Biopolymer compositions, scaffolds and devices

Abstract

To provide surgically implantable devices.SOLUTION: Compositions and blends of biopolymers and copolymers are described, along with use of the compositions and blends in preparing biocompatible scaffolds and surgically implantable devices for use in supporting and facilitating the repair of soft tissue injuries.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Cross-reference to related patent applications This application is related to U.S. Provisional Patent Application No. 62 / 603,026, filed May 16, 2017, the contents of which are incorporated herein by reference in their entirety.

[0002] Statement Regarding Federally Sponsored Research The data presented in this application was supported, at least in part, by U.S. DARPA Contract No. HR0011-15-9-0006. The U.S. Government has certain rights in this invention.

[0003] The present invention relates to compositions of biopolymers and biodegradable copolymers, such as collagen, methods for their incorporation into fibers and various scaffolds, and implantable biocompatible devices prepared with such compositions. More particularly, the present invention relates to the fabrication of biocompatible implants and devices useful for supporting and promoting the repair of soft tissue injuries, such as ruptured Achilles, patellar, and rotator cuff tendons. [Background technology]

[0004] Various approaches have been taken to develop components for implantable devices useful as scaffolds to promote repair or replace damaged soft tissues, such as tendons and ligaments. Such products must function in a variety of challenging biomechanical environments in which multiple functional parameters, such as compatibility, strength, flexibility, and biodegradability, must be addressed.

[0005] Surgical repair procedures for ligaments and tendons of the foot and ankle (e.g., Achilles tendon), shoulder (e.g., rotator cuff), and knee (e.g., anterior cruciate ligament) reach approximately 800,000 cases per year in the United States alone, yet the current standard of care, which involves the implantation of replacement and support elements, is generally considered suboptimal by physicians.

[0006] The predominant ligament and tendon graft production, aimed at providing a biocompatible soft-tissue support scaffold, often requires a 20-year-old technique that sometimes relies on cadaveric tissue or invasive autografting procedures. Allografts are in limited supply, promote scar formation, can provoke an immune response, and have an undefined turnover rate, all of which inhibit healing. Autograft procedures also increase surgical time, associated trauma, and often require a costly second surgery to restore the autologous tissue.

[0007] For example, GRAFTJACKET® Regenerative Tissue Matrix (http: / / www.wright.com / footandankleproducts / graftjacket) is a sheet-like product formed from allograft donated human dermis that has been aseptically decellularized and then lyophilized. ArthroFLEX® Decellularized Dermal Allograft (https: / / www.arthrex.com / orthobiologics / arthroflex) is a similar acellular dermal extracellular matrix.

[0008] Among these approaches and products are those disclosed by Ratcliffe et al. in U.S. Pat. No. 9,597,430 (2017) entitled "Synthetic structure for soft tissue repair." This patent describes various synthetic fibril structures, for example, single-layer or multi-layer planar fibril forms of woven mesh. According to Ratcliffe, these structures can be made from any biocompatible polymeric material that can provide suitable mechanical properties, bioabsorbable or not. Collagen and lactide are mentioned as being suitable. Synthasome's medical device "X-Repair" appears to be related, as it has been granted FDA 510(k) clearance by the U.S. Food and Drug Administration (FDA) (http: / / www.synthasome.com / xRepair.php).

[0009] Another approach is described by Qiao et al. in "Compositional and in Vitro Evaluation of Nonwoven Type I Collagen / Poly-dl-lactic Acid Scaffolds for Bone Regeneration," Journal of Functional Biomaterials 2015, 6, 667-686; doi:10.3390 / jfb6030667. This paper describes electrospun blends of type I collagen and poly-d,l-lactic acid (PDLLA). Various blends are described with polymer:collagen blends in weight ratios of 40 / 60, 60 / 40, and 80 / 20. Qiao described a cosolvent system and reported that chemical crosslinking was essential to ensure the long-term stability of this material in cell culture. According to Qiao, a PDLLA / collagen scaffold with a weight ratio of 60:40 provided the greatest stability over a 5-week culture period.

[0010] U.S. Patent No. 9,421,305 (2016) to Lee et al., entitled "Aligned Scaffolding System for Skeletal Muscle Regeneration," describes the use of a muscle graft construct. The patent discusses anisotropic muscle grafts fabricated by orienting and crosslinking electrospun fibers along their longitudinal axis to form a scaffold. Cells are seeded onto the fibers to form myotubes. The fibers can be formed from natural and / or synthetic polymers. Examples of natural polymers include collagen, elastin, proteoglycans, and hyaluronic acid. Examples of synthetic polymers include polycaprolactone (PCL), poly(d,l-lactide-co-glycolide) (PLGA), polylactic acid (PLA), and poly(lactide-co-captrolactone) (PLCL). The fibers may also contain hydrogels, microparticles, liposomes, or blebs. When blended, the weight ratio of natural polymer to synthetic polymer is 2:1 to 1:2.

[0011] Electrospun scaffolds for soft tissue production are described by Sensini et al., "Biofabrication of bundles of poly(lactic acid)-collagen blends mimicking the fascicles of the human Achilles tendon," Biofabrication 9 (2017) 015025. Two different blends of PLLA and collagen were compared to pure collagen bundles. Summary of the Invention

[0012] The present invention relates to biocompatible, bioactive, biodegradable and absorbable biopolymer and copolymer compositions, and to scaffolds and implantable devices made from such compositions and blends thereof, which are useful for supporting and promoting soft tissue injury repair.

[0013] A preferred embodiment of such a blend comprises about 10-50% by weight biopolymer, preferably about 15-40% biopolymer, more preferably about 20-35% biopolymer, more preferably about 27.5-32.5% biopolymer, and most preferably about 30% biopolymer. The copolymer, which is also biocompatible, bioactive, biodegradable, and absorbable, is present in the range of about 50-90% by weight.

[0014] Preferred types of biopolymers include collagen, extracellular matrix proteins, fibrin, fibrinogen, gelatin, and laminin, as well as combinations thereof. Preferred types of collagen include human, bovine, porcine, and marine telocollagen, atelocollagen, and mixtures of these types of collagen, in native, processed, placental, and recombinant forms. Preferred collagen is of bovine origin. Another preferred collagen is type I collagen. Generally, human collagen is preferred, such as that from placental tissue or recombinant human collagen, and mixtures thereof. The use of both telocollagen and atelocollagen is contemplated. Sources of marine collagen include jellyfish, sea cucumber, and cuttlefish.

[0015] In one embodiment of the present invention, the composition comprises about 10-50% by weight collagen, preferably about 15-40% collagen, more preferably about 20-35% collagen, more preferably about 25-35% collagen, more preferably about 27.5-32.5% collagen, and most preferably about 30% collagen, and a biodegradable copolymer in an amount of about 50-90% by weight.

[0016] Various copolymers are suitable for the scaffolds and other products and methods described herein. Preferred copolymers are biodegradable or absorbable, such as PLLA, PDLA, and PDLLA, and mixtures thereof. Preferred copolymers are PDLA, low molecular weight PDLLA, medium molecular weight PDLLA, high molecular weight PDLLA, and combinations thereof.

[0017] In the compositions of the present invention, blends of biopolymers, such as collagen, and copolymers can be formed into fibers. Optionally, the compositions, fibers, and other forms of implantable scaffolds may or may not be treated with chemical crosslinkers. In certain embodiments of the present invention, particularly by techniques such as electrospinning, the fiber diameter ranges from about 150 to 4,500 nm, preferably about 400 to 2,000 nm, more preferably about 600 to 1,500 nm, and most preferably about 750 to 1,200 nm. In other embodiments, particularly by melt electrospinning or electrowriting, the average diameter of the fibers generally ranges from about 1 to 200 μm, preferably about 10 to 100 μm, more preferably about 15 to 50 μm, and most preferably about 20 μm.

[0018] The present invention also relates to fibers prepared as described herein and processed into the form of a single- or multi-layered sheet-like scaffold. In one embodiment, the scaffold is composed of about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more layers of substantially aligned telocollagen and PDLLA fibers, each about 0.2 mm thick, with a small portion of the fibers laid down in cross section around the edges to provide biaxial strength for suture retention. In another embodiment, the multi-layer scaffold measures approximately 4 cm x 7 cm x 1 mm. An alternative embodiment is a single layer scaffold of similar dimensions.

[0019] In another aspect of the invention, the compositions according to the invention may be prepared and used to prepare scaffolds in the form of films, aerosols, droplets, adhesives or porous structures.

[0020] Possible techniques for making the fibers and various scaffolds include electrospinning, melt electrospinning, electrowriting, extrusion, spraying and three-dimensional fabrication.

[0021] Yet another aspect of the present invention relates to an implantable medical device for supporting the repair of soft tissue injuries in a mammal, comprising the composition of claim 1. In yet another aspect, the present invention relates to methods for promoting the repair and healing of soft tissue injuries via surgical implantation of the scaffolds and medical devices described herein. The methods, scaffolds, and disclosed medical devices are intended for use in mammalian subjects, particularly humans. In one embodiment, the present invention relates to a method for repairing an Achilles tendon rupture in a human subject by surgically implanting and fixating a device such that the device spans the repaired area of the tendon and provides mechanical support.

[0022] Brief description of the table Table 1 shows a comparison of peak stress (MPa) and modulus (MPa) for several blends with PDLLA and collagen. DETAILED DESCRIPTION OF THE INVENTION

[0023] definition As used herein, the terms are as follows: "Biopolymer" means a naturally occurring protein-derived macromolecule found naturally in connective and other soft tissues and in the extracellular matrix, such as collagen, fibrin, fibrinogen, gelatin, and laminin.

[0024] "Copolymer" means a synthetic polymer that can be dissolved in a non-toxic solvent system and mixed or blended with a biopolymer to impart various desired properties, e.g., strength or stiffness that would otherwise be provided by the biopolymer alone.

[0025] "High molecular weight PDLLA" means a PDLLA product having an average inherent viscosity (IV) of about 0.55 dL / g to 4.5 dL / g or higher.

[0026] "Scaffold" refers to constructs formed from biopolymers and copolymers, preferably substantially aligned fibers formed into layers, mats, sheets, and tubes.

[0027] "Substantially aligned fibers" means that at least about half of the fibers within a 15-20 degree range of a reference in a scaffold are oriented along a common axis. This is to be interpreted as opposed to randomly oriented fibers.

[0028] Object of the invention An object of the present invention is to provide synthetic fibers and related sheet-like and bundled fiber products for tissue engineering as soft tissue supports, particularly useful for repairing injured tendons and ligaments. For example, according to the present invention, tissue-engineered ligament and tendon scaffolds formed from collagen and biodegradable polymers can be used to repair injured Achilles tendons. A further object of the present invention is to create scaffolds with appropriate fiber orientation for specific tissues or defects, such as partially or completely ruptured Achilles tendons, thereby providing synthetic materials with the tensile strength, flexibility, modulus, and other biomechanical properties that support native human tendons and ligaments of similar size. The present invention provides sheet-like and bundled fiber scaffold products with tensile strength and modulus that, when incorporated by host cells and over time form new tendon-like connective tissue, will enhance healing, such as in reuniting tendons where the ruptured ends are sutured together, without yielding or breaking prior to tissue damage.

[0029] Biopolymers: The biopolymers of the present invention are biomolecules capable of forming stable extracts, particularly in the form of scaffolds prepared from biopolymer fibers, and are preferably proteins from native biological structures and extracellular matrices. Examples of these include collagen, elastin, fibrin, fibrinogen, and gelatin. Other proteins known to those skilled in the art may also be utilized in the methods of the present invention.

[0030] collagen: A preferred biopolymer is collagen. The type I collagen used in the biocompatible scaffolds of the present invention is generally extracted from mammalian tissues, particularly bovine and porcine tendons, although recombinant collagen may also be used, as is the case for current clinical products. Human placenta may also be used for such purposes. Type I collagen is available and marketed in two common forms, both research-grade and clinical-grade products. A more common collagen variant is produced by acid and enzymatic digestion of tissue with pepsin, resulting in deletion of the terminal region of the collagen protein (the terminal peptide sequence of "DEKSTGISVP" as opposed to pQLSYGYDEKSTGISVP), a form of collagen termed "atelocollagen" because it cleaves the telopeptides and aids in the recovery of collagen from the parent tissue. Less commonly, collagen can be solubilized with mild acid to collect collagen in solution, known as "telocollagen," which retains both telopeptides within the collagen monomer.

[0031] Telocollagen has been reported to form stronger hydrogels than gels made from atelocollagen, although their relative strengths when produced as electrospun nanofibers for tissue engineering have not been well investigated. Experiments were conducted in which telocollagen and atelocollagen were dissolved in 40% acetic acid and electrospun to prepare scaffolds.

[0032] The inventors found that the strength of such scaffolds was generally similar to that of native collagen, but other properties of the scaffolds were not optimal, as shown in Table 1. Therefore, blends of collagen with various polymers were evaluated, and the experimental results are described below. Selecting a higher molecular weight PDLLA resulted in an increase in the peak stress and modulus of the construct. Therefore, high molecular weight (HMW) PDLLA is preferred.

[0033] [Table 1]

[0034] Acid-soluble (telocollagen) and pepsin-soluble (atelocollagen) lyophilized collagen are suitable starting materials. Preferred GMP-grade type I collagen from bovine dermis is available in its native form from Collagen Solutions, Inc. http: / / www.collagensolutions.com / products / medical-grade-collagen. The Collagen Solutions website, http: / / collagensolutions.com / resource-library#technical-services, provides general information on the use and preparation of collagen. Collagen is also available in a variety of species from other manufacturers, such as Sigma-Aldrich, http: / / www.sigmaaldrich.com / life-science / metabolomics / enzyme-explorer / learning-center / structural-proteins / collagen.html.

[0035] Copolymer: A wide variety of biodegradable and bioactive copolymers have been investigated for use in soft tissue repair, either alone or in blends with other polymers, and sometimes including natural tissue components such as collagen, fibrin, and elastin. Among these, the present inventors have discovered surprising biomechanical and biodegradable results from blends of collagen with polylactic acid, including both L- and D-isoforms, and in particular its amorphous mixture, referred to as poly(DL-lactic acid) or PDLLA.

[0036] Other copolymers that may be useful for specific products or devices, or when added to blends of polylactic acid and collagen, include 1,3-propanediol (PDO), polycaprolactone (PCL), and poly(lactic-co-glycolic acid) (PLGA). Those skilled in the art will know of other useful polymers and copolymers, such as polyglycolic acid, polyesters, trimethylene carbonate, polydioxanone, caprolactone, alkylene oxides, orthoesters, hyaluronic acid, alginic acid, synthetic polymers from natural fats and oils, and combinations thereof.

[0037] Regarding polylactic acid, the PLLA isoform alone is relatively strong, but brittle rather than elastic. It lasts approximately 36-48 months in vivo. A preferred PLLA is available from Sigma-Aldrich: http: / / www.sigmaaldrich.com / content / dam / sigma-aldrich / articles / material-matters / pdf / resomer-biodegradeable-polymers.pdf

[0038] PDLA isoforms are more elastic and less brittle and typically last 12-18 months in vivo. A preferred PDLA is available from Sigma-Aldrich, http: / / www.sigmaaldrich.com / catalog / product / SIGMA / 67122?lang=en®ion=US.

[0039] PDLLA lies between PLLA and PDLA in terms of strength, stability, and in vivo longevity, which ranges from approximately 18 to 36 months, long enough to allow for resorption but short enough to prevent encapsulation. PDLLA is an amorphous polymer formed by polymerization of a racemic mixture of L-lactic acid and D-lactic acid. The precise composition of the polymer determines its mechanical and hydrolytic properties.

[0040] PDLLA generally exhibits better degradability due to the level of water accessibility within the amorphous phase and hydrolysis of the polymer's ester bonds. The inventors have found that PDLLA, when blended with type I collagen, is surprisingly effective in fabricating fibers and implantable support devices for the applications described herein.

[0041] Preferred suppliers of PDLLA include Polysciences, Evonik, and Sigma-Aldrich. For example, PDLLA with an inherent viscosity of 1.6 to 2.4 dL / g is available from Polysciences (http: / / www.polysciences.com / default / polydl-lactic-acid-iv-20-28dlg) and has an average molecular weight in the range of about 300,000 to 600,000 daltons. PDLLA with a lower inherent viscosity (IV of 1.3 to 1.7 dL / g) is available from Evonik (http: / / healthcare.evonik.com / product / health-care / en / products / biomaterials / resomer / pages / medical-devices.aspx). PDLLA with an even lower inherent viscosity of 0.55-0.75 dL / g is available from Sigma-Aldrich, Inc., http: / / www.sigmaaldrich.com / catalog / product / sigma / p1691?lang=en®ion=US, and has a molecular weight ranging from about 75,000 to 125,000 daltons. Another preferred PDLLA ("PURASORB PDL 45"), available from Corbion, Inc., http: / / www.corbion.com / static / downloads / datasheets / 31d / PURASORB%20PDL%2045.pdf, has a relatively high inherent viscosity of 4.5 dL / g.

[0042] Copolymer functionalization: Copolymers can be pretreated with one or more functionalizing agents to prepare copolymers that are crosslinked after extraction of the biopolymer-copolymer blend via fabrication techniques such as electrospinning. For example, PDLLA can be functionalized by aminolysis to add amino groups. See, e.g., Min et al., "Functionalized Poly(D,L-lactide) for Pulmonary Epithelial Cell Culture," Advanced Engineering Materials 12(4):B101-B112 (2010), available at http: / / onlinelibrary.wiley.com / doi / 10.1002 / adem.200980031 / abstract. Alternatively, PDLLA can be functionalized by plasma treatment to introduce carboxyl and amino groups into the matrix.

[0043] As a general method, for example, PDLLA can be functionalized with OH groups prior to electrospinning. PDLLA pellets are immersed in a mixture of 10 mM to 1 M sodium hydroxide in a 10% to 20% Milli-Q aqueous solution of ethanol. The pellets are immersed for 10 to 60 minutes at either room temperature or 37°C. After incubation, the pellets are rinsed in Milli-Q (ultra-purified) water and air-dried in a biosafety cabinet. The functionalized PDLLA chip is then dissolved in a suitable electrospinning solution as described herein.

[0044] Collagen-copolymer blend: In a preferred embodiment of the present invention, the tensile strength of scaffolds produced from collagen, e.g., telocollagen, and a polymer, e.g., PDLLA, is comparable to or exceeds the biomechanical properties of, e.g., bovine caudal ligament. However, as will be apparent to those skilled in the art, similar blends made with atelocollagen from different sources may exhibit lower tensile strength. For example, one lot of electrospun telocollagen and lactic acid polymer exhibited nearly 50% higher strength than atelocollagen prepared in a similar manner, approximately 5.5 MPa compared to approximately 4 MPa. Furthermore, with a relatively higher molecular weight PDLLA (450,000 versus 75,000-120,000), the strength of the construct more than doubled to approximately 13.1 MPa.

[0045] Both telocollagen blended with PDLLA and atelocollagen blended with PDLLA were evaluated for long-term stability in tissue culture medium to ensure stability in long-term cell culture studies. Collagen-PDLLA scaffolds exhibit acceptable stability in tissue culture medium over 28 days of incubation. Similar to the dry test results of tensile strength tests, PDLLA and telocollagen blends also exhibited surprisingly higher mechanical strength (wet tests) compared to PDLLA and atelocollagen blends.

[0046] According to the present invention, preferred compositions comprise about 10-50% collagen, preferably about 15-40% collagen, more preferably about 20-35% collagen, more preferably about 25-35% collagen, more preferably about 27.5-32.5% collagen, and most preferably about 30% collagen by weight, together with about 50-90% lactic acid copolymer by weight.

[0047] Bovine-derived type I collagen is preferred as the biopolymer, and lactic acid polymers, particularly high molecular weight PDLLA, are preferred as copolymers. Telocollagen is preferred over atelocollagen. Such compositions exhibit desirable biomechanical performance and biostability parameters, such as wettability.

[0048] Preparation and processing of collagen-polymer blends: The preparation of the collagen and lactic acid polymer blends is described in detail in the examples that follow. Generally, both components are dissolved in hexafluoro-2-propanol (HFP). Preferably, no cross-linking agents are added to the blend of reagents before processing into fibers. Optionally, various conventional cross-linking compounds may be blended with the collagen and polymer, i.e., the resulting material may be cross-linked after electrospinning.

[0049] Although other approaches will be known to those skilled in the art, electrospinning is a preferred processing technique for producing fibers from the compositions of the present invention. However, other approaches for separating the blend from the solvent system are known to those skilled in the art, such as pneumatospinning, extrusion, cold drawing, or casting. Electrospinning is a fiber manufacturing technique in which threads of charged polymer solution or molten polymer are drawn into fibers of various diameters and lengths. Collagen electrospinning has been broadly described as a one-step process for forming fibrous materials that mimic native tissue structures. Electrospinning equipment is conventional and readily available from product brands such as Nanospinner, Elmarco, and SprayBase. Electrospinning possesses characteristics of both electrospraying fibers, conventional solution dry spinning, extrusion, or pultrusion.

[0050] Properties of fibers made with the composition of the present invention: Electrospun fibers were prepared using the polymer blends of the preferred embodiments described above and in the Examples below. The preferred fiber diameters are in the range of about 150 to 4,500 nm, preferably about 400 to 2,000 nm, more preferably about 600 to 1,500 nm, and most preferably about 750 to 1,200 nm. The preferred fiber strength range is about 4 to 16 MPa. The preferred modulus is preferably substantially similar to that of human ligaments, particularly Achilles tendons, and is about 35 to 750 MPa. Within this range, the preferred fiber is about 35 to 200 MPa. Additionally, the preferred strain to failure is 50 to 200% (0.5 to 2.0 mm / mm) when tested in a hydrated state at 1 mm / s.

[0051] Scaffold preparation: A preferred biopolymer structure is a scaffold suitable for implantation as a support to aid in the repair of soft tissue damage or as a replacement for such tissue, e.g., tendons or ligaments. Scaffolds suitable for implantation can be produced by a variety of techniques. For example, a scaffold in sheet form can be produced by electrospinning a collagen and copolymer blend onto a high-speed drum (surface speed of the order of 1-20 m / s, e.g., about 18 m / s). The fibrous sheets are easily peeled off one by one from the electrospinning drum or recovered by conventional techniques.

[0052] The scaffold can be dried under vacuum after electrospinning to remove residual solvent. For example, the sheet is preferably stored under vacuum at about 30-37°C for about 1-3 days to remove residual processing solvent. The sheet can then be cut or oriented to create secondary and tertiary structures and, optionally, laminated by welding or stitching / sewing.

[0053] Such sheets may be laminated by welding or stitching or sewing. Typically, sheets of electrospun material are stacked. Typically, sheets of electrospun material are stacked. Heat (30-100°C, e.g., about 60°C) is then applied locally to bond the sheets. Additional material may be added to the weld to reinforce the material to aid in suture retention. Optionally, an adhesion barrier may be included, which will consist of a pure polymer backing (away from the tendon) to prevent exogenous cell infiltration. The polymer layer may be electrospun, cast, foamed, extruded, or fabricated by other conventional techniques.

[0054] For scaffolds prepared from the fibers, the wettability of the scaffold is preferably stable in tissue culture medium upon incubation for approximately 28 days at 37°C in 5% CO2, 100% humidity. Generally, as described in the Examples, seeded cells should exhibit robust cell adhesion, with more than half of the cells preferably adhering to the scaffold. Preferably, the initial retention of growth factors is substantially similar to that of human tendons, particularly Achilles tendons.

[0055] Those skilled in the art will be aware of techniques suitable for the assembly, fabrication and construction of three-dimensional scaffolds according to the compositions and methods of the present invention. Such techniques are described, for example, in Bhatia et al., "Microfabricated biopolymer scaffolds and method of making same," published as U.S. Patent Application Publication No. 2005 / 0008675; Hoque et al., "Extrusion-based rapid prototyping technique: An advanced platform for tissue engineering scaffold fabrication," Biopolymers 97: 83-93, 2012, https: / / doi.org / 10.1002 / bip.21701; Lu et al., "Techniques for fabrication and construction of three-dimensional scaffolds for tissue engineering," Int. J. Nanomedicine. 2013; 8: 337-350; Li et al., "3D-Printed Biopolymers for Tissue Engineering Application," International Journal of Polymer Science, Volume 2014, Article ID 829145, http: / / dx.doi.org / 10.1155 / 2014 / 829145; and Ma, "Scaffolds for tissue fabrication," Materials Today Volume 7, Issue 5, May 2004, Pages 30-40.

[0056] Additional scaffolding treatment: Generally, if the copolymer is functionalized to introduce amino groups before dissolving in the solvent system, the biopolymer and copolymer may be crosslinked with glyoxal or aldehyde crosslinkers after its extraction into the scaffold. If the copolymer is functionalized with carboxyl groups, EDC and other carbodiimides may be used for crosslinking. Isocyanates react with both OH groups and amines. Therefore, isocyanate-based crosslinkers may be used, for example, to crosslink OH groups to each other (an OH group bonds to another OH group) within the functionalized PDLLA to improve medium stability and / or strength. Isocyanates may also be used to bond collagen to OH groups within the functionalized PDLLA via the collagen's NH2 groups (i.e., amine groups). Additionally, photocrosslinkers may be used.

[0057] Additionally, biopolymers can be physically post-treated, for example, by thermal annealing with or without mechanical stretching, or by combined cycles of annealing, stretching, and relaxation. These physical post-treatment steps can be added to adjust or otherwise modify the material properties of the resulting scaffold, for example, by changing the fiber diameter, fiber alignment, and porosity or void volume of the resulting scaffold.

[0058] Implantable devices: As explained above, the present invention is directed to the production and use of synthetic fibers and related sheet-like and bundled fiber products as soft tissue supports useful for tissue engineering, particularly for repairing injured tendons and ligaments. For example, in accordance with the present invention, tissue-engineered ligament and tendon scaffolds formed from elongated fibers of collagen and biodegradable copolymers can be used to repair injured Achilles tendons. Scaffolds of the present invention can be in the form of mats, tubes, single-layer sheets, and multi-layer sheets.

[0059] In a preferred embodiment, the present invention relates to fibers prepared as described above and processed into the form of a single- or multi-layered sheet-like scaffold. In one embodiment, the scaffold is composed of about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more layers of aligned telocollagen and PDLLA fiber blends, each about 0.4 mm thick, with a small portion of the fibers placed in cross-section around the edges to provide biaxial strength for suture retention. In another embodiment, the multi-layered scaffold measures about 4 cm x 7 cm x 1 mm. An alternative embodiment is a single-layered scaffold of similar dimensions.

[0060] Generally, the scaffolds of the present invention are easy to handle in an operating room or other critical care environment and can be easily cut and shaped to conform and support a given soft tissue site. The scaffold can be attached, for example, with sutures, suture anchors, or surgical adhesives, proximal to or in contact with the torn and repaired tissue. The scaffold provides support and reinforcement to soft tissues, such as tendons and ligaments, including the Achilles tendon, rotator cuff, patellar tendon, biceps tendon, and quadriceps tendon. The scaffold shares some of the mechanical stresses and loads with the repaired tissue.

[0061] The fibrous, optionally sheet-like structure of the scaffold allows for ingrowth of host cells and tissues, and also vascularization of the scaffold. The scaffold is absorbed over time and replaced by the patient's own tissue through a remodeling process, or otherwise dissolves, degrades, and is eventually removed. Scaffolds can be packaged individually, in pairs, or in bulk in sterile containers.

[0062] A. Sheet Material Sheet material is available in a variety of standard sizes, including 1x2, 2x2, 3x3, 2x4, 4x6, and 6x9 cm, and can be cut to custom sizes and shapes. B. Mesh Materials Randomly aligned materials can be manufactured as nonwoven mesh in standard sizes such as 1x2, 2x2, 3x3, 2x4, 4x6, 6x9 cm with isotropic fibers and isotropic fiber strength, and can be cut to custom sizes and shapes. C. Wraps Sheet or mesh materials can be used as onlays or wrapped around tissue defects. D. Sutures Materials may be synthesized as threads, yarns or other monofilament and multifilament threads for use as sutures to hold, position, support or reinforce a surgical site. E. Internal Brace Materials may be synthesized as threads, yarns or other monofilament and multifilament threads used as sutures to tension, support or reinforce the surgical site, preventing overstretching of the joint and reducing the risk of re-rupture. [Example]

[0063] Example 1: Preparation of 10% atelocollagen-90% PDLLA and electrospinning of fibers In a 5 mL glass vial (Wheaton), 36.2 mg of lyophilized atelocollagen and 324.5 mg of poly(DL-lactic acid) (PDLLA) were dissolved in 3 mL of hexafluoro-2-propanol (HFP). Collagen was obtained from Collagen Solutions, Inc. (San Jose, CA), and PDLLA was obtained from Polysciences, Inc. The vial was placed on a rocking platform shaker, such as that from VWR, until the reagents dissolved. The solution was then electrospun using a 50 mm / 2 inch drum disk equipped with an electric motor, a 5 mL glass syringe with an 11.7 mm diameter and a 2 inch, 18-gauge all-stainless steel needle with a 100 mm tip. The flow rate was 1.5 mL / hr, and +17.8 kV was applied to the needle. A spinning time of 90 minutes was used at 21 °C and a relative humidity below the lower detection limit of 25%. The resulting fibers were scraped from the drum and placed in a desiccator.

[0064] Example 2: Preparation of 30% atelocollagen-70% PDLLA and electrospinning of fibers In a 5 mL vial, 72.3 mg of atelocollagen and 168 mg of PDLLA were dissolved in 2 mL of HFP and then dissolved generally according to Example 1. This solution was then electrospun using a 25 mm / 1 inch drum disk equipped with an electric motor, a 2 mL glass syringe with an 8.9 mm diameter and a glass luer, and a 2 inch, 18 gauge, all-stainless steel needle at a 100 mm tip. The flow rate was 1.5 mL / hr, and +17.0-17.1 kV was applied to the needle. A spinning time of 60 minutes was used at 22.2 °C and less than 25% relative humidity.

[0065] Example 3: Preparation of 15% Telocollagen-85% PDLLA and Electrospinning of Fibers In a 5 mL vial, 36.0 mg of telocollagen and 204 mg of PDLLA were dissolved in 2 mL of HFP and then dissolved generally according to Example 1. This solution was then electrospun using a 25 mm / 1 inch drum disk equipped with an electric motor, a 2 mL glass syringe with an 8.9 mm diameter and a glass luer, and a 2 inch, 18 gauge all stainless steel needle at a 100 mm tip. The flow rate was 1.5 mL / hr, and +17.8 was applied to the needle. A spinning time of 60 minutes was used at 22.1°C and less than 25% relative humidity.

[0066] Example 4: Preparation of 35% Telocollagen-65% PDLLA and Electrospinning of Fibers In a 5 mL vial, 84.0 mg of telocollagen and 156 mg of PDLLA were dissolved in 2 mL of HFP and then dissolved generally according to Example 1. This solution was then electrospun using a 25 mm / 1 inch drum disk equipped with an electric motor, a 2 mL glass syringe with an 8.9 mm diameter and a glass luer, and a 2 inch, 18 gauge, all-nickel stainless steel needle at a 100 mm tip. The flow rate was 1.5 mL / hr, and +18.0 was applied to the needle. A spinning time of 55 minutes was used at 22.1°C and less than 25% relative humidity.

[0067] Example 5: Preparation of 25% Telocollagen-75% PDLLA and Electrospinning of Fibers A 12% telocollagen solution in HFP was combined with a 12% PDLLA solution in HFP. Each was dissolved in a separate vial. Collagen was prepared by dissolving 60.6 mg of telocollagen powder (Collagen Solutions) in 0.5 mL of HFP in a 5 mL vial. PDLLA was prepared by dissolving 239.1 mg of PDLLA in 2 mL of HFP in a 5 mL vial. Both solutions were placed on a rocking shaker platform at maximum speed and tilt for 2.5 hours. 250 μL of the 12% (w / v) collagen solution was mixed with 750 μL of the 12% (w / v) PDLLA solution, and the two were mixed on a platform shaker for 20 minutes. The solutions were then electrospun using a 25 mm / 1 inch drum disk with an electric motor, a 1 mL glass syringe with an 8.9 mm diameter and a 2 inch, 18-gauge needle, and a 100 mm needle tip. The flow rate was 1.0 mL / hr, and +20.0-20.1 KV was applied to the needle. A spinning time of 55 minutes was used at 23.2°C and 48% relative humidity.

[0068] Example 6: Preparation of collagen-polymer scaffolds Five sheets, each approximately 0.2 mm thick, were laminated together by welding with a soldering iron at approximately 100°C or with a short pulse of heat from an impulse sealer. Additional orthogonally oriented fibers filled the weld and provided reinforcement for suture retention. The average load pulled on one suture through the weld was approximately 28.3 N, with a peak stress of 4.1 MPa.

[0069] Example 7: Seeding of electrospun fiber scaffolds with human tenocytes Human tenocytes (5 × 10 4 Cells (0.1% / well) were suspended in serum-free medium and then seeded onto the scaffolds prepared according to Example 6 above. After 15, 30, and 60 minutes in culture, the plates were gently shaken to remove unattached cells. The number of suspended unattached cells in each well was counted, and the percentage of cells attached to each scaffold disc was determined based on the total number of cells seeded. More than 50% of the cells remained attached.

[0070] While certain exemplary embodiments have been described in detail above, it should be understood that these embodiments are merely illustrative of the broad invention, not limiting thereof. It should be appreciated that the teachings of the present invention have application to a wide variety of compositions and devices made from the formulations and compositions described. Those skilled in the art will recognize that various modifications can be made to the above-described embodiments of the invention without departing from the broad inventive scope thereof. It is therefore understood that the present invention is not limited to the disclosed embodiments or arrangements, but rather is intended to cover all modifications, adaptations, or variations within the scope and spirit of the invention as defined by the appended claims.

[0071] References All documents identified herein, including the following articles, are incorporated by reference in their entirety: JPEG2025120178000002.jpg173164 JPEG2025120178000003.jpg176165 JPEG2025120178000004.jpg83166

Claims

1. A composition comprising about 10-50% by weight collagen, preferably about 15-40% collagen, more preferably about 20-35% collagen, more preferably about 25-35% collagen, more preferably about 27.5-32.5% collagen, and most preferably about 30% collagen, and a biodegradable copolymer in an amount of about 50-90% by weight.

2. 2. The composition of claim 1, wherein the collagen is selected from the group consisting of human, bovine, porcine and marine telocollagen, atelocollagen, and mixtures thereof, in native, processed, placental and recombinant forms.

3. The composition of claim 1 , wherein the collagen is type I collagen.

4. The composition of claim 1 , wherein the biodegradable copolymer is a member selected from the group consisting of PLLA, PDLA, and PDLLA.

5. 5. The composition of claim 4, wherein the PDLLA copolymer is a high molecular weight PDLLA.

6. The composition of claim 1 in the form of a fiber, a film, an aerosol, droplets, an adhesive, or a porous structure.

7. The composition of claim 6 , wherein the composition has not been treated with a chemical crosslinker.

8. The composition of claim 6 , wherein the composition is treated with a chemical crosslinking agent.

9. 7. The composition of claim 6, wherein the plurality of fibers are fabricated by electrospinning, melt electro-writing, extrusion, spraying, or three-dimensional fabrication.

10. 7. The composition of claim 6, in the form of a plurality of fibers, the fibers having an average diameter in the range of about 150 to 4,500 nm, preferably about 400 to 2,000 nm, more preferably about 600 to 1,500 nm, and most preferably about 750 to 1,200 nm, and wherein the fibers are produced by an electrospinning process.

11. 7. The composition of claim 6, in the form of a plurality of fibers, the fibers having an average diameter in the range of about 1 to 200 μm, preferably about 10 to 100 μm, more preferably about 15 to 50 μm, and most preferably about 20 μm, and wherein the fibers are made by a technique selected from the group consisting of electrowriting and melt electrospinning.

12. The composition of claim 10 wherein the fibers are processed into a sheet form.

13. 10. An implantable medical device for supporting the repair of soft tissue damage in a mammal, comprising the composition of claim 1.

14. 14. A method of promoting repair of soft tissue damage, comprising implanting the medical device of claim 13.

15. 14. A method of promoting repair of an Achilles tendon rupture, comprising the step of securing the device of claim 13 so that the device spans the repaired area of the tendon and provides mechanical support.

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