one aspect of the invention, a tubular device
is provided comprising three layers. FIG. 1A depicts a tubular
device 10 according to one aspect of the invention, having a lumen
12, and a longitudinal axis L. FIG. 1B, depicts a cross section of
a tubular device 10, e.g., as shown in FIG. 1A, taken perpendicular
to a longitudinal axis of the device 10 and having a lumen 12.
FIGS. 1A and 1B are not to scale. FIG. 1B further shows the
three-layer structure of device 10, depicting a first layer 20
disposed concentrically about the lumen 12 and defining the lumen
12, a second layer 30 disposed about at least a portion of the
circumference of the first layer 20, and a third layer 40 disposed
about at least a portion of the circumference of the second layer
30.
[0058] As used herein stating that a layer is said to be disposed
"over" a referenced layer, or "about a circumference of" a
referenced layer, or "about at least a portion of the circumference
of" a referenced layer, does not imply the layer is directly
adjacent to the referenced layer, and may comprise one or more
additional layers therebetween, and further does not imply that the
layer completely covers the referenced layer, and may only cover,
surround, contact, etc. only a portion of the referenced layer.
That said, if a layer is said to be disposed "directly about" or
"directly over" a referenced layer, it is meant the two layers
contact each other, though an intermediary layer, such as an
adhesive layer, or a blended layer that results from directly
contacting the two layers during the process of formation of the
device may be present between the two stated layers. Also, if a
layer is said to "completely cover" a referenced layer, it is meant
the second layer covers the entirety of the referenced layer.
Stating that a layer is said to be disposed "over" another layer,
or "about a circumference of" a referenced layer, or "about at
least a portion of the circumference of" a referenced layer
includes where the stated layers are directly contacting each other
and/or that the layer completely covers the referenced layer.
Further, as used herein, recited dimensions are dimensions of the
device taken at two or more points, e.g., three points over the
longitudinal direction of the device, for example, at the center
and at the edges of the segment. Diameters and thicknesses are
measured along lines perpendicular to a longitudinal axis of the
tubular structures described herein.
[0059] In one aspect, in reference to FIG. 1B, the first layer 20
of tubular device 10 does not support cell growth, and, therefore,
can be described as a barrier layer. In one aspect the first layer
10 is a dry electrospun bioerodible polymer. In practice,
dry-electrospun bioerodible polymers typically do not support
substantial migration of and/or proliferation of vascular cells
such as vascular smooth muscle cells, thereby discouraging stenosis
(e.g., neointimal hyperplasia) of the nascent arterial wall, which
often arises from proliferation of vascular smooth muscle cells
into the lumen of the artery. The first layer 20 will eventually
degrade, but the use of a barrier polymer will prevent stenosis
during the formation of the vessel.
[0060] Any biocompatible, bioerodible polymer can be used to form
the first layer 20, such as a polyester; a polyurethane; a
poly(ester urethane) urea (PEUU); poly(ether ester urethane)urea
(PEEUU); poly(ester carbonate)urethane urea (PECUU);
poly(carbonate)urethane urea (PCUU); a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones including
polycaprolactone; or a polymer comprising monomers derived from
carbonates including polycarbonate, polyglyconate,
poly(glycolide-co-trimethylene carbonate), or
poly(glycolide-co-trimethylene carbonate-co-dioxanone).
Non-erodible polymers, e.g., as described above, can also be
utilized, though may not be preferred. The first layer 20 can be
electrodeposited, or formed by any other suitable method, such as
NIPS or TIPS, though in one aspect, dry electrospinning is used to
retard or prevent stenosis.
[0061] The second layer 30 comprises an ECM gel, such as a vascular
ECM gel. The gel optionally comprises a cell, such as a vascular
smooth muscle cell, a vascular endothelial cell, or a progenitor
cell of either, such as a mesenchymal stem cell or an
adipose-derived stem cell, as are broadly-known and are described
elsewhere herein. ECM gels and methods of making such ECM gels are
described elsewhere herein.
[0062] The third layer 40 is supportive of cell growth, and is a
porous, biocompatible, biodegradable polymeric matrix. Any
biocompatible, bioerodible polymer can be used to form the first
layer 20 and, independently, the third layer 40, such as a
polyester; a polyurethane; a poly(ester urethane) urea (PEUU);
poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polymer comprising monomers derived from alpha-hydroxy
acids such as: polylactide, poly(lactide-co-glycolide),
poly(L-lactide-co-caprolactone), polyglycolic acid,
poly(dl-lactide-co-glycolide), and/or
poly(I-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones including
polycaprolactone; or a polymer comprising monomers derived from
carbonates including polycarbonate, polyglyconate,
poly(glycolide-co-trimethylene carbonate), or
poly(glycolide-co-trimethylene carbonate-co-dioxanone).
Non-erodible polymers, e.g., as described above, can also be
utilized, though may not be preferred. The first layer 20 and third
layer 40, independently, can be electrodeposited, or formed by any
other suitable method, such as NIPS or TIPS, though in one aspect,
dry electrospinning is used to retard or prevent stenosis. In one
aspect, the first layer 20 comprises dry electrospun PEUU and the
third layer 40 comprises PEUU prepared by TIPS.
[0063] In another aspect, in reference to FIG. 1B, the first layer
20 of tubular device 10 supports cell growth, and the third layer
40 does not, and for example and without limitation, the third
layer 40 is a dry electrospun cell growth barrier, and the first
layer 20 is supportive of cell growth, and is for example and
without limitation, prepared by phase separation or wet
electrospinning. A device of this structure is useful for
determining the contribution of blood-borne cell infiltration on
tissue regeneration in blood vessel grafts as compared to the
contribution of infiltrating anastomosis derived cells migrating
from adjacent tissue to the graft.
[0064] In one aspect, the device has a wall thickness (e.g., in
reference to FIG. 1B, a sum of thicknesses of the first layer 20,
the second layer 30, and the third layer 40) ranges from 200 .mu.m
to 1 mm, from 250 .mu.m to 750 .mu.m, for example 500 .mu.m. In
another aspect, the thickness of the combined layers of the first
tubular, porous, biodegradable polymer matrix plus the ECM gel
(e.g. in reference to FIG. 1B, a sum of thicknesses of the first
layer 20 and the second layer 30) ranges from 100 .mu.m to 500
.mu.m, from 150 .mu.m to 350 .mu.m, or from 175 .mu.m to 250 .mu.m.
In yet another aspect, the thickness of the second tubular, porous,
biodegradable polymer matrix plus the ECM gel (e.g. in reference to
FIG. 1B, a sum of thicknesses of the second layer 30 and the third
layer 40) ranges from 50 .mu.m to 250 .mu.m, from 75 .mu.m to 125
.mu.m, for example 100 .mu.m. In a further aspect, the lumen of the
device has an inner diameter (e.g., in reference to FIG. 1B, a
diameter of lumen 12) ranging from 1 mm to 2 mm, from 1.5 mm to 3.5
mm, or 2 mm.
[0065] A porous polymer tube is prepared from a suitable
biodegradable polymer composition by any method, e.g., by
electrospinning or TIPS or molding, and may comprise one or more
concentric layers with one layer having a first composition and/or
physical structure, a second layer having a second composition
and/or a second physical structure, and a third layer having a
third composition and/or third physical structure. For example, a
first layer may be produced by a electrospinning method, a second
layer may be formed/molded around (e.g., concentrically around) the
first layer, and a third layer may be deposited by a TIPS method
about (e.g., concentrically around) the second layer.
[0066] In one aspect, the device is useful for coronary artery
repair or bypass and has an internal lumen diameter or dimension
approximating that of a coronary artery, e.g., having an inside
(lumen) diameter ranging from 1.0 mm to 3.5 mm, and an outer
diameter ranging from 2.0 mm to 4.5 mm. In use, the device is
anastomosed to existing coronary arteries or to other suitable
source blood vessels in order to transfer blood from the source
blood vessel into the heart tissue, thereby bypassing a blocked or
damaged coronary artery. In another aspect, the device is used to
repair or bypass a peripheral blood vessel, and once again having
dimensions, such as a lumen diameter and an external diameter
approximating native blood vessel dimensions. In that instance, the
blood vessel is anastomosed to existing arteries or to other
suitable source blood vessels in order to transfer blood from the
source blood vessel into the destination tissue, thereby bypassing
a blocked or damaged blood vessel. The device can be used for
venous or arterial blood vessel repair.
[0067] In one aspect, the device is not seeded with cells prior to
implantation. Native cells will migrate into the device, either
from sources external to the device, e.g., from the anastomosis or
other external sources, and/or from blood passing through the
device, and populate the device. The materials used to form the
device are biodegradable, such that as the device becomes populated
with cells, and the cells mature into blood vessel tissue, the
scaffolding of the device erodes until only newly-formed blood
vessel tissue remains.
[0068] In certain aspects, cells are added to the composition.
Non-limiting examples of useful cells include: stem cells,
progenitor cells and differentiated cells; recombinant cells;
muscle cells and precursors thereof; nerve cells and precursors
thereof; mesenchymal progenitor or stem cells; bone cells or
precursors thereof, such as osteoprogenitor cells, pre-adipocytes,
etc. Cells may be from any useful source, including autologous,
allogeneic, or from xenogeneic sources, and may be
genetically-modified in any useful manner, such as by direct
nucleic acid transfer, viral transduction, or gene/genome editing
(e.g., CRISPR-Cas, TALEN, meganuclease, or ZFN systems). In one
aspect, the cells are vascular endothelial cells, vascular smooth
muscle cells, and/or a mesenchymal stem cell, such as an
adipose-derived mesenchymal stem cell. Differentiated cells can
either be harvested from a patient (e.g., autologous), or
differentiated, e.g., from mesenchymal stem cells or
adipose-derived stem cells, e.g., autologous adipose-derived stem
cells of a patient. Differentiated cells can either be harvested
from a patient (e.g., autologous), or differentiated according to
broadly-known methods. For example, differentiated blood vessel
cells can be harvested directly from venous or arterial tissue of a
patient, or mesenchymal stem cells can be encouraged to
differentiate into blood vessel cells by culturing on
static/dynamic bioreactors with basic or specific cell culture
media cell with supplements optimized for specific applications.
Matrices as described herein can be populated with live cells by
any useful manner. For example, the ECM gel may be mixed with live
cells harvested from blood vessels or culture immediately prior to
forming an ECM gel layer in the described device. For
wet-electrospun layers, cells can be co-deposited with a polymer,
for instance by electrospraying, for example, concurrently with the
electrodeposition of fiber layers forming the matrix. In another
aspect, cells can by vacuum-deposited by application of a vacuum
across the walls of the device, thereby forcing cells into the
porous structure. Cells further can be incorporated by culturing
the device in cell culture medium comprising the cells to be seeded
onto the device. In any case, one of ordinary skill can incorporate
cells into the device ("seed the device") by any useful method, as
are broadly-known in the field of the invention. In one aspect, a
compact seeding device is used, essentially as described in Soletti
et al. ("A seeding device for tissue engineered tubular structures"
Biomaterials 27, 2006), which combines synergic action of vacuum,
rotation and flow; providing a rapid and uniform seeding of tubular
porous structures with no generation of injurious mechanical
conditions for cells.
[0069] In certain aspects, one or more layers of the device
independently comprise a therapeutic agent. For example, at least
one therapeutic agent is added to the ECM gel composition, or
otherwise included within or at the second, middle layer, and/or is
added to or otherwise combined with or included within the first
and third layers, e.g. the inner or outer layer of the device.
Generally, the therapeutic agents include any substance that can be
coated on, embedded into, absorbed into, adsorbed to, or otherwise
attached to or incorporated onto or into one or more layers of the
multi-layer device described herein. Non-limiting examples of such
therapeutic agents include antimicrobial agents, antiinflammatory
agents, growth factors, cytokines, antibodies or other binding
reagents, cofactors, and steroids. Each therapeutic agent may be
used alone or in combination with other therapeutic agents,
independently in one or more layers.
[0070] In certain non-limiting aspects, the therapeutic agent is a
growth factor, such as a neurotrophic or angiogenic factor, which
optionally may be prepared using recombinant techniques.
Non-limiting examples of growth factors include basic fibroblast
growth factor (bFGF), acidic fibroblast growth factor (aFGF),
vascular endothelial growth factor (VEGF), hepatocyte growth factor
(HGF), insulin-like growth factors 1 and 2 (IGF-1 and IGF-2),
platelet derived growth factor (PDGF), stromal derived factor 1
alpha (SDF-1 alpha), nerve growth factor (NGF), ciliary
neurotrophic factor (CNTF), neurotrophin-3, neurotrophin-4,
neurotrophin-5, pleiotrophin protein (neurite growth-promoting
factor 1), midkine protein (neurite growth-promoting factor 2),
brain-derived neurotrophic factor (BDNF), tumor angiogenesis factor
(TAF), corticotrophin releasing factor (CRF), transforming growth
factors .alpha. and .beta. (TGF-.alpha. and TGF-.beta.),
interleukin-8 (IL-8), granulocyte-macrophage colony stimulating
factor (GM-CSF), interleukins, and interferons. Commercial
preparations of various growth factors, including neurotrophic and
angiogenic factors, are available from R & D Systems,
Minneapolis, Minn.; Biovision, Inc, Mountain View, Calif.;
ProSpec-Tany TechnoGene Ltd., Rehovot, Israel; and Cell
Sciences.RTM., Canton, Mass.
[0071] In certain non-limiting aspects, the therapeutic agent is an
antimicrobial agent, such as, without limitation, isoniazid,
ethambutol, pyrazinamide, streptomycin, clofazimine, rifabutin,
fluoroquinolones, ofloxacin, sparfloxacin, rifampin, azithromycin,
clarithromycin, dapsone, tetracycline, erythromycin, ciprofloxacin,
doxycycline, ampicillin, amphotericin B, ketoconazole, fluconazole,
pyrimethamine, sulfadiazine, clindamycin, lincomycin, pentamidine,
atovaquone, paromomycin, diclazaril, acyclovir, trifluorouridine,
foscarnet, penicillin, gentamicin, ganciclovir, iatroconazole,
miconazole, Zn-pyrithione, and silver salts such as chloride,
bromide, iodide and periodate.
[0072] In certain non-limiting aspects, the therapeutic agent is an
anti-inflammatory agent, such as, without limitation, an NSAID,
such as salicylic acid, indomethacin, sodium indomethacin
trihydrate, salicylamide, naproxen, colchicine, fenoprofen,
sulindac, diflunisal, diclofenac, indoprofen, sodium salicylamide;
an anti-inflammatory cytokine; an anti-inflammatory protein; a
steroidal anti-inflammatory agent; or an anti-clotting agents, such
as heparin. Other drugs that may promote wound healing and/or
tissue regeneration may also be included.
[0073] Any useful cytokine, chemoattractant, drug or cells can be
mixed into, mixed with, co-applied or otherwise combined with or
incorporated into any device as described herein. For example and
without limitation, useful components include growth factors,
interferons, interleukins, chemokines, monokines, hormones,
angiogenic factors, drugs, and antibiotics.
[0074] As used herein, the terms "drug" and "drugs" refer to any
compositions having a preventative or therapeutic effect, including
and without limitation, antibiotics, peptides, hormones, organic
molecules, vitamins, supplements, factors, proteins, and
chemoattractants.
[0075] In one aspect, a TEVG device is provided having an inner
diameter of 2 mm and an outer diameter of 3 mm, a wall thickness of
0.5 mm and an average length of 2 cm. The three graft layers were
processed with: 1) electrospinning (ES); 2) thermal induced phase
separation (TIPS); 3) molding of decellularized cardiac tissue gel
(cECM). Each layer was modeled to duplicate the native tunicae
(e.g. intima, media, adventitia) function. Degradable PEUU has been
synthesized as previously described in (J. Guan, et al., Synthesis,
characterization, and cytocompatibility of elastomeric,
biodegradable poly(esterurethane) ureas based on poly(caprolactone)
and putrescine, Journal of Biomedical Materials Research 61(3)
(2002) 493-503). The electrospinning protocol in (J. T. Krawiec, et
al., In vivo functional evaluation of tissue-engineered vascular
grafts fabricated using human adipose-derived stem cells from high
cardiovascular risk populations, Tissue Engineering Part A 22(9-10)
(2016) 765-775) was used to fabricate the first layer (tunica
intima). Different layer thickness were produced in order to tune
scaffold suture retention properties. The TIPS layer (tunica
adventitia) was processed as described in (L. Soletti, et al., A
bilayered elastomeric scaffold for tissue engineering of small
diameter vascular grafts, Acta Biomaterialia 6(1) (2010) 110-122)
with a custom-made mold, made of a stainless steel rod (ID 3.8 mm)
covered with poly(tetrafluoroethylene) (PTFE) tubing and
concentrically aligned with a tubular glass sheath using two PTFE
sealing stoppers. Decellularized ECM solution with concentration of
15 mg/mL was obtained as reported in (A. D'Amore, et al.,
Bi-layered polyurethane--Extracellular matrix cardiac patch
improves ischemic ventricular wall remodeling in a rat model,
Biomaterials 107 (2016) 1-14).
[0076] According to one aspect of the invention a method of
producing, repairing or replacing a tissue in a patient is
provided. The method comprises implanting in the patient any aspect
of the device as described herein. In one aspect, the device is
tubular. In another aspect, the device is anastamosed to a blood
vessel of the patient, for example to repair an injured or occluded
vessel to treat an ischemic condition in the patient. In one
aspect, the device is anastomosed to an a coronary artery. In a
further aspect, the patient may be is suffering from an ischemic
event, such as an embolism, thrombosis, stenosis, or restenosis. In
yet another aspect, the ischemic event is a coronary artery
disease, such as a myocardial infarction, and the device is
anastamosed to a coronary artery. Also provided is a kit comprising
the device according to any aspect as described herein. The device
is packaged in suitable packaging, such as a foil and/or plastic
pouch or container, such as a mylar-containing package, e.g.
according to any acceptable and/or appropriate aspect as are
broadly-known in the medical device arts for sterile packaging,
storing, distributing, and otherwise handling bandages or
implants.
Preparation and Testing of a Multi-Layer TEVG
[0077] The full processing cascade is summarized in FIG. 2.
Briefly, the electrospun layer (see FIG. 3 for additional details
on electrospinning) is positioned on a steel rod and secured with
sutures at the edges (panel A). The sample is then inserted into
the custom-made mold and maintained co-axial with the mold cavity
(panel B). ECM gel solution is injected into the mold (panel C).
The mold is closed and left overnight in an incubator at 37.degree.
C. so that the ECM solution can transition to the gel state (panel
D). Finally, the sample is removed (panel E) and a TIPS outer layer
is gently slipped on the gel layer so that the three-layered
structure is obtained (panel F) (see, FIG. 4, panels A-E for
photographs of a device as-made).
[0078] A prototype was fabricated, and evaluation of the native and
synthetic vessel were performed. (FIGS. 2-10D) Morphological
properties were evaluated with images from histological staining
and Scanning Electron Microscopy. Compliance was tested on intact
samples approximately 20 mm long with a custom-made pressure-volume
test device in the range 80-120 mmHg, as in Ye, S. et al.
(Nonthrombogenic, Biodegradable Elastomeric Polyurethanes with
Variable Sulfobetaine Content. ACS Appl. Mater. Interfaces, 2014, 6
(24), pp 22796-22806). Suture retention force was tested on
rectangular specimens (10 mm length, 4 mm width). The short edge of
each specimen was originally oriented circumferentially on the
tubular scaffold. A single loop of 7-0 poly(propylene) suture was
created at approximately 2 mm from the short edge of each sample
and secured to a custom-made clamp provided with a hook connected
to the clamp of the testing device. A normal clamp was used to fix
the other end of the sample to the bottom of the device An
extension rate of 1 mm/s was used to pull the suture. Suture
retention strength was taken as the maximum force recorded prior to
pull-out of the suture. The results obtained from this
characterization and can be summarized as follows: [0079] A.
capacity to assess mechanism for in situ tissue regeneration: blood
derived host cell recruitment vs. anastomosis derived recruitment.
The dry electrospun layer, generally an network with reduced pore
size, functions as barrier to cell infiltration. This layer can be
positioned as layer proximal or distal to the lumen
(intima/adventitia position); [0080] B. capacity to combine
synthetic polymeric layers with ECM layer/bioactive component layer
to promote tissue formation and mitigate intima hyperplasia; [0081]
C. capacity to duplicated functional heterogeneity (e.g., three
layer structure including tunica intima, media and adventitia) of
native blood vessels at macroscopic--organ level (See, FIG. 7);
[0082] D. capacity to duplicate functional heterogeneity (e.g.,
three layer structure including tunica intima, media and
adventitia) of native blood vessels at mesoscopic--tissue level
(See, FIG. 5); [0083] E. capacity to duplicated functional
heterogeneity (e.g., three layer structure including tunica intima,
media and adventitia) of native blood vessels at microscopic--cell
level (See, FIG. 6); [0084] F. capacity to modulate/tune global
compliance mimicking native tissue mechanical response (See, FIGS.
8 and 9A-9D); [0085] G. capacity to modulate/tune scaffold suture
retention mimicking native tissue mechanical properties (See, FIGS.
10A-10D).
[0086] The following clauses illustrate various aspects of the
invention:
[0087] Clause 1. A method of making a synthetic tubular graft
device, comprising: depositing an ECM gel layer over a first
tubular, porous, biodegradable polymer matrix; and depositing a
second tubular, porous, biodegradable polymer matrix over the ECM
gel to produce a tubular structure.
[0088] Clause 2. The method of clause 1, wherein the first tubular,
porous, biodegradable polymer matrix is a dry-electrospun
matrix.
[0089] Clause 3. The method of clause 1 or 2, wherein the ECM gel
is prepared from vascular tissue.
[0090] Clause 4. The method of any of clauses 1-3, wherein the
second tubular, porous, biodegradable polymer matrix is prepared by
phase separation.
[0091] Clause 5. The method of clause 4, wherein the phase
separation is thermal-induced phase separation.
[0092] Clause 6. The method of any one of clauses 1-5, wherein the
first tubular, porous, biodegradable polymer matrix comprises one
or more of: poly(lactic acid) (PLA); poly(trimethylene carbonate)
(PTMC); poly(caprolactone) (PCL); poly(glycolic acid) (PGA);
poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(I-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones; or a polymer comprising
monomers derived from carbonates including polycarbonate,
polyglyconate, poly(glycolide-co-trimethylene carbonate), or
poly(glycol ide-co-tri methylene carbonate-co-dioxanone).
[0093] Clause 7. The method of any one of clauses 1-6, wherein the
second tubular, porous, biodegradable polymer matrix comprises one
or more of: poly(lactic acid) (PLA); poly(tri methylene carbonate)
(PTMC); poly(caprolactone) (PCL); poly(glycolic acid) (PGA);
poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones; or a polymer comprising
monomers derived from carbonates including polycarbonate,
polyglyconate, poly(glycolide-co-trimethylene carbonate), or
poly(glycol ide-co-tri methylene carbonate-co-dioxanone).
[0094] Clause 8. The method of clause 1, comprising:
dry electrospinning a poly(ester urethane) urea onto a mandrel to
form the first tubular, porous, biodegradable polymer matrix;
placing the mandrel comprising the first tubular, porous,
biodegradable polymer matrix within a cylindrical mold having an
inside diameter greater than an outside diameter of the first
tubular, porous, biodegradable polymer matrix; depositing an ECM
pre-gel about the first tubular, porous, biodegradable polymer
matrix; gelling the ECM pre-gel about the first tubular, porous,
biodegradable polymer matrix; and inserting the ECM gel-coated
first tubular, porous, biodegradable polymer matrix into a tube of
a porous poly(ester urethane) urea matrix.
[0095] Clause 9. The method of any one of clauses 1-8, wherein the
polymer of one or both of the first tubular, porous, biodegradable
polymer matrix and the second tubular, porous, biodegradable
polymer matrix comprises one or more of a PEUU, a PEEUU, a PECUU,
and a PCUU.
[0096] Clause 10. The method of any one of clauses 1-8, wherein the
polymer of one or both of the first tubular, porous, biodegradable
polymer matrix and the second tubular, porous, biodegradable
polymer matrix comprises a PEUU.
[0097] Clause 11. The method of any one of clauses 1-10, wherein
the first tubular, porous, biodegradable polymer matrix has an
inner diameter of from 1 mm to 2 mm, from 1.5 mm to 3.5 mm, or 2
mm.
[0098] Clause 12. The method of any one of clauses 1-11, wherein
the device has a wall thickness of from 200 .mu.m to 1 mm, from 250
.mu.m to 750 .mu.m, for example 500 .mu.m.
[0099] Clause 13. The method of any one of clauses 1-12, wherein
the thickness of the combined layers of the first tubular, porous,
biodegradable polymer matrix plus the ECM gel ranges from 100 .mu.m
to 500 .mu.m, from 150 .mu.m to 350 .mu.m, or from 175 .mu.m to 250
.mu.m.
[0100] Clause 14. The method of any one of clauses 1-13, wherein
the thickness of the second tubular, porous, biodegradable polymer
matrix plus the ECM gel ranges from 50 .mu.m to 250 .mu.m, from 75
.mu.m to 125 .mu.m, for example 100 .mu.m.
[0101] Clause 15. The method of any one of clauses 1-14, wherein
either or both of the first tubular, porous, biodegradable polymer
matrix and the second tubular, porous, biodegradable polymer matrix
comprises an anti-thrombogenic polymer composition.
[0102] Clause 16. The method of clause 15, wherein the
anti-thrombogenic polymer composition comprises a zwitterionic
moiety that is optionally pendant from the polymer backbone,
wherein the polymer composition optionally is a polyanhydride, a
polyester, a polyurethane, PCUU, PECUU, PEUU, PEEUU, or a
polyacrylate modified with a zwitterion moiety.
[0103] Clause 17. The method of clause 16, wherein the zwitterionic
moiety is a sulfobetaine or and phosphorylcholine moiety.
[0104] Clause 18. A multi-layer synthetic graft device
comprising:
a first porous, biodegradable polymer matrix; an ECM gel layer over
the first porous, biodegradable polymer matrix; and a second
porous, biodegradable polymer matrix over the ECM gel.
[0105] Clause 19. A multi-layer synthetic graft device
comprising:
a first tubular, porous, biodegradable polymer matrix; an ECM gel
layer disposed circumferentially about the first tubular, porous,
biodegradable polymer matrix; and a second tubular, porous,
biodegradable polymer matrix disposed circumferentially about the
ECM gel.
[0106] Clause 20. The device of clause 18 or 19, wherein the first
tubular, porous, biodegradable polymer matrix is a dry-electrospun
matrix.
[0107] Clause 21. The device of any one of clauses 18-20, wherein
the ECM gel is prepared from vascular tissue.
[0108] Clause 22. The device of any one of clauses 18-21, wherein
the second tubular, porous, biodegradable polymer matrix is
prepared by thermally induced phase separation.
[0109] Clause 23. The device of clause 22, wherein the phase
separation is thermal-induced phase separation.
[0110] Clause 24. The device of any one of clauses 18-23, wherein
the first tubular, porous, biodegradable polymer matrix comprises
one or more of: poly(lactic acid) (PLA); poly(trimethylene
carbonate) (PTMC); poly(caprolactone) (PCL); poly(glycolic acid)
(PGA); poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones; or a polymer comprising
monomers derived from carbonates including polycarbonate,
polyglyconate, poly(glycolide-co-trimethylene carbonate), or
poly(glycol ide-co-tri methylene carbonate-co-dioxanone).
[0111] Clause 25. The device of any one of clauses 18-24, wherein
the second tubular, porous, biodegradable polymer matrix comprises
one or more of: poly(lactic acid) (PLA); poly(tri methylene
carbonate) (PTMC); poly(caprolactone) (PCL); poly(glycolic acid)
(PGA); poly(glycolide-co-trimethylenecarbonate) (PGTMC);
poly(L-lactide-co-glycolide) (PLGA); polyethylene-glycol (PEG-)
containing block copolymers; polyphosphazene; poly(ester urethane)
urea (PEUU); poly(ether ester urethane)urea (PEEUU); poly(ester
carbonate)urethane urea (PECUU); poly(carbonate)urethane urea
(PCUU); a polyurethane; a polyester; a polymer comprising monomers
derived from alpha-hydroxy acids such as: polylactide,
poly(lactide-co-glycolide), poly(L-lactide-co-caprolactone),
polyglycolic acid, poly(dl-lactide-co-glycolide), and/or
poly(l-lactide-co-dl-lactide); a polymer comprising monomers
derived from esters including polyhydroxybutyrate,
polyhydroxyvalerate, polydioxanone, and/or polyglactin; a polymer
comprising monomers derived from lactones; or a polymer comprising
monomers derived from carbonates including polycarbonate,
polyglyconate, poly(glycolide-co-trimethylene carbonate), or
poly(glycol ide-co-tri methylene carbonate-co-dioxanone).
[0112] Clause 26. The device of any one of clauses 18-25, wherein
the polymer of one or both of the first tubular, porous,
biodegradable polymer matrix and the second tubular, porous,
biodegradable polymer matrix comprises one or more of a PEUU, a
PEEUU, a PECUU, and a PCUU.
[0113] Clause 27. The device of any one of clauses 18-25, wherein
the polymer of one or both of the first tubular, porous,
biodegradable polymer matrix and the second tubular, porous,
biodegradable polymer matrix comprises a PEUU.
[0114] Clause 28. The device of any one of clauses 18-27, wherein
the first tubular, porous, biodegradable polymer matrix has an
inner diameter ranging from 1 mm to 2 mm, from 1.5 mm to 3.5 mm, or
2 mm.
[0115] Clause 29. The device of any one of clauses 18-28, wherein
the device has a wall thickness of from 200 .mu.m to 1 mm, from 250
.mu.m to 750 .mu.m, for example 500 .mu.m.
[0116] Clause 30. The device of any one of clauses 18-29, wherein
the thickness of the combined layers of the first tubular, porous,
biodegradable polymer matrix plus the ECM gel ranges from 100 .mu.m
to 500 .mu.m, from 150 .mu.m to 350 .mu.m, or from 175 .mu.m to 250
.mu.m.
[0117] Clause 31. The device of any one of clauses 18-30, wherein
the thickness of the second tubular, porous, biodegradable polymer
matrix plus the ECM gel ranges from 50 .mu.m to 250 .mu.m, from 75
.mu.m to 125 .mu.m, for example 100 .mu.m.
[0118] Clause 32. The device of any one of clauses 18-31, wherein
either or both of the first tubular, porous, biodegradable polymer
matrix and the second tubular, porous, biodegradable polymer matrix
comprises an anti-thrombogenic polymer composition.
[0119] Clause 33. The device of clause 32, wherein the
anti-thrombogenic polymer composition comprises a zwitterionic
moiety that is optionally pendant from the polymer backbone,
wherein the polymer composition optionally is a polyanhydride, a
polyester, a polyurethane, PCUU, PECUU, PEUU, PEEUU, or a
polyacrylate modified with a zwitterion moiety.
[0120] Clause 34. The device of clause 33, wherein the zwitterionic
moiety is a sulfobetaine or and phosphorylcholine moiety.
[0121] Clause 35. A method of producing, repairing or replacing a
tissue in a patient, comprising implanting in the patient the
device of any one of clauses 18-34 in the patient.
[0122] Clause 36. The method of clause 35, wherein the device is
tubular.
[0123] Clause 37. The method of clause 35 or 36, wherein the device
is anastamosed to a blood vessel of the patient.
[0124] Clause 38. The method of any one of clauses 35-37, wherein
the device is anastomosed to an a coronary artery.
[0125] Clause 39. The method of any one of clauses 35-38, wherein
the patient is suffering from an ischemic event, such as an
embolism, thrombosis, stenosis, or restenosis.
[0126] Clause 40. The method of clause 39, wherein the ischemic
event is a coronary artery disease, such as a myocardial
infarction, and the device is anastamosed to a coronary artery.
[0127] Clause 41. A kit comprising the device according to any one
of clauses 18-34 in suitable packaging, such as a foil and/or
plastic pouch or container, such as a Mylar package.
[0128] While the present invention is described with reference to
several distinct embodiments, those skilled in the art may make
modifications and alterations without departing from the scope and
spirit. Accordingly, the above detailed description is intended to
be illustrative rather than restrictive.
* * * * *