Water-activated hydrogel-based medical patches, flexible substrates, and methods of making and using such patches

Abstract

The medical patch may include a biocompatible substrate and a dried hydrogel precursor layer on the substrate, the dried hydrogel precursor layer comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups, a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and about 2 weight percent or less of water. Both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and are blended or in direct contact with each other. The medical patch may be formed by coating a melt blend of the hydrogel precursors in a dry environment or based on solution coating from a dry non-aqueous solvent onto a porous hydrophilic substrate, such as a compressed gelatin substrate. A flexible medical patch may be formed by a method including compressing the coated substrate, for example, by calendaring. The medical patch may be used to place over a bleeding wound or the like and may function as a hemostatic patch.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This PCT application claims priority to co-pending U.S. patent application Ser. No. 17 / 738,847, filed May 6, 2022 to Bassett et al., entitled "Water Activated Hydrogel-Based Medical Patches, and Methods of Making and Using Such Patches," and Ser. No. 18 / 142,956, filed May 3, 2023 to Bassett et al., entitled "Water Activated Hydrogel-Based Medical Patches, Flexible Substrates, and Methods of Making and Using Such Patches," both of which are incorporated herein by reference.

[0002] The present invention relates to hydrogel-based medical patches, and more particularly to methods of using such patches as hemostatic patches to control bleeding, surgical seals, promote healing, and for localized drug delivery. The present invention further relates to methods of making the patches, such as forming a melt blend that is cast onto a suitable substrate. The flexible substrate allows the folded patch to be delivered for placement in otherwise difficult to reach locations. [Background technology]

[0003] Hydrogels have found a range of uses in medical applications for surgical seals, drug delivery, tissue fillers, spacers, etc. In the context of wound healing, hydrogel materials can provide a hydrophilic environment to separate tissues and promote healing. Existing products for hemostasis and other wound healing applications have limitations that limit their effective use. Summary of the Invention [Means for solving the problem]

[0004] In a first aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, the dry hydrogel precursor layer comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups, a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and about 2 weight percent or less of water. Generally, both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and are blended or in direct contact with each other.

[0005] In a further aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, the dry hydrogel precursor layer comprising PEG-electrophilic hydrogel precursors having multiple arms with reactive terminal electrophilic groups, PEG-nucleophilic hydrogel precursors having multiple arms with terminal protonated amine groups, and about 2 weight percent or less water. Typically, both the PEG-electrophilic hydrogel precursors and the PEG-nucleophilic hydrogel precursors are substantially uncrosslinked, and the dry hydrogel precursor layer forms a crosslinked hydrogel in 5 minutes or less upon hydration with physiological solution.

[0006] In another aspect, the present invention relates to a method of forming a medical patch, the method comprising: Applying one or more layers of a liquid onto a porous hydrophilic substrate in a dry atmosphere to form a hydrogel precursor layer on the porous hydrophilic substrate, the hydrogel precursor layer comprising a blend of an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, or a stack of sublayers of electrophilic hydrogel precursor and protected nucleophilic hydrogel precursor, respectively, where adjacent sublayers are in direct contact with each other. The protected nucleophilic hydrogel precursor comprises an acidified amine, and the liquid comprises an electrophilic hydrogel precursor and / or a protected nucleophilic hydrogel precursor. The liquid comprises a melt or a non-aqueous solution of the electrophilic hydrogel precursor and / or the protected nucleophilic hydrogel precursor.

[0007] In another aspect, the present invention relates to a method of using a medical patch, the method comprising: The method includes placing one or more medical patches on or within a bleeding defect associated with an organ, the medical patch including a biocompatible substrate and an initially dry, substantially uncrosslinked layer of hydrogel precursors on the substrate, the layer including electrophilic hydrogel precursors and nucleophilic precursors, either as a blend or in multiple stacked sublayers in direct contact with each other.

[0008] In an additional aspect, the present invention relates to a granular composition comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups, a nucleophilic hydrogel precursor having a plurality of protonated amine groups, a blend of the hydrogel precursors with a porous hydrophilic material, the blend comprising about 2 weight percent or less of water. Generally, the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are both substantially uncrosslinked and are in the same granules, or separate granules, or a combination thereof. The granular composition can be placed within the bleeding defect where it gels.

[0009] In a further aspect, the present invention relates to a medical patch comprising a biocompatible substrate and a hydrogel precursor presenting a surface along one side of the biocompatible substrate, the hydrogel precursor comprising an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, the biocompatible substrate comprising thermally crosslinked gelatin. The hydrogel precursor extends at least partially into the surface of the biocompatible substrate to form a cohesive hydrogel precursor structure. The cohesive hydrogel precursor structure comprises a blended layer and / or separate adjacent layers of electrophilic and nucleophilic hydrogel precursors, and the medical patch relates to the fractured surface of the cohesive hydrogel precursor.

[0010] In another aspect, the invention relates to a method of forming a medical patch, the method comprising compressing a structure comprising a biocompatible substrate and one or more hydrogel precursor layers coated onto the substrate from a melt, presenting a surface along one side of the biocompatible substrate, to form a medical patch, the biocompatible substrate comprising expanded gelatin with a broken cell structure, the one or more hydrogel precursor layers extending at least partially into the broken cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure, which upon wetting with physiological fluid or physiological buffered saline crosslinks to form a cohesive hydrogel structure.

[0011] In an additional aspect, the present invention relates to a method of using a flexible medical patch, the method comprising placing one or more flexible medical patches on or in a target bleeding site, the flexible medical patch comprising a biocompatible substrate and a hydrogel precursor presenting a surface along one side of the biocompatible substrate. The hydrogel precursor comprises an electrophilic hydrogel precursor and a nucleophilic hydrogel precursor as a blend and / or in a plurality of stacked regions in direct contact with each other, the biocompatible substrate having a broken cell structure. Generally, the hydrogel precursor is initially dry and substantially uncrosslinked and extends at least partially into the broken cell structure of the biocompatible substrate to form a coherent hydrogel precursor structure, and the medical patch hemostatically adheres to the target bleeding site.

[0012] In an additional aspect, the present invention relates to a method of forming a medical patch, the method comprising applying a liquid hydrogel precursor onto a porous hydrophilic substrate in a dry atmosphere, the application being performed with a print head compressing the substrate at a print station to inject the liquid hydrogel precursor into the compressed substrate, the liquid hydrogel precursor comprising an electrophilic hydrogel precursor and a protected nucleophilic hydrogel precursor, the protected nucleophilic hydrogel precursor comprising an acidic amine, and the liquid hydrogel precursor comprising a melt or non-aqueous solution of the electrophilic hydrogel precursor and / or the protected nucleophilic hydrogel precursor.

[0013] In an additional aspect, the present invention relates to a medical patch comprising a biocompatible substrate and hydrogel precursors, the hydrogel precursors comprising a solid blend and / or separate solid layers of an electrophilic hydrogel precursor having a plurality of electrophilic functional groups and a nucleophilic hydrogel precursor having a plurality of nucleophilic functional groups, both of which are substantially uncrosslinked. The biocompatible substrate comprises thermally crosslinked gelatin having a broken cell structure, and the hydrogel precursors extend at least partially into the broken cell structure of the biocompatible substrate to form a cohesive hydrogel precursor structure. [Brief description of the drawings]

[0014] [Figure 1A] FIG. 1 is a perspective view showing a hemostatic patch structure. [Figure 1B] FIG. 1 is a perspective view showing a layered hemostatic patch structure. [Figure 1C] FIG. 1 is a perspective view showing a hemostatic patch structure having a compressed substrate. [Figure 1D] FIG. 1 is a perspective view of a hemostatic patch structure having a compressed substrate and a cohesive hydrogel precursor network with a fractured surface. [Diagram 2] FIG. 1 is a perspective view of an apparatus for spray coating a blend precursor composition onto a substrate to make a hemostatic patch. [Figure 3A] FIG. 1 is a side view of an apparatus for slot die coating a blend precursor composition onto a substrate to make a hemostatic patch. [Figure 3B] FIG. 3B is a side view of an apparatus for slot die coating, similar to that of FIG. 3A, with the coating head adjusted to press against the substrate during coating. [Figure 4A] FIG. 1 is a side view of an apparatus for continuous roll slot die coating of a blend precursor composition onto a substrate to make a hemostatic patch. [Figure 4B] 1 is a flow chart of a two-stage compression process according to an embodiment of the present disclosure. [Figure 4C]FIG. 1 is a side view of a process flow for making a flexible hemostatic patch product from gelatin sheets and a hydrogel precursor composition. [Figure 4D] FIG. 2 is a side view of the gap between the calender rollers. [Diagram 5] FIG. 1 is a diagram of a hemostatic patch wrapped around a tubular organ. [Figure 6] FIG. 1 is a diagram of a hemostatic patch placed on a non-tubular organ. [Figure 7] FIG. 1 is a diagram of a hemostatic patch placed on the skin. [Figure 8A] 1 is a depiction of a cross-sectional view of a bleeding defect in tissue. [Figure 8B] FIG. 8B is a depiction of a cross-sectional view of the hemostatic patch after placement in the bleeding defect of FIG. 8A. [Figure 8C] 8C is a depiction of a cross-sectional view of the hemostatic patch of FIG. 8B adhered to a bleeding defect. [Figure 8D] 1 is a cross-sectional depiction of healed tissue following absorption of a hemostatic patch. [Figure 9] FIG. 1 shows the Adam's Scale for scoring defect bleeding. [Figure 10A] Photograph of initial placement of the patch into the passageway defect. [Figure 10B] This is a photograph taken one minute after placement as shown in FIG. 10A. [Figure 11] 1 is a plot of force versus time for a representative patch sample as evaluated by a commercially available texture analyzer. [Figure 12A] FIG. 13 is a diagram of a conical hemostatic patch placed into the cervix using a conical mandrel. [Figure 12B] 1 is a diagram of a conical hemostatic patch placed within the cervix, the left inset shows the conical mandrel pushing the patch into the cervix, and the right inset shows the conical mandrel removed and the conical patch remaining within the cervix. In the left inset, only the conical end of the mandrel is shown, the handle of the conical mandrel is not shown. [Figure 13A] FIG. 1 is a perspective view of a bellows-folded flexible hemostatic patch. [Figure 13B] FIG. 13 is a diagram of a bellows-folded flexible hemostatic patch being introduced into a cannula using forceps. [Figure 13C] FIG. 1 illustrates a flexible hemostatic patch that is accordion-folded and folded laterally. [Figure 13D] FIG. 13 is a diagram of a concertina, transversely folded flexible hemostatic patch being introduced into a cannula using forceps. [Figure 14] FIG. 13 is a diagram of a bellows-folded flexible hemostatic patch being introduced into a laparoscopic surgical site using forceps. [Figure 15A] 1 is an SEM image of a cross-linked gelatin substrate. [Figure 15B] FIG. 15B is an SEM image of the cross-linked gelatin substrate of FIG. 15A after calendaring. [Figure 15C] 1 is an SEM image of a cross-linked gelatin substrate. [Figure 15D] FIG. 15D is an SEM image of the cross-linked gelatin substrate of FIG. 15C after calendaring. [Figure 16A] 1 is an SEM image of the surface of a precursor-coated gelatin substrate. [Figure 16B] FIG. 13 is an SEM image of the surface of a precursor coated gelatin substrate after compression with calender rollers set at a gap of 5 mm. [Figure 16C] FIG. 13 is an SEM image of the surface of a precursor coated gelatin substrate after compression with calender rollers set at a 2 mm gap. [Figure 16D] FIG. 13 is an SEM image of the surface of a precursor coated gelatin substrate after a first compression with calender rollers set at a gap of 5 mm and a second compression with calender rollers set at a gap of 2 mm. [Figure 17A] 1 is a SEM image of a cross section of a precursor coated gelatin substrate. [Figure 17B] FIG. 17B is a SEM image of a cross section of the precursor coated gelatin substrate after calendaring in FIG. [Figure 18A] 1 is a first photograph of a precursor coated substrate where the substrate was not compressed prior to coating. [Figure 18B] 13 is a second photograph of a precursor coated substrate where the substrate was not compressed prior to coating. [Figure 18C] Photograph of a precursor coated substrate where the substrate was calendered prior to coating. [Figure 19] 1 is a plot of average fluid absorption as a function of time for uncompressed and compressed substrates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The medical patch is formed with a dried layer of hydrogel precursors on a substrate, either as a blend or as an adjacent sublayer in direct contact, where upon hydration with biological fluids, they spontaneously crosslink to form a hydrogel that can adhere to tissue. Generally, the hydrogel precursors do not need to react with blood or tissue, since any physiological fluid can activate crosslinking with equal or nearly equal amounts of nucleophilic and electrophilic functional groups reacting. The processing to form the layer of hydrogel precursors is generally selected to avoid substantial crosslinking during processing by protection of the nucleophilic groups and avoiding moisture even when the reactive species are in contact. Processing can include forming an anhydrous melt blend of the precursors, which can then be coated or cast to form a layer, or coating a non-aqueous solution of the blend to remove the solvent. The substrate supporting the dried hydrogel can be selected to be absorbent, so that the substrate further assists in the hemostatic function of the patch. Furthermore, patch fabrication and hydrogel precursor deposition can be designed to achieve a flexible patch with good adhesion of the hydrogel precursor material to the substrate and good cohesion of the hydrogel precursor material that presents a surface for adhering to the wound in the finished patch. By using a flexible, biodegradable substrate, placement of the patch in difficult to reach locations and / or on wounds with abnormal shapes can be achieved. Tissue contact during the crosslinking process can encourage the formation of the desired adhesive bond, whether or not any covalent bonding with the tissue occurs and whether or not blood is present. Depending on the components selected, the patch can be folded without crushing so that it can be delivered through a trocar in a laparoscopic procedure, and / or folded for insertion into the wound rather than covering it. Increased flexibility of the patch can be achieved by appropriate selection of the substrate, and the desired patch can include a compressed gelatin sponge, which is infiltrated with a properly integrated precursor layer. The surprisingly good adhesion of the hydrogel precursor layer to the surface provides for bonding along the edges of the patch without the need for direct contact with blood or the wound.The results seen with these patches indicate significant utility of the material as a filler for wounds or the like, which may be formed from shredded patches or from equivalently formed materials in which the components are separately shredded, pulverized or otherwise ground.

[0016] The gelatin substrate may provide the desired absorption of fluids as well as biodegradation within an appropriate time frame. In particular, foamed gelatin meets these properties, but other porous gelatin forms may have similar properties, such as fused fibrous gelatin. It has been found that a greater degree of flexibility than is directly available in these materials is desirable. Compression of the substrate, such as calendaring before and / or after deposition of the precursor materials, may be desirable to impart significantly greater flexibility. In the context of using porous gelatin substrates, the precursor materials are coated onto the surface of the substrate as a blend of precursors and / or as separate precursors to provide a blend layer and / or separate adjacent layers of electrophilic and nucleophilic hydrogel precursors. It is desirable that the coated substrate is both flexible and mechanically robust in terms of the cohesive strength of the blend layer and / or separate adjacent layers as well as the adhesive strength to the substrate, so that the precursors do not delaminate or fall off from the dry patch. Injecting the hydrogel precursor onto the substrate as one or more melts or one or more non-aqueous solutions under mild compression has been found to improve adhesion of the hydrogel precursor to the porous substrate while maintaining good cohesion of the hydrogel precursor. Although the elasticity of the substrate may result in restoration of the substrate thickness after deposition of the hydrogel precursor, deposition of the hydrogel precursor with good penetration into the substrate provides good adhesion of the hydrogel precursor to the substrate while still presenting the surface of the hydrogel precursor over most or all of the surface to establish adhesion of the patch to the tissue surface during use. After deposition of the hydrogel precursor, the structure may be compressed, such as by calendaring, to further improve the flexibility of the patch and thereby break the surface of the precursor into pieces. The resulting patch structure may have the desired flexibility, but maintain good cohesion and adhesion of the hydrogel precursor, so delamination or peeling of the hydrogel precursor may be avoided. Although the hydrogel precursor has some characteristics of a surface layer, the hydrogel precursor also has some characteristics of an integral structure since it at least partially penetrates the substrate. The cohesive hydrogel precursor structure can be adhered to the substrate via a diffusion boundary between the hydrogel precursor and the substrate.A small amount of gelatin from the substrate may penetrate into the hydrogel precursor present along the surface of the substrate because the substrate surface is not microscopically smooth, and the hydrogel precursor may penetrate and embed portions of the substrate to form a diffusion boundary between the hydrogel precursor and the substrate within the cohesive hydrogel precursor structure. In various circumstances, the hydrogel precursor may instead be described as one or more layers or coatings, or as a cohesive hydrogel precursor structure (or a cohesive hydrogel precursor network) that presents a surface of hydrogel precursors. Although a clear boundary may not separate the substrate and the hydrogel precursor, the hydrogel precursor nevertheless still presents a surface along the substrate that allows for adhesion of the patch to wet tissue when the hydrogel precursor hydrates.

[0017] A dry layer of hydrogel precursors, such as a blend, typically includes a first hydrogel precursor with multiple electrophilic functional groups and a second hydrogel precursor with multiple protonated amine groups, typically primary amines. In particular, the nucleophilic amines can be protonated to form cationic ammonium groups, which protect the amines from nucleophilic reactions until they are deprotonated. A halide, such as chloride, or other strong acid conjugate anion can be the counterion. Once the blend is hydrated and the ammonium groups are deprotonated due to dilution of the acid by hydration, the electrophilic and nucleophilic functional groups can react to form covalent crosslinks. Thus, in patch products, the hydrogel precursors are substantially uncrosslinked, as further described below. In some embodiments, the patch or portions thereof can be degradable. The precursors are applied as separate layers or as a pre-blended melt. If a melt is selected, it is advantageous to use the melting point of the blended precursors so that they remain solid at room temperature to maximize storage stability. The precursor blend may include components that are liquid at room temperature, but the melting point of the blend is above room temperature. In principle, the precursor blend may be a viscous liquid at room temperature, but the resulting patch may require refrigerated storage to ensure storage stability. The patch may be used for implantable applications or for healing exposed or dermal tissue. The substrate may be selected accordingly. The patch may be effective for hemostatic applications. For hemostatic applications, absorbent substrates are highly desirable. Absorbent substrates may be formed from natural materials, such as collagen, gelatin, cellulose, or other similar biopolymers, or from polymers including synthetic hydrogels, such as poly(ethylene glycol), poly(vinyl alcohol), or other water-soluble or water-swellable synthetic polymers, or from combinations with biopolymers. Substrates that are flexible and provide good drapeability will generally provide the desired patch properties, or substrates that soften rapidly upon contact with moisture to be drapeable may also provide properties desired for many applications.

[0018] In some embodiments, no buffer is added to the precursor layer, and as a result, it demonstrates rapid and good gelation without any buffering agent. Some appropriately selected buffering agents may be present without interfering with the function of the precursor layer. In this case, an inorganic buffering agent may be desirable because it may remain in a separate phase until such time as it is activated by physiological fluids. Carbon dioxide from the air or as present in the laparoscopic environment may dissolve in water to form carbonic acid, which may provide a small amount of buffering capacity. Carbonic acid evaporates as carbon dioxide, rather than concentrating as water is removed. An improperly selected buffering agent may be undesirable by causing undesirable premature crosslinking of the precursor before use, or by slowing crosslinking after application to tissue. Water is removed from the patch during processing, but traces of water may still cause some crosslinking if a higher pH buffer was present, and more acidic buffering agents may slow crosslinking upon contact with physiological solutions that generally have a slightly basic pH. Based on experience with these polymer systems, generally, phosphate buffers, perhaps other neutral to weakly acidic buffers, may be used with adequate slow gelation. Evidence indicates that patches without buffers may provide desirable performance with adequate storage stability. Patches with no significant buffering or with acceptable levels of buffering may be more easily described in terms of patch functions such as storage stability and gelation rate, which are described in detail below. If buffers are included, they may be disposed, for example, as a powder on the substrate, and may be blended into the hydrogel precursor layers if the hydrogel precursor layers cover them or are compatible with the non-aqueous format of the precursor layers.

[0019] Various suitable substrates are described below. Particularly effective patch properties are found in gelatin-based sponge patches. Enhanced flexibility can be obtained with these sponges as substrates when the sponges are compressed to break the sponge's cell structure. Compression of the gelatin cell structure reduces the mechanical strength of the substrate, but the substrate correspondingly becomes significantly more flexible while maintaining sufficient mechanical stability for applying the hydrogel precursor layer and for attaching the patch to the substrate. Although various processing protocols can be effectively used, particularly desirable results are obtained from a two-stage compression process. A hydrogel precursor layer can be added after the first compression and before the subsequent compression. The hydrogel precursor penetrates the broken cell structure of the sponge to stabilize the patch, and the hydrogel precursor layer breaks during further compression, thereby not only improving the flexibility of the coated substrate, but also promoting and speeding up the hydration of the precursor layer to speed up the adhesive effect.

[0020] As described in more detail below and clearly illustrated, the patch has very good adhesion to wet tissue. An effective manufacturing approach is described. The hydrogel is designed to have approximately equal amounts of electrophilic and nucleophilic functional groups, so that sufficient crosslinking can and is expected to occur between the hydrogel precursors without the precursors ever needing to bind to functional groups in blood or tissue. The strong adhesion of the patch in the absence of covalent bonds to blood or tissue is a surprising result based on the teachings of the art. This improved design results in superior performance, including, for example, strong adhesion and rapid gelation, while maintaining a good shelf life. If it is desired to speed up the gelation time, a buffer / accelerator solution can be used, for example by backing, immediately after the patch is applied to the tissue to further speed up the gelation process. In principle, the buffer / accelerator solution can be added to the patch just before application to the tissue, but this approach may result in too rapid gelation for good adhesion.

[0021] Patches are particularly well suited for sealing active bleeding or leaks. Such sealing is not usually possible with liquid precursors, since the precursor is displaced by active fluid outflow only when delivered as a spray sealant. In the case of the patch-based sealants that are the subject of the present invention, manual compression applied as part of patch application temporarily controls the active fluid outflow, allowing the sealant to activate and adhere to the tissue surface, thus forming an effective seal.

[0022] For some wounds, such as those that have cavities and may not bleed profusely, the insertion of shredded patch material may be effective to stabilize the wound by bridging the material in place. The physician may shred the patch itself for use, or the shredded patch material may be distributed in that form. To create a shredded patch composition, the patch does not need to be fully formed to yield a similar material. The substrate, such as a gelatin substrate, may be shredded and a precursor blend may be formed that may be pulverized / reduced to fine particles. For example, a melt blend or solution may be spray-dried / cooled to directly form a particulate-type material, which may be further milled or sieved if desired. The separately shredded / pulverized materials may then be mixed for distribution and use. Formation of a blend of precursors to pulverize may be desired for rapid gelation / crosslinking, but alternatively separate powders of precursors may be blended. The relative amounts of the components may follow the ranges described for the patch, but depending on clinical experience, slightly altered amounts may be selected for commercialization of these embodiments.

[0023] A granular composition that is a blend of a porous hydrophilic material and a hydrogel precursor can be prepared from the chopped patch, the porous hydrophilic material being the substrate of the patch, and the hydrogel precursor being the dried layer of the hydrogel precursor on the substrate. The blend can be homogeneous or heterogeneous. In some embodiments, the granular composition is a blend in which the porous hydrophilic material is provided separately from the hydrogel precursor. For example, the porous hydrophilic material can be a chopped, uncoated substrate, or a porous hydrophilic material provided in particulate form, such as gelatin microparticles or gelatin powder. In some embodiments, the porous hydrophilic material can be a foam, a nonwoven tufted material, or a nonwoven felt material. Two or more porous hydrophilic materials may be used together. Examples of separate hydrophilic porous materials include, for example, substrates of the same material but different porosity, pore size, and / or particle size, or substrates of different compositions. The hydrogel precursors may be provided as a blend of electrophilic and nucleophilic hydrogel precursors in the same granules, or as separate granules of electrophilic and nucleophilic hydrogel precursors, or combinations thereof. In some embodiments, the weight ratio of chopped substrate / porous hydrophilic material in the chopped patch composition may be about 5 weight percent (wt%) to about 75 wt%, in some embodiments about 7 wt% to about 50 wt%, and in further embodiments about 10 wt% to about 35 wt%. In other embodiments, the weight ratio of chopped substrate may be less than 25%, less than 10%. In other embodiments, the precursor granular composition may be used without any chopped substrate, such that the weight ratio of the chopped patch is 0 wt%. One of ordinary skill in the art will recognize that additional ranges of porous hydrophilic material compositions within the explicit ranges above are contemplated and are within the present disclosure.

[0024] The granular composition may have granules composed of any combination of porous hydrophilic material and hydrogel precursors. Granules of different compositions may have different average particle sizes from each other. In one embodiment, the porous hydrophilic material and hydrogel precursors form a composite within the granules. In another embodiment, the porous hydrophilic material and electrophilic hydrogel precursors form a composite within the granules and the nucleophilic hydrogel precursor is in a separate / separate granule. In another embodiment, the porous hydrophilic material and nucleophilic hydrogel precursors form a composite within the granules and the electrophilic hydrogel precursor is in a separate / separate granule. In another embodiment, the porous hydrophilic material is within the granules and the composite of hydrogel precursors is within a separate / separate granule. In another embodiment, the porous hydrophilic material, the electrophilic hydrogel precursor, and the nucleophilic hydrogel precursor are in a separate / separate granule. The granular composition may be provided as granules of porous hydrophilic material coated or at least partially coated with one or both of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor. The coating of one or more precursors may be performed by spraying a melt or solution of one or more precursors. Multiple layer coatings can be applied, for example a layer of one precursor over a layer of a different precursor.

