Tissue repair membrane adapted for adhesion and lubrication, and preparation method therefor

Abstract

To provide a tissue repair membrane and a method for preparing the same.SOLUTION: A tissue repair membrane comprising a tissue repair membrane substrate, a first coating applied to at least a portion of a surface of the tissue repair membrane substrate, the first coating comprising a first hydrogel composition formed from a solution of hyaluronic acid and an alginate, and a second coating applied over the first coating, the second coating comprising a second hydrogel composition formed from a solution of hyaluronic acid without an alginate; Wherein at least one of the first coating and the second coating provides one or more of self-adhesion and lubrication to the tissue repair membrane in a hydrated state.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates generally to the treatment of damaged tissue. More specifically, the present disclosure relates to films that can be used to strengthen, protect or treat damaged tissue and to provide adhesion and / or lubrication to the film. [Background technology]

[0002] Injuries to the nervous system, whether central nervous system (CNS) or peripheral nervous system (PNS), can be caused by physical injury, neurological disorders, certain medical procedures or therapies, ischemia, tumors, metabolic or nutritional disorders, cognitive or mood disorders, exposure to chemicals or drugs, infections, and various diseases. Because axonal regeneration is limited to a few millimeters per day and significant levels of growth inhibitors can be present, recovery from nervous system injury is often long. There remains a need for the development of effective treatments and methods that can assist nerve regeneration after injury.

[0003] Known treatments for nerve injuries involve encircling or wrapping the injured nerve with a membrane that is typically secured with sutures or microclips during surgery. This procedure requires additional medical equipment (such as sutures and clips), additional surgical time, and may require significant microsurgical skill, especially when sutures are used. Additionally, the procedures and additional materials used for fixation (e.g., suture knots and / or microclips) may increase potential trauma to the nerve and surrounding tissue, and the risk of adhesions due to reaction with the material of the fixation device.

[0004] There are several existing membrane products available for treating nerve injuries, including SepraFilm, a sterile, bioresorbable, translucent adhesive barrier membrane composed of two anionic polysaccharides, namely sodium hyaluronate and carboxymethylcellulose. Additionally, amniotic sac-based products are also available. Summary of the Invention [Problem to be solved by the invention]

[0005] A significant drawback of these products is that they are mechanically weak and therefore cannot be effectively handled within the surgical field. This mechanical weakness also prevents them from being mechanically fixed, and the devices do not adhere strongly to the nerve, risking migration after placement and consequent failure of the protective procedure. [Means for solving the problem]

[0006] The present disclosure relates to devices that can surround injured tissue, may be self-adhesive, or may be capable of providing lubrication to reduce undesirable interactions, such as friction, with surrounding or adjacent materials, such as tissue. Additionally, the present disclosure may, in some use cases, reduce the number of products / components required to immobilize injured tissue.

[0007] Consistent with several aspects of the present disclosure, use of the devices of the present disclosure can simplify surgical procedures and reduce overall surgical time. In some embodiments, the present disclosure may allow for a reduction in the risk of fibrosis and complications from fastening / securing devices, such as sutures and clips, currently used in tissue repair.

[0008] In some implementations consistent with the present disclosure, self-adhesion of the tissue repair membrane, which minimizes adhesion to surrounding or adjacent materials, such as tissue, can greatly facilitate application of the tissue repair membrane and, consequently, overall tissue repair. This can lead to increased control, adaptability, and flexibility for the surgeon, as they may be able to adjust the membrane's position during surgery to better surround / support the damaged tissue. The surgeon may be able to adjust the membrane's position multiple times rather than just once (due to the current requirement to secure the membrane to the damaged tissue with sutures or other fastening devices).

[0009] In some embodiments, the present disclosure may provide self-adhesive capabilities to tissue repair membranes by adding a surface layer of a biocompatible hydrogel material. In some exemplary embodiments, the hydrogel material may exhibit low cell adhesion properties and may add minimal, if any, bulk effect to the tissue repair membrane.

[0010] In some embodiments, the tissue repair membrane may be modifiable (chemically or physically) to accept biocompatible hydrogel materials. In some embodiments, the tissue repair membrane may be capable of binding polyanionic and / or polycationic materials.

[0011] In one exemplary embodiment consistent with the present disclosure, the tissue repair membrane may be treated with a hydrophilic material to provide the tissue repair membrane with an adhesive and lubricious surface. In one exemplary embodiment, the tissue repair membrane may be a neuroprotective membrane. In some embodiments consistent with the present disclosure, the membrane's sliding against surrounding or adjacent materials, e.g., tissue, may be improved, and soft tissue adhesion to the membrane may be reduced. Lubrication may also increase the surgeon's options for early or late mobilization.

[0012] An example of a biocompatible hydrogel material may include hyaluronic acid. Hyaluronic acid is an anionic, non-sulfated glycosaminoglycan that is widely distributed throughout connective, epithelial, and neural tissues. Human synovial hyaluronic acid ranges from approximately 3 to 7 million daltons per molecule. In some embodiments, the use of hyaluronic acid may improve membrane remodeling properties.

[0013] In one exemplary embodiment, the present disclosure may utilize bonding of a biocompatible hydrogel material to a tissue repair membrane. In one exemplary embodiment, the present disclosure may provide for covalent bonding of the biocompatible hydrogel material and the tissue repair membrane. This can be achieved by using a tissue repair membrane with chemical bonds on its outer surface that allow it to covalently bond with the biocompatible hydrogel material. Some embodiments consistent with the present disclosure may provide a method for modifying a tissue membrane to add suitable chemical bonding groups. In one exemplary embodiment, the membrane may contain primary amines or other aldehyde-reactive groups that can covalently bond with suitable bonding groups on the biocompatible hydrogel material. The biocompatible hydrogel material may also be incorporated into the underlying tissue repair membrane through interpenetration of polymer chains, such as physical bonding. Bonding the tissue repair membrane and the biocompatible hydrogel material may provide a stronger retention of the coating on the membrane than is possible with a non-bonded coating.

[0014] Additionally, biocompatible hydrogel materials such as hyaluronic acid or equivalent materials, due to their hydrophilicity, can provide lubrication to the membrane relative to surrounding or adjacent materials, such as tissue. Similar equivalent materials can include alginate, chondroitin sulfate, dermatan sulfate, or similar glycosaminoglycans and related polymers.

[0015] Some embodiments consistent with the present disclosure may provide for the incorporation of polycationic and polyanionic surface regions into the surface of the tissue repair membrane. These regions may form polyelectrolyte complexes when in contact with one another. This interaction between the positively and negatively charged groups may provide for adhesion of the membrane to itself (e.g., in some embodiments, with only limited adhesion to surrounding tissue).

[0016] The present disclosure may have varying degrees of polyanionic and polycationic coating on the tissue repair membrane. Coating levels ranging from 1:99 polyanionic / polycationic to 99:1 polyanionic / polycationic are within the scope of the present disclosure. In one exemplary embodiment, the polyanionic coating may be used over the majority of the membrane area. This reduces the friction and / or adhesion of the membrane to surrounding or adjacent materials, such as tissue, while still allowing the membrane to adhere to itself, thereby allowing adhesion with the polycationic area and may also provide a high degree of lubrication for the tissue to which the tissue repair membrane may be applied.

[0017] The present disclosure may provide a method for applying a hydrogel material to a tissue repair membrane. The present disclosure may provide benefits for all types of tissue repair. Types of tissue that may be suitable for the present invention include nerve tissue, muscle tissue, tendons, ligaments, skin tissue, cardiac tissue, vascular tissue, dura tissue, fascial tissue, serous tissue surrounding an organ, or periosteum.

[0018] The present invention is not limited to human use and may also be compatible with veterinary use. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows an illustrative example of an "aldehyde HA" structure according to one exemplary embodiment. [Figure 2] FIG. 1 shows an illustrative example of aldehydes generated within the backbone of a hydrogel polymer according to one illustrative embodiment. [Figure 3] FIG. 1 shows an illustrative example of an imine residue (non-covalent aldehyde motif) reduced with a mild reducing agent, according to one exemplary embodiment. [Figure 4] FIG. 1 shows an illustrative example of polyelectrolyte complexation that can occur when a positively charged polymer ionically interacts with a negatively charged polymer to produce a solid / gel according to one illustrative embodiment. [Figure 5]FIG. 1 shows an illustrative example of hydrogel polymer / membrane and polycationic polymer complex formation according to one illustrative embodiment. [Figure 6] FIG. 10 shows a chart illustrating experimental evaluation of the static friction coefficient of several test samples according to an example embodiment. [Figure 7] FIG. 10 shows a chart illustrating experimental evaluation of the static friction coefficient of several test samples according to an example embodiment. [Figure 8] FIG. 10 shows a chart illustrating experimental evaluation of the static friction coefficient of several test samples according to an example embodiment. [Figure 9] FIG. 10 shows a chart illustrating experimental evaluation of the static friction coefficient of several test samples according to an example embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] A description of several embodiments consistent with the present disclosure will now be given. Because the present disclosure can take many other forms and shapes, the following disclosure is intended to be illustrative and not limiting, the scope of which should be determined by reference to the appended claims.

[0021] Examples of suitable hydrogel materials include, but are not limited to, extracellular matrix components such as polyanionic polymers (net negative charge relative to the polymer), such as chondroitin sulfate and hyaluronic acid. These materials are typically highly hydrophilic polysaccharides with a relatively high degree of biocompatibility, as both materials are components of the natural extracellular matrix. Suitable polymers may have poor cell adhesion. Cell membranes typically have a negative charge potential (typical values ​​for most cells range from -40 to -80 mV). Therefore, negatively charged polymers such as chondroitin sulfate and hyaluronic acid or their equivalents generally do not adhere (or only weakly adhere) to cellular tissue. Additionally, this may be one of the ways in which the lubrication benefits of hydrogel polymers may be provided.

[0022] Hyaluronic acid can have complex molecular weight-driven interactions. In certain embodiments, high molecular weight hyaluronic acid can provide anti-cell adhesion and block and / or inhibit cell migration. This can provide additional barriers to damaged tissue. In other embodiments, low molecular weight hyaluronic acid can act as an angiogenic factor.

[0023] Additional anionic polymeric materials can be selected from, but are not limited to, chondroitin, alginate, oxidized cellulose, particularly non-regenerated oxidized cellulose (the grades of oxidized cellulose containing both carboxylic acid and aldehyde groups), heparin, and sulfated versions of these aforementioned polymers, and combinations thereof.

[0024] Additional cationic polymeric materials may be selected from, but are not limited to, polylysine, polyornithine, polyhexamethylene biguanide (PHMB), polyethyleneimine (PEI), diethylaminoethyldextran (DEAE-dextran), poly(amidoamine) (PAMAM), and quaternary ammonium forms of these aforementioned polymers, and combinations thereof.

[0025] Tissue repair membranes suitable for use in connection with the present disclosure may be prepared from human tissue, including cadaveric tissue, animal tissue, such as, but not limited to, porcine tissue and ruminant tissue, placental tissue, stem cell tissue, or combinations thereof. According to other embodiments, a variety of additional and / or alternative tissue repair membranes may be utilized, including both natural and synthetic materials, such as, but not limited to, woven or nonwoven collagen, polycaprolactone, or polylactic acid fibrous membranes.

[0026] Membranes consistent with the present disclosure may be capable of receiving hydrogel materials through various treatments. One such treatment may include providing a covalent bond between an aldehyde reactive group and a primary amine. Polycationic materials may also be attached to the membrane via covalent bonds or any other known method.

[0027] Multiple embodiments consistent with the present disclosure use an oxidation procedure to cleave a portion of the heterocyclic ring of the polysaccharide backbone (such as hyaluronic acid) of the hydrogel material, resulting in two aldehyde motifs, while the polymer itself can be maintained by ether bonds of the original backbone bonds.

[0028] Suitable exemplary oxidizing agents may include sodium periodate and lead tetraacetate. Alternatively, primary alcohol groups may be partially oxidized to aldehydes by TEMPO catalysis or equivalent chemistry.

[0029] FIG. 1 shows oxidized hyaluronic acid monomers (e.g., an example of an "aldehyde HA" structure) in preparation for attachment to primary amines on a membrane surface consistent with one illustrative embodiment.

[0030] Some embodiments consistent with the present disclosure may use hydrogel polymers with varying degrees of substitution. One exemplary substitution level may be approximately 5%. Substitution levels from about 1% to about 100% are within the scope of the present disclosure.

[0031] As shown in Figure 2, aldehydes generated within the backbone of hydrogel polymers, such as those in the hyaluronic acid shown above, can readily react with free amine groups present in protein-based membranes, tethering the hyaluronic acid polymer to the membrane via imine bonds. Other linkages are within the scope of this disclosure. Examples of other linkages include peptide, ether, ester, and disulfide bonds with different chemistries.

[0032] The imine residue (non-covalently bound aldehyde motif) can then be reduced with mild reducing agents such as cyanoborohydride, triacetoxybororbydride, or borohydride (especially the sodium salts of these ions), as shown in Figure 3. Alternatively, in some cases, even milder reducing agents such as foramide, solid zinc, ascorbic acid, sodium thiosulfate, or sodium dithionite may be useful. Reducing the imine can help remove the associated color (e.g., typically reddish-brown) and improve stability.

[0033] Reaction conditions can be carefully monitored and applied to limit modification to the hydrogel polymer and membrane, particularly to the regions of each material treated with the polymer. Some embodiments consistent with the present disclosure may provide bonding between the hydrogel material and the tissue repair membrane. Particular embodiments may have a high degree of bonding between the two components. In one exemplary embodiment, the level of bonding may be from approximately every monomer in the polymer (100% modification) to every 1000 monomers (0.1% modification). Other embodiments may have approximately 5% to 20% bonding.

[0034] Other bonding techniques between the hydrogel material and the membrane are within the scope of this disclosure. The hydrogel material can be grafted to the membrane surface via other known bonding techniques. Possible techniques include, but are not limited to, EDC / NHS esters, sulfhydryl / disulfide bonds, thio-ene reactions, maleimides, epoxides, imide esters, any "click" chemistry, or combinations thereof.

[0035] EDC (1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide) is a zero-length crosslinker used to attach carboxyl or phosphate groups to primary amines. EDC can be used to form amide bonds. To increase the stability of EDC, N-hydroxysuccinimide (NHS) or N-hydroxysulfoxuccinimide (sulfo-NHS) can be used. The addition of sulfo-NHS can stabilize the amine-reactive intermediate by converting it to an amine-reactive sulfo-NHS ester, increasing the efficiency of EDC-mediated coupling reactions.

[0036] In one exemplary embodiment, similar to malemide chemistry, oxidation of hyaluronic acid (discussed above) can be continued until the aldehyde is converted to a carboxylic acid. The close spatial positioning of the two carboxylic acids can mimic the activity of malemide chemistry, whereby two carboxylic acid moieties are attached to a single central carbon, creating an unusually strong ionic bond with the amine.

[0037] Membranes bearing aldehyde-reactive groups, such as primary amines, tertiary amines, quaternary amines, or substituents with similar chemistry, may be incorporated into the present disclosure and may similarly react with hydrogel materials to form bonds with the aldehyde groups or equivalent binding substituents to form membrane / hydrogel polymeric materials suitable for use as tissue repair membranes as described herein.

[0038] Additionally, physical bonding may be achieved by immersing the membrane in a sol-gel before drying, resulting in a micro- or macro-scale interpenetrating polymer network (basement membrane and hydrogel).

[0039] There are a variety of methods that can be used to prepare hydrogel polymer-membrane composites consistent with the present disclosure. In one exemplary embodiment, the membrane can be soaked in a solution of hydrogel polymer before drying and sterilization. When hydrated, the hydrogel polymer can be present on the surface and in the bulk of the membrane, providing similar functions (adhesion and / or lubrication) as described herein, but without being covalently bonded to the membrane. This can allow the hydrogel polymer to be retained on the surface of the membrane and facilitate its movement and diffusion around the membrane. In such an exemplary embodiment, reactive species between the hydrogel polymer and the membrane may not be required, as the binding interaction can be physical entanglement of the polymer chains. When alginate salts or another ionically crosslinked polymer are present, this physical entanglement effect can be further enhanced by introducing calcium ions to ionically crosslink the polymer components.

[0040] In another exemplary embodiment, prior to complexation with the membrane, the hydrogel polymer may be partially oxidized to generate reactive groups within certain monomers of the polymer chain. In one embodiment, hyaluronic acid may be oxidized with sodium periodate to generate reactive aldehyde groups within the polymer chain. The aldehyde groups may then react with primary amine groups within the tissue-based membrane to form imine bonds and membrane / hydrogel polymer complexes. The remaining reactive groups (aldehydes) may then be reduced to alcohol groups. Examples of suitable reducing agents include, but are not limited to, sodium cyanoborohydride. Other reducing agents that may be used in connection with the present disclosure may optionally include sodium triacetoxyborate, sodium borohydride (especially the sodium salts of these ions), formamide, solid zinc, ascorbic acid, sodium thiosulfate, and sodium dithionite.

[0041] In further embodiments consistent with the present disclosure, a polycationic polymer may be added onto at least a portion of the polyanionic hydrogel polymer / membrane complex. Alternatively, the order of application may be reversed (e.g., polycationic polymer, then polyanionic).

[0042] Polyelectrolyte complexation can occur when a positively charged polymer ionically interacts with a negatively charged polymer to produce a solid / gel. This can typically occur with chitosan and hyaluronic acid at physiological conditions, as shown in Figure 4.

[0043] Hyaluronate salts modified to contain aldehyde groups (e.g., formyl sodium hyaluronate, shown in Figure 5) can be reacted sequentially with the membrane and then with chitosan. This can generate imine bonds between the hyaluronic acid and the membrane surface (and possibly within the bulk of the membrane), as well as between the chitosan and the hyaluronic acid surface-modified membrane. Polyelectrolyte complexation can also occur. Figure 5 generally illustrates embodiments consistent with the present disclosure, including hydrogel polymer-membrane and polycationic polymer complexation.

[0044] Not all carboxylic acid groups and primary amine groups ionize appropriately under physiological conditions. Reagents may be required to adjust the pH or other characteristics of the forming solution to provide the necessary reaction conditions. Residual aldehyde groups in hydrogels, such as oxidized hyaluronic acid, can be neutralized with various chemicals, if desired. In one embodiment, aldehydes can be reduced to alcohol groups by reacting with a reducing agent, such as sodium triacetoxyborohydride. Other suitable reducing agents may optionally include, but are not limited to, sodium triacetoxyborate, sodium borohydride (especially the sodium salts of these ions), formamide, solid zinc, ascorbic acid, sodium thiosulfate, and sodium dithionite.

[0045] In some further illustrative example embodiments, neutralization can be performed with small amines such as glycine, resulting in additional imine bonds, or with sulfur-based reducing agents such as sodium bisulfite or sodium dithionite, which generate bisulfite adducts. An added advantage of bisulfite adducts is that they can also participate in polyelectrolyte complexation.

[0046] The molecular weight of the polycationic and polyanionic polymers can affect the binding strength of the membrane-polymer complex. Specifically, a larger molecular weight can correlate with increased interaction and binding strength. Examples of molecular weights for polyanionic polymers range from 10,000 Da to over 4,000,000 Da. In some embodiments, the molecular weight of the polyanionic polymer ranges from 1,000,000 to 2,000,000 Da. Examples of molecular weights for polycationic polymers range from 10,000 Da to over 4,000,000 Da. In some embodiments, the molecular weight of the polycationic polymer ranges from 80,000 to 120,000 Da. In addition, branched or crosslinked polymers with increased molecular weights can also be used.

[0047] With regard to hyaluronic acid in particular, molecular weight may be an important characteristic of the cell-cell interaction / biocompatibility of polymer-membrane complexes. Adjusting the degree of substitution, such as the number of aldehydes per molecule, can affect the average size of the complexed hyaluronic acid fragments. In some embodiments, molecular weights in the range of about 1000 kDa or greater may be associated with preventing inflammation and cell migration. Smaller molecular weight fragments, particularly polymers with molecular weights less than about 10 kDa, may be associated with promoting angiogenesis and wound healing. These low molecular weight polymers may also be associated with increased inflammation. In some embodiments, the highest molecular weight polymers may offer bioregenerative benefits in view of the many enzymes common in the extracellular environment that can continue to reduce polymer fragment size.

[0048] Additionally, in some embodiments, higher molecular weight aldehyde-modified molecules may have larger hydrodynamic radii, which may allow the polymers to have a higher degree of interaction and binding with the membrane surface. In contrast, lower molecular weight polymers may, in some circumstances, penetrate membranes to a higher degree.

[0049] Consistent with the foregoing, the present disclosure generally provides tissue repair membranes that are uniquely self-adhesive (i.e., the tissue repair membrane can adhere to itself) and exhibit little adhesion to surrounding or adjacent materials, e.g., tissues, and / or may even provide a lubricating effect and / or a relatively low coefficient of friction between the tissue repair membrane and surrounding or adjacent materials, e.g., tissues. In some implementations, the tissue repair membrane may include polyanionic and polycationic surface regions thereon. In some implementations, these polyanionic and polycationic surface regions may form polyelectrolyte complexes when they contact each other. The interaction between the positively and negatively charged groups may provide preferential adhesion of the tissue repair membrane to itself, with limited, if any, adhesion to surrounding or adjacent materials, e.g., tissues. In some implementations, the polyanionic surface region may act as a lubricating layer for the tissue repair membrane with respect to surrounding or adjacent materials, e.g., tissues (i.e., tissues contacted by the tissue repair membrane). When acting as a lubricating layer, the polyanionic surface region, in some embodiments, can reduce friction and / or adhesion of the tissue repair membrane to its surroundings, e.g., tissue (i.e., tissue contacted by the tissue repair membrane), while still allowing the tissue repair membrane to adhere to itself. As generally described above, in some exemplary embodiments, polyelectrolyte complexation can occur when a positively charged polymer ionically interacts with a negatively charged polymer, resulting in a solid and / or gel material in some implementations. In some exemplary embodiments, polyelectrolyte complexation can occur between polycationic polymers, including chitosan, and polyanionic polymers, including hyaluronic acid, at physiological conditions. As described above, other suitable polycationic and polyanionic polymers can also be used to achieve desired performance.

[0050] Consistent with some embodiments, the hydrogel polymers herein, including one or more of polycationic and polyanionic polymers, may be used in conjunction with applications other than tissue repair matrices. For example, in some embodiments, the hydrogel polymers described herein may be used to treat and / or coat at least a portion of fabrics, gauzes, or other types of materials that may be used in conjunction with nerve repair and / or other therapeutic fields or endeavors. In such applications, the hydrogel may be applied to any suitable substrate. Exemplary substrates may include natural and / or synthetic materials, including polymeric materials, films, fabrics, paper, and the like. Substrates coated with the hydrogel material may exhibit little adhesion to surrounding or adjacent materials and / or may even provide a lubricating effect and / or a relatively low coefficient of friction between the coated material and surrounding or adjacent materials, while providing self-adhesive properties.

[0051] The lubricity of exemplary formulations was experimentally evaluated by testing the static friction coefficient of test membranes treated with sample formulations against a cellulose sheet. For experimental purposes, small intestine submucosa (SIS) sheets consistent with Axoguard Nerve Protector, available from Axogen Corporation, were used as test membranes, and printing paper was used as the cellulose sheet substrate to simulate tissue. SIS membranes were used both neat (no test formulation applied) and with various formulations containing hyaluronic acid, alginate, and / or chondroitin sulfate. SIS membranes (neat and / or treated with test formulations) were hydrated for approximately 15 seconds in saline (approximately 0.9 wt% NaCl) containing a physiological concentration of calcium chloride (approximately 1.3 mM) and wrapped around a metal block. The SIS membranes (treated and untreated) were placed on top of a cellulose sheet submerged in saline and calcium chloride solutions, and a hanging mass holder was attached to the block using a string-pulley system. A small amount of mass (in the form of water) was added to the mass holder using a pipette until the block (containing the SIS membrane placed against the cellulose sheet) began to slide across the cellulose sheet. The weight of the mass holder plus the added water was recorded, and the coefficient of static friction was calculated as follows: coefficient of static friction = mass (hanging) / mass (heavy block). Evaluation of the coefficient of static friction was performed on day 0, when SIS membranes (untreated and treated) were hydrated in saline containing calcium chloride for approximately 15 seconds and tested against the cellulose surface. Evaluation of the coefficient of static friction was also performed on day 1, when SIS membranes (untreated and treated) were left to soak in saline containing calcium chloride for 24 hours at 4°C.

[0052] Test samples of different test formulations were prepared by submerging approximately 3.5 x 5 cm SIS membranes in 50 ml conical tubes containing approximately 40 ml of the desired formulation for approximately 27 hours at 4 °C. After 27 hours, the membranes were removed from the formulation, placed on a Tyvek sheet, and covered with another Tyvek sheet. The membranes were then placed in a vacuum oven and covered with a compatible set at 15 mbar pressure and 35 °C overnight to allow for the formation of a thin, dried layer of the lubricant formulation. Two layers of silicone pads (each approximately 5 mm thick) were added on top of the Tyvek sheet to keep the membrane flat during drying. Excess dried lubricant was removed from the edges of the membrane. The membranes were then stored in airtight containers at 4 °C until use.

[0053] As shown in Figure 6, hyaluronic acid showed a greater reduction in the static friction coefficient than alginate compared to untreated SIS. However, alginate showed better retention of lubrication properties, as indicated by a comparison of the Day 0 and Day 1 results. Both hyaluronic acid and alginate exhibited greater lubrication properties than PVA as the standard. In addition, as shown in Figure 7 and Table 1 below, higher molecular weight hyaluronic acid (HMW HA tested = 1-1.5 million daltons) retained its lubrication properties better than lower molecular weight hyaluronic acid (LMW HA tested = 0.8-1 million daltons), as indicated by a comparison of the Day 0 and Day 1 results. In addition, higher viscosity alginate (MV ALG tested = 1320 MPa in a 1% aqueous solution) showed longer retention of lubrication properties compared to lower viscosity alginate (LV ALG tested = 2,000 CP or greater in a 2% aqueous solution). The reference formulation numbers for the results shown in Figure 7 are listed in Table 1.

[0054] [Table 1]

[0055] Consistent with some embodiments of the present disclosure, membranes with relatively high levels of lubricity can be provided by physical interpenetration of polymers into the membrane substrate. For example, a membrane substrate, such as SIS or other suitable substrate, can be soaked in a blend of hyaluronic acid and alginate. A higher solids content of the solution can result in a more viscous solution, making it difficult to handle and apply. The membrane can be exposed to the solution for a sufficient time for the polymer to at least partially diffuse into the membrane. This time will be affected by the molecular weight of the polymer, as larger molecular weights diffuse more slowly, and by the pore size of the membrane substrate, as larger pores require less diffusion time. However, in most cases, there will be little risk in extending the incubation of the solution beyond the minimum time. The solvent and pH of the polymer solution should be selected so that the polymer is soluble. When using ionic gelling polymers, care should be taken to avoid calcium or other multivalent cations during soaking, as this can cause the solution to gel prematurely. For 2% medium viscosity (MV) alginate and 2% high molecular weight (HMW) hyaluronate in water, hydration with the polymer solution appears to occur rapidly (e.g., within 20 minutes in some embodiments), but can be extended to approximately 27 hours at 4°C to ensure consistency and saturation. Once the membrane substrate is saturated with the hyaluronic acid and alginate blend to the desired degree, it can be dried. In some embodiments, the alginate may provide some degree of ionic cross-linking in the presence of calcium ions and / or other divalent cations. Examples of divalent cation sources include, but are not limited to, calcium chloride, calcium acetate, magnesium chloride, and magnesium acetate. In some embodiments, ionic cross-linking may improve retention of hyaluronic acid and alginate over time and enhance the lubricity of the treated membrane over time, compared to embodiments with less or no ionic cross-linking.

[0056] Referring to Figure 8, a comparison of a formulation containing a combination of hyaluronic acid and alginate (Alg / HA) is shown on days 0 and 1. Additionally, the comparison shown includes a bilayer coating formed from an initial coating of hyaluronic acid and alginate applied to a membrane substrate (e.g., SIS) and an additional layer of hyaluronic acid (Alg / HA+HA) applied over the initial coating. The hyaluronic acid and alginate coating can be formed in a manner generally similar to that described above (e.g., immersing an SIS membrane or other membrane in a solution of the desired formulation, followed by drying the coated membrane). In one exemplary embodiment, the bilayer coating can be formed by immersing a dried membrane containing a hyaluronic acid and alginate coating in a solution of hyaluronic acid. Desirably, the viscosity of the solution for the second coating can be low enough to allow uniform coating of the membrane and can limit the total solids content of the solution. Because the second hydrogel layer only needs to interact with the first hydrogel layer and does not need to diffuse into the membrane substrate, shorter incubation times can be used. In one example, a 2% solution of high molecular weight sodium hyaluronate in water can be applied for approximately 2 minutes, although other durations may be used to provide acceptable coatings. The static friction coefficient was evaluated in a manner generally corresponding to previous testing protocols. As shown, films coated with hyaluronic acid and alginate provide improved lubricity (e.g., compared to the single-component coatings described with reference to Figures 6 and 7 and Table 1). In addition, a bilayer configuration further improved lubricity. In some embodiments, the improved lubricity of the hyaluronic acid and alginate coating over time (e.g., compared to the single-component coating) may be provided by the sustained release of hyaluronic acid linked between the alginate hydrogels. Additionally, in some embodiments, the improved lubricity of the bilayer coating may result from the initial lubricity provided by the outer layer of hyaluronic acid.

[0057] Also, referring to Figure 9, the long-term lubricity is shown for a coating comprising the hyaluronic acid and alginate coating discussed with respect to Figure 8. In the illustrated embodiment, samples were tested 0, 1, 3, and 5 days after initial hydration, with one set of samples tested on days 0 and 1 and a second set of samples tested on days 3 and 5. When not being tested, the samples were stored at 4-8°C in a solution of 0.9% NaCl containing 13 mM CaCl. As shown, the hyaluronic acid and alginate coated membranes exhibited significantly improved lubricity over the long-term test compared to the untreated SIS control sample.

[0058] Continuing with the foregoing, in some exemplary embodiments, the tissue repair membrane may be formed from more than one layer of membrane substrate, such as SIS. In certain exemplary embodiments, the tissue repair membrane may include four layers of SIS, although it will be understood that more or fewer layers may be utilized (e.g., 1-8 layers, 2-6 layers, 2-4 layers, etc., and various additional layers within numerical ranges). In one embodiment, a layer of SIS may be immersed in a solution of 2% alginate and 2% hyaluronic acid (which may be provided in various forms, such as sodium hyaluronate), where the solution concentrations indicate relative weight percents relative to the total weight of the solution. It will be understood that other solution concentrations may be utilized, and the relative concentrations of alginate and hyaluronic acid need not be the same. The concentration range of alginate and hyaluronic acid may be approximately 0.5-5%, although combinations may experience solubility limitations at the upper end of the numerical range. The layered SIS immersed in the solution may then be dried to provide a coating on both sides of the layered SIS membrane. The "sol" gel that permeates the membrane may provide interpenetration of the alginate / hyaluronic acid polymer chains with the SIS collagen. Exposure to calcium ions, either during the manufacturing process of the dry tissue repair membrane and / or during subsequent hydration of the dry tissue repair membrane (e.g., at the time of use), may ionically crosslink the alginate, which may help maintain the gel layer.

[0059] In some embodiments, the SIS membrane base can provide desirable handling characteristics. For example, the tissue repair membrane can be easily moved and handled within the surgical field. Additionally, the SIS membrane can be adapted to secure the tissue repair membrane with sutures or clips. Additionally, as with other SIS-based products, remodeling of the SIS can occur, resulting in a new connective tissue layer in the correct application.

[0060] Consistent with some embodiments of the present disclosure, high molecular weight hyaluronic acid (e.g., 1 million daltons or greater) can provide a highly biocompatible lubrication layer (e.g., because the hyaluronic acid molecule is closely / substantially identical to that naturally occurring in human tissue). Alginate can also provide some lubrication itself. Furthermore, alginate can function as an ionically crosslinked polymer, which can facilitate long-term retention of the hyaluronic acid at the implantation site. The hydrogel film formed can function as a lubrication layer that reduces the forces seen by gliding tissue. The gel can also function as a temporary barrier layer, which typically dissolves within a few days to a few weeks (e.g., in some embodiments, within 7-10 days). This temporary barrier can provide at least two notable benefits. First, it can physically separate tissues during initial healing. This can prevent early soft tissue adhesions that can occur over time, particularly when splinting injuries associated with tissue repair membranes, which can interfere with normal movement and tissue gliding and increase the risk of soft tissue adhesions. Additionally, the temporary barrier may provide a degree of self-sizing of the nerve wrap product (i.e., tissue repair membrane) because the gel layer is deformable. For example, if the nerve swells after removal of a tourniquet or during early healing, the gel layer may be "squeezed" out of the nerve wrap product, preventing and / or reducing the degree of nerve compression (as long as the thickness of the gel layer is not exceeded). Both hyaluronic acid and alginate are substantially non-adhesive to cells.

[0061] According to some embodiments, tissue repair membranes containing hyaluronic acid may offer a wide range of potential benefits and applications. For example, they may aid in maintaining tissue planes and long-term tissue gliding. For example, this aspect may be facilitated, at least in part, by the ability of the SIS to remodel into a new connective tissue layer. Additionally, in some situations, tissue repair membranes consistent with the present disclosure may improve options for early mobilization (e.g., by reducing frictional forces and the risk of irritation or rupture). Furthermore, in some situations, tissue repair membranes consistent with the present disclosure may also improve options for late mobilization (e.g., by providing a temporary layer that can help prevent premature attachment formation during splinting), depending on the surgical situation and patient needs. In some implementations, tissue repair membranes consistent with the present disclosure may help prevent and / or reduce nerve compression after a tourniquet is removed or during early healing, for example, when deformation of the gel layer causes the nerve to swell. In some implementations, the lubrication provided by tissue repair membranes consistent with the present disclosure can also be "sticky" (a paradoxical behavior of some lubricants, such as shear-flowing fluids), which can be helpful in surgical placement, as the tissue repair membrane tends to stay where it is placed (e.g., by exhibiting a high zero-shear viscosity), yet can reduce frictional forces (e.g., by exhibiting a low viscosity under shear). Various additional benefits and advantages can be provided by tissue repair membranes consistent with the present disclosure.

[0062] The foregoing description and examples are set forth merely to illustrate the present disclosure and are not intended to be limiting. Since modifications of the described embodiments incorporating the technical idea and essence of the present disclosure may occur to those skilled in the art, the present disclosure should be broadly construed to include all modifications within the scope of this application, including but not limited to the scope of the appended claims and their equivalents.

Claims

1. A tissue repair membrane, comprising: A tissue repair membrane substrate; a first coating applied to at least a portion of a surface of the tissue repair membrane substrate, the first coating comprising a first hydrogel composition formed from a solution of hyaluronic acid and alginate; a second coating applied over the first coating, the second coating comprising a second hydrogel composition formed from a solution of hyaluronic acid without alginate; A tissue repair membrane, wherein at least one of the first coating and the second coating provides one or more of self-adhesion and lubrication to the tissue repair membrane in a hydrated state.

2. The tissue repair membrane of claim 1 , wherein the tissue repair membrane substrate is selected from one of human tissue and animal tissue, and combinations thereof.

3. 10. The tissue repair membrane of claim 1, wherein the tissue repair membrane substrate comprises one or more of human cadaver tissue, human placental tissue, porcine tissue, ruminant tissue, films and woven or nonwoven fabrics of natural and synthetic polymers, and combinations thereof.

4. The tissue repair membrane of any one of claims 1 to 3, wherein the first hydrogel composition comprises about 0.5% to about 5% by weight of alginate and about 0.5% to about 5% by weight of hyaluronic acid.

5. The tissue repair membrane of claim 4 , wherein the first hydrogel composition comprises 2% by weight alginate and 2% by weight hyaluronic acid.

6. The tissue repair membrane of any one of claims 1 to 3, wherein the tissue repair membrane substrate comprises 1 to 8 layers.

7. The tissue repair membrane of claim 6, wherein the tissue repair membrane substrate comprises 2 to 6 layers.

8. The tissue repair membrane of claim 7, wherein the tissue repair membrane substrate comprises 2 to 4 layers.

9. The tissue repair membrane of claim 8 , wherein the tissue repair membrane substrate comprises four layers.

10. 4. The tissue repair membrane of any one of claims 1 to 3, wherein the level of bonding between the first hydrogel composition and the tissue repair membrane substrate is approximately every monomer in the first hydrogel composition, i.e., 100% modified to every 1000 monomers (0.1% modified).

11. The tissue repair membrane of claim 10, wherein the level of bonding between the first hydrogel composition and the tissue repair membrane substrate is approximately every 20 monomers (5% modification) to every 5 monomers (20% modification).

12. 4. The tissue repair membrane of any one of claims 1 to 3, wherein the bonding between the first hydrogel composition and the tissue repair membrane substrate comprises a technique selected from the group consisting of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide / N-hydroxysuccinimide (EDC / NHS) ester, sulfhydryl / disulfide bond, thioene reaction, malemide, epoxide, imide ester, any "click" chemistry, or a combination thereof.

13. The tissue repair membrane of any one of claims 1 to 3, wherein the tissue repair membrane has an average coefficient of friction of less than 0.

2.

14. The tissue repair membrane of any one of claims 1 to 3, wherein at least one of the first hydrogel composition and the second hydrogel composition covers the first and second sides of the tissue repair membrane.

15. The tissue repair membrane according to any one of claims 1 to 3, wherein the tissue repair membrane is a sheet.

16. A tissue repair membrane, comprising: A tissue repair membrane substrate; a first coating applied to at least a portion of a surface of the tissue repair membrane substrate, the first coating comprising a first hydrogel composition formed from a solution of hyaluronic acid and alginate; a second coating applied over the first coating, the second coating comprising a second hydrogel composition formed from a solution of hyaluronic acid; A tissue repair membrane, wherein at least one of the first coating and the second coating reduces the static coefficient of friction when the hydrogel composition is in a hydrated state.

17. 17. The tissue repair membrane of claim 16, wherein the tissue repair membrane substrate comprises one or more of tissue-derived membranes, films and woven or nonwoven fabrics of natural and synthetic polymers, and combinations thereof.

18. The tissue repair membrane of claim 16, wherein the tissue repair membrane substrate is prepared from a small intestinal submucosa sheet.

19. 17. The tissue repair membrane of claim 16, wherein the tissue repair membrane substrate further comprises divalent ions that provide at least partial ionic cross-linking of the alginate.

20. 17. The tissue repair membrane of claim 16, wherein the first hydrogel composition at least partially physically interpenetrates the tissue repair membrane substrate.

21. The tissue repair membrane of any one of claims 16 to 20, wherein the first hydrogel composition comprises about 0.5% to about 5% by weight of alginate and about 0.5% to about 5% by weight of hyaluronic acid.

22. 22. The tissue repair membrane of claim 21, wherein the first hydrogel composition comprises 2% by weight alginate and 2% by weight hyaluronic acid.

23. The tissue repair membrane of any one of claims 16 to 20, wherein the tissue repair membrane substrate comprises 1 to 8 layers.

24. The tissue repair membrane of claim 23, wherein the tissue repair membrane substrate comprises 2 to 6 layers.

25. The tissue repair membrane of claim 24, wherein the tissue repair membrane substrate comprises 2 to 4 layers.

26. 26. The tissue repair membrane of claim 25, wherein the tissue repair membrane substrate comprises four layers.

27. 21. The tissue repair membrane of any one of claims 16-20, wherein the level of bonding between the first hydrogel composition and the tissue repair membrane substrate is approximately every monomer in the first hydrogel composition, i.e., 100% modified to every 1000 monomers (0.1% modified).

28. 28. The tissue repair membrane of claim 27, wherein the level of binding between the first hydrogel composition and the tissue repair membrane substrate is approximately every 20 monomers (5% modification) to every 5 monomers (20% modification).

29. 21. The tissue repair membrane of any one of claims 16 to 20, wherein the bonding between the first hydrogel composition and the tissue repair membrane substrate comprises a technique selected from the group consisting of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide / N-hydroxysuccinimide (EDC / NHS) ester, sulfhydryl / disulfide bond, thioene reaction, malemide, epoxide, imide ester, any "click" chemistry, or a combination thereof.

30. The tissue repair membrane of any one of claims 16 to 20, wherein at least one of the first coating and the second coating provides one or more of self-adhesion and lubrication to the tissue repair membrane in a hydrated state.

31. 31. The tissue repair membrane of claim 30, wherein the first hydrogel composition has polyanionic regions, and the polyanionic regions of the first hydrogel composition provide lubrication.

32. The tissue repair membrane of any one of claims 16 to 20, wherein the tissue repair membrane has an average coefficient of friction of less than 0.

2.

33. The tissue repair membrane of any one of claims 16 to 20, wherein at least one of the first hydrogel composition and the second hydrogel composition covers the first and second sides of the tissue repair membrane.

34. The tissue repair membrane according to any one of claims 16 to 20, wherein the tissue repair membrane is a sheet.

35. 1. A method for preparing a tissue repair membrane, comprising: applying a first coating of a first hydrogel composition formed from a first solution comprising hyaluronic acid and alginate to at least a portion of the tissue repair membrane substrate; drying the tissue repair membrane substrate with the first coating applied thereto to provide at least a partial coating of a dried first hydrogel composition on the tissue repair membrane substrate; applying to the first coating a second coating of a second hydrogel composition formed from a second solution comprising alginate-free hyaluronic acid; drying the tissue repair membrane substrate with the second coating applied; A method for preparing a tissue repair membrane comprising:

36. 36. The method for preparing a tissue repair membrane of claim 35, wherein the tissue repair membrane substrate comprises one or more of tissue-derived membranes, films or woven or nonwoven fabrics of natural and synthetic polymers, and combinations thereof.

37. 36. The method for preparing a tissue repair membrane according to claim 35, wherein the tissue repair membrane substrate is prepared from a small intestinal submucosa sheet.

38. 36. The method for preparing a tissue repair membrane of claim 35, further comprising adding divalent ions that provide at least partial ionic cross-linking of the alginate salt of the first hydrogel composition.

39. 36. The method for preparing a tissue repair membrane of claim 35, wherein the first hydrogel composition at least partially physically interpenetrates the tissue repair membrane substrate.

40. 40. A method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein the first hydrogel composition comprises from about 0.5% to about 5% by weight of alginate and from about 0.5% to about 5% by weight of hyaluronic acid.

41. The method for preparing a tissue repair membrane according to claim 35, wherein the tissue repair membrane substrate comprises 2 to 6 layers.

42. 42. The method for preparing a tissue repair membrane according to claim 41, wherein the tissue repair membrane substrate comprises 2 to 4 layers.

43. 43. The method of preparing a tissue repair membrane of claim 42, wherein the tissue repair membrane substrate comprises four layers.

44. 40. The method of preparing a tissue repair membrane according to any one of claims 35 to 39, wherein the level of bonding between the first hydrogel composition and the tissue repair membrane substrate is approximately every monomer in the first hydrogel composition, i.e., from 100% modification to every 1000th monomer (0.1% modification).

45. 45. The method for preparing a tissue repair membrane of claim 44, wherein the level of binding between the first hydrogel composition and the tissue repair membrane substrate is approximately every 20 monomers (5% modification) to every 5 monomers (20% modification).

46. 40. The method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein the bonding between the first hydrogel composition and the tissue repair membrane substrate comprises a technique selected from the group consisting of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide / N-hydroxysuccinimide (EDC / NHS) ester, sulfhydryl / disulfide bond, thioene reaction, malemide, epoxide, imide ester, any "click" chemistry, or a combination thereof.

47. A method for preparing a tissue repair membrane described in any one of claims 35 to 39, wherein at least one of the first coating and the second coating provides one or more of self-adhesion and lubrication to the tissue repair membrane in a hydrated state.

48. A method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein the tissue repair membrane has an average coefficient of friction of less than 0.

2.

49. 40. The method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein the duration of application of the first hydrogel composition to the tissue repair membrane substrate is about 2 minutes.

50. 40. The method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein one or both of applying the first coating and applying the second coating is achieved by one or more of soaking, coating, substantially coating, grafting, submerging, hydrating, and saturating the tissue repair membrane substrate with the corresponding one of the first and second hydrogel compositions.

51. A method for preparing a tissue repair membrane according to any one of claims 35 to 39, wherein applying the first coating is carried out for a longer period of time than applying the second coating.

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