[0025] The granular composition may have granules ranging from a powder, to small particles, to coarse pieces such as those obtained by shredding the substrate or patch. The average diameter of the small particles may be about 0.001 mm to about 5 mm, or about 0.01 mm to about 3.5 mm. The granules may be approximately spherical or not, and may be of any reasonable shape. The granular composition may further include a visualization agent and / or a therapeutic agent, as described in the patch. The granular composition may be placed on or in the bleeding defect, and pressure may be optionally applied. The bleeding defect may be partially or fully filled or thinly coated with the granular composition. One of ordinary skill in the art will recognize that additional ranges of average diameters within the explicit ranges above are contemplated and are within the present disclosure. When the patch is shredded for use by a physician, the resulting patch pieces may generally have a wide variation in size and shape depending on the needs of the physician.

[0026] Rapid gel formation is possible due to the ability to mix the precursors well, even though the amines are initially protected. Crosslinking begins as soon as the acid protecting groups are neutralized upon dilution with physiological solutions. Physiological solutions are generally slightly basic at physiological pH (e.g., blood plasma), ranging from 7.32 to 7.42 pH units. In the PEG-NH2 group, -NH3 + The moiety must deprotonate to form a nucleophilic active form even at neutral aqueous pH values. Thus, with proper hydration, the patch can gel in less than a minute, and the examples demonstrate fast gelation. Because of the chemistry used, the patch will generally adhere to any moist tissue surface in the presence of physiological solutions; direct blood and / or wound contact is not required, although it may be present. The patch is designed for rapid and predictable efficacy to significantly aid in the delivery of effective medical treatments.

[0027] The precursor compositions may each be selected to form a thermally flowable composition without decomposition, which may be blended as a liquid. The thermally flowable composition or a blend of two or more thermally flowable compositions may each be a neat melt or a neat melt blend, with "neat" referring to a liquid phase composition with no added solvent. The melt blend may then be coated onto a substrate and cooled to form a patch. In particular, precursors with a polyethylene glycol core generally form a flowable liquid at relatively low temperatures. Slot coating, extrusion, screen printing or other suitable coating processes may be used to form the coated substrate. In some embodiments, the precursors may be dissolved in some organic solvents in which the precursors are suitably stable, such as aprotic polar solvents. A solution of the mixed precursors may be coated, e.g., spray coated, onto a substrate and dried to remove the solvent. In an alternative embodiment, the precursors may be processed using a non-aqueous solvent solution, where the solvent is selected to avoid deprotonating the acidic amine groups. The precursor solution may be deposited using similar techniques as the precursor melt.

[0028] The medical patch may find great value in wound closure, either within the patient's body as part of a treatment, or along the skin for wound healing or end of treatment, or in a variety of other uses. The patch offers great benefit of activation by any physiological fluid, such that contact with blood or tissue is not explicitly required. Thus, all of the patch can form an effective seal, even if parts of the patch are in direct contact with blood or tissue, even along edges that may not be in direct contact with blood or tissue. For example, an absorbent substrate can absorb physiological fluid and wet multiple parts of the patch with physiological fluid along the entire patch surface. And, since direct contact with blood or tissue is not required for any part of the patch to adhere if there is adequate moisture, the patch can be effectively activated, for example, by lymphatic fluid directly contracting or displacing from the substrate. The patch may be used for human medical or veterinary purposes. The patch as prepared may be free of blood and body components.

[0029] The patch may generally have a substrate layer and a hydrogel precursor layer on the substrate layer, where the precursor layer may be a blend of precursors and / or sublayers of the same and / or different compositions. The substrate layer may be homogenous or structured with multiple layers and / or structural layers. Generally, when the patch is formed, the substrate layer is dry and formed from a biodegradable material, although in some applications it may be desirable to use a non-degradable substrate. The substrate may be highly capable of absorbing liquids, which may aid in the management of blood and other fluids while the hydrogel seals the wound. The patch generally has a sufficient thickness to provide the desired mechanical integrity, but is not excessively thick; a patch of appropriate thickness may provide the desired crosslinking and hydration within the desired period of time and degradation within the appropriate time, without being excessively bulky.

[0030] The precursors may be selected to be processable using heat to form a flowable state at an appropriate temperature. In embodiments where the precursors are blended in a flowable state during processing, the formation of the molten blend should be thermally stable with respect to each of the precursors. Processing may be performed in a low moisture environment, so that hydroscopic materials do not absorb undesirable moisture from the air. In general, the flow properties of the heated precursor composition are strongly influenced by the polymer core with pendant functional groups. In particular, polyethylene glycol-based precursors have the advantage of relatively low flow temperatures and acceptance of approved implantable medical products, although other hydrophilic precursor cores may be used.

[0031] In some embodiments, if the precursors are soluble in a suitable organic solvent that does not induce crosslinking, the precursors may be blended in an organic solution. A variety of solution coating techniques may be suitable for forming the precursor coating by solution blending. After forming the coating, the organic solvent may be removed by evaporation to form a dry coating. After drying, the patch may be packaged in a waterproof pouch or the like, similar to patches formed from a cooled melt.

[0032] In order to obtain the desired shelf life, suitable handling and processing properties, and solidification upon application, the amine precursor is provided as an acid salt / acid conjugate, and the blend precursor is either buffer-free or has only a properly selected buffer that does not excessively slow down gelation or destabilize the storage of the patch. The presence of a basic pH buffer tends to amplify the instability to crosslinking during processing by the possibility of removing protons from the amine. Since water is kept away during synthesis, it is not possible to obtain extremely low levels of water, even with all hydrophilic components. On the other hand, the amine is selected to deprotonate immediately upon contact with physiological fluids, so a buffer is not necessary to achieve rapid gelation.

[0033] Other hemostatic hydrogel patches are known. For example, fibrin-based patches are available on the market. TACHOSIL® is a fibrin-based patch from Baxter. Similar powder and syringe-deliverable matrices based on fibrin or other blood-based components are also available. Another approach to the patch involves partially crosslinking the hydrogel in the patch to leave unreacted electrophilic groups. Partial crosslinking provides for solution processing to create the hydrogel precursor layer of the patch, with precursors having intentionally functional group ratios (lacking nucleophiles) resulting in a significant number of unreacted electrophilic groups. The unreacted electrophilic groups are intended to react with nucleophilic groups, such as naturally occurring amines, in the blood or tissue at the wound site. This approach has the disadvantage that the edges of the patch do not directly interact with the wound as the patch only adheres to tissue or blood, and may not be placed in direct contact with blood or tissue, resulting in partial and / or insufficient patch adhesion. Hydrogels based on this approach have been described using polyoxazoline copolymers as the core of functionalized precursors. See US Patent Application Publication No. 2019 / 0231923 to Hoogenboom et al., entitled "Cross-Linked Polymers and Implants Derived From Electrophilically Activated Polyoxazoline," incorporated herein by reference. These polyoxazoline-based cross-linked polymers are described as adhesives and not explicitly described as hydrogels. In contrast, the hydrogels described herein result from all or essentially all of their cross-linking occurring after application and do not rely on reaction with tissue, blood, or other nucleophiles provided by the patent for cross-linking, although some reaction of the precursors with blood and tissues may occur. Although the hydrogel precursors for the current patches effectively only react with themselves, they achieve excellent adhesion.

[0034] Polyethylene glycol-based (PEG-based) hemostatic patches are sold under the trade name Veriset™ (Medtronic). Veriset™ is believed to include the technology described in U.S. Patent Application Publication No. 2010 / 0100123A ('123 Application) to Bennett (entitled "Hemostatic Implant"), which is incorporated herein by reference. These patches include isolated precursor components. In contrast, the approach herein includes blended or intimately contacted hydrogel precursor components that can rapidly form a highly crosslinked homogenous hydrogel upon contact with the patient. As a result of the mixing or intimate contact of multiple uncrosslinked precursors, the hydrogel can gel rapidly and form a homogenous hydrogel with good mechanical stability, good adhesion, and predictable properties. Another hemostatic patch uses a PEG-based NHS hydrogel precursor and is sold under the name HEMOPATCH™ by Baxter International, Inc. (IL, USA). The precursor coating of HEMOPATCH is intended to crosslink amines in tissue and blood.

[0035] Generally, Applicant's patches herein include a substrate and a hydrogel precursor layer. After placement at a tissue site, crosslinking of the hydrogel precursor layer serves to adhere the patch to the site. The substrate is generally adhered to the precursor layer and may serve to facilitate hydration and stabilization of the patch during use, particularly in the context of hemostasis. For these purposes, the substrate is generally highly absorbent and porous while maintaining mechanical integrity. In this manner, the substrate can absorb fluids such as blood, helping to stabilize the patch site and helping to hydrate the hydrogel to facilitate crosslinking, while not being too porous to cause blood passing through the substrate to adhere to the substrate surface, e.g., gauze or surgical gloves. Substrate absorption may be assessed based on swelling, and the substrate may form a hydrogel, but the hydrogel does not exhibit further crosslinking upon hydration. The porosity of the substrate generally allows some penetration of the hydrogel precursor into adjacent substrate surfaces.

[0036] In the hydrogel precursor layer of the patch, two precursors for crosslinking under dehydrated conditions can be mixed or formed as sublayers in the precursor layer. The amine groups are in a protonated acidic state. The precursor layer can be effectively buffer-free to support relatively more rapid crosslinking upon hydration with physiological fluids. The precursor layer is stable under dry storage for a period suitable for product distribution with a commercially suitable shelf life. Of course, the precursor may contain trace amounts of anionic contaminants, but a suitably pure precursor should eliminate any quality concerns. One or more amine-terminated precursors may be used, and one or more precursors that react with nucleophilic end groups may also be used to form the patches described herein.

[0037] The crosslinking reaction involves a nucleophilic amine reacting with a suitable group to carry out the addition reaction. The addition reaction generally proceeds at a moderate rate at higher pH values, generally pH 7 or higher. Without the use of an activation solution, deprotonation of the amine can occur relatively quickly upon hydration with a physiological solution, allowing the crosslinking reaction to occur within a short period of time (e.g., <3 minutes). The results of the examples support the rapid gelation. Because the precursors are mixed or in close proximity within the dry patch, the reactive crosslinking groups can be in close proximity without significant movement of the polymeric precursor molecules involved in the crosslinking. As explained and exemplified below, the initially uncrosslinked precursors can gel quickly to induce the adhesive strength of the patch. Generally, the use of a high pH buffer is not necessary to induce gelation at a suitable rate, and such a high pH buffer, such as a borate buffer, can contribute to a shorter storage time. Low pH buffers, such as phosphate-based buffers, generally prolong the gelation time, but in appropriate amounts, they may not slow down gelation by an unacceptable amount. The low pH buffer may not adversely alter storage time, and if so desired, additional external higher pH buffer may be provided to the patch after placement on the patient for the selected application to speed up reaction time, but is not required.

[0038] The substrate for supporting the hydrogel precursor may be absorbent, which may provide several advantages. First, it may absorb fluids, such as blood, lymph, etc., and thus aid medical professionals in managing the wound while applying the patch. Absorption of physiological fluids by the absorbent substrate may also aid in hydration of the hydrogel precursor. Thus, the absorbent substrate may speed up the gelation time, which may be less than one minute. The substrate is generally biodegradable, but in some embodiments, the substrate may be non-degradable over a suitable time scale, such as some applications involving external application of the patch. If external application of the patch is envisaged, the backing substrate may not be biodegradable, and the patch may either be removed once healing is complete, or the hydrogel formed by the precursor in contact with the tissue may be absorbent, releasing the patch substrate after a few days. In selected cases, it may be advantageous to deliver the hydrogel by itself, in which case a non-porous backing substrate may be used, which may release the hydrogel onto the wet tissue without adhering to the hydrogel itself. In such applications, substrates made from polymeric materials that exhibit low adhesion to the hydrogel precursors may be useful, such as polytetrafluoroethylene, polyethylene, polyurethane, etc. Release layers for bandages and the like may be adapted for this use.

[0039] For most hemostatic applications of the patch, it is desirable that the substrate be biodegradable into non-toxic degradation products within a reasonable period of time of removal from the patient. The substrate may desirably interface with a precursor layer that absorbs and penetrates bodily fluids. A variety of natural and artificial materials, typically polymers, may provide these characteristics, but gelatin sponge materials have been found to work particularly well in patch construction. To achieve the desired level of flexibility, the gelatin sponge may be compressed to break the gelatin cell structure, and the precursor layer may penetrate the broken cell structure to form a stable, integral structure with the desired absorption properties.

[0040] Gelatin is the hydrolysis product of collagen, the main component of the extracellular matrix in animals. Collagen is commonly harvested from various livestock. In its native form, collagen is an insoluble fibrous protein. Hydrolysis breaks down the protein polymer strands into smaller units, making the resulting gelatin processable. The exact nature of gelatin may depend on the process. However, in general, gelatin is soluble in hot water and some other polar solvents. To return gelatin to insolubility, it may be crosslinked to control certain properties. To avoid using toxic chemicals for crosslinking, sufficient crosslinking may be achieved using heat. To form an absorbent substrate, gelatin is formed into a sponge with a cellular structure. Expanded gelatin cellular structures may be formed without crosslinking.

[0041] Formation of gelatin sponges is known and is generally stabilized by chemical crosslinking. See, for example, U.S. Patent Application Publication No. 2007 / 0077274 ('274 Application) to Ahlers (entitled "Method for Producing Shaped Bodies Based on Crosslinked Gelatin"), which is incorporated herein by reference. The '274 patent refers to previous crosslinked gelatin products that are not durable enough for some applications. The crosslinked gelatin is formed using a pore former, such as air, to introduce pores into the sponge structure. The product in the '274 patent is still biodegradable. Gelatin sponges are commercially available for use as hemostatic materials. For example, gelatin sponges are available from Gelita AG (Germany, applicant of the '274 patent) and Ethicon (USA). Non-crosslinked gelatin sponges can be obtained. Gelita and Ethicon sell gelatin sponges as hemostatic patches, Surgi-Foam® (Ethicon) and Gelita-Spon® (Gelita).

[0042] Chemical crosslinking may be desirable, albeit for longer durability, and may involve the use of toxic chemicals or other moieties that may result in materials that are too long-lasting and may not be desirable with respect to the biodegradation of the material. Chemical crosslinking may also change the mechanical properties of the substrate, making it more fragile. On the other hand, fully uncrosslinked gelatin may degrade too quickly before reaching hemostasis, thereby resulting in loss of absorbency to bodily fluids. Thermal crosslinking may achieve the desired balance of properties without introducing chemicals that may make biocompatibility difficult. As described in the '274 patent, thermal crosslinking of gelatin may result in dehydration, thereby forming crosslinked bonds. Thermal crosslinking is further described below.

[0043] Previous studies have suggested that compression of gelatin sponges may increase flexibility. The '274 application describes "mechanical action" including passing through rollers to increase the flexibility of cross-linked gelatin sponges. Although it is proposed that the density is increased by 2-10 times, the mechanical properties of the material after mechanical action are not described, except that dissolution over time is proposed to be unaffected, although no data is presented in the reference. The use of compressed gelatin substrates with hydrogel precursors is described in U.S. Patent Application Publication No. 2021 / 0213157 to DeAnglis et al. (the '157 application) (entitled "Flexible Gelatin Sealant Dressing With Reactive Components"), which is incorporated herein by reference. The '157 application describes compression of gelatin, preferably after cross-linking. Correspondingly, although the '157 application states that the strength of compressed gelatin sponges is increased due to a higher crosslink density resulting from closer physical proximity of the amine groups of the proteins, the '157 application suggests that crosslinking is optional, and the '157 application does not appear to suggest the possibility of thermal crosslinking.

[0044] The '157 application references earlier U.S. patent application publications that teach the association of hydrogel precursors with absorbent substrates (see U.S. Patent Application Publication No. 2011 / 0045047 to Bennett et al., entitled "Hemostatic Implant," which appears to be a follow-up to the above-cited '123 application, and is incorporated herein by reference). The '157 application points out undesirable aspects of the previous work and is directed to an alternative that uses dry precursor powders that are deposited on a porous substrate.

[0045] The '157 application illustrates the use of commercially available substrate materials, specifically SURGIFOAM® product codes 1974 and 1975, which are alleged to be compressed, and SPONGOSTAN® gelatin membranes. Detailed characteristics of these substrates are not described in the '157 application, and no further specific processing is performed prior to application of the hydrogel precursor. As mentioned above, the precursor is applied as a dry fine powder that is a blend of 4-arm PEG-SG (succinimidyl glutarate) (MW 4000 Da), 4-arm PEG-amine (MW=3,000 Da), and sodium bicarbonate powder. The powder is used in suspension with an organic solvent that can then be evaporated. Powder precursors do not have the advantages of the solid precursor layers described herein.

[0046] Commercially available gelatin sponges for hemostatic purposes are generally chemically crosslinked, for example with an aldehyde, such as formaldehyde or glutaraldehyde, which is believed to stabilize the structure for a reasonable duration upon contact with biological fluids. As noted above, the '157 application does not detail the production or specific properties of the substrate other than dimensions, and uses a commercially available substrate from Ethicon, Inc. As described herein, the fabrication involves a coating process to form a continuous layer of precursor that is designed to be stable and uncrosslinked until activated by biological fluids or water. Thus, the precursor layer exhibits a synergistic relationship with the substrate where the precursor layer stabilizes the substrate, and penetration of the hydrogel precursor into the substrate may stabilize the hydrogel precursor against delamination or flaking off.

[0047] In applicant's processing, compression of the patch structure is performed after application of the hydrogel precursor layer. This compression step generally breaks or shatters the as-formed precursor layer, forming microfractures and / or cracks and the like across the surface. The microfractures and / or cracks are consistent with increased flexibility of the resulting patch. The hydrated patch adheres to tissue whether or not it is in direct contact with the wound along multiple portions of the patch. The gelatin sponge may include additives, such as plasticizers, and possibly other agents, and it is believed that the improvement in mechanical properties of the patch is greater if the patch material is not too elastic so that compression reduces the thickness more and rebounds less after compression. The cell structure of the gelatin sponge may then be broken, thereby promoting further hydration and improving flexibility. The gelatin patch may also be compressed prior to application of the precursor layer in addition to compression after placement of the precursor layer. Initial compression may facilitate penetration of the precursor layer into the gelatin while maintaining the surface of the precursor layer.

[0048] It has been discovered that to improve adhesion of the hydrogel precursor to the porous gelatin substrate, the hydrogel precursor can be deposited on the substrate in a lightly compressed state. The print head can be adjusted to produce the desired deposition morphology. Since the porous gelatin substrate can be somewhat elastic, moderate compression in the hydrogel precursor layer may not result in a lasting change in the substrate thickness. Nevertheless, deposition on the substrate under compressive forces appears to result in greater penetration of the hydrogel precursor into the substrate. The resulting patch structure exhibits the desired degree of hydrogel precursor adhesion and cohesion, reducing or eliminating any peeling or delamination of the hydrogel precursor from the dried patch. The resulting hydrogel precursor structure presents a surface for application to a wound, where the surface can be fully or at least significantly covered with the hydrogel precursor even when it is broken into pieces. The hydrogel precursor structure may be referred to as one or more layers or using terms reflecting its penetration into the substrate to form a cohesive hydrogel precursor or a coating of a more complex structure, such as a cohesive hydrogel precursor structure, a cohesive hydrogel precursor network, or a cohesive network, which are used interchangeably herein.

[0049] In principle, compression of the gelatin sponge can be performed in various ways, such as placing the patch between two plates that are clamped onto a structure. A convenient way to apply compression is to pass the patch through a calender roller. The spacing of the calender rollers can be set to achieve the desired compression. The use of rollers to perform compression is also convenient from a process flow approach to perform shear to break the precursor layer. The rollers can be used repeatedly to progressively achieve the desired compression. The first compression without the precursor layer can be performed with a larger roller spacing compared to the subsequent passes through the rollers with the precursor layer.

[0050] For the hydrogel precursor layer, the protected nucleophilic precursor generally has an acidic amine group. For example, the amine can be reacted with a strong acid, such as hydrochloric acid, leaving a chloride ion or other corresponding conjugate base associated with the precursor. The acidification of the amine stabilizes the precursor layer by preventing crosslinking reactions until the amine can deprotonate. This selection of precursors allows the resulting patch to be stable for a significant period of time in dry storage. The nucleophilic precursor generally has multiple functional groups, with three or more groups allowing for a more highly crosslinked structure. The nucleophilic precursor may have a hydrophilic core, which may be highly branched with pendant amine groups. A low pH buffer may not destabilize the acidic amine group.

[0051] The electrophilic precursor has electrophilic groups that can react with amines to form covalent crosslinks. The electrophilic groups generally only react with amine groups, not with protonated amine groups, ammonium acid conjugates. The electrophilic precursor has multiple functional groups, and with three or more functional groups, it can form highly crosslinked hydrogels. The electrophilic groups are generally pendant off a hydrophilic core, such as polyethylene glycol, which can be appropriately branched to form the desired degree of crosslinking.

[0052] The electrophilic precursor and the protected nucleophilic precursor can be designed to have a flow temperature lower than the decomposition temperature of either precursor. Thus, a melt blend can be formed with the two compounds. The melt blend can be formed as a good mixture. The melt blend can then be processed to form a patch. If the precursor layer includes sublayers, these can be applied successively over one another. The sublayers can include the blend or one of the precursors. Generally, processing can be performed under low humidity conditions to reduce any absorption of moisture from the surrounding atmosphere. The melt blend can be directly formed into a coating for the patch, although the melt blend can in principle be solidified in a later process. For example, the melt blend can be slot coated onto the substrate, although other processing techniques, such as extrusion, screen printing, spraying, or the like, can be used. Slot coating or other coating techniques can be performed on a sheet of substrate for efficient processing. After the coating has solidified, the coated sheet can be cut to the desired patch size. Alternatively, the coating can be formed on a pre-cut patch substrate. Suitable packaging may be used to distribute the patch so that it remains dehydrated.

[0053] In some embodiments, the precursors may be dissolved in an inert organic solvent. Suitable solvents may be aromatic liquids, such as toluene, xylene, dimethyl carbonate, or the like, or aprotic solvents. In general, the solutions may be highly concentrated to reduce solvent usage, as long as the fluid properties allow for proper processing. Coating techniques for solvent-based deposition may generally be the same as for melt blending, and the concentration may be adjusted appropriately for the particular deposition technique.

[0054] The components of the patch tend to be hydrophilic and / or hygroscopic. Therefore, synthetic or commercially available components may be dried / dehydrated prior to processing to form the patch. Some substrates may be lyophilized. In some embodiments, it may be desirable to obtain hydration levels of up to 5 weight percent or less, or significantly lower. Processing may be performed in a controlled atmosphere, under dry air, nitrogen, or the like, with the application of heat and vacuum. Processing may include sweeping techniques using limited streams of inert dry gas in combination with heat, under partial vacuum, to enhance drying. Conditions may be provided for moisture reduction. After formation of the patch, it may be packaged in a moisture-resistant package under dry air. The patch may be sterilized, for example, using ethylene oxide gas during packaging or by radiation after packaging. Sterilization may be under conditions that do not induce significant amounts of cross-linking.

[0055] The hydrogel patches described herein are particularly well suited for use as implantable hemostatic patches that can be absorbed after a reasonable period of time ranging from several days to a month or more. The hydrogel patches can be used to control bleeding or seal wounds for open surgery or laparoscopic procedures. The hydrogel patches can generally be used in any wound healing situation, including superficial placements rather than implanted placements. The properties of fast sealing, good adhesion and adjustable absorption time provide desirable features for a range of applications.

[0056] Patch Structure and Hydrogel Precursor The hydrogel precursor patches described herein generally include a substrate and a layer of hydrogel precursors on the substrate as a blend or sublayer, but generally penetrating the substrate to some degree. The substrate may be selected to be suitable for the desired application of the patch. Generally, the substrate is absorbent, and the substrate may be absorbable in situ within a reasonable period of contact with the patient. The patch may be suitable for implantation within the patient's body, and in these embodiments, the substrate is generally absorbent. The precursors are generally substantially uncrosslinked and blended within the layer. The layer may be uniform or variable across the substrate. The precursors are selected to crosslink relatively quickly upon exposure to physiological solutions and tissue. The patch may be suitable as a hemostatic patch to help control and limit bleeding.

[0057] In the patch prior to use, the hydrogel precursors in the layer on the substrate are not substantially cross-linked. Although precise quantification may not be practical, the obvious importance of the concept and the fulfillment of these conditions is very clear. First, the chemistry is designed such that cross-linking is not expected due to the protection of the amine groups by acid modification, which serves to prevent nucleophilic reactions. Significant cross-linking results in the binding of the various precursor molecules into a network structure. At some level of cross-linking, the material no longer has independent precursor molecules, but becomes an essentially cohesive mass of covalently bonded materials. This process is evaluated in terms of gelation, and the cohesive mass can be called the resulting gel, in this case a hydrogel. Over additional time, the degree of cross-linking of the hydrogel precursors increases beyond gelation toward sufficient cross-linking, making the gel strong and rigid. Gelation time (gel time) can be measured, for example, as described below. Conversely, at intermediate points before gelation, some cross-linking occurs and the properties change, which changes the behavior of the composition. When the precursor is substantially uncrosslinked, the properties of the fully hydrated precursor do not change significantly and the flow properties and rheology do not change appreciably for the precursor composition relative to the as-formed uncrosslinked composition, although these properties can change rapidly once crosslinking is allowed to initiate.

[0058] 1A shows the structure of one embodiment of a hemostatic patch. The hemostatic patch 100 has a substrate 102 and a precursor layer 104. The substrate 102 may be a gelatin substrate or other suitable substrate as described below. For example, the substrate 102 may be a gelatin substrate that has not been supplemented with blood components such as fibrinogen or thrombin or platelets. In some embodiments, the substrate 102 is porous and absorbent. In additional or alternative embodiments, the substrate 102 is biodegradable. Generally, the substrate is relatively thin, e.g., having an average thickness of one centimeter or less, and the area of ​​the patch may be selected as appropriate for a particular application.

[0059] The precursor layer 104 may be a blend of electrophilic and nucleophilic hydrogel precursors. Alternatively or additionally, the precursor layer 104 may be structured as sublayers of electrophilic and nucleophilic hydrogel precursors, which may or may not include a blend, but generally along the sublayer is an interface of electrophilic and nucleophilic hydrogel precursors. In some embodiments, the sublayers applied to the substrate as liquids form a single homogenous layer on the substrate after cooling and / or drying. In other embodiments, the sublayers form a continuous layer having a compositional gradient. FIG. 1B shows an alternative structure of a hemostatic patch. The hemostatic patch 150 has a substrate 152 and a precursor layer 154. The precursor layer 154 is structured as a stack of sublayers 160 and 164. The sublayers 160 and 164 are in direct contact with each other. In some embodiments, sublayer 160 is a sublayer of an electrophilic hydrogel precursor and sublayer 164 is a sublayer of a nucleophilic hydrogel precursor. In other embodiments, the composition of the sublayers is reversed, with sublayer 160 being a sublayer of a nucleophilic hydrogel precursor and sublayer 164 being a sublayer of an electrophilic hydrogel precursor. In some embodiments, precursor layer 154 is structured as three or more alternating sublayers, e.g., sublayer 160 / sublayer 164 / sublayer 160, with adjacent sublayers in direct contact with each other. As used throughout this specification, direct contact between hydrogel precursors refers to more than just accidental or inadvertent contact involving significant surface areas of the respective components along the layer in an extended dimension; generally, this includes layer on layer interaction. The sublayers may be of the same thickness or of different thicknesses. In some embodiments, the precursor layer 104 / 154 has a visualization agent such that the precursor layer 104 / 154 is visually distinct from the substrate 102 / 152. In a preferred embodiment, the precursor layer 104 / 154 has a blue or green tint due to the presence of a dye.

[0060] FIG. 1C illustrates another structure of a hemostatic patch. Hemostatic patch 170 has a compressed substrate 172 and a precursor layer 174. Generally, compressed substrate 172 is porous and absorbent. In some embodiments, precursor layer 174 penetrates the porous structure of compressed substrate 172. Precursor layer 174 may be prepared from the same compositions and / or have the same sublayer structures as described above with respect to precursor layer 104 and / or precursor layer 154. In some embodiments, precursor layer 174 has fractures, e.g., microfractures and / or cracks. FIG. 1D illustrates another structure of a hemostatic patch. Hemostatic patch 180 has a compressed substrate 182 and a cohesive hydrogel precursor structure 184 with a fractured surface 186. Generally, cohesive hydrogel precursor structure 184 presents a surface located on one side of compressed substrate 182 while having precursor material embedded in the substrate material. In some embodiments, the surface area of ​​the compressed substrate 182 associated with the cohesive hydrogel precursor network 184 is sufficiently coated with the hydrogel precursor blend. Generally, the compressed substrate 182 is porous and absorbent. Generally, the hydrogel precursors have good cohesion within the cohesive hydrogel precursor structure 184 to resist collapse and loss of precursor material if the surface is broken into pieces. Generally, the hydrogel precursors within the cohesive hydrogel precursor structure 184 have good adhesion to the compressed substrate 182. In some embodiments, good cohesion and / or good adhesion may be characterized by a cohesive hydrogel precursor structure 184 that resists flaking during handling and / or further processing. Handling and / or further processing may include calendaring, inducing the surface 186 of the cohesive hydrogel precursor structure 184 to break into pieces, and handling subsequent to formation of the patch includes, for example, bending, folding, packaging, and / or shipping. Generally, the compressed substrate area 183 opposite the cohesive hydrogel precursor structure 184 is free of hydrogel precursors.A cohesive hydrogel precursor structure 184 may be prepared by applying a blend of electrophilic and nucleophilic hydrogel precursors onto a porous hydrophilic substrate, such as a cross-linked gelatin substrate, or by applying separate precursors as adjacent adjacent layers that may blend to some extent during application but are otherwise adjacent along the area of ​​the patch. In some embodiments, the porous hydrophilic substrate has a disrupted cell structure.

[0061] In some embodiments, applying the precursor material is performed using a porous hydrophilic substrate under compression, for example using a print head to inject the hydrogel precursor into the substrate. In some embodiments, the cohesive hydrogel precursor structure 184 has a surface that coincides with one surface of the substrate 182. In other embodiments, the cohesive hydrogel precursor structure 184 has a surface that extends beyond the surface of the substrate 182 opposite the compressed substrate region 183. The hydrogel layer 174 (FIG. 1C) extends beyond the surface of the substrate 172 and can be considered to be one embodiment of the cohesive hydrogel precursor structure 184. In some embodiments, the porous substrate is prepared by calendaring prior to printing. In some embodiments, the cohesive hydrogel precursor structure 184 has breaks, such as microfractures and / or cracks. The compressed substrate 172 / 182 can be a crosslinked gelatin substrate. In some embodiments, the compressed substrate 172 / 182 is a cellular sponge substrate. In some embodiments, the compressed substrate 172 / 182 is a compressed gelatin substrate, for example formed by compression of a rigid and / or cross-linked gelatin substrate. In additional or alternative embodiments, the compressed substrate 172 / 182 is biodegradable. Generally, the hemostatic patch 170 / 180 is relatively thin, such as having an average thickness of one centimeter or less, and is relatively flexible. The thickness, width, and length of the patch may be selected as appropriate for a particular application. The presentation of Figures 1A, 1B, 1C, and 1D as separate figures does not imply that features of different figures cannot be combined or suitably interchanged under the overall description of this specification.

[0062] The dimensions of the hydrogel precursor patch may be selected as appropriate for the appropriate application. Furthermore, the total thickness is divided into the thickness of the substrate and the thickness of the hydrogel precursor. In this paragraph and the next paragraph, the dimensions refer to the dimensions of the dry patch, and swelling from hydration is further described below. The area of ​​the patch is generally not particularly limited and may be selected based on the desired placement of the patch. In commercial applications, different sizes may be distributed as selected by the user. Practical constraints generally suggest that the patch area is 20 centimeters (cm) x 20 cm or less for human patients, but larger patches may be used and within these values, any smaller range may be selected, such as 5 cm x 5 cm, 10 cm x 5 cm, 2 cm x 4 cm, etc. By convention, several dimensions may be suggested for several applications. Different sizes may be sold for medical professionals to select the desired size. Generally, the patch may also be cut to size to fit the specific situation encountered, using tools available in an operating room environment.

[0063] The thickness of the patch may depend on a balance between the ability of the patch to bend to conform to the application site and the ability to absorb a desired amount of fluid in addition to resorption time. A thicker patch may be less flexible and take longer to hydrate and degrade, but a thicker patch may absorb more blood and other fluids. Similarly, a thinner patch may generally absorb less, be more flexible, and degrade faster, resulting in a shorter duration. The crosslinked hydrogel precursor layer generally provides all or most of the adhesion of the patch during initial application of the patch. The substrate may be selected to provide a significant amount of absorption of fluid. In some embodiments, the average dry thickness of the patch may be from about 0.25 mm to about 10 mm, in additional embodiments from about 0.3 mm to about 9 mm, in further embodiments from about 0.35 mm to about 8 mm, and in other embodiments from about 0.4 mm to about 6 mm. The average dry thickness of the substrate 102 / 152 / 172 / 182 may be about 10 mm or less, in some embodiments about 0.2 mm to about 8 mm, in further embodiments about 0.25 mm to about 7 mm, and in additional embodiments about 0.3 mm to about 5.5 mm. The average thickness of the precursor layer 104 / 154 / 174 may be about 25 microns to about 2 mm, in further embodiments about 30 microns to about 1.75 mm, and in other embodiments about 40 microns to about 1.5 mm. The precursor layer may partially penetrate the substrate. In some embodiments, a significant proportion of the precursor layer remains on the substrate, presenting a dry precursor layer for application of the patch. With regard to the evaluation of the average precursor layer thickness, the precursor load per unit surface area (g / cm) is used to calculate the average thickness. 2 ) to the precursor density (g / cm 3) or by applying the precursor layer over a non-porous substrate and measuring the average dry thickness, since the relatively dense nature of the precursor layer should not be substantially altered by the substrate. Generally, the patch may have these ratios for the thickness of the substrate and the hydrogel precursor coating, but in some embodiments, it is desirable for the dry substrate to be at least as thick as the dry hydrogel precursor layer, and the substrate thickness is at least about 60%, in further embodiments, 65% to 95%, and in other embodiments, about 70% to about 90% of the dry patch thickness. For ease of measurement, the substrate thickness includes any hydrogel precursor that penetrates the substrate. One of skill in the art will recognize that additional ranges of dimensions and thicknesses within the explicit ranges above are contemplated and are within the present disclosure. In general, the hydrogel precursor layer may be added without significantly impairing the porous and absorbent nature of the substrate material.

[0064] More generally, besides gelatin-based substrates, suitable substrates for patches can in principle be made of natural materials, synthetic materials, or combinations thereof. Synthetic materials for absorbent substrates include, for example, polyesters, polyurethanes, high molecular weight polyethylene oxide (PEO), or other reasonable synthetic polymers. Resorbable polyesters include, for example, poly(lactic acid), poly(glycolic acid), or copolymers thereof. High molecular weight PEO can be slowly soluble in water. Natural materials are generally modified to various degrees from their natural form, since they are generally appropriately processed for inclusion in medical products. Nevertheless, natural materials can provide desirable properties suitable for substrates, such as high absorbency of aqueous solutions, and degradation within a reasonable period of time for in vivo applications. Suitable natural materials include, for example, polysaccharides, and materials derived from extracellular matrix proteins. For example, polysaccharides that are derivatives of cellulose, pectin, hyaluronic acid, or chitosan can be used to make absorbent sheets. Commonly used materials are forms of cellulose including, for example, ester and ether derivatives such as cellulose acetate, or ethyl cellulose. Oxidized cellulose is a material that aids in hemostasis, but this material is generally considered to be poorly absorbent and may lead to post-operative complications, so hydroxycellulose, nitrocellulose or other forms may be suitable.

[0065] Collagen is an extracellular matrix protein that can be found in its native form in tristrand fibrils. Purified collagen can take a variety of forms, and gelatin is a partially hydrolyzed form of collagen. Collagen can be derivatized in other ways if desired. Highly absorbent, absorbent collagen sponges have been developed that can be used alone as hemostatic materials. Commercial versions are sold, for example, by Becton, Dickinson and Company under the Trademarks Avitene™ MCH and Avitene™ Ultrasponge. Gelita Medical GMBH sells gelatin (collagen-based) hemostatic materials that can provide the basis for patch substrates. Custom substrates can be formed using commercially available medical grade collagen or gelatin (e.g., from Gelita Medical or other sources) formed into sheets, optionally crosslinked, e.g., glutaraldehyde crosslinked, and dried, lyophilized. Crosslinking stabilizes collagen, but strong chemical crosslinks can significantly increase duration.

[0066] Gelatin can be thermally crosslinked and / or chemically crosslinked, for example with formaldehyde or glutaraldehyde, to mechanically stabilize the material suitable for substrates. Gelatin is a hydrolyzed form of collagen. The length of the thermal crosslinking again affects the duration. Without wishing to be limited by theory, it is believed that thermal crosslinking can affect the crosslinking of suitable groups that are in close proximity in the structure. In contrast, chemical crosslinking can form more complex crosslinked structures that can result in significant entropic stabilization. Sufficiently extended chemical crosslinks can result in an essentially permanent / non-degradable material. Chemically crosslinked collagen has been used for decades in prosthetic tissues, heart valves and other prosthetics. Prior to thermal crosslinking, the gelatin is placed into the desired shape and then heated, for example in an oven or similar. Generally, thermal crosslinking may be carried out at a temperature of about 100°C to about 200°C, and in further embodiments, about 120°C to about 180°C, for about 15 minutes to about 4 hours, and in further embodiments, about 25 minutes to about 3 hours. One of skill in the art can adjust the time and temperature to achieve the desired properties, such as porosity and mechanical stability, along with the duration of implantation in vivo, as further described below. Using thermally crosslinked gelatin materials, the substrate can be a foam, a nonwoven tufted material, or a nonwoven felt material. One of skill in the art will recognize that additional ranges of temperatures and times within the explicit ranges above are contemplated and are within the present disclosure.

[0067] Commercially available gelatin sponges are available in which the gelatin is foamed and may or may not be chemically cross-linked. The exemplary gelatin sponge in the examples is a commercially available material that is foamed and not cross-linked. The use of uncross-linked gelatin avoids concerns regarding the release of potential toxic chemicals used in cross-linking. The resulting foamed gelatin material has a porous structure with a sponge-like cell structure. The density and pore size can be adjusted by processing parameters. Commercially available materials can be designed with appropriate absorbency to absorb fluids in wounds. Compression of gelatin substrates has been found to significantly improve flexibility and not significantly change absorbency. Absorbency can be assessed by placing the sponge in a large volume of saline solution and the weight can be evaluated after the sponge is saturated and reaches a plateau for liquid absorption. In dense substrates, the swelling plateau may not be reached for a longer period of time, but in highly porous gelatin sponges, the plateau is reached more quickly, typically with the majority of the swelling reached after about 10 minutes. Waiting longer to measure after the swelling plateau is well reached, but measurements can be taken after 24 hours to capture swelling effortlessly if desired, but swelling measurements should be taken before the hydrogel significantly degrades. In highly expanded gelatin sponges, a significant proportion of swelling can occur in less than one minute, and substrates of higher density may not plateau for significantly longer periods. Substrates generally absorb liquids at least about 100%, in some embodiments at least about 150%, in further embodiments at least about 200%, in other embodiments at least about 250%, and in additional embodiments at least about 350% of their dry weight, and generally biocompatible substrates can absorb water in the range of 100 wt% to 2500 wt% of the dry patch weight. Generally, the initial uncompressed volume allows for some swelling and provides an approximate upper limit on the solvent swelling weight.In some embodiments, the compressed substrate (without the hydrogel precursor layer) can absorb at least about 80% of the liquid as the uncompressed substrate, in further embodiments at least about 90%, and in some embodiments at least about 92.5% of the liquid as the uncompressed initial substrate, which suggests possible swelling of the compressed substrate close to its uncompressed value. In examples, the compressed substrate absorbs liquid at greater than 98% relative to the uncompressed substrate material. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

[0068] With regard to the improvement in flexibility after compression, this can be evaluated against the corresponding uncompressed substrate material. Furthermore, a thinner uncompressed material may be more flexible than a thicker version, whose absorbency is roughly reduced by the change in thickness and the corresponding loss of mass. Therefore, it is appropriate to compare versions with approximately the same absorbency. Since flexibility also depends on the initial thickness of the substrate, as well as the material used to form the substrate, an attempt to quantify the improvement in flexibility may not be particularly meaningful. The flexibility of the substrates can be qualitatively compared by wrapping the substrate around a mandrel, where a more flexible substrate can generally be wrapped around a thinner mandrel without breaking. Thus, in some embodiments, a compressed substrate can be bent around a mandrel with a diameter of 5 mm and with parallel folded sides. However, the compressed substrate may lose mechanical strength. With regard to the force to bend the material, this force (bending strength) is reduced, so the material can be bent or folded more easily. Because the columnar strength is reduced, squeezing the two opposing sides together allows the material to be crushed with less force, which is reasonably subsequent to having already broken cells. The hydrogel precursor layer provides mechanical stabilization to the compressed substrate without a significant loss of flexibility along the axis parallel to the calendar rolls, which would result from breakage of the hydrogel precursor layer.

[0069] The compression of the substrate may be performed in one or more compression steps. In particularly interesting embodiments, at least the final compression is performed after the precursor layer is added onto the substrate, and at least one compression step is performed before the precursor layer deposition to allow the precursor layer to penetrate more while leaving the top surface of the precursor layer. Subsequent compression steps may be performed at progressively smaller compression thicknesses, but due to some reactivity of the material, subsequent compressions may be performed at compression thicknesses that may be the same or slightly wider. The initial gelatin sponge thickness provides the fundamental parameters for the final assembled structure, as modified by processing, which collectively determine the properties. The final compression is generally about 85% or less of the initial substrate average thickness, in embodiments about 65% or less, in some embodiments about 55% or less of the initial substrate average thickness, and in further embodiments in the interval of about 20% to about 50%. In some embodiments, the compression range may have a lower limit of 5%, 10%, 15%, 20%, 25% or 30%, and an upper limit may be 85%, 75%, 65%, 60%, 55%, 50% or 45%, and the range may include any one of these lower limits in combination with any one of these upper limits. The substrate material may recover to some extent from compression, but it may be desirable for at least about 40% of the compression step to be maintained (recovery of about 60% or less), thus preventing the gelatin from becoming too elastic, with a compression of 2 mm to 1.5 mm with recovery to a final average thickness of about 1.8 mm or less, although in some embodiments the recovery may be 100% without net compression. Generally, the recovery may be from about 0% to about 100%, in some embodiments from about 10% to about 90%, in other embodiments from about 15% to about 80%, and in other embodiments from about 20% to about 70%. A person of ordinary skill in the art will recognize that additional ranges of relative compression amounts and recovery within the explicit ranges above are contemplated and are within the present disclosure.

[0070] In principle, various techniques may be suitable for applying compression, but the use of calender rollers or the like introduces shear in addition to compression, as for example with respect to the use of flat plates. The shear along the edges passing through the rollers applies additional force to break the sponge's cell structure. In particular, when the hydrogel precursor layer is on a substrate, the shear tends to crack the hydrogel precursor layer, which further contributes to flexibility and faster hydration upon contact with bodily fluids. The nature of the cracks generally depends on the amount of compression and material properties, but the cracks or breaks may or may not extend through the entire thickness of the hydrogel precursor layer. Precise characterization of the breaks is not particularly relevant since they are randomly located, but generally, in some embodiments, there is a visible break for every square centimeter of the finished structure. Calender rollers are also particularly desirable for process flows for continuous production.

[0071] Calender rollers and related conveying systems are well known in various industrial contexts. Calender rolls are well established in polymer processing and food processing, and some equipment may be shared between different industries. A pasta roller is used in the example for convenience. Generally, commercially available calender rollers have an adjustable thickness. Several calender rollers may be arranged in series to perform successive calendering steps, for example with decreasing thickness, but other production forms may use the same calender roller in succession with appropriate adjustments between runs. As mentioned above, a hydrogel precursor layer may be formed before a calendering step, for example the last calendering step. The formation of the hydrogel precursor layer is described in detail below. Although a roll-to-roll process can in principle be performed, foamed gelatin is generally formed into blocks and other set shapes, which can be cut to the desired dimensions, including thickness. Therefore, the process system may be designed to handle sheets of gelatin sponge. In some embodiments, the sheets may be relatively large for subsequent cutting into individual patches for packaging. If the sheet is cut into individual sheets, this allows for the potential for waste of edge sections of the larger sheets, which may not be very uniform depending on process considerations.

[0072] Since the components of the patch tend to be hydrophilic and / or hygroscopic, the components may be dried / dehydrated prior to processing to form the patch. Suitable drying techniques may include, for example, drying under vacuum, drying under heat, drying under a desiccant, lyophilization, or the like, or combinations thereof. It may be desirable to obtain hydration levels of up to 5 weight percent water or less, in further embodiments about 3 weight percent or less, in further embodiments about 2 weight percent or less, or in some embodiments much lower. Water content may be determined by coulometric titration (Karl Fischer) or loss on drying methods. A person of ordinary skill in the art will recognize that additional ranges within the above explicit ranges of water content are contemplated and are within the present disclosure.

[0073] The hydrogel precursors can be selected to contact physiological solutions to provide the desired absorption and crosslinking, while remaining stable as a coating during storage under dry, typically refrigerated conditions for a suitable shelf life, e.g., at least 2 months, in some embodiments at least about 6 months. The nucleophilic group can be a protonated amine, where the acidic amine is protected from crosslinking reactions in its protonated form. A suitable electrophilic group crosslinks with the unprotonated amine upon contact in the same phase, whether co-melted in the mixture or dissolved in a solvent, which generally has a pH of at least about 7.1, causing the initially protonated amine to deprotonate.

[0074] With regard to buffering agents, the hydrogel precursors are not considered to be buffering agents, whether they change the pH or not, and in principle may provide some buffering functionality. The amine precursors are provided in an acidified form with acidic protons that function as protective groups to prevent crosslinking. Upon contact with body fluids at physiological pH, the acidic amines may be deprotonated and therefore crosslinked with the electrophilic precursor. The layer of uncrosslinked precursor may not contain any significant additional buffering agent, and the desired patch performance is found without the addition of buffering agents. The buffering agent may be considered to be any Bronsted base, which is generally an anion (B - ) Anions corresponding to strong acids, such as halide anions, do not act as aqueous buffers, and the amine precursors are generally provided as HCl salts or similar strong acid analogs.

[0075] Typically, pH is used to gate the crosslinking reaction, and the amines are provided in an acidified form that inhibits crosslinking. Therefore, avoidance of high pH buffers in the precursor layer avoids any premature crosslinking reaction due to activation by the buffer. As physiological fluids soak into the patch upon use, pH changes induced by physiological fluids rapidly deprotonate the amines and induce crosslinking. As the precursors are mixed or in direct contact within the dry patch, they crosslink rapidly, and the relatively high initial crosslink density results in good adhesion without the need to wait longer for more complete crosslinking. Gel time is further discussed below.

[0076] In hydrogel systems, a macromer, as defined below, may be advantageously used, which contains functional groups suitable for crosslinking monomers to form adhesive patches in situ, such as monomers, generally electrophilic groups that exhibit activity towards amine functional groups. Thus, multi-component hydrogel systems crosslink spontaneously upon activation of the components in contact with physiological fluids, but the two or more components are adequately stable for a reasonable process time prior to activation by physiological fluids. Such systems include, for example, a monomer (generally, but not necessarily, a macromer) that is a bifunctional or multifunctional amine in one component, and a macromer, such as an N-hydroxysuccinimide ester-containing moiety, with bifunctional or multifunctional electrophilic groups in the other component. The N-hydroxysuccinimide ester functional group promotes amide bond formation in reaction with amines and has been used in other medical hydrogels, and other suitable electrophilic precursors are described below. The N-hydroxysuccinimide ester is generally pendant to a hydrophilic core.

[0077] The hydrogel precursors may be crosslink-activated by physiological fluids with which they come into contact after delivery. The hydrogel precursors described herein may be designed to hydrate relatively quickly. The properties of the hydrogel and precursor solutions are further described below. Parameters that affect the properties include: functional group chemistry, crosslink density / molecular weight of the monomers, monomer composition, substrate composition, and patch structure.

[0078] The crosslink density of the resulting biocompatible crosslinked polymer is controlled by the overall molecular weight of the macromer and the number of functional groups available per molecule. Lower molecular weight between crosslinks, e.g., 600 Da, gives higher crosslink density compared to higher molecular weight, e.g., 10,000 Da. Higher molecular weight macromers with significant branching provide the desired gelatin time, in some embodiments, greater than 2500 Da to obtain an elastic gel. In some embodiments, the nucleophilic acid conjugated polymer (with amine) is not significantly lower in molecular weight than the electrophilic one. In some embodiments, it is the same or larger size.

[0079] Crosslink density can also be controlled by the ratio of nucleophilic and electrophilic groups in the mixed precursor materials. In a dry solid precursor layer, the gelation time depends heavily on the time to hydration, since crosslinking reactions can occur in water and amines deprotonate to become available for nucleophilic substitution. A rapidly hydrating substrate can aid in the hydration of the dried hydrogel precursor, and the size of the hydrophilic core in the precursor molecule can affect the hydration time. Without wishing to be limited by theory, it is believed that longer gelation times may be related to slower diffusion of physiological fluids into and / or acid-conjugated species from the in situ placed patch. Yet another method for controlling crosslink density is by adjusting the stoichiometry of nucleophilic to electrophilic functional groups. A 1:1 ratio of electrophilic to amine groups should provide the highest crosslink density, but the electrophilic groups in the precursor can in principle react with amines in physiological solutions as well as proteins in tissues. In the examples, the desired performance is obtained with a 1:1 ratio of functional groups.

[0080] monomer Monomers that can be crosslinked to form biocompatible structures, such as implants, may be used. As mentioned above, the monomers may be macromers, which may or may not be polymeric. The term polymer as used herein refers to a molecule formed of at least three repeating groups, which in turn may have reactive functional groups pendant to the polymer. In general, the term "reactive precursor species" refers to a polymer, functional polymer, macromolecule, or small molecule that can participate in a reaction to form a network of crosslinked molecules, such as a hydrogel. As mentioned above, to form a rapidly crosslinking hydrogel precursor system, the monomers are generally, although not necessarily, macromers, as defined below, because macromers generally allow for more rapid hydration in conjunction with more rapid deprotonation of amines.

[0081] The monomers may include, for example, biodegradable water-soluble macromers as described in U.S. Pat. No. 7,332,566 to Pathak et al. (hereinafter the '566 patent), entitled "Biocompatible Crosslinked Polymers With Visualization Agents," which is incorporated herein by reference. These monomers are characterized by having at least two polymerizable groups, which may or may not be separated by at least one degradable region. Upon crosslinking, the resulting polymer forms a coherent hydrogel that may persist indefinitely or until removed by degradation, which may include, for example, enzymatic reaction or hydrolysis. Generally, the macromers are formed by a core of a water-soluble, biocompatible polymer, such as a polyalkylene oxide, e.g., polyethylene glycol, which may be flanked by hydroxy-carboxylic acids, e.g., lactic acid, to form degradable esters or non-degradable amides. Suitable monomers, in addition to being biocompatible and non-toxic, may also be at least somewhat elastic after crosslinking or curing. For electrophilic compounds or compounds with amine groups, the core of the compound may have multiple arms or branches, each with a functional group suitable for crosslinking. PEG-based polymers with three or more arms are generally star polymers with a branched core from which extend the PEG polymer arms. As mentioned above, polyethylene glycol (PEG)-based monomers are well-established medical hydrogel precursors, and precursor compounds are commercially available with a variety of numbers of arms, molecular weights, and functional groups.

[0082] The nucleophilic functional group is typically an amine group. The amine group may be protonated as a protecting group or gated to control crosslinking. The nucleophilic amine group of the precursor may be designed to deprotonate significantly at physiological pH values, e.g., pH units of about 7.1 to about 7.6, while blood and tissues are generally in a narrower pH range in healthy individuals. Although macromers are exemplified to provide the desired properties, trilysine has been used as a poly-amine monomer in medical hydrogels, and similar compounds can be used. The electrophilic functional group may be selected to react with the amine in an addition reaction to form crosslinks. N-hydroxylsuccinimide ester is a desired electrophilic group, but other suitable groups are described below. One or both of the functional groups may be pendant to a hydrophilic core, which may help provide the desired swelling with liquids upon hydration. In some embodiments, the polymer may have hydrolytically biodegradable moieties or linkages, e.g., esters, carbonates, or other suitable linkages, although enzymatically degradable linkages may also be present in addition or in place of them. Several such linkages are well known in the art and are derived from α-hydroxy acids, their cyclic dimers (anhydrides), or other chemical species used in the synthesis of biodegradable moieties, such as glycolide, dl-lactide, l-lactide, caprolactone, dioxanone, trimethylene carbonate, or copolymers thereof. In particular, electrophilic monomers may be advantageously equipped with degradable linkages.

[0083] Generally, monomers that provide electrophilic functional groups and monomers that provide amine groups are macromers that result in more rapid hydration of the dried precursor layer. Macromers generally have a biologically inert water-soluble core with pendant reactive functional groups for crosslinking. When the core is a water-soluble polymeric region, the polymers that can be used can be natural or synthetic polymers. Suitable polymers for the core can include polyethers, such as polyalkylene oxides, such as polyethylene glycol ("PEG"), polyethylene oxide ("PEO"), polyethylene oxide-co-polypropylene oxide ("PPO"), co-polyethylene oxide block or random copolymers, poloxamers, such as Pluronic® F-127; and polyoxazolines, polyvinyl alcohol ("PVA"); poly(vinylpyrrolidinone) ("PVP"); and polysaccharides, such as hyaluronic acid, chitosan, dextran or digested cellulose and their derivatives. Based on the experience of many existing medical products, star-branched polyethers, more specifically polyethylene glycols (also known as poly(oxyalkylenes) or poly(ethylene oxides)), are particularly suitable. The acidic amine or electrophilic group can be located at the end of the arms of each branch or a portion thereof. For PEG precursors, a common designation in the field of medical hydrogels refers to the number and molecular weight of the arms together with the functional groups on the arms, for example, 4A15K NH2-HCl for a 4-arm PEG with a molecular weight of 15,000 Daltons and an acidic amine with chloride ion, or 8A20K NHS ester for an 8-arm PEG with a molecular weight of 20,000 Daltons and an N-hydroxysuccinimidyl ester functional group.

[0084] PEG-based hydrogels have found widespread use in medical products. As a result, they have been widely accepted and PEG-monomers with a range of functionalities are commercially available in medical grade. Polyoxazolines have attracted attention as a potentially desirable alternative to PEG-based products. Poly(2-oxazolines) have the structure -(CH2CH2N(COR))-, where the R group can be H, alkyl groups or other functionalities. Amine-terminated poly(2-ethyl-2-oxazolines) are available from Sigma-Aldrich. Terminal functional monomers do not allow crosslinking, but multifunctional electrophilic monomers with three or more functional groups can result in crosslinking. Poly(2-R-2-oxazoline) with 25% of the side chains carrying N-hydroxylsuccinimide (NHS)-ethyl groups was synthesized as described in U.S. Patent Application Publication No. 2019 / 0125922 to Bender et al. (entitled "Tissue-Adhesive Porous Hemostatic Product"), which is incorporated herein by reference.

[0085] Hydrogels formed by macromers with longer distances between crosslinks have generally been determined to be softer, more compliant, and more elastic. Thus, the polymers of the '566 patent may be enhanced in elasticity by increasing the length of the water-soluble segments, e.g., polyethylene glycol. The molecular weight of hydrophilic macromers as used herein, e.g., macromers with a polyethylene glycol macromer core, is generally at least about 2,000 Da, in some embodiments from about 2500 Da to about 500,000 Da, in other embodiments from about 5,000 Da to about 250,000 Da, in further embodiments from about 7500 Da to about 100,000 Da, in additional embodiments from about 10,000 Da to about 50,000 Da, and in other embodiments from about 15,000 Da to about 40,000 Da. PEG precursors in the lower portion of these molecular weight ranges may be liquid. As used herein, molecular weight (mass) has conventional units which may equivalently be Daltons or molar mass-grams / mole (in either case assuming the presence of natural isotopes), and for polymers, the molecular weight is generally reported as an average if there is any molecular weight distribution. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

[0086] The hydrogel precursors in the hydrogel precursor solution have a ratio of electrophilic functional groups to amine functional groups. The ratio of functional groups can change the crosslink density and properties of the resulting hydrogel. Generally, when the ratio of the number of electrophilic functional groups to amines is 1 to 1, the hydrogel can be sufficiently crosslinked, given sufficient time and lack of constraints. In some embodiments, the ratio of nucleophilic functional groups to electrophilic functional groups is 1 or greater. Generally, the ratio of electrophilic functional groups to nucleophilic functional groups can be about 0.8 to 1.2, in further embodiments about 0.9 to about 1.1, in further embodiments about 0.95 to about 1.05, in other embodiments about 0.98 to about 1.02, in additional embodiments about 0.99 to 1.01, and in some embodiments about 0.995 to about 1.005, although the ratio can be approximately 1:1. One of ordinary skill in the art will recognize that additional ranges of ratios within the explicit ranges above are contemplated and are within the present disclosure.

[0087] To achieve the desired ratio of functional groups, the functional groups can be distributed in various ways. The pendant functional groups extending from the core can be referred to as being associated with the arms of the precursor. The precursors generally have 2, 3, 4, 5, 6, 7, 8, 9, 10 or more arms. At least one precursor generally has at least 3 arms to obtain crosslinking, and 4, 6 or 8 arm precursors may be advantageous to obtain the desired hydrogel properties. To obtain a 1:1 ratio of functional groups, equimolar amounts of precursors can be used when they have the same number of arms, or the molar ratio can be adjusted accordingly when there are different numbers of arms in each precursor. Thus, twice the molar amount of a 4-arm precursor can be combined with an 8-arm precursor to obtain a 1:1 functional group ratio. With respect to weight ratios, the molar ratios can be adjusted accordingly based on relative weights, such as an 8-arm 10K MW (10,000 molecular weight) precursor being combined with twice the mass of an 8-arm 20K MW precursor to obtain a 1:1 functional group ratio. One of skill in the art can adjust these calculations to obtain a different number ratio of functional groups.

[0088] Functional Groups and Crosslinking Reactions The crosslinking reaction is generally designed to occur upon hydration with aqueous fluids that are essentially physiological fluids in vivo, surrounded by physiological conditions, although medical treatments may include some local dilution or modification of physiological fluids from their pure natural state, such as with disinfectants or other therapeutic measures, without altering the basic processing of the hydrogel precursors. To aid in hydration, the substrate may be wetted prior to application of the patch to tissue, as described further below. Unless specifically stated, references herein to physiological fluids may include some modification of natural fluids resulting from medical treatments. Thus, the crosslinking reactions occur "in situ", that is, they occur at localized sites, such as on organs or tissues within the body of a living animal or human. Due to the in situ nature of the reaction, the crosslinking reaction may be designed not to release undesirable amounts of heat of polymerization. Gel times for the desired treatment are described above, and sufficient crosslinking may generally be completed after 2 minutes to 10 hours, although other times outside this range may be acceptable. Longer complete crosslinking times may begin to compete with degradation times.

[0089] Some functional groups, such as alcohols or carboxylic acids, do not usually react with other functional groups, such as amines, under physiologically acceptable pH. However, such functional groups can be made more reactive by using an activating group, such as N-hydroxysuccinimide or its derivatives. Generally, several methods are known in the art for activating such functional groups. Suitable activating groups include, for example, carbonyldiimidazole, sulfonyl chloride, chlorocarbonate, aryl halide, sulfosuccinimidyl ester, N-hydroxysuccinimidyl ester (NHS), succinimidyl ester, succinimidyl amide, epoxide, aldehyde, maleimide, imide ester, etc. N-hydroxysuccinimide ester or N-hydroxysulfosuccinimide groups are desirable groups for crosslinking amine-functionalized polymers, such as amino-terminated polyethylene glycols ("APEG"), because they have been found to be acceptable for medical implants due to their long-term use in approved products. A more extensive description of medical hydrogels in general can be found in US Pat. No. 7,332,566 to Pathak et al. (entitled "Biocompatible Crosslinked Polymer With Visualization Agents"), which is incorporated herein by reference.

[0090] A suitable nucleophilic functional group is a polymer with a primary amine conjugated to an acid. Therefore, the other functional group used for crosslinking is generally an amine. The amine is a weak base. In some embodiments, the acid conjugate is HCl, forming an HCl salted amine, such as a PEG amine. The acid conjugate can be selected to match the approximate molar concentration of the amine. The advantage of the NHS-amine reaction is that the reaction kinetics results in rapid gelation, usually within about 10 minutes, more usually within about 1 minute, and most usually less than 30 seconds. The gelation time can be limited by the hydration time of the dried hydrogel precursor. Protonated amines are generally not suitable for carrying out nucleophilic substitution. Therefore, the precursor blend can be prepared at a suitable pH to maintain the amines substantially protonated before being delivered for contact with physiological solutions.

[0091] The crosslink density of the resulting biocompatible crosslinked hydrogel is controlled by the overall molecular weight of the monomers and the number of functional groups available per molecule. A lower molecular weight between crosslinks, e.g., 2000 Da, gives a higher crosslink density compared to a higher molecular weight, such as 100,000 Da. Higher molecular weight monomers can be used to obtain more elastic hydrogels, and correspondingly lower molecular weight monomers can be used to obtain less elastic hydrogels. Different applications may suggest different properties for the hydrogel.

[0092] Another way to control the crosslink density is by adjusting the stoichiometry of nucleophilic to electrophilic functional groups. A 1:1 ratio leads to the highest crosslink density. Generally, over time, as the hydrogel completes curing, the available crosslinking sites form crosslinks. If equal equivalents of electrophilic and nucleophilic are provided, nearly all functional groups can be expected to form crosslinks after sufficient curing. An equal number (or reactively equal) of the two types of agents generally results in the highest crosslink density. If different ratios of functional groups are used, the properties of the cured hydrogel will differ somewhat accordingly. Crosslink density can depend on the number of functional groups on the precursor molecules as well as the ratio of the precursor molecules. Non-stoichiometric ratios of electrophilic and nucleophilic groups can be used to vary the crosslink density if desired. The ratio of functional groups is further described above.

[0093] Degradable or non-degradable bonds In general, it is desirable for the patch to be degradable, and in some embodiments relatively quickly degradable. Therefore, when the patches are implanted, they do not last forever. For the patch to degrade, both the substrate and the hydrogel formed in situ degrade. Depending on the application, it may or may not be desirable for the hydrogel to be degradable by hydrolysis or biodegradation by enzymatic activity, but for hemostatic patches, the patch is generally designed to degrade quickly, so that it does not remain long after stable clotting. If it is desired that the biocompatible crosslinked hydrogel polymer is degradable or absorbable, one or more precursors may be used in which there is a degradable bond between the functional groups. As used in the art, an absorbable polymer may be referred to as biodegradable when absorbed under physiological conditions, whether or not it is degraded by biological action such as enzymatic cleavage. The degradable bond may also optionally function as part of the water-soluble core of one or more of the precursors. Alternatively, or in addition, the functional groups of the precursors may be selected such that the product of the reaction between them results in a degradable bond. For each approach, the degradable linkages can be selected such that the resulting degradable biocompatible crosslinked hydrogel polymer degrades or is absorbed within a desired time period, hi other embodiments, the functional groups and linkages to the functional groups can be selected to resist degradation under physiological conditions to substantially reduce or eliminate absorption of the patch.

[0094] In general, the degradable linkages are selected to degrade the hydrogel under physiological conditions into non-toxic products for removal from the patient by natural pathways. Illustrative enzymatically hydrolyzable biodegradable linkages include peptide bonds cleavable by metalloproteinases or collagenases. Additional illustrative biodegradable linkages can be functional groups on the core polymers and copolymers, such as hydroxy-carboxylic acid, orthocarbonate, anhydride, lactone, amino acid, carbonate, phosphonate, or combinations thereof. In an exemplary embodiment, the degradable linkages are esters formed by hydroxy-carboxylic acid moieties adjacent to electrophilic groups used for crosslinking. The esters can degrade gradually by hydrolysis under physiological conditions, with duration depending on the specific structure. To have non-degradable hydrogels, the esters formed by the hydroxy-carboxylic acid moieties can be replaced by amide groups, which generally do not hydrolyze under physiological conditions. Monomers with PEG cores are commercially available, for example, from Jenkem Technology, TX, USA, with N-hydroxysuccinimide electrophilic groups attached to amide bonds or alternatively to ester bonds. PEG-amines are also available from Jenkem with various numbers of arms and molecular weights. Desirable degradable electrophilic groups include, for example, N-hydroxysuccinimidyl succinate (SS), N-hydroxysulfosuccinimidyl succinate, N-hydroxysulfosuccinimidyl gluterate, succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ), or mixtures thereof. An example of a fast-degrading patch with a SS linker is described below. A mixture of degradable and non-degradable bonds, such as the amides described above, can be used to tailor duration, for example to form oligomeric species for removal by the body.

[0095] Hydrogel and Patch Properties The evaluation of patch properties can be performed in vitro under defined conditions, so that the properties are independent of biological conditions. Such evaluation is useful to describe patch properties that are important for practical use in vivo. In this context, the applicants describe measurements of gelation time, swelling, substrate porosity, burst strength and duration, and present corresponding measurements in the examples. However, for evaluation of patch performance in practical treatments, protocols can be used to provide appropriate limits of patch behavior under test conditions that mimic bleeding tissue, in order to provide reproducible conditions for patch evaluation. The following examples present the results of the in vitro tests, together with a comparison in practical use in an animal model. For dry patches, the density of the patch (substrate and precursor layer) is about 0.075 g / cm 3 ~about 0.5g / cm 3 The precursor layer alone may have a density of about 0.050 g / cm 3 ~Approx. 0.450g / cm 3 A person of ordinary skill in the art will recognize that additional ranges of densities within the explicit ranges above are contemplated and are within the present disclosure.

[0096] The gel time of the sample patch can be evaluated in the laboratory to provide a reasonable estimate of in vivo performance. The examples provide measurements made on specific samples. The gel time is evaluated by a commercially available texture analyzer. Texture analyzers are available from Texture Technologies Corp. / Stable Microsystems, Ltd. (e.g., model TA-XT Plus) and Brookfield Technologies (e.g., model CTX texture Analyzer). These systems are designed to analyze food and soft medical materials. The instrument is first calibrated with a standard test block according to the instrument's standard procedure. A TA-005 probe (Texture Technologies) with a 1 / 4 inch diameter and flat (or hemispherical) shape can be used with a 5 kg load cell. The sample holder is heated to 37° C. to track standard body temperature. The sample holder is a non-porous polymer foam block with a 1.5 mm hole in the center. An 8 mm diameter punch sample from the patch is placed precursor layer down and centered over the hole in the sample holder. To begin the test run, the tester is started and 67 microliters (μl) of 37° C. buffer solution (pH 8.0) is added to the center of the test sample for the 8 mm punch sample. The texture analyzer can be programmed accordingly to match these parameters. The force required to deform the patch by 0.4 mm is determined as a function of time.

[0097] A plot as a function of time produces a characteristic curve. Since the patch starts in a stiff, dehydrated state, the force is relatively high initially. Over the course of a few seconds, the patch hydrates and the force reaches a minimum. Crosslinking can be expected to begin and undergo initial processing during hydration. As crosslinking continues, the force begins to increase, indicating that a point has been reached where the material hardens due to crosslinking. The time at which the force begins to increase is considered to be the gelation time, which indicates the gelation point where the gel begins to harden. In these systems, use of the patch involves hydration, during which the solid precursor hydrates and begins to crosslink. Dissolution of the precursor is therefore negated by crosslinking. As hydration begins, the solid becomes soft until crosslinking has progressed sufficiently to begin to harden the hydrogel. The gelation process has different characteristics than solution-based hydrogel systems that start with dissolved precursors. As crosslinking continues after the onset of gelation, the force continues to increase. Measurements are taken in triplicate on three identical punches from the same patch, and the results are averaged. In the patches described herein, the gelation time is generally about 5 minutes or less, in further embodiments from about 3 seconds to about 3 minutes, in some embodiments from about 4 seconds to about 2 minutes, and in additional embodiments from about 5 seconds to about 1 minute. A person of ordinary skill in the art will recognize that additional ranges of gelation times within the explicit ranges above are contemplated and are within the present disclosure.

[0098] Patch samples may also be tested for burst pressure, and these values ​​are desirable to ensure that the samples have the desired performance in actual use. Burst pressure measurements are designed to provide standard test conditions for patches adhering to bleeding tissue. As described above, some patches may be formed with a compressed gelatin substrate, thereby desirably providing a more flexible structure and / or a more uniform substrate surface, while maintaining sufficient rigidity to resist substrate warping / distortion during coating. Results shown in the examples below suggest that patches with compressed gelatin substrates exhibit approximately the same burst pressure. Experience to date suggests that patches with compressed gelatin substrates exhibit more uniform performance. As described, following the description of the burst test, swelling may be evaluated using the same samples. The burst test may be evaluated on an apparatus designed to simulate bleeding tissue adapted for measurement according to ASTM F2392-04(2015). The ASTM protocol provides information regarding the surface of the test fixture that is adapted for use with the perforated plate of the test apparatus. Although commercial versions of such testing equipment are not available, a corresponding test is believed to be highly desirable for testing patches for clinical use. Therefore, as further described in the Examples below, a comparable testing apparatus was constructed with adjustments in its design that take into account and conform to the above-mentioned ASTM protocols.

[0099] The test used a calibrated syringe pump with a 60 ml syringe tube filled with saline and the pump set at 2 ml / min. A burst fixture was used with a cavity connected to the syringe pump, the cavity having a circular opening at the top. A pressure sensor, e.g., a digital manometer, is similarly connected to the cavity to measure the pressure in the cavity. To start the test, the cavity is filled using the syringe pump until it is almost full. The test block with the patch sample from the gel test is placed over the hole on the fixture with the patch punch sample facing up. Similarly, a hydrated patch pressed against the test block could have been used as well, but the use of the patch provides a uniformly prepared patch for burst testing after the gel test. In this configuration, the hole in the sample holder is centered in the burst fixture cavity. The top half of the fixture is then clamped on the top side of the test block to secure the sample holder, such that the hole associated with the cavity extends through the top half of the fixture to expose the sample from above. The pressure measured by the manometer is expected to increase once the upper fixture secures the test block.

[0100] With the top mounted fixture in place, the pump begins to pump water into the cavity, continuing to increase the pressure within the cavity. The pump is run until 1) liquid appears on the surface of the patch sample, 2) a popping sound is heard, or 3) the maximum pressure registered on the manometer remains constant for 30 seconds. Once the condition is reached, the pump is stopped and the maximum pressure value obtained is recorded as the burst pressure, which is recorded in millimeters of mercury (mm Hg). For patch samples as described herein, the burst pressure may be at least about 10 mm Hg, in further embodiments at least about 15 mm Hg, in further embodiments at least about 50 mm Hg, and in other embodiments from about 20 mm Hg to about 1500 mm Hg. One of ordinary skill in the art will recognize that additional ranges of burst pressures within the explicit ranges above are contemplated and are within the present disclosure.

[0101] Upon hydration, both the substrate and the precursor layer swell. Swelling can in principle be assessed in several reasonable ways, but here swelling is assessed by weight due to water retention. In embodiments based on compressed substrates, swelling by weight may not change appreciably, so the overall swelling assessment may be approximately unchanged compared to a comparable patch assembled on a non-compressed substrate. The dry weight of the patch before testing may be the initial reference point. Finally, swelling may be assessed based on incubation with aqueous fluid, but over a longer period of time the patch material may degrade. Essentially, swelling as described herein is assessed for a sufficient period of time for swelling to plateau when incubated in phosphate buffered saline at 37° C. (which may be after about 24 hours for dense substrates or around 10 minutes for highly expanded gelatin sponges). The sample for evaluation may be the same sample used for other property measurements, which gives a consistent estimate of swelling using the hydrated non-immersed weight as the reference point. If swelling is evaluated directly from a dry sample, air may be squeezed out of the sample in the early stages of swelling to achieve a suitable measurement without significant delay. In some embodiments, the last sample from the burst test may be used to further evaluate swelling. After completion of the burst test, the sample may be carefully removed from the sample holder. The sample is then weighed to obtain the initial weight. The weighed sample is then placed in a 50 ml tube with approximately 45 ml of phosphate buffered saline (PBS) and sealed. PBS is a standard buffer for medical and other biological applications, and generally contains sodium chloride, some potassium chloride, and phosphate. PBS is available from standard sources (Fisher Scientific, Sigma-Aldrich, etc.) and is classified in PubChem (https: / / pubchem.ncbi.nlm.nih.gov / compound / Phosphate-Buffered-Saline). The sealed tube is placed in a 37°C water bath. After 24±2 hours, the tube is removed from the water bath. The incubated samples are then removed, patted dry and weighed. The percentage swelling value is determined from the following formula: % swelling = 100 x (weight out-weight in) / weight in.

[0102] The "weight-in" value may be the dry weight, i.e., weight corresponding to an alternative reference point, such as weight after burst testing. For the patches described herein, swelling (after burst testing and after 22-26 hours of incubation in PBS) may be at least about 100%, in further embodiments from about 135% to about 350%, and in other embodiments from about 150% to about 300%. One of skill in the art will recognize that additional ranges of swelling within the above stated ranges are contemplated and are within the present disclosure.

[0103] Although the substrate has a high swelling weight, the volumetric swelling may be attenuated because it is initially porous. If the substrate is initially compressed to its initially formed dimensions due to broken cells, the swelling may restore some or most of the initial dimensions of the structure. Upon crosslinking and swelling, the volumetric change is generally more significant for crosslinked hydrogels, since the hydrogel precursor is initially dense. Therefore, after hydration and swelling, the increase in volume of the hydrogel layer may be more significant than the volumetric change of the substrate.

[0104] Another important characterization is the persistence of the patch. In vitro measurements can be performed for consistent measurements to mimic in vivo behavior. The persistence of the substrate and associated crosslinked hydrogel layer can differ from each other. The persistence behavior of the substrate can be evaluated by continuing the swelling test. Specifically, a sample packed in a tube with PBS can be kept in a heat bath at 37°C until the substrate of the patch sample is no longer visible. The point at which the substrate of the sample disappears is considered to be the end of the substrate's persistence. Generally, the substrate disappears in 96 hours or less, in further embodiments about 84 hours or less, and in additional embodiments about 15 minutes to about 72 hours. In some embodiments, it may be desirable for the substrate to disappear in about 48 hours or less. One of skill in the art will recognize that additional ranges of degradation times within the stated ranges are contemplated and are within the present disclosure. Generally, the hydrogel formed in situ will persist longer than the substrate.

[0105] Visualization Agent Advantageously, biocompatible crosslinked hydrogel polymers may contain a visualization agent to enhance their visibility during medical procedures, allowing for rapid confirmation of the orientation of the patch with respect to the surface to be placed against the wound. In principle, the substrate may have a visualization agent in addition to (same or different) or as an alternative to the hydrogel precursor layer. In an embodiment, the substrate has a patch with a blue visualization agent only in the hydrogel precursor layer. As used herein, visualization agent may refer to optical visualization (by color) or visualization using imaging modalities such as x-ray or ultrasound. Visualization agents are particularly beneficial when used in procedures with minimally invasive surgery (MIS, e.g., laparoscopy) due, among other reasons, to their enhanced visibility on color monitors. It is sometimes beneficial to provide color by adding a colored visualization agent to the precursor melt before casting the hydrogel layer on the substrate.

[0106] The visualization agent (optical) may be selected from any of a variety of non-toxic coloring substances suitable for use in medical implantable devices, such as FD&C BLUE dyes 1, 2, 3 and 6, indocyanine green, or dyes commonly found in synthetic surgical sutures. In some embodiments, green or blue colors are desirable because their visibility is good in the presence of blood or against a pink or white tissue background. Dyes may be added in trace amounts as a dehydrating compound in the melt blend to form a dry hydrogel layer.

[0107] The coloring material selected may or may not become chemically bound to the hydrogel. Additional visualization agents may be used, such as fluorescent (e.g., green or yellow fluorescent under visible light) compounds (e.g., fluorescein or eosin), x-ray contrast agents for visibility under x-ray imaging equipment (e.g., iodine compounds), ultrasound contrast agents (e.g., microbubbles), or MRI contrast agents (e.g., gadolinium-containing compounds). For some applications, the biocompatible visualization agents FD&C BLUE#1 and fluorescein-NHS may be particularly desirable. The visualization agent may also be a biologically active agent suspended or dissolved in the hydrogel matrix, or a material used to encapsulate the biologically active agent, if present.

[0108] As mentioned above, visually observable visualization agents may be advantageously used in some embodiments. Wavelengths of light between about 400 and 750 nm are observable as colors by humans (RK Hobbie, Intermediate Physics for Medicine and Biology, 2009). ndEd., pages 371-373). Blue is perceived when the eye receives light with wavelengths of about 450-500 nm, and green is perceived when the eye receives light with wavelengths of about 500-570 nm (ibid.). Furthermore, since the eye detects red or green or blue, combinations of these colors may be used to simulate any other color by simply exposing the eye to a proportion of red, green, and blue that is perceived by the human eye as the desired color. Blue as used herein means the color perceived by a normal human eye stimulated by wavelengths of about 450-500 nm, and green as used herein means the color perceived by a normal human eye stimulated by wavelengths of about 500-570 nm.

[0109] One or more visualization agents are present in the final electrophilic-nucleophilic precursor layer at a concentration suitable for visualization, e.g., about 0.0001 per square centimeter (g / cm 2 ) ~ approx. 0.5g / cm 2 The visualization agent may be present in a concentration range of from about 100 to about 1500 ppm, although higher concentrations up to the solubility limit of the visualization agent may potentially be used. In some applications, these concentration ranges have been found to impart the desired color to the hydrogel without interfering with the crosslinking time (as measured by the time for the reactive precursor species to gel). The visualization agent is generally not covalently bonded to the hydrogel. One of ordinary skill in the art will recognize that additional ranges of visualization agent concentrations within the explicit ranges above are contemplated and are within the present disclosure.

[0110] The visualization agent may serve to aid in visualization of the interface between the patch and the underlying tissue. In some embodiments, dyes are conjugated to electrophilic or nucleophilic end groups, allowing them to be incorporated into the patch for visualization in direct correlation with persistence. In some cases, the dyes are fluorescent, allowing visualization only under special lighting conditions, rendering the homogeneous gel otherwise invisible under normal visual conditions.

[0111] A user may use the visualization agent to view the hydrogel with the human eye or with an imaging device, such as a video camera, that detects the visually observable visualization agent. A visually observable visualization agent is an agent that has a color detectable by the human eye. Properties that result in imaging to an x-ray or MRI machine are not sufficient properties to establish functionality as a visually observable visualization agent. An alternative embodiment is a visualization agent that may not normally be visible to the human eye, but is detectable at different wavelengths, such as infrared or ultraviolet, when used in conjunction with a suitable imaging device, such as a video camera. Similarly, echolucent agents, such as air bubbles, may enhance imaging by ultrasound. Hydrogels with visualization agents for x-ray and / or ultrasound visualization are further described in U.S. Pat. No. 8,383,161 to Campbell et al., entitled "Radiopaque Covalently Crosslinked Hydrogel Particle Implants," which is incorporated herein by reference.

[0112] Radiopaque moieties can be introduced or covalently attached to the hydrogel functional groups by radiopaque precursor molecules. For example, triiodobenzoate can be attached to one of the arms of the precursor at an ester group. The total number of arms can be selected to achieve the desired crosslinking and radiopacity. CT numbers (also called Hounsfield units or numbers) are a measure of visibility under indirect imaging techniques. CT numbers of at least about 50 may be used, and in some embodiments, CT numbers can be from about 70 to about 2000.

[0113] Patch Formation and Storage The patch preparation method includes the steps of obtaining a substrate, applying a precursor layer, and packaging in a waterproof package, as well as one or more optional drying steps throughout the process. If the substrate is not commercially available, the method may further include preparing the substrate. If the substrate is commercially available, the processing may include cutting the substrate into appropriate sizes from a large block of material or a sheet of material. Some suppliers may provide sheets of gelatin substrates at the desired initial thickness. In commercial production, the processing may produce a sheet of patch material with a hydrogel precursor layer, which may then be cut to size, if appropriate. The size may generally include a set of commercial sizes for selection as appropriate by a medical professional, and with due care, the patch may be cut to size at the time of use, if desired, as described above. Applying the precursor layer may include delivering a melt blend or solution coating with a non-aqueous precursor solution, and layer deposition may optionally include forming sublayers. The moisture content can be reduced below a target amount for packaging, and processing is generally carried out in a closed environment with low water vapor levels since the materials are generally hygroscopic. The packaged patches are labeled for use and dated to reflect proper shelf life and proper distribution.

[0114] Substrates may be purchased in the form to be used or processed from suitable starting materials. For gelatin substrates, they may be obtained as foam sheets, which are then calendered, coated, and further processed in other ways. Purchased materials may be procured according to product specifications, the desired patch properties are described above, and substrates are correspondingly selected to meet these properties. Whether procured or further processed to prepare the material for patch formation, the substrate may be further dried before adding the precursor layer. Drying may be performed by various techniques, such as placement in a drying oven, contact with drying gas, isolation with a desiccant, combinations thereof, or the like. A suitable drying oven may be selected based on the size of the substrate material, and heating may be continued until the relative humidity falls below the target value. The heat treatment may be performed under appropriately mild conditions, so that the properties of the material are not altered in an undesirable way. Suitable desiccants, such as zeolites, calcium chloride, calcium sulfate, and the like, are commercially available.

[0115] In some embodiments based on gelatin sponge material as the substrate, the starting material can be purchased or produced. In either case, the material can be cut to a specified thickness for further processing, if appropriate. Generally, a specified patch size may not be cut to size until the hydrogel precursor layer is applied and compression is performed, although some final processing can be performed after cutting to size. Commercial sources of gelatin sponge material include, for example, Ethicon (USA), Gelita (Germany), Pfizer (Gelfoam®).

[0116] In some embodiments, the precursor layer may be formed using a solvent coating technique. The precursor solution may be non-aqueous to avoid introducing water (which must be removed to avoid deprotonation of the amine). Nevertheless, the precursor should be soluble in the solvent. Suitable solvents may include, for example, aromatic liquids such as toluene, xylene, chlorobenzene, ethylbenzene, or the like, alkanes such as hexane, or aprotic solvents such as tetrahydrofuran, ethyl acetate, acetone, acetonitrile, dimethylsulfoxide, blends of any two or more of these liquids, or the like. Generally, the concentration is selected to be as high as is compatible with the process conditions, e.g., viscosity, so that a uniform coating can be applied with less solvent. One skilled in the art may select the concentration based on the selected coating technique and the selected solvent. The solution may include a visualization agent and possibly other additives, e.g., a biologic / therapeutic agent. Suitable coating techniques include, for example, spray coating, jet printing, slot coating, screen printing, extrusion, or the like. As is well known in the art, extrusion generally offers a different range of viscosities and solids concentrations than spray coating.

[0117] The use of a solvent-free process has the advantage of avoiding the use of solvents and associated waste cleanup. The flow temperature of polyethylene glycol (PEG)-based precursors is fairly low, generally below 100°C, and is relatively weakly dependent on molecular size. Some low molecular weight PEG-based precursors may be liquid at room temperature, which may be blended with precursors that are solid at room temperature to form solid blends. Polyoxazolines generally have a moderately high flow temperature, which may be about 150°C to 250°C, depending on the side chains and molecular weight. Thus, the blend of PEG-based precursors can be formed at a relatively low temperature and suitably coated onto a substrate using any reasonable technique. The precursor layer may include visualization agents and possibly other additives, such as biologics / therapeutic agents. Although other coating techniques may be used for melt deposition, slot die coating may be a convenient technique, as suitable commercially available equipment can maintain the material at a suitable temperature while setting an adjustable coating thickness. Equipment may be selected to match the desired substrate size, and the substrate may be conveniently supplied as sheets or rolls of material. Suitable commercially available slot coating equipment includes, for example, FOM Technologies (Denmark), Yasui Seiki (Miriwek Film, Ink, IN, USA), and Coating Tech Slot Dies, Corp. (WI, USA).

[0118] 2-4 show various apparatus for forming a sealant patch 100 that may be used as a hemostatic patch. Referring to FIG. 2, a spray coating apparatus 200 has a precursor blend 202, which may be a molten blend or an organic solvent blend, in a bath 204. The precursor blend 202 may be a neat mixture of molten precursors. Alternatively, the precursor blend 202 may be a molten blend having one or more additional components to reduce viscosity. The additional components may include a solvent, such as, for example, an anhydrous organic solvent. The bath 204 may be capable of mixing and / or heating the precursor blend 202 prior to delivery through the spray nozzle 205. The precursor blend spray 206 is deposited on a substrate 208 to form a sealant patch composition having a coating of mixed, unreacted precursors on the substrate 208. In some embodiments, the formed sealant patch composition is dried to remove solvent and / or residual water. In some embodiments, the formed sealant patch composition is cut into individual patches and stored in a moisture-controlled package or container.

[0119] Referring to FIG. 3A, a slot die coating apparatus 300 has a molten blend 302 in a tank 304. The molten blend 302 can be a pure mixture of precursors. Alternatively, the molten blend 302 can have one or more additional components, such as organic solvents, to modify the viscosity. The tank 304 may be capable of mixing and / or heating the precursor blend 302 prior to delivery of the molten blend 302 through a slot die 306 to form a film 308 on a substrate 310. The apparatus 300 may use additional equipment between the tank 304 and the slot die 306, such as filters, pumps, pulsation dampeners, degassing units, and / or flow regulators. Generally, the film 308 is a continuous liquid film. Suitable slot coaters are commercially available, and the use of one commercially available slot coater is described in the examples. The slot die 306 can have a variety of head sizes, viscosity ratings, and stripe pattern options. The width of the film 308 can be selected based on the selection of the slot die 306. The width of the membrane and slot die may be selected to match the width of the desired product, or may be wider and cut to size, such as a multiple of the product width after coating, to form multiple products of each length of coated substrate. The slot die 306 may be used to control the deposition rate of the molten blend 302 onto the substrate 310, which correlates to the thickness of the precursor on the substrate. To perform coating deposition with a slot die, the die and substrate are moved relative to one another, which may include substrate movement, slot coater and die movement, or both. The apparatus 300 may be similarly used to coat solvent blends.

[0120] As mentioned above, it may be desirable to deposit liquid hydrogel precursor material, either melt or non-aqueous solution, onto and / or into a porous substrate under some degree of compression. As shown in FIG. 3B with respect to slot die coating apparatus 350, a slot die 356 may be used to control the deposition rate of molten blend 302 and to inject molten blend 302 into substrate 310. To effect injection of molten blend 302, slot die 356 and substrate 310 are moved relative to one another with slot die 356 compressing substrate 310 at the injection point. The force applied to substrate 310 through slot die 356, the depth of compression of slot die 356 into substrate 310, and / or the deposition rate may be adjusted to match the cohesive hydrogel precursor structure being formed. In some embodiments, the depth of compression is between about 0.02 mm and 2 mm, in further embodiments between about 0.05 mm and about 1 mm, and in additional embodiments between about 0.2 mm and about 0.8 mm. In other embodiments, the depth of compression is about 5% to about 30% or about 5% to about 15% of the thickness of the substrate before coating. One of ordinary skill in the art will recognize that additional ranges of compression for coating within the above stated ranges are contemplated and within the present disclosure. The porous substrate 310 may be somewhat elastic. Thus, with relatively light compression during coating, the substrate may recover to approximately the initial substrate thickness, as shown in FIG. 3B. A slot-die printhead, as appropriately modified, may be effective in applying the appropriate compression, although ancillary structures may be used adjacent the printhead to effect the appropriate compression, such as calender rollers or the like, which may be used for such purposes.

[0121] In some embodiments, referring to FIG. 3A, the substrate 310 may be moved as shown by directional arrow 312 during deposition of the melt blend 302, and the slot die 306 may be held in place. The rate of substrate translation along directional arrow 312 and the parameters of the slot die 306 may be adjusted to vary the thickness of the film 308. If multiple layers are desired, the substrate may be translated back in the opposite direction to form a second layer, or translated back uncoated and translated forward along directional arrow 312 to further apply a subsequent coating layer. Similar multiple coatings may be performed according to the embodiment of FIG. 3B. The substrate may be supplied as individual units that are coated and then cooled and / or dried for packaging. In other embodiments, the substrate may be provided as a larger sheet, which is cut to size after coating, and the larger sheet may or may not be provided in a roll. The dry gelatin substrate may generally be provided as a relatively stiff sheet.

[0122] In other embodiments, the substrate 310 does not move during deposition of the molten blend 302, but rather the slot die 306 (FIG. 3A) or slot die 356 (FIG. 3B) moves along directional arrow 314. In further embodiments, the substrate 310 does not move, and the slot die 306 or 356 moves along a direction indicated by directional arrow 314 for a period of time or until a selected travel distance is reached, and then moves in the opposite direction indicated by directional arrow 316 for a period of time or until a selected travel distance is reached. The film 308 can be formed from a single deposited layer of the molten blend 302, or multiple deposited layers of the molten blend 302. In some embodiments, the film 308 is formed by alternately depositing the molten blend 302 while moving the slot die 306 or 356 along directional arrow 314 to form a first deposited layer, and then depositing the molten blend 302 while moving the slot die 306 or 356 along directional arrow 316 to form an additional deposited layer over the first deposited layer. The alternating deposition may be repeated a selected number of times to achieve a film 308 of a desired thickness.

[0123] In some embodiments, the film 308 cools to form a coating 309 as a solid on the substrate. In many applications, the coating 309 may be a continuous, solid-phase hydrogel precursor network that coalesces with and is at least partially embedded in the substrate 310. In some embodiments, the film 308 and / or coating 309 are dried to remove solvent and / or residual water. The apparatus 300 may be used in forming a hydrogel precursor patch composition including the coating 309 on the substrate 310. In some embodiments, the formed structure comprising the hydrogel precursor patch composition on the substrate is cut into individual patches and stored in moisture-controlled packaging.

[0124] FIG. 4A is an embodiment of a roll slot die coating apparatus 400 having a substrate roll 402 from which a substrate 404 is moved under a slot die 405 by a belt 401 moving at a selected speed. The belt 401 can be any convenient conveyor system and can be replaced by a series of rollers or the like. A tank 406 holds a precursor blend 408, which can be a molten blend or an inert organic solvent solution. The precursor blend 408 can be a pure mixture of precursors. Alternatively, the precursor blend 408 can have one or more additional components, such as a solvent, to modify the viscosity. The tank 406 may be capable of mixing and / or heating the precursor blend 408 prior to delivery of the precursor blend 408 through the slot die 405, which can form a film 410 on the substrate 404. The coating apparatus 400 can use additional equipment between the tank 406 and the slot die 405, such as filters, pumps, pulsation dampeners, degassing units, and flow regulators. In some embodiments, the film 410 can be a continuous liquid film as deposited. The slot die 405 can have a variety of head sizes and viscosity ratings and stripe pattern options. The width of the film 410 can be varied by the selection of the slot die 405. In some embodiments, the width of the film 410 is between 1 cm and 10 cm. The slot die 405 can be used to control the deposition rate of the precursor blend 408 onto the substrate 404, which can affect the thickness of the film 410. In some embodiments, the slot die 405 can be used to control the deposition rate of the precursor blend 408 and to inject the precursor blend 408 into the substrate 404. To perform the injection of the precursor blend 408, the substrate 404 is moved under the slot die 405 with the slot die 405 compressing the substrate 404 at the injection point, for example as shown in FIG. 3B. The force applied to the substrate 404 through the slot die 405, the depth of compression of the slot die 405 into the substrate 404, and / or the deposition rate can be adjusted to suit the cohesive hydrogel precursor network that is formed.In some embodiments, the compression depth is about 0.02 mm to 2 mm, further embodiments about 0.05 mm to about 1 mm, some embodiments about 0.1 mm to about 0.8 mm, and additional embodiments about 0.2 mm to about 0.75 mm. In other embodiments, the compression depth is about 5% to about 30% or about 5% to about 15% of the thickness of the substrate before coating. One of ordinary skill in the art will recognize that additional ranges of compression of the substrate within the explicit ranges above are contemplated and within the present disclosure. The translation speed of the belt 401 can also be adjusted to affect the thickness of the film 410. The film 410 can be formed from a single deposited layer of the precursor blend 408 or multiple deposited layers of the precursor blend 408.

[0125] In some embodiments, the film 410 cools to form a coating 412. Generally, the coating 412 is a coherent solid coating, although portions of the substrate may remain uncoated if desired, and the coating may have cracks. The film 410 and / or coating 412 may be dried to remove solvent and / or residual water. The coating apparatus 400 forms a hydrogel precursor patch sheet including the coating 412 on the substrate 404. In some embodiments, a cutting unit 414 is used to cut the hemostatic patch sheet into patches 416. The patches 416 may then be placed into a waterproof package 418.

[0126] Figure 4B is an overview of a process 430 for enhancing medical patch properties by using a two-stage compression process. In the process 430, calendering the substrate 434 is the first compression step. Applying the precursor as a melt onto the substrate 438 is followed by a second compression step, calendering the coated substrate 442. Of course, other processing steps may be grouped around the steps identified in Figure 4B, such as additional calendering steps, cutting steps, drying, sterilization, packaging, and other suitable processing steps.

[0127] The methods and structures described herein improve the properties of the medical patch by contributing to the preparation of the substrate to receive the precursor composition. Calendering the substrate 434 may facilitate more consistent application 438 of the precursor onto the substrate as a melt, generally as a non-aqueous coating, while maintaining a relatively stiff substrate for carrying out the coating. Generally, calendering the substrate 434 may reduce the variability in thickness of the substrate and may also introduce minor breaks into the substrate's cell structure. The minor breaks may improve the penetration of the precursor into the substrate while maintaining adequate stiffness of the substrate, e.g., avoiding twisting or warping of the substrate during and / or after applying the precursor onto the substrate 438 as a melt. Calendering the substrate 434 may reduce the thickness of the substrate by up to 65% in some embodiments. In other embodiments, calendering the substrate 434 may reduce the thickness of the substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. In some embodiments, the compression of the substrate induced by calendaring the substrate 434 is at least partially reversible. In some embodiments, after calendaring the substrate 434, the thickness of the substrate partially recovers from the fully compressed thickness. In some embodiments, the recovery of the substrate thickness may ultimately result in a final thickness reduction of 75%, 60%, 50%, 40%, or 25% of the initial thickness reduction. After calendaring the substrate 434, applying the precursor to the substrate as a melt 438 is performed, and FIG. 4A illustrates one embodiment of this step. As described above, compression during deposition of the hydrogel precursor may be relatively light, resulting in little or no loss in thickness of the substrate after formation of the hydrogel precursor coating. A second compression step, forming a calendared coated substrate 442, is performed after the precursor coating is applied to the substrate and solidified. Solidification of the precursor layer may occur relatively quickly, either by exposure to the environment or, optionally, with a cooling step.Calendering the coated substrate 442 may improve the flexibility and hemostatic performance of the coated substrate, for example, by introducing appropriately induced breaks in the precursor coating and by introducing additional breaks in the substrate. Generally, calendering the coated substrate 442 may also introduce relatively minor to relatively significant breaks in the precursor coating. In some embodiments, the breaks include micro-scale breaks having a range of widths, lengths, and densities across the surface, which may be referred to as being broken into pieces to reflect the overall surface change. Some of the breaks may be surface breaks, while other breaks may have a depth similar to the penetration depth of the precursor into the substrate. Calendering the coated substrate 442 may reduce the thickness of the coated substrate by up to 65% in some embodiments. In other embodiments, calendering the coated substrate 442 may reduce the thickness of the coated substrate by 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40%. One of ordinary skill in the art will recognize that additional ranges of dimensional changes within the explicit ranges above are contemplated and are within the present disclosure.

[0128] Calendering the substrate 434 and / or calendering the coated substrate 442 may change the size, shape, and structure of the cells / pores in the substrate. Generally, the process 430 collapses the pores and breaks the scaffolding around the pores. Without wishing to be limited by theory, it is believed that the change in substrate porosity upon compression is related to improved performance of the flexible medical patch. In some embodiments, the process 430 imparts significant flexibility and other performance improvements to the coated substrate.

[0129] FIG. 4C is a diagram of a substrate process flow 450 through a processing device that creates patches 487 from gelatin sheets 451. The processing device may or may not be configured for continuous processing with the substrate sheet introduced at one end and patches exiting from the other end. To provide for cooling steps, solidification steps or the like, components of the processing device may be correspondingly configured to allow for these steps that may take longer than the active processing steps. Some processing parts may be configured for continuous performance of some of the processing steps as is convenient. Of course, an overall steady-state processing rate may be achieved to allow for efficient utilization of the processing equipment.

[0130] In some embodiments, the gelatin sheet 451 has a thickness of about 0.5 mm to about 1.5 cm. In the process flow 450, the gelatin sheet 451 is thermally crosslinked 452 in an oven 453 or other suitable heating device, the thermal processing unit also optionally including a control component. The oven 453 may be any convenient oven or the like that accommodates one or more gelatin sheets 451. In general, the gelatin sheet 451 may be of any convenient width and length. The thermal crosslinking 452 may be performed at a constant temperature for a selected period of time or may be performed using a selected heating profile. The oven 453 may optionally be integrated with a heater conveyor system (not shown), which may move the gelatin sheet 451 at a selected speed to achieve a target heating time or other target heating profile, the heater conveyor system may or may not be directly interfaced with other processing equipment.

[0131] 4C, following thermal crosslinking 452, crosslinked substrate 454 may undergo substrate compression 455. In some embodiments, crosslinked substrate 454 is at room temperature prior to substrate compression 455. In some embodiments, crosslinked substrate 454 has a thickness of about 0.5 mm to about 1.5 cm. Substrate compression 455 is performed using calender rollers 456 and 457. Calender rollers 456 and 457 are at a selected distance from each other and form a gap 458. Generally, gap 458 is less than the thickness of crosslinked substrate 454. In some embodiments, gap 458 is 65% or less of the thickness of crosslinked substrate 454. In other embodiments, gap 458 is 5% to 65%, 10% to 50%, 15% to 40%, or 20% to 40% of the thickness of crosslinked substrate 454. Calender rollers 456 and / or 457 may or may not be heated. Compared to the crosslinked substrate 454, the compressed substrate 459 has a broken cell structure instead of an intact cell structure. Generally, the compressed substrate 459 has a thinner and more consistent thickness than the crosslinked substrate 454. In some embodiments, the thickness of the compressed substrate 459 is from about 0.25 mm to about 1 cm, from about 0.5 mm to about 7 mm, from about 3 mm to about 6 mm. In some embodiments, the substrate compression 455 is integrated with a conveyor system 460 having a belt 461. The conveyor system 460 can be any convenient conveyor system, and the belt 461 can be replaced by a series of rollers or the like. In some embodiments, the calender roller 457 can be part of the conveyor system 460. A person of ordinary skill in the art will recognize that additional ranges of thicknesses and percentages within the explicit ranges above are contemplated and are within the present disclosure.

[0132] Now, referring to FIG. 4C, the compressed substrate 459 is subjected to a coating 462 using a coating apparatus 491. The coating apparatus 491 is similar to the roll slot die coating apparatus 400 of FIG. 4A, except that it is not configured for roll-based substrates. The tank 463 holds a precursor blend 464, which may be a molten blend or an inert organic solvent solution. The precursor blend 464 may be a pure mixture of molten precursors. Alternatively, the precursor blend 464 may have one or more additional components, such as a non-aqueous solvent, to modify the viscosity. The tank 463 may be capable of mixing and / or heating the precursor blend 464 prior to delivery of the precursor blend 464 through the slot die 465, which forms a film 466 on the compressed substrate 467. The coating 462 may use additional equipment between the tank 463 and the slot die 465, such as filters, pumps, pulsation dampeners, degassing units, and flow regulators. In some embodiments, the film 466 may be a continuous liquid film as deposited. The slot die 465 may have a variety of head sizes and viscosity ratings and stripe pattern options. Suitable slot die coaters are commercially available. The width of the film 466 may be varied by the selection of the slot die 465, and generally the width may be any reasonable value. In some embodiments, the width of the film 466 is between 1 cm and 100 cm, or in some embodiments, between about 2 cm and about 20 cm. The slot die 465 may be used to control the deposition rate of the precursor blend 464 onto the compressed substrate 467, which affects the thickness of the film 466. The translation speed of the belt 461 may also be adjusted to affect the thickness of the film 466. The film 466 may be formed from a single deposited layer of the precursor blend 464 or multiple deposited layers of the precursor blend 464. In some embodiments, the film 466 may be formed as a coherent hydrogel precursor network. In some embodiments, the film 466 is formed by injecting the precursor blend 464 into the compressed substrate 467 while further compressing the compressed substrate 467 at the injection point. In some embodiments, the film 466 cools to form a coating 468 .Generally, coating 468 is a continuous solid coating, although portions of the substrate may remain uncoated if desired. Film 466 and / or coating 468 may be dried to remove solvent and / or residual water. In some embodiments, the thickness of coating 468 is within the ranges as described above, which may penetrate into the compressed substrate. In some embodiments, coating 468 is part of a coherent hydrogel precursor structure that at least partially penetrates into compressed substrate 467. In some embodiments, coating 468 is part of a coherent hydrogel precursor structure that has a surface that matches one surface of compressed substrate 467. In some embodiments, cutting unit 469 is used to remove leading portion 470. Removal of leading portion 470 may provide a more consistent coating on patch 487.

[0133] Next, coated substrate 471 having coating 472 and compressed substrate 473 undergoes coated substrate compression 476 to form compressed coated substrate 477. Coated substrate compression 476 may be performed using calender rollers 478 and 480. Calender rollers 478 and 480 are at a selected distance from each other to form gap 481, as shown in FIG. 4D. Generally, gap 481 is less than the thickness of coated substrate 471. In some embodiments, gap 481 may be 75% or less of the thickness of coated substrate 471. In other embodiments, gap 481 is 15%-70%, 20%-65%, 22%-62%, or 30%-60% of the thickness of coated substrate 471. In some embodiments, the thickness of compressed coated substrate 477 is about 0.3 mm to about 1 cm, and in other embodiments, about 0.5 mm to about 5 mm. Calender rollers 478 and / or 480 may or may not be heated. Compressed coated substrate 477 includes a broken coating 482 and a broken substrate 483. Generally, compressed coated substrate 477 is thinner and more flexible than coated substrate 471. In some embodiments, broken coating 482 has microfractures of varying width, length, and depth across its surface, essentially exhibiting a shattered surface. In some embodiments, broken coating 482 has a relatively constant ratio of broken surface area to total surface area across the majority of its surface area. In some embodiments, edges of broken coating 482 are different than other areas of broken coating 482. In some embodiments, broken coating 482 has a thickness of about 0.1 mm to about 8 mm, about 0.15 mm to about 7 mm, about 0.2 mm to about 5.5 mm, about 0.25 mm to about 5 mm, about 0.35 mm to about 4.5 mm, and in some embodiments, about 0.5 mm to about 4 mm. In some embodiments, the thickness of the compressed substrate 483 is from about 0.1 mm to about 9 mm, from about 0.15 to about 8 mm, from about 0.25 mm to about 6 mm, from about 0.5 mm to about 5.5 mm, from about 0.75 mm to about 5 mm, and from about 1 mm to about 4 mm. In some embodiments, the coated substrate press 476 is integrated into a conveyor system 460 having a belt 461, which also conveys the substrate through the substrate press 455.In some embodiments, the calender rollers 480 may be part of the conveyor system 460 .

[0134] Next, the flexible hemostatic patch sheet 486 may undergo cutting 484. During cutting 484, a cutting unit 485 is used to cut the flexible hemostatic patch sheet 486 into patches 487, which may include cutting in terms of length and / or width. During optional packaging 488, the patches 487 may be placed in a waterproof package 490.

[0135] Processing may be performed in a controlled atmosphere, e.g., under dry nitrogen, other inert gas, or the like. After formation of the patch, it may be packaged in a moisture resistant package, e.g., a polymeric and / or foil pouch, or the like, under dry inert gas. The patch may be heated, e.g., at 40°C to 90°C, to induce further drying. The package may include a packet where an internal desiccant helps maintain dryness. The patch may be sterilized, e.g., using radiation after packaging. Sterilization may be under conditions that do not induce significant amounts of cross-linking. The package is appropriately labeled under regulatory guidelines for medical use and marked with an expiration date.

[0136] Storage of the patch is typically performed in moisture-resistant packaging. In some embodiments, the patch is heat-sealed in a foil pouch. To extend storage time, it may be desirable to store the patch under refrigerated conditions. Generally, the patch may be stored at a temperature of about 5° C. or below, or perhaps at standard refrigerator temperatures ranging from 1° C. to 7° C., although lower temperatures may be used as desired. For shorter storage periods, the patch may be stored at room temperature. At refrigerated temperatures, the patch may be stored for at least 2 months, in further embodiments at least 1 year, in additional embodiments 3 months to 3 years, and in some embodiments 6 months to 2.5 years. One of skill in the art will recognize that additional ranges of storage temperatures and times within the above stated ranges are contemplated and within the present disclosure. Patches that exceed their storage life may be identified by a lack of sufficient adhesion due to premature crosslinking or premature hydrolysis that removes electrophilic groups for crosslinking.

[0137] Biologics and Drugs The patch may include a biologic in addition to an optional visualization agent. The optional biologic or drug may be, for example, an agent that promotes blood clotting and / or healing. Thrombin may be added to the patch, but good hemostatic function was obtained without the complications of adding blood products to the patch composition. Due to the rapidly resorbing patch material, the patch may degrade before any significant concerns regarding adhesion formation or microbial contamination arise. However, an antimicrobial agent may be added if desired. In further embodiments, the therapeutic agent may include an analgesic, an anesthetic, a steroid, an antibiotic, a steroid, an anti-infective, an anti-inflammatory, a non-steroidal anti-inflammatory, an anti-proliferative, or a combination thereof. These modalities may be effectively used for localized drug delivery, thanks to the patch providing local adhesion and a depot for the added drug or biologically active agent.

[0138] Patch Use and Medical Indications The medical patch described herein is particularly useful for use as a hemostatic patch. Hemostatic patches are applied over an area with compressive force to stop bleeding with minimal, light or moderate bleeding. The patch may or may not contain a therapeutic agent, such as a compound that promotes clotting, and in the examples, effective hemostasis is demonstrated without any bioactive agent. The patch may be used more generally in contact with exposed tissue without the need to address controlling significant bleeding, such as for surgical closure applications. Activation of the crosslinks of the patch is triggered upon contact with any biological fluid. With the appropriate substrate and thickness, the patch may be relatively flexible and conformable even when dry, a feature that may be exploited in some applications.

[0139] Generally, the patch can be delivered directly onto the wound site, for example, in an open surgical procedure. In an alternative embodiment, the patch can be used in a laparoscopic procedure, since the patch is flexible enough for delivery through a trocar. The patch is conveniently applied over the wound with the hydrogel precursor layer facing the wound, but instead, the patch can be inserted into the wound, for example, folded with the hydrogel precursor side facing outward, so that the patch seals the wound.

[0140] To provide further patch delivery options, FIG. 13A shows patch 750 folded into a loose bellows shape. FIG. 13B shows a process 800 in which bellows-folded patch 801 is introduced into cannula 803 by forceps 805. Process 800 can be used to present bellows-folded patch 801 to a treatment site. FIG. 13C shows an embodiment in which patch 806 is bellows-folded and then laterally folded. FIG. 13D shows a process 810 in which bellows-folded and laterally folded patch 812 is introduced into cannula 814 by forceps 816. Process 810 can be used to present bellows-folded and laterally folded patch 812 to a treatment site. In some embodiments, process 800 / 810 can be used to preload cannula 803 / 814 for future use. In some embodiments, process 800 / 810 may be used to preload cannula 803 / 814 for packaging as a "preloaded" patch. In some embodiments, process 800 / 810 may be used with a tubular applicator in place of cannula 803 / 814. Patch 750 and patch 806, respectively, provide a more compact shape than a flat patch, which may be advantageous in some applications, such as laparoscopic surgical applications.

[0141] 14 is an illustration of a patch delivery for use in a laparoscopic procedure 820, where a bellows fold patch 824 is introduced to a laparoscopic site 831 via a cannula 826 using forceps 828. Forceps 830 are introduced to the laparoscopic site 831 via a cannula 834. Forceps 830 may help guide the bellows fold patch 824 to a treatment site 838. In some embodiments, the treatment site 838 may be a wound site or a surgical site that is being prepared for closure. In some embodiments, the bellows fold patch 824 may be used in a laparoscopic procedure 820 to provide hemostasis. In some embodiments, the coating of the bellows fold patch 824 may be cracked at the folds. In some embodiments, the cracks in the coating of the bellows fold patch 824 may extend to the substrate surface. Generally, the bellows fold patch 824 may self-heal the cracks due to swelling when hydrated by fluid at the treatment site.

[0142] The hemostatic patch can be ground or chopped as desired for use as a filler, either separately or together with another patch or patch portion. Granular compositions of the chopped patch formulations or analogs described above can be delivered through a cannula attached to a bellows-type device. Such formulations can be useful in sealing or controlling bleeding from extensive oozing areas of tissue.

[0143] In some embodiments, the patch may be moistened with a sterile aqueous solution, such as saline or water for injection, immediately prior to application to the tissue to initiate hydration. Generally, the patch is applied to the tissue with a sterile gauze pad or the like over the surface of the patch to facilitate the application process, and as used herein, a gauze pad refers to a pad of any non-adhesive absorbent material. Approximately equal pressure may be applied to the patch using the gauze pad for a period of time to allow adhesion. The selected time is generally at least about 5 seconds, in further embodiments at least about 8 seconds, in some embodiments from about 10 seconds to about 4 minutes, and in other embodiments from about 12 seconds to about 2 minutes. One skilled in the art will recognize that additional ranges of times within the above stated ranges are contemplated and are within the present disclosure. The placement of the patch may include the use of a single patch or the placement of multiple medical patches over the bleeding defect. The additional medical patches may overlap at least a portion of the first medical patch.

[0144] With respect to wounds, bleeding can be stopped by the use of the patch in a process called hemostasis. Hemostasis involves clotting so that bleeding stops and can be considered the first stage of wound healing. After hemostasis, there is no more blood from the wound. Using the patches described herein, hemostasis can generally be achieved within about 5 minutes, and in some embodiments, 3 minutes or less. A person of ordinary skill in the art will recognize that additional ranges of hemostasis times within the explicit ranges above are contemplated and are within the present disclosure.

[0145] A specific use of interest includes applying the patch to wounds on or in organs or on blood vessels. Broadly speaking, hemostasis can include any wound repair, but the degree of bleeding can vary widely. The patches described herein can be used in the context of any degree of bleeding, but as demonstrated in the examples, they can be effective in heavy bleeding. In the context of surgical procedures, the patch can be used to place in blood vessels, liver, intestines, uterus, pancreas, other organs, orthopedic applications such as bone and connective tissue, or in general any surgical wound, as well as procedures involving wounds caused by injury. In some embodiments, the patch can be placed along the skin to close wounds on the surface of a patient or to terminate a surgical intervention.

[0146] While any tissue wound in general may be effectively covered by the patch described herein, the patch may be particularly effective for covering wounds in organs with significant bleeding tendency. Suitable organs include, for example, bones, glands, digestive organs, pulmonary organs, urinary organs, reproductive organs, blood vessels, interfaces with natural or synthetic grafts, or combinations thereof. In some embodiments, the organ is an artery or vein, and the organ may be generally natural, graft, or combinations thereof. In particular, the patch may be applied to a bleeding defect. The bleeding defect may be, for example, a suture line, a puncture wound, a bullet wound, a cavity, a gouge, a biopsy punch hole, a graft interface, or combinations thereof. The placement of one or more patches may include placing one or more medical patches on a bleeding defect of a non-flat geometric shape, which is often determined by the shape of the organ. The placement of the patch may include wrapping one or more medical patches on the organ. The degree of bleeding from the organ may be evaluated based on the Spot Grade bleeding score or other recognized bleeding scale.

[0147] In some embodiments, the patch itself is rolled in a pre-folded or "pre-loaded" form, such as shown in Figures 13A and 13C, allowing deployment from a tubular applicator using a mandrel or plunger-like mechanism to present the patch near the treatment site. Pre-loading the patch is useful for laparoscopic applications, where insertion through a thin tubular passageway is involved, and the patch can be further moved to the hemostasis site upon introduction through a laparoscopic manipulator, which also applies pressure to the patch to apply it to the wound. In other embodiments, the pre-loaded form places a rolled or cylindrical patch that can be delivered to defects such as bullet or puncture wounds where hemostasis due to the geometry of a flat substrate is less than ideal. In more embodiments, the pre-formed patch-mandrel relationship can result in delivery of a geometry less than ideal for hemostasis using a flat patch, where the mandrel surface has a desired shape that allows the patch to conform to the wound.

[0148] One application envisioned is a conical preformed shaped patch mated with a conical mandrel to produce hemostasis after loop excision of cervical tissue (LEEP). In this situation, the mandrel and preformed patch shape act to fill the irregular conical depression left from the LEEP procedure, and the mandrel can be removed after the patch is adhered and achieves hemostasis. Figures 12A and 12B show one embodiment of the above application. Figure 12A shows a conical hemostatic patch 700 being placed into the cervix 704 using a conical mandrel 702. Figure 12B shows a hemostatic patch 710 placed within the cervix 704. The left inset shows the conical mandrel 702 providing pressure to the conical hemostatic patch within the cervix 704. The inset on the right shows the conical mandrel 702 removed and the placed hemostatic patch 710 adhered to the irregular conical depression in the cervical tissue. In this and similar shaped embodiments, the patch is heated to soften the precursor layer so that it molds to the mandrel or is otherwise molded just to the desired shape. When cooled on the mandrel, the shape can be essentially maintained for deployment.

[0149] In more embodiments, the patch is soft, conformable, and can be used for additional gynecological applications through processing or pre-wetting. Some embodiments use conformable patches to stop bleeding at hysterectomy after performing a cesarean section. In additional applications, the softening patch can be used transcervically for postpartum bleeding stasis. Postpartum bleeding can be a serious concern for the mother causing rapid blood loss, hypotension and shock, which can lead to death. In some circumstances, following failure of therapeutic procedures and manual compression to stop bleeding, a softening patch that can be delivered transvaginally / transcervically to conform to the irregular intrauterine surfaces would eliminate the need for more extreme outcomes of surgical intervention, hysterectomy, or death. Ideally, rapid hemostasis by the patch within 1-2 minutes would be followed by rapid resorption, reducing interference with any additional future medical diagnosis. Multiple patches can be used until hemostasis is achieved.

[0150] In some embodiments, the patch is wetted immediately prior to delivery to the application site, although placement of the patch or patches may be performed without pre-wetting the medical patch or patches. In some embodiments, placement of the patch or patches includes wetting the medical patch or patches with unbuffered water or unbuffered saline before and / or after placement. Whether or not the patch is pre-wetted, the patch hydrates relatively quickly. The precursor crosslinks to form a hydrogel, so that the precursor layer becomes adhesive to the application site. Typically, the precursor layer hydrates and adheres to an organ or other tissue in about 2 minutes or less.

[0151] Ophthalmic applications may include patches with a substrate that serves to prevent adhesion of the reactive precursor to the applicator or user during application to a wet ocular surface. In some embodiments, the substrate is rapidly dissolving or removable and is present only long enough to prevent adhesion during application. In other embodiments, the substrate is non-resorbable and continues to provide structural support to the blended molten precursors and is removed after the precursors are applied. Ophthalmic applications of premixed precursor melts containing therapeutic agents for the treatment of ocular surface conditions (e.g., to control post-operative pain) and / or for the treatment of the anterior chamber are envisioned. In such embodiments, a peelable backing may be used to apply the molten precursor plus therapeutic agent to the fornix of the eye and then removed following the initiation of crosslinking. In some cases, the melt blend of precursors may be less compatible with the substrate, reducing adhesion to the substrate during application. In other situations, the molten precursors are preformed and cut to the insertion shape, with the substrate backing added only afterwards or prior to application. If the substrate is added after making the unreacted blend, a binder such as low Mw PEG liquid may be used to improve attachment of the melt blended precursor to the substrate during storage or immediately prior to application. One embodiment may include molten precursor water attached to a disposable applicator substrate that can be administered to the fornix of a patient's eye and then discarded.

[0152] From this embodiment, various therapeutic agents can be delivered in sufficiently large amounts for a potentially short period of time under patient self-administration. The larger therapeutic loading allows the use of a wider range of drug substances with low potency. High potency candidates are restricted to ocular implants that are limited to low-volume applications, such as punctal plugs, anterior, posterior and suprachoroidal injections. An example is the use of NSAIDs or bupivacaine for local fornix delivery instead of highly potent corticosteroids, which may have off-target issues such as elevated intraocular pressure resulting from long-term use. In these embodiments, removing the need for only highly potent therapeutic agents broadens ocular applications to the eye, such as treating inflammatory pain, dry eye, and infection.

[0153] In terms of surgery, the patch generally provides the desired burst strength, although sutures, such as dissolving sutures, may be used if desired. In degradable patches, the applied patch may be sealed within the patient's body and left to safely degrade at a time appropriate for hemostatic stabilization. Generally, no further intervention is required for the patch, although in rare cases, supplemental wound care may be provided. In in vivo use, the patch generally resorbs into the body by degradation for removal, generally through the kidneys, completely within 28 days, within 21 days in further embodiments, and within 7 to 14 days in additional embodiments. One of skill in the art will recognize that additional ranges of time within the above stated ranges are contemplated and are within the present disclosure. In alternative embodiments, the patch may be designed such that the hydrogel is essentially non-resorbable so that it may last for an extended period of time.

[0154] FIG. 5 is a diagram of a hemostatic patch 501 wrapped around a tubular organ 504. In some embodiments, the tubular organ 504 is an artery or a vein. The wrapped hemostatic patch 501 may have a tail 506 formed by connecting two ends of the hemostatic patch 501. The hemostatic patch 501 may be dry before wrapping or pre-wetted. Examples 5 and 6 illustrate wrapping of a suture on a femoral artery with a hemostatic patch 501. Example 6 illustrates wrapping of a hemostatic patch 501 using two layers of wet gauze and the hemostatic patch 501. As illustrated in Example 5, the hemostatic patch may be placed on a tubular organ and / or a tubular graft without wrapping. Example 6 illustrates a non-wrapping process using a disk-shaped hemostatic patch to establish hemostasis in a cavity-type bone defect.

[0155] Figure 6 is a diagram of a hemostatic patch 512 placed on a non-tubular organ 514. Examples 3 and 4 illustrate the placement of a hemostatic patch 512 on a liver defect including concave and convex defect surfaces. Figure 7 is a diagram of a hemostatic patch 518 placed on skin 520.

[0156] 8A-8D illustrate the method of operation of the hemostatic patch. FIG. 8A shows a bleeding defect 600 in tissue 604 through which blood 606 is flowing. FIG. 8B shows a hemostatic patch 607 placed on tissue 604. The hemostatic patch 607 is placed with the substrate 608 facing away from the bleeding defect 600 and the molten blend layer 610 facing towards the bleeding defect 600. Blood 612 from the bleeding defect 600 is drawn into the hemostatic patch 607, causing the precursors in the molten blend layer 610 to dissolve and interact to form a crosslinked hydrogel layer 616 (FIG. 8C). In some embodiments, the molten blend layer 610 reacts to form a crosslinked hydrogel layer 616 within 30 seconds of placing the hemostatic patch 607 on the bleeding defect 600. Figure 8C also shows that the substrate 618 is adapted to allow the hemostatic patch 620 to adhere to tissue 622 to seal the bleeding defect 600, creating a hemostatic defect 624. Figure 8D shows the healing tissue 626 into which the hemostatic patch 620 has been absorbed. EXAMPLES

[0157] Examples 1-8 relate to the overall formation of hydrogel precursor layers and demonstration of hemostatic efficacy for several model systems. Example 9 relates to the evaluation of compressed substrate properties, as well as patch formation and properties of the resulting patches.

[0158] Example 1: Preparation of Hemostatic Patch Samples This example describes the preparation of a hemostatic patch sample.

[0159] Hemostatic patch samples were prepared by melt coating a dry blend of two hydrogel precursors onto a porcine gelatin substrate. Various gelatin / collagen substrates were prepared, as shown in Table 1. Each substrate was crosslinked, with light crosslinking referring to less than about 20% crosslinking and high crosslinking referring to greater than about 20% crosslinking. Substrates A, B, and D were characterized by having small (micron-sized or smaller) pores and greater than 80% porosity as measured by mercury intrusion porosimetry. Each substrate was prepared for coating by drying in an oven under ambient air at a temperature of 35° C. for 18 hours or until the relative humidity of the oven was less than 5%. The thickness of the gelatin substrate after drying was approximately the same as the thickness before drying. For each patch sample, the first hydrogel precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 15,000 Da and succinimidyl glutarate (SG) functional end groups (8A15k PEG SG, Jenkemusa). The second hydrogel precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 20,000 Da and HCl chloride amine functional end groups (8A20k PEG Amine-HCl, Jenkemusa). The first and second precursors were measured in powder form and then melt blended in a glove box with a trace amount of FD&C Blue#1 in a heated roller system at a temperature above 45°C. The molten precursor blend was delivered to a liquid dispensing system (Vulcan™ Jet Dispenser, Nordson). A single coating layer of the molten blend was applied to a dry gelatin substrate under inert gas conditions with a width of 0.5 mm per pass and a line speed of 50 mm / s until the total width of the coating was approximately 20 cm. The coating thickness was approximately 0.25 mm. The mixed precursor coated substrate was allowed to solidify at room temperature under inert gas conditions. The resulting thickness of the coated substrate was measured to be approximately 1.25 mm. The coated substrate was cut into individual hemostatic patches measuring approximately 2 x 4 cm and packaged in foil containers or disposable pouches (both designed to maintain the initial relative humidity of the inert gas within the container below about 20 ppm).Suitable commercially available medical packaging materials include Amcor PerfecFlex 35772-E or Paxxus Symphony 26-1010. The patches were sterilized after packaging. The mixed precursor coated side of each patch (the "active side") was identified by its blue color, which was absent from the substrate backing on the opposite side of each patch.

[0160] [Table 1]

[0161] Example 2: In vitro testing of hemostatic patch samples and substrates This example evaluates the gel time, burst pressure, swelling, and durability of a set of hemostatic patches prepared according to Example 1. This example also evaluates the swelling and durability of the substrate.

[0162] Part A. Test Samples and Test Procedures Hemostatic test patches prepared according to Example 1 using Substrate Type A ("Test Patch A") were used in this study. Separately, (uncoated) samples of Substrate A and Substrate D, with low and high crosslinking, respectively, were also tested. Individual samples for testing were cut from a single Test Patch A or a single Substrate A or Substrate D. The test methods used in this example are described in the "Hydrogel and Patch Properties" section above.

[0163] Part B. Substrate Testing Samples of Substrate A were evaluated for swelling. Samples of Substrate A were weighed and then immersed in a phosphate buffered saline (PBS) solution maintained at 37° C. for a selected period of time. Tables 2-4 show the swelling of the samples at 30 seconds, 1 minute, and 2 minutes, respectively. The swelling of the samples at 30 seconds, 1 minute, and 2 minutes averaged 814 wt%, 973 wt%, and 1053 wt%, respectively. The results show that biocompatible substrates can be prepared with high swelling ratios and high swelling extents in 30 seconds.

[0164] [Table 2]

[0165] [Table 3]

[0166] [Table 4]

[0167] Samples of Substrates A and D were evaluated for persistence in PBS solution. The samples were immersed in PBS solution maintained at 37°C. The samples were visually evaluated after 67 hours (2.8 days), 96 hours (4.0 days), and 114 hours (4.8 days). As shown in Table 5, each of the Substrate A samples (Samples 1-10) was observed to have partially persisted after 67 hours. Samples 1-10 were not visible at 96 hours, indicating that the persistence window for Substrate A was about 2.8 to about 4 days. Each of the Substrate B samples (Samples 11-15) was observed to have persisted after 114 hours.

[0168] The results show that the persistence of the substrate within a simulated in vivo environment can be well controlled by substrate engineering. The results also show that biocompatible, absorbent substrates have been prepared with high rates and total amounts of water absorption, and that these highly absorbent substrates can be designed to persist within a controlled time window.

[0169] [Table 5]

[0170] Part C. Patch testing Patch samples were cut into 8 mm disks from one 2×4 cm test patch A using an 8 mm biopsy punch.

[0171] The gelation time of the patch samples was evaluated using a commercially available texture analyzer as described in the "Hydrogel and Patch Properties" section above. Figure 11 shows a typical force versus time plot for a patch sample evaluated immediately after activation with a pH 8 buffer solution. The arrow in Figure 11 indicates the time point on the plot corresponding to the lowest force. The gelation time for this sample was measured to be 25 seconds.

[0172] After the gel time test, the patch samples were tested for burst pressure. Table 6 shows the burst pressure results. Sample 1 was recorded as having a burst pressure of 0, indicating that the sample did not adhere to the test block after the gel test. Samples 2-5 had burst pressures of 10 mm Hg to 65 mm Hg. Samples 6-10 had burst pressures of over 140 mm Hg, and sample 9 had a burst pressure of 188.2 mm Hg. Table 6 also shows the mass of the patch samples before and after the burst test. The swelling of the patch samples during the burst test ranged from about 340% to about 510%.

[0173] [Table 6]

[0174] After the burst test, the patch samples were evaluated for persistence and swelling from the hydration state after the burst test. The results are summarized in Table 7. Samples 1-5 were immersed in a PBS solution maintained at 37°C. These samples swelled an average of 203 wt% over 24 hours. This swelling, following hydration achieved at the end of the burst test, determined that the cumulative swelling from the dry state for patch samples 1-5 after approximately 24 hours was 1412%-1903%. Samples 1-5 were not visible after 114 hours (4.8 days). Samples 6-10 were immersed in a PBS solution maintained at 50°C. In this accelerated aging study, each of the samples had essentially disappeared in 24 hours.

[0175] [Table 7]

[0176] The results show that biocompatible absorbent patches were prepared with gel times of less than 30 seconds and burst pressures of greater than 140 mm Hg. These patches were also shown to have a relatively high swelling ratio and overall degree of swelling, but a relatively short durability of less than about 5 days. The results show that the test patches had similar durability compared to the isolated substrate (Substrate A). The results suggest that the precursor layer and substrate may be matched such that the durability of both the resulting hydrogel layer and substrate are similar. Alternatively, the precursor layer and / or substrate may be matched such that either the resulting hydrogel layer or substrate has a shorter durability.

[0177] Example 3: Liver defect study 1 (Comparative example) This example evaluated a hemostatic patch prepared according to Example 1 for hemostasis in a porcine liver defect model. A comparison was made with a commercially available fibrin sealant patch.

[0178] Part A. Test and Control Patches Three hemostatic test patches prepared according to Example 1 using Substrate Type A ("Test Patch A"), Substrate Type B ("Test Patch B"), and Substrate C ("Test Patch C"), respectively, were used in this study. A comparative fibrin sealant patch ("Control Patch A") was purchased from Baxter (TachoSil® Fibrin Sealant Patch, 0.5 cm x 4.8 cm, product code 1144922). Each patch was trimmed to an approximate size of 2 x 2 cm for application. The active side of the test patch was blue and the active side of the control patch was yellow.

[0179] Part B. Preparation of Animal Defect Model One acute (Yorkshire) pig was opened along the anterior (ventral) midline and the liver was isolated. The animal had the following details: weight (48.2 kg); sex (M); anticoagulation (ACT: 242). ACT was recorded before the first placement. Defects were created in both the left and right median lobes of the liver. An 8 mm biopsy punch was used to penetrate the liver to a depth of approximately 4 mm. The plug created by the punch was then removed using Metzenbaum scissors. At this point bleeding was assessed using the Adam's scale as described in Adams et al, Journal of Thrombosis and Thrombolysis (2009) 28:1-5 (DOI 10.1007 / s11239-008-2049-3), which is incorporated herein by reference. A target bleeding score of > 3 per Adam's scale was desired. (See FIG. 9). If the target score was not achieved, a biopsy punch was used to re-enter the liver until the target score was reached. The bleeding scores of the defects created for each trial were recorded as the initial score, as shown in Tables 8 and 9. The bleeding defects for Test Patch A were severe or massive (trials 2-1 and 2-2), moderate (trial 2-3), and slight (trial 2-4). The bleeding defects for Control Patch A were massive (trials 2-1C and 2-2C), slight (trial 2-3C), and slight / moderate (trial 2-4C). Bleeding at the defect site was managed with clean, dry gauze prior to patch placement.

[0180] [Table 8]

[0181] [Table 9]

[0182] Part C. Patch Assessment Procedures and Results Clean gauze was moistened using clean sterile saline. Test patch A samples were placed backing down on the moist gauze with the active side of the patch facing away from the gauze, although in general use the patch can be placed without gauze to facilitate proper placement, so gauze can be used to maintain some pressure while the patch is attached. The gauze used to manage bleeding at the defect site was removed from the defect site. The patch was immediately placed over the defect site so that the active side of the patch was in contact with the defect and centered over the defect as much as possible. Without holding anything in the hand, firm and even pressure was applied to the backside of the patch with the moist gauze and held for 1 minute (first interval). Pressure was then slowly released and the gauze was carefully removed from the backside of the attached patch. If there was any adhesion of the gauze to the patch, a clean surgical instrument was gently used on the edge of the patch or light irrigation was used to pull the gauze away from the patch with minimal disturbance. After a 30-second evaluation period, a 1-minute bleeding score was recorded based on the Adam's scale, as shown in Table 8. Then, the wet gauze was again used to apply firm, even pressure to the backside of the patch for an additional 2 minutes. Again, the pressure was slowly eased and the gauze was carefully removed from the backside of the applied patch. After a 30-second evaluation period, a 3-minute bleeding score was recorded based on the Adam's scale, as shown in Table 8. Then, a pair of forceps was used to gently pinch off the edge of the patch to test for adhesion. The procedure was repeated with three additional defects for a total of four trials with Test Patch A. All of the test patch samples adhered well to the target site and were not affected by the removal of the wet gauze. Furthermore, the edges of the test patch samples could not be pulled up when pulled / pinched off by the forceps. No oozing was observed through any of the test patch samples. The results show that all trials with Test Patch A achieved hemostasis within one minute of placement.

[0183] The above procedure was repeated for Control Patch A with minor modifications. For Trials 2-3 and 2-4 of Control Patch A, the target bleeding score was lowered from ≧3 to ≧2 due to poor performance of the control sample in Trials 2-1C and 2-2C. The results are shown in Table 9. Trial 2-4C of Control Patch A 3 minutes after placement recorded a bleeding score of 0, but there was swelling on the underside of the patch. When pressed, blood came out from just under the patch and bleeding continued. This trial was considered non-hemostatic. The results show that despite the lowering of the target bleeding score in the second two trials, none of the trials with Control Patch A achieved hemostasis 3 minutes after placement. Additionally, it was observed that the Control Patch A samples did not adhere to the target site and were easily removed. Extreme care was required during removal of the wet gauze to avoid disturbing the patch from the placement site.

[0184] Test Patch B and Test Patch C were evaluated in the liver defects created in Trials 2-2C and 2-3C of Control Patch A, respectively, after these control patch samples were allowed to continue bleeding heavily or slightly, respectively, at the 3 minute time point. Two test patch samples were able to restore hemostasis within 1-3 minutes, as shown in Table 10. Initial placement of Test Patch B was not centered over the defect. A second Test Patch B was placed in the defect 1 minute after initial placement. Hemostasis was achieved 3 minutes after initial placement, corresponding to 2 minutes after the second placement.

[0185] [Table 10]

[0186] Part D. Additional Patch Assessments Test patch A was further evaluated using uneven placement into a defect created on the surface of the liver using a scalpel. The channel-shaped defect was approximately 3 mm deep and 5 mm long. Test patch A was cut to a size of 2 x 4 cm, wetted with saline, folded in half lengthwise, and then placed into the defect. Figure 10A shows Test patch A after initial placement. A piece of wet gauze was used to apply pressure to the test patch sample. As shown in Figure 10B, hemostasis was achieved in 1 minute where the test patch touched the defect. Figure 10B also shows continued bleeding from areas of the defect that were not in contact with the test patch.

[0187] This example shows that a hemostatic patch prepared according to Example 1 achieved hemostasis both 1 and 3 minutes after placement onto a porcine liver defect, significantly outperforming a commercially available fibrin sealant patch. The reactive precursors in the hemostatic patch allowed for flat and non-flat placement, as well as brief periods of manual compression after placement, resulting in fast, conformable, and easy application of the patch to minor to major bleeding defects in the liver.

[0188] Example 4: Liver defect study 2 (Comparative example) This example evaluated a hemostatic patch prepared according to Example 1 for hemostasis in a porcine liver defect model. Comparison was made against a commercially available fibrin sealant patch.

[0189] Part A. Test and Control Patches A set of hemostatic test patches prepared according to Example 1 using substrate type A ("Test Patch A") was used in this study. A comparative sealant patch embedded with human fibrinogen and human thrombin ("Control Patch B") was purchased from Johnson and Johnson (Evarrest® Fibrin Sealant Patch, 5.1 cm x 10.2 cm, product code EVT5024). Each patch was trimmed to approximately 2 x 2 cm size for application. The active side of the test patch was blue and the active side of the control patch was yellow.

[0190] Part B. Preparation of Animal Defect Model One acute (Yorkshire) pig was opened along the anterior (ventral) midline and the liver was isolated. The animal had the following details: weight (57.4 kg); sex (F); anticoagulated (ACT: 294). ACT was recorded before the first placement. Defects were created in both the left and right median lobes of the liver. An 8 mm biopsy punch was used to penetrate the liver to a depth of approximately 4 mm. Metzenbaum scissors were then used to remove the plug created by the punch. Bleeding was assessed at this point. A goal of ≧3 per Adam's scale was desired. (See FIG. 9). If the target score was not achieved, a biopsy punch was used to re-invade the liver until the target score was reached. The bleeding score of the defects created for each trial was recorded as the initial score, as shown in Tables 11 and 12. All bleeding defects for Test Patch A were voluminous. Bleeding defects in control patch B were moderate (Trial 3-1C) or heavy (Trials 3-2C, 3-3C, and 3-4C). Bleeding at the defect site was managed with clean, dry gauze.

[0191] [Table 11]

[0192] [Table 12]

[0193] Part C. Patch assessment procedures and results. The procedure described in Example 2 was followed for Part C for this example, with the modification that the first score was performed after 30 seconds. All of the Test Patch A samples adhered well to the target site and were not affected by removal of the wet gauze. Furthermore, the edges of the Test Patch A samples could not be lifted when pulled / picked up with forceps. No exudation was observed through any of the Test Patch A samples. As shown in Table 11, all trials with Test Patch A achieved hemostasis within 30 seconds after placement.

[0194] The results of Control Patch B are shown in Table 12. Only one Control Patch B sample (Control Patch B Trial 3-4C) achieved hemostasis after 3 minutes. However, later in the study, the patch was removed and bled again. The removed patch was later placed in the thoracic cavity. The other three Control Patch B trials showed oozing (Control Patch B Trial 3-1C and 3-2C) or moderate bleeding (Control Patch B Trial 3-3C) at the 3 minute mark. Great care was required not to disturb the control patch during removal of the wet gauze. When assessed at the 3 minute mark, Control Patch B was observed to have adhered to the wound only at the actively bleeding site. The control patch area extending beyond the wound did not adhere to the tissue and remained a loose / elevated flap.

[0195] Part D. Additional Patch Assessments Test Patch A was further evaluated using multiple non-flat (convex) placements on a partially resected liver lobe. The placements were a pre-wetted 2x4 cm patch, a 2x4 cm dry patch, and a 2x2 cm dry patch. It was observed that applying pressure to the dry patch was less difficult compared to the pre-wetted patch as there was less slippage. After placement of all three patches, hemostasis was achieved throughout the defect. Each placement achieved hemostasis in the area in contact with the respective patch.

[0196] This example shows that the hemostatic patch prepared according to Example 1 achieved hemostasis of moderate to heavy bleeding at 30 seconds, 1 minute, and 3 minutes after placement in a porcine liver defect, significantly outperforming the commercially available fibrin / thrombin sealant patch. Despite the fibrin / thrombin sealant patch having a reactive species (thrombin), the patch did not actually seal the wound as the hemostatic patch did. While pinch testing at the edges of the hemostatic patch showed no delamination, the fibrin / thrombin patch was merely attached to the wound site. There was removal of the control patch in two of four attempts.

[0197] Example 5: Cardiovascular defect study This example evaluated hemostatic patches prepared according to Example 1 for hemostasis after various placements in a porcine cardiovascular defect model.

[0198] Part A. Test Patches A set of hemostatic patches prepared according to Example 1 using substrate type A ("Test Patch A") was used in this study. All placement was performed with the patch in a dry state. The patch was made flexible after placement by either hydrating with saline solution directly against the patch or by applying pressure to the patch with pre-wetted gauze.

[0199] Part B. Initial preparation of the animal defect model One female 60 kg acute (Yorkshire) pig was used in this study. The skin was incised across the ventral midline of the neck to expose the carotid artery. Blunt dissection was performed through the underlying subcutaneous and muscular tissue. The muscle was retracted and the fascia around the target vessel was peeled away from the vascular surface. Side branches of the vessel were ligated using silk suture material and clips. After gaining proximal and distal control of the artery using vessel loops and vascular clamps, the vessel was temporarily occluded. An arteriotomy was performed and graft material (Gore Acuseal) was anastomosed end-to-end using non-absorbable sutures. Upon completion of the anastomosis, blow flow was re-established by removing the vessel loops and clamps.

[0200] A groin incision was made to expose each femoral artery. Blunt dissection was performed through the underlying subcutaneous and muscular tissue. The muscle was retracted and the fascia around the target vessel was dissected away from the vascular surface. Side branches of the vessel were ligated using silk suture material and clips. After gaining proximal and distal control of the artery using a vascular loop and vascular clamp, the vessel was temporarily occluded.

[0201] Part C. Defect creation, patching procedures, and outcomes Step 1: Thigh placement Blood flow was stopped over a 3-5 cm segment of the left femoral artery using a clamp and a vascular loop. The vessel was punctured four times using a 25-gauge needle to simulate the sutures of the vascular repair procedure. The artery was unclamped to ensure a bleeding defect had been created, and bleeding was graded using Adam's scale. Pulsatile bleeding was determined to be massive (Adams scale rating of 4). The artery was re-clamped to stop blood flow, and the area was cleared of pooled blood. Test patch A was cut to approximately 1 x 1.7 cm. The dry test patch was placed over the defect site, covering the defect with the blue side facing the target bleed. Manual pressure was applied to the test patch for 30 seconds using a piece of pre-wetted gauze. Blood flow to the area was then restored by removing both the vascular loop and the clamp. After 30 seconds of manual pressure, the gauze was removed. The patches were evaluated for hemostasis and adhesion. Flow through the artery was confirmed by noting a pulse on either side of the placed patch. It was observed that the site achieved hemostasis 30 seconds after patch placement and good adhesion to the surrounding tissue. Approximately 1 hour after placement, the hind leg was "exercised" to simulate movement. The patch remained adherent to the defect and surrounding tissue during and after this movement. A pulse was seen on either side (distal and proximal) of the placed patch.

[0202] Step 2: Thigh placement in pulsatile flow Working at the same site as described in procedure 1, a 25 gauge needle was used to puncture the vessel once proximal to the defect from procedure 1. Pulsatile bleeding from the puncture was determined to be profuse (Adams scale rating of 4). The puncture was immediately covered by applying manual pressure until patch placement was imminent. Manual pressure was removed and a dry patch approximately 1.5 x 2 cm in size was immediately placed over the actively bleeding site. Manual pressure was applied to the patch for 30 seconds using a piece of pre-moistened gauze. After 30 seconds of manual pressure, the gauze was removed. The patch was evaluated for hemostasis and adhesion. Flow through the artery was confirmed by checking for a pulse on either side of the placed patch. It was observed that the site had achieved hemostasis 30 seconds after patch placement and good adhesion to the surrounding tissue. Approximately 1 hour after placement, the hind leg was "exercised" to simulate movement. The patch remained adherent to the defect and surrounding tissue during and after this movement. Pulses were observed on both sides (distal and proximal) of the placed patch.

[0203] Step 3: Thigh wrapping placement A clamp and vascular loop were used to stop blood flow over a 3-5 cm segment of the right femoral artery. A scalpel was used to create a small longitudinal defect along the artery. The defect was closed with 2-3 sutures. The bleeding defect was confirmed by removing the proximal clamp and graded as having copious pulsatile bleeding. A clamp was again used to stop blood flow and the area was cleared of pooled blood. A dry patch was placed under the defect site with the blue side facing up. The patch was then hydrated with saline and wrapped around the defect site with the blue side in contact with the target bleeding. Manual pressure was applied to the patch for 30 seconds using a piece of pre-wetted gauze. After 30 seconds of manual pressure, the gauze was removed. The patch was evaluated for hemostasis and adhesion. Flow through the artery was confirmed by checking for a pulse on both sides of the placed patch. It was observed that the site achieved hemostasis 30 seconds after patch placement and good adhesion to the surrounding tissue. Approximately 15 minutes after placement, the hind leg was "exercised" to simulate movement. The patch remained adherent to the defect and surrounding tissue during and after this movement. Pulses were evident on both sides (distal and proximal) of the placed patch.

[0204] Step 4: Placement on the bleeding suture line Animals were heparinized and the procedure was completed with anticoagulated blood. The right carotid artery was isolated and end-to-end anastomosed with graft material (Gore Acuseal, ECH060020A). With active blood flow through the artery and graft material, a bleeding area was created by manipulating / removing the suture at the distal anastomosis. Bleeding was rated as 3 (moderate) using Adam's scale. Two (2 x 2 cm) test patches A were placed along the suture patch with the blue side facing the target bleeding to cover the defect. A piece of pre-moistened gauze was used for manual pressure and manual pressure was held for 30 seconds. After 30 seconds of manual pressure, the gauze was removed and the patch was evaluated for hemostasis and adhesion. After 30 seconds, hemostasis was achieved. The patch adhered to the suture but only minimally to the graft material. It was observed that the suture seal worked just as well after anticoagulation as it did before anticoagulation.

[0205] Step 5: Placement of the graft over the defect The procedure was completed using anticoagulated blood. Working at the same site as described in Procedure 4, the graft material was punctured using a 14 gauge needle. The puncture was assessed to ensure a consistent and adequate flow of blood from the defect (Adams score of 3). Test patch A was placed over the graft defect. Manual pressure was applied to the patch for 30 seconds using a piece of pre-moistened gauze. After 30 seconds of manual pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion. After 30 seconds, the initiation of sealing of the target bleed was observed. Minimal adhesion of the patch to the graft material was observed. The patch could be peeled away from the bleeding site with forceps.

[0206] This study demonstrated that placement of Test Patch A successfully sealed defects commonly found in cardiovascular procedures involving pulsatile femoral punctures as well as end-to-end anastomoses between the carotid artery and graft material. Hemostasis (or sealing) was achieved in all applications of Test Patch A at or before 30 seconds after placement. The patch was stable and remained adherent to the tissue at the placement site after flexion of the hind limb. The patch successfully controlled bleeding from the graft material. Additionally, the sealing performance of the patch remained consistent following administration of heparin to the animals.

[0207] Example 6: Orthopedic and cardiovascular defect studies This example evaluated hemostatic patches prepared according to Example 1 for hemostasis after various placements in an acute non-GLP porcine orthopedic and cardiovascular defect model.

[0208] Part A. Test Patches A set of hemostatic patches prepared according to Example 1 using substrate type A ("Test Patch A") were used in this study. All placement was performed while the patch was dry, with pressure applied via wet gauze. Both 2x2 cm and 2x4 cm patches were used. The patches were made flexible after placement by applying pressure with pre-wetted gauze.

[0209] Part B. Initial animal defect model preparation One male 27 kg acute (Yorkshire) pig was used in this study. The skin was incised to expose the tibial shaft. Blunt dissection was then performed through the underlying subcutaneous and muscular tissue. The muscle was retracted and the fascia around the target vessel was dissected from the bone surface. A dental drill with an approximately 2-3 mm ball-tip bit was used to create a target cortical bleeding defect. The defect was irrigated with saline to remove debris and avoid heating of the tissue during creation.

[0210] The skin was then incised to expose the femoral condyle. Blunt dissection was performed through the underlying subcutaneous and muscular tissue. The muscle was retracted and the fascia around the target vessel was dissected away from the bone surface. A dental drill with an appropriate 2-3 mm ball-tip bit was used to create a bleeding defect in the target cortex. The defect was irrigated with saline to remove debris and avoid heating of the tissue during creation.

[0211] Finally, a groin incision was made to expose each femoral artery. Blunt dissection was performed through the underlying subcutaneous and muscular tissue. The muscle was retracted and the fascia around the target vessel was peeled away from the vascular surface. Side branches of the vessel were ligated using silk suture material and clips. After gaining proximal and distal control of the artery using a vascular loop and a vascular clamp, the vessel was temporarily occluded.

[0212] All assessments of bleeding were performed using Adams' scale.

[0213] Part C. Defect creation, patching procedures, and outcomes Step 1: Tibial shaft defect A dental drill and ball drill bit were used to create a defect in the tibial shaft, ~3mm in diameter and ~4mm deep. Bleeding was noted and assessed as very slight (Adams' score of 1). The patch was cut into approximately 1x2cm pieces. The patch was placed over the defect with the blue side facing the targeted bleeding. Manual pressure was applied to the patch for 30 seconds using a piece of pre-moistened gauze. After 30 seconds of manual pressure, the gauze was removed. The patch was assessed for hemostasis and adhesion. The site was observed to be sealed 30 seconds after patch placement. As the site was observed over time, the site remained sealed and the patch remained well adhered, although there was evidence of continued bleeding on the underside of the patch.

[0214] Step 2: Larger defect in the tibial shaft Working at the same site as described in step 1, a large defect (diameter 6mm and depth 9mm) was created in the tibial shaft using a dental drill and ball drill bit. Bleeding was noted and assessed as very slight (Adams' score 1). One 2x2cm patch was cut into disks to fit the size of the defect by using a 6mm biopsy punch. Two of these disks were placed in the defect using forceps with the blue side of the first patch facing the target bleeding at the bottom of the defect. Each subsequent patch was stacked on top of the previous with the blue side against the previous patch. They were positioned to address bleeding from the walls of the created defect. A piece of pre-wetted gauze was used to apply manual pressure to the top patch for 30 seconds. After applying pressure for 30 seconds, the gauze was removed. The site was evaluated for patch hemostasis and adhesion. Hemostasis was observed to be achieved 30 seconds after patch placement.

[0215] Step 3: Femoral condyle defect A dental drill and ball drill bit were used to create a defect in the femoral condyle, 6 mm in diameter and 3 mm deep. Bleeding was noted and assessed as very slight (Adams' score of 1). One 2x2 cm test patch A was cut into a disk to fit the size of the defect using a 6 mm biopsy punch. The disk was placed into the defect using forceps with the blue side of the patch facing the target bleed. A piece of pre-wetted gauze was used to apply pressure to the patch for 30 seconds using the plunger from a 1 ml syringe. After applying pressure for 30 seconds, the gauze was removed. The site was evaluated for patch hemostasis and adhesion. Hemostasis was observed to be achieved 30 seconds after patch placement.

[0216] Step 4: Deeper defect in femoral condyle A dental drill and ball drill bit were used to create a defect in the femoral condyle, 6 mm in diameter and 9 mm deep. Bleeding was noted and assessed as minimal (Adams' score of 2). One 2 x 2 cm test patch A was cut into disks using a 6 mm biopsy punch. Four of these disks were placed into the bottom of the defect, with the blue side of the first patch facing the bleeding target, so that it would fit into the defect. Each subsequent patch was stacked on top of the previous, with the blue side against the previous patch. These were positioned to address any bleeding from the walls of the created defect. A piece of pre-wetted gauze was used to apply pressure to the patch for 30 seconds using the plunger from a 1 ml syringe. After applying pressure for 30 seconds, the gauze was removed. The site was evaluated for patch hemostasis and adhesion. Hemostasis was observed to be achieved 30 seconds after patch placement.

[0217] Step 5: Femoral artery suture defect A clamp and vascular loop were used to stop blood flow over a 3-5 cm segment of the femoral artery. The vessel was punctured twice using a 25-gauge needle to simulate the sutures of a vascular repair procedure. The artery was unclamped to ensure a bleeding defect was created, and bleeding was graded using the Adams scale. Pulsatile bleeding was assessed as massive (Adams' score of 4). The artery was re-clamped to stop blood flow, and the area was cleared of pooled blood. A piece of gauze was cut and wetted with clean saline. A 2 x 4 cm patch was placed on top of the wet gauze with the blue side facing away from the gauze. The patch / gauze pair was then slid directly under the artery with the blue side of the patch facing the target bleed. The user held both ends of the gauze and lifted them up against each other until the gauze ends touched. Pressure was then applied to the patch-patch contact area ("tail") such that the central area of ​​the patch was wrapped around the vessel and the tails of the patch were adhered to each other. Care was taken to ensure that the channel formed by the two tails did not directly cover the bleeding site. Manual pressure was then applied to the patch through the gauze for 30 seconds. After 30 seconds of manual pressure, the gauze was removed. Blood flow to the area was then restored by removing both the vessel loop and the clamp. Flow through the artery was confirmed by checking for a pulse on both sides of the deployed patch. The patch was then evaluated for hemostasis and adhesion. The tail of the patch was trimmed using Metzenbaum scissors leaving approximately 2-3 mm of tail along the length of the patched section of the artery. It was observed that at the 30 second mark, hemostasis was achieved at the application site, good adhesion to the artery was achieved, and pulses were seen on both the distal and proximal sides of the patch.

[0218] Step 6: Contralateral femoral artery defect The procedure described in procedure 5 was applied to the contralateral femoral artery. A pulsatile bleeding defect was formed which was assessed as massive (Adams' score of 4). Again, it was observed that the application site achieved hemostasis at the 30 second mark, good adhesion to the artery was achieved, and pulsation was evident both distal and proximal to the patch.

[0219] An additional study evaluated Test Patch A in a chronic sheep carotid artery arteriotomy patch closure model. After seven days of implantation in the model, Test Patch A produced stable vascular repair without any evidence of bleeding as assessed by angiography.

[0220] This study showed that placement of Test Patch A successfully sealed both condylar and diaphyseal bone defects with very minimal to minimal bleeding, and bilateral pulsatile femoral artery defects with extensive bleeding. In both cases, hemostasis (or sealing) was achieved at or before 30 seconds after placement of the dry patch. A syringe plunger was successfully used to apply pressure to the patch placed in the deeper bone defect. An alternative wrap-around placement method was successfully used to treat pulsatile femoral artery punctures.

[0221] Example 7: Study of soft organ and orthopedic defect combinations This example illustrates the use of both soft organ and orthopedic surgical patches in a patient.

[0222] Part A. Test Patches and Control Products Three types of hemostatic patches prepared according to Example 1 using substrate type A ("Test Patch A"), substrate type B ("Test Patch B"), and substrate type C ("Test Patch C"), respectively, were used in this study. The control product was a 2 mm thick water-insoluble porcine gelatin sponge (Surgifoam® Absorbable Gelatin Sponge, Johnson and Johnson, product code 1975) to which recombinant thrombin (Baxter, Recothrom®) was added ("Control Patch C"). Both dry and pre-wet configurations were tried for each sample.

[0223] Part B. Animal defect model preparation In the training laboratory, surgeons were provided with patches as described in Part A. One acute (Yorkshire) pig was opened along the anterior (ventral) midline and the liver was isolated. Animals had the following details: weight (48.2 kg); sex (M); anticoagulation (ACT: 242). ACT was recorded prior to first placement. Defects were created in both the left and right median lobes of the liver as well as the spleen. An 8 mm biopsy punch was used to penetrate each organ initially to a target depth of approximately 7 mm. Later, a target depth of approximately 2 mm was used. Metzenbaum scissors were then used to remove the plug created by the punch. Bleeding was assessed at this point. A target of ≧3 per Spot Grade SBSS was desired. If the target bleeding score was not achieved, the organ was penetrated again using a biopsy punch until the target score was reached. Bleeding defects were moderate to profuse. Bleeding at the defect site was managed with clean dry gauze prior to product placement.

[0224] Part C. Patch Assessment Procedures and Results Clean gauze was moistened using clean sterile saline. The test patch sample was placed backing down on the wet gauze with the blue side of the patch facing away from the gauze. The gauze to control bleeding was removed from the defect site. The patch was immediately placed over the defect site, centered over as much of the defect as possible, with the blue side of the patch in contact with the defect. Without holding anything in the hand, firm and even pressure was applied to the backside of the patch with the wet gauze and held for 30 seconds. The pressure was then carefully released and the gauze was carefully removed from the backside of the attached patch. If there was any adhesion of the gauze to the patch, a clean surgical instrument was gently used on the edge of the patch or light irrigation was used to pull the gauze away from the patch with minimal disturbance. After the 30-second evaluation period, the 30-second bleeding score was recorded based on the Spot Grade SBSS. A pair of forceps was then used to gently pinch the edge of the patch to test for adhesion. The procedure was repeated for each patch sample, using a modified procedure for each patch sample, where the patch was placed without pre-wetting the gauze.

[0225] Part D. Findings Test Patch A produced hemostasis with every application. Sealing of the defect was more effective when pressure was applied into the hollow defect and when the patch was pre-wetted rather than applied dry across the hollow core organ defect. Application of the pre-wetted patch did not result in any bulging / doming of the patch and did not result in a red core of blood in the patch covering the hollow core defect. Test Patch B produced similar results to Test Patch A, producing hemostasis with every application. Successful application of Test Patches A and B improved the surgeon's experience with the patch as well as the length of time after patch placement. Multiple samples of Test Patch C were tried, and in each case the patch stuck to the gauze during placement. Removal of the gauze tore the substrate, thereby causing rebleeding. Control Patch C was used successfully to produce hemostasis in both the liver and spleen. However, Control Patch C adhered poorly to the tissue and there was concern from the surgeon regarding a high risk of the product becoming dislodged. Both the test and control patches exhibited a "dome effect" due to swelling of blood under the patch / product at the defect site. By applying pressure to the applied patch / product, the dome effect was generally avoided.

[0226] The results showed that Test Patch A and Test Patch B had good adhesion to tissue and were relatively easy to use to provide rapid hemostasis. Test Patch C was unable to achieve sustained hemostasis using the process used. It is believed that the substrate of Test Patch C was too porous, which was related to the excessive flow of blood from the defect through the active surface and into the substrate, as the hydrogel migrates through a highly porous substrate. This study demonstrated that the active surface composition used with a suitable substrate contributes to the performance and usefulness of the patch. Control Patch C was unable to achieve good adhesion to tissue.

[0227] Example 8: Simulated cervical defect study This example illustrates the use of a conical mandrel to achieve hemostasis in a simulated neck defect.

[0228] Part A. Test Patches A set of cone-shaped hemostatic patches were prepared using substrate type A according to the general procedure of Example 1. The patches were further shaped into cones by a series of manufacturing steps as follows: the patch was cut along the side to approximately the center of the patch, then slightly heated and contoured to roughly a cone shape, and the overlapping cut portions were then held together to set the shape until the PEG was cooled.

[0229] Part B. Animal defect model preparation One acute (Yorkshire) pig was opened and the pig's abdominal wall was isolated. Anticoagulation (ACT) was >300 prior to first placement. An 8mm biopsy punch was used to penetrate the abdominal wall to a target depth of approximately 7mm. Metzenbaum scissors were then used to remove the plug created by the punch. Bleeding was assessed at this point. A Spot Grade SBSS scale of 3 was achieved. Bleeding at the defect site was managed with clean dry gauze prior to product placement.

[0230] Part C. Patch Assessment Procedures and Results The test patch sample was placed into the defect with the blue side of the cone-shaped patch facing the defect. The mandrel handle was held to press the cone-shaped portion of the mandrel with the cone-shaped patch into the defect. Light but steady pressure was applied by the mandrel to the patch for 30 seconds. The pressure was then carefully released and the mandrel was carefully removed from the convex (back) side of the applied patch. Some adhesion of the patch to the mandrel was observed and clean surgical instruments were used to pull the mandrel away from the patch with minimal disturbance. After the 30 second evaluation period, hemostasis was evaluated. A modified procedure was used for the second application in which a piece of wet gauze was placed between the cone-shaped patch and the mandrel before the mandrel pressed the patch into the defect. During removal of the mandrel and gauze from the applied patch, no adhesion of the patch to the mandrel or gauze was observed. After the 30 second evaluation period, hemostasis was evaluated.

[0231] Part D. Findings In both applications, hemostasis and good adhesion of the patch to the defect were achieved in 30 seconds. While adhesion of the patch to the mandrel in the first application caused loss of hemostasis upon removal of the mandrel, the modified placement procedure used by the second application allowed hemostasis to be maintained after the mandrel was removed. The results showed that the shaped mandrel could be used to attach a pre-shaped patch to a site that is not easily accessible for direct manual application ("remote site"). The results also showed that the pre-shaped patch and corresponding shaped mandrel could be advantageously used to aid in the alignment, placement, and application of the pre-shaped patch to both remote and non-remote sites. The shaped mandrel allows for more consistent pressure to be applied across the entire surface of the pre-shaped patch that contacts the defect. Consistent pressure promotes rapid hemostasis by reducing the chance of bleeding underneath the patch. Based on the findings, it is expected that a cone-shaped patch and corresponding cone-shaped mandrel, as shown, for example, in Figures 12A and 12B, will be suitable for use in achieving hemostasis in bleeding defects in the neck.

[0232] Example 9: Preparation of a flexible hemostatic patch with a compressed substrate This example describes a compression process for preparing a flexible hemostatic patch.

[0233] Part A. Substrate Compression Test Two types of substrates were used in this study, as shown in Table 13. Substrate E and Substrate F were both foamed gelatin / collagen substrates obtained from different commercial sources. The commercially available foamed gelatin substrates were thermally crosslinked in an oven for several hours according to the time and temperature ranges mentioned above. The substrate samples were approximately 10 cm wide by 20 cm long and 7 mm thick.

[0234] [Table 13]

[0235] Substrates E and F were compressed using a calender roller. For convenience, compression was performed using a pasta roller with a setting corresponding to a distance between adjacent surfaces (i.e., gap) of the calender rollers of about 5 mm. Figures 15A and 15B are SEM images of the surface of a sample of Substrate E before and after compression, respectively. Figures 15C and 15D are SEM images of the surface of a sample of Substrate F before and after compression, respectively. Figures 15A-15D were taken using a magnification of 25x with backscattering. The difference in the pore structure of Substrate E and Substrate F before compression can be visually shown in Figures 15A and 15C. Both Figures 15A and 15C show a range of pore sizes, with the larger pores in Figure 15A being generally larger than the larger pores in Figure 15C. Furthermore, the scaffolding of material surrounding the larger pores of Substrate E (Figure 15A) is significantly thinner than the scaffolding of material surrounding the pores of Substrate F (Figure 15C). With reference to FIG. 15B, after compression, the pore structure of Substrate E appears to be collapsed and damaged, lacking the overall thin scaffold material shown in FIG. 15A. With reference to FIG. 15D, after compression, the pore structure of Substrate F appears to be a similar but denser version of the structure of the uncompressed sample (FIG. 15C). Table 14 shows the average porosity area fraction and average pore size of the SEM images of FIGS. 15A-15D, as determined using ImageJ image analysis software. The average porosity area fraction measurement is semi-quantitative, since both the pores at the surface of the image and some of the pores below the surface of the image were captured. The data in Table 14 show that the average porosity area fraction is similar for the uncompressed and compressed samples. The results show a significant difference in the foam / scaffold structure of Substrate E and Substrate F.

[0236] [Table 14]

[0237] A set of samples of Substrate E were further evaluated for fluid absorption, flexural strength, shear force, compression force, and conformability, both before and after compression. For each measurement, results from 10 replicate samples were recorded as shown in Table 15. Fluid absorption was tested by weighing each of the 10 uncompressed samples when dry (initial dry weight) and after immersion in saline for 15 seconds (final weight). The fluid absorption of each sample was calculated as (final weight-initial dry weight) / 100% initial dry weight. The average fluid absorption of uncompressed Substrate E was recorded as the average of the fluid absorption of the 10 uncompressed samples. Flexural strength was measured by subjecting the 10 dry, uncompressed samples of Substrate E to a 3-point bend test individually using a Texture Analyzer machine (Model TA-XT Plus C) equipped with a 3-point bend apparatus in accordance with ASTM D790-17, which is incorporated herein by reference. Each specimen was approximately 2.5 cm wide by 6.5 cm long. The maximum shear force was measured by loading the dry, uncompressed specimens as a cantilever and applying a force. The maximum shear force was recorded as the force at failure. Each specimen was approximately 2.5 cm wide by 6.5 cm long, with 1 cm being held by the test grips. The column strength (or maximum compression force) was measured by subjecting ten dry, uncompressed samples of Substrate E to individual uniaxial compression using a Texture Analyzer machine (Model TA-XT Plus C). Each specimen was a dog-bone test sample measuring 2.5 cm wide by 7.5 cm long. The column strength was recorded as the force at failure. Conformity was tested by wrapping the dry samples around a ½ inch mandrel. The absence of cracks or breaks in the sample during the test was indicated as positive for conformity, and the results were recorded as the ratio of the number of positive samples per ten samples tested. The average thickness of each sample was measured by caliper.

[0238] The above tests were repeated using sets of 10 compressed substrate samples for each test. The results are shown in Table 15. Comparison of the average measurements of the uncompressed substrate samples to the average measurements of the compressed substrate samples shows that there was essentially no change in fluid absorption (360% vs. 356%), but the mechanical properties of the samples did change. The compressed samples had lower average bending, shear, and column strengths, but all (10 / 10) of the compressed samples fit the ½ inch diameter mandrel. Only 3 of the 10 uncompressed samples fit the same ½ inch mandrel test. The results show that compressing the substrate imparts flexibility / compliance to the substrate without changing the fluid absorption. Additionally, the results show that the compressed samples retain a greater percentage of their original compressive and tensile strengths compared to the shear strength (maximum shear force) as predicted by the column strength and bending strength measurements. The shear strength of the compressed samples is approximately 10% of the shear strength of the uncompressed samples. The results suggest that compression of Substrate E using calendaring can cause significant shear-induced failure, but is mild enough to allow the substrate to remain relatively stiff. The results show that compression, particularly by calendaring, imparts flexibility to the crosslinked gelatin substrate through collapse of the pore structure, without measurable loss of fluid absorbency, and without significant loss of stiffness. The results also show that the thickness variation of the compressed substrate samples was less than that of the uncompressed substrate samples.

[0239] [Table 15]

[0240] Additional fluid absorption data as a function of time was collected for both uncompressed and compressed samples. Figure 19 shows the average fluid absorption for substrate samples submerged for 15 seconds, 1 minute, 5 minutes, or 10 minutes. At 20 hours (not shown in plot), the average fluid absorption for uncompressed and compressed substrate samples was approximately 1200%. The results show that the substrates initially absorbed fluid rapidly, with the absorption leveling off at approximately 10 minutes. The average percentage fluid absorption for uncompressed and compressed substrates at the required measurement time points was generally within measurement error.

[0241] Part B. Preparation and Testing of Coated Substrates The coated substrates were prepared by melt coating a dry blend of the two hydrogel precursors onto a set of compressed samples of Substrate E. The substrate samples were prepared for coating by drying in an oven under ambient air at a temperature of 35° C. for 18 hours or until the relative humidity of the oven was less than 5%. The thickness of each substrate sample after drying was approximately the same as the thickness before drying. For each coated substrate sample, the first hydrogel precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 15,000 Da and succinimidyl glutarate (SG) functional end groups (8A15k PEG SG, Jenkemusa). The second hydrogel precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 20,000 Da and HCl chloride amine functional end groups (8A20k PEG amine-HCl, Jenkemusa). The first and second precursors were measured in powder form and then melt blended in a glove box with a trace amount of FD&C Blue#1 in a heated roller system at a temperature of more than 45° C. The molten precursor blend was delivered to a liquid delivery system (FOM Coater, FOM Technologies). A single coating layer of the molten blend was applied to each substrate sample under inert gas conditions. The precursor was applied through a heated slot die head positioned at a gap of 4.5 mm above the bottom surface of the approximately 5 mm thick substrate. By this process, coating of the substrate involved injecting the molten blend into the substrate due to compression of the substrate by the slot die head. The average thickness of the precursor-impregnated region of each substrate (the "precursor / substrate network region") was approximately 0.25 mm and typically extended at least about 0.05 mm above the substrate surface. The mixed precursor-coated substrates were allowed to solidify at room temperature under inert gas conditions. The thickness of each of the resulting coated substrates was measured to be approximately 5.25 mm.

[0242] One of the coated substrates (Sample 1) was kept as the "uncompressed sample," while the remaining coated substrate samples (Samples 2-4) were subjected to post-coating compression using calender rollers. SEM images of representative portions of the surfaces of Samples 1-4 are shown in Figures 16A-D, respectively. For the uncompressed sample (Sample 1), Figure 16A shows that the coated sample has relatively non-uniform cracking on the surface, including some relatively large cracks compared to the post-compression cracks in Figures 16B-D (note that Figure 16A is at a lower magnification than Figures 16B-D). The large cracks seen in Figure 16A are the result of handling / shipping the sample and indicate the stiffness and brittleness of the solidified precursor after coating if no strain relief is provided. Despite the brittleness of the solidified precursor in Figure 16A (Sample 1), the precursor was observed to adhere well to the substrate. For Samples 2-4, post-coating compression was performed using a calender roller at a setting corresponding to the distance (i.e., gap) between adjacent surfaces of the calender rollers. One coated sample (Sample 2, FIG. 16B) was compressed at a setting corresponding to a gap of about 5 mm. Another coated sample (Sample 3, FIG. 16C) was compressed at a setting corresponding to a gap of about 2 mm. Another coated sample (Sample 4, FIG. 16D) was subjected to a two-stage compression with a first compression of a gap of about 5 mm followed by a compression of a gap of about 2 mm. FIGS. 16B-D show that compression of the coated substrate introduces surface failure, while direct compression at a gap of 2 mm (Sample 3, FIG. 16C) introduces significant surface failure. The SEM image of Sample 4 (FIG. 16D) suggests that a two-stage compression may result in more consistent failure by relieving some strain with the first compression step and introducing additional failure with the second compression step. SEM images of Samples 2-4 (Figures 16B-D) qualitatively show that compressed Samples 2-4 were less brittle than uncompressed Sample 1 (Figure 16A) due to the absence of uneven / width cracks shown in Figure 16A. All of the samples showed good adhesion of the precursor to the substrate, including during handling / shipping.

[0243] 17A and 17B show SEM images of cross-sections of representative portions of Sample 1 and Sample 2. Uncompressed Sample 1 (FIG. 17A) and compressed Sample 2 (FIG. 17B) have lower substrates similar to the uncompressed and compressed substrates described in Part A. In particular, the lower substrate of Sample 1 (FIG. 17A) shows relatively large pores surrounded by a thin gelatin scaffold. The lower substrate of Sample 2 (FIG. 17B) shows a collapsed / broken pore structure. The precursor / substrate network region ("network") of Sample 1 was measured to be about 200-230 microns thick. The precursor / substrate network region of Sample 2 was measured to be about 170-320 microns thick. The wider range of network thicknesses for the compressed samples appears to be related to compression, causing more breakage of the precursor to become more incorporated into the substrate, resulting in a broader overall footprint of the cross-section of the network. FIGS. 17A and 17B also show that the precursor penetrates relatively uniformly across the substrate surface. The precursor does not penetrate completely through the substrate.

[0244] In addition to the above tests, the effect of coating on compressed versus uncompressed substrates was also studied. Figures 18A and 18B show coated substrates prepared as described above, except that the coating was applied to uncompressed substrate E. The white areas in Figures 18A and 18B are areas that are not well covered by the precursor coating. In contrast, Figure 18C shows a coated substrate where the coating has been applied to compressed substrate E. There are no white areas, and the blue coating is evenly distributed up to and along the edge, up to the excluded border of the edge (note that the images in Figures 18A-C were taken through the glass of a glove box, so that there is some reflection in the images).

[0245] The results of this part of the study show that the compressed coated patches show more breakage in the PEG-based network than the uncompressed patches. The compressed coated patches also show more penetration of the precursor into the substrate layer, suggesting that delamination will be reduced (i.e., adhesion of the precursor to the substrate will be improved). Furthermore, the results of this study show that pre-coating compression can be used to remove pitting and other inconsistencies in the substrate prior to coating, thereby visually improving the consistency of the coating.

[0246] Part C. Patch testing Four coated substrate samples were prepared using the method described in Part B. Two of the samples, Patch Samples 1 and 2, were not compressed. Two of the samples, Patch Samples 3 and 4, were compressed using a calendar roller with a 5 mm gap. For all of the patch samples, the precursor adhered well to the substrate. There was no evidence of the precursor peeling off from the substrate during handling.

[0247] Following these initial observations, each patch sample was cut into 8 mm disk specimens using an 8 mm biopsy punch and tested for burst pressure. Table 16 shows the burst pressure results. Patch samples 1 and 2 (uncompressed) and patch samples 3 and 4 (compressed) showed similar average burst pressure results, but the compressed samples showed lower standard deviation burst pressure results. This result suggests that compression can improve the consistency of patch performance. The improved consistency may be the result of a more collapsed pore structure of the substrate, reduced variability in substrate thickness, improved consistency of the precursor / substrate network, increased flexibility / compliance of the hemostatic patch, and / or improved adhesion of the precursor to the substrate.

[0248] [Table 16]

[0249] The results of this study show that compression of the crosslinked gelatin substrate during coating with the precursor melt blend created a consistent and cohesive precursor / substrate network on top of the substrate. The precursor adhered to the substrate and did not fall off the substrate during handling / shipping. The results of this study further show that compression can be used to increase flexibility / compliance and improve the consistency of performance of the hemostatic patch without measurable changes in fluid absorbency or burst pressure. The results suggest that the compressed hemostatic patch mitigates some of the variability associated with manually squeezing the patch to the target surface, which contributes to better adhesion to the target surface and higher burst strength. The results also suggest that the shear forces introduced by compression through calendaring may contribute to improved flexibility and performance. The results also suggest that a two-stage or multi-stage compression process is advantageous. In particular, the results suggest that an initial compression of the bare substrate is performed to initiate pore failure / collapse, and then a second compression after coating further breaks / collapses the substrate pores and also breaks the coating.

[0250] The above-mentioned embodiments are intended to be illustrative rather than limiting. Additional embodiments are within the scope of the claims. Moreover, although the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the present invention. The incorporation of the above-mentioned documents is limited such that the subject matter is not incorporated contrary to the express disclosure of the present specification. To the extent that a particular structure, composition and / or process is described herein with components, elements, ingredients or other categories, it is understood that the disclosure of the present specification covers the particular embodiment, an embodiment that includes the particular components, elements, ingredients, other categories or combinations thereof, as well as an embodiment that essentially consists of such particular components, ingredients or other categories or combinations thereof, which may include additional features that do not change the basic nature of the subject matter as presented in the description. The use of the term "about" herein refers to the uncertainty expected in the relevant value as understood in a particular context by a person skilled in the art. With respect to the set of ranges presented by any of the parameters herein, these should be expressly construed to also recite the relevant ranges in which the lower limit from one range is combined with the upper limit from another particular range.

Claims

1. A medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises an electrophilic hydrogel precursor having a plurality of electrophilic functional groups, a nucleophilic hydrogel precursor having a plurality of protonated amine groups, and water at a rate of 2% by weight or less, and both the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are substantially uncrosslinked and are blended or in direct contact with each other.

2. The medical patch according to claim 1, wherein the dried hydrogel precursor layer comprises a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

3. The medical patch according to claim 1, wherein the substrate lasts for less than 30 days in an in vitro physiological solution maintained at 37°C.

4. The medical patch according to claim 1, wherein the substrate lasts for less than two weeks in an in vitro physiological solution maintained at 37°C.

5. The medical patch according to claim 1, wherein the substrate can absorb 300 wt% to 3000 wt% of water.

6. The medical patch according to claim 1, wherein the base material contains gelatin.

7. The medical patch according to claim 6, wherein the substrate is partially thermally crosslinked, and the substrate is a foam, a nonwoven material, or a nonwoven felt material.

8. The medical patch according to claim 1, wherein the dried hydrogel precursor layer comprises a plurality of layers of a blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

9. The medical patch according to claim 8, wherein the dried hydrogel precursor layer is formed from a pure molten blend of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor.

10. The medical patch according to claim 1, wherein the dried hydrogel precursor layer comprises a stack of one or more sublayers of the electrophilic hydrogel precursor and one or more sublayers of the nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other.

11. The medical patch according to claim 1, wherein the substrate essentially consists of gelatin, and the dried hydrogel precursor layer consists of a single solid layer essentially consisting of the electrophilic hydrogel precursor, the nucleophilic hydrogel precursor, and an optional visualization agent, the visualization agent being biocompatible.

12. The medical patch according to claim 1, wherein the electrophilic hydrogel precursor has a first hydrophilic core containing a polymer with a molecular weight of at least 5000 Da, and the nucleophilic hydrogel precursor has a second hydrophilic core containing a polymer with a molecular weight of at least 2500 Da.

13. The medical patch according to claim 12, wherein the first hydrophilic core and the second hydrophilic core independently have a molecular weight of 10 K Da to 25 K Da and 4 to 8 arms.

14. The medical patch according to claim 12, wherein the first hydrophilic core and / or the second hydrophilic core comprises polyethylene glycol, polyvinyl alcohol, polyoxazoline, copolymers thereof, or mixtures thereof, or other water-soluble, medically acceptable polymers having a modifiable functional group, and the first hydrophilic core and the second hydrophilic core comprise the same polymer.

15. The medical patch according to claim 12, wherein each of the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor independently comprises 3 to 8 arms, and the first hydrophilic core and the second hydrophilic core contain polyethylene glycol.

16. The medical patch according to claim 1, wherein the electrophilic functional group comprises an ester.

17. The medical patch according to claim 16, wherein the ester is succinimidyl ester.

18. The medical patch according to claim 1, wherein the ratio of electrophilic functional groups to protonated amine groups is 1 or less.

19. The medical patch according to claim 1, wherein the ratio of the electrophilic functional group to the protonated amine group is approximately 1.

20. The medical patch according to claim 1, wherein the ratio of the electrophilic functional group to the protonated amine group is 0.95 to 1.

05.

21. The medical patch according to claim 20, wherein the electrophilic hydrogel precursor and the nucleophilic hydrogel precursor are each water-soluble.

22. A medical patch according to any one of claims 1 to 21, further comprising a therapeutic agent.

23. The medical patch according to claim 22, wherein the therapeutic agent comprises an analgesic, an anesthetic, a steroid, an antibiotic, an anti-infective agent, an anti-inflammatory agent, a non-steroidal anti-inflammatory agent, an antiproliferative agent, or a combination thereof.

24. The medical patch according to claim 1, wherein the dried hydrogel precursor layer further comprises a visualization agent.

25. The medical patch according to claim 24, wherein the visualization agent is biocompatible and comprises a colorant, a fluorescent molecule, a contrast agent, or a combination thereof.

26. The medical patch according to claim 24, wherein the medical patch has a first side surface including the substrate and a second side surface including the dried hydrogel precursor layer and the visualization agent, and the first side surface is essentially free of the visualization agent.

27. The medical patch according to claim 26, wherein the medical patch is flexible and conformable when dry.

28. The medical patch according to claim 27, wherein the patch can be rolled up for laparoscopic delivery through a trocar.

29. The medical patch according to claim 1, having a thickness of 0.5 mm to 5 mm and independently a width and length of 1 cm to 15 cm.

30. A medical patch according to claim 1, which is free of blood components and human components.

31. The medical patch according to claim 1, wherein the dried hydrogel precursor layer forms a hydrogel upon contact with a related physiological fluid.

32. The medical patch according to claim 1, wherein the substrate, when dry or wet, is non-adherent to surgical gloves or gauze wet with a non-buffering solution.

33. The medical patch according to claim 1, which has storage stability for at least one year under refrigerated conditions against significant gelation.

34. The medical patch according to claim 1, wherein sufficient absorption of the medical patch occurs within 28 days or less upon contact with physiological fluids.

35. The medical patch according to claim 1, wherein sufficient absorption of the medical patch occurs within nine days or less upon contact with physiological fluids.

36. A medical patch according to claim 1, having a three-dimensional contour shape.

37. The medical patch according to claim 36, wherein the three-dimensional shape is a standard cone or frustum of a cone.

38. A wound filling composition comprising a certain amount of shredded material from the patch described in claim 1.

39. A medical patch comprising a biocompatible substrate and a dry hydrogel precursor layer on the substrate, wherein the dry hydrogel precursor layer comprises a PEG-electrophilic hydrogel precursor having a plurality of arms having reactive terminal electrophiles, a PEG-nucleophilic hydrogel precursor having a plurality of arms having terminal protonated amine groups, and 2% by weight or less of water, both of which are substantially uncrosslinked, and the dry hydrogel precursor layer forms a crosslinked hydrogel in 5 minutes or less when hydrated with a physiological solution.

40. The medical patch according to claim 39, wherein the substrate is biodegradable, contains gelatin, and is partially thermally crosslinked, and the substrate is a foam, a nonwoven material, or a nonwoven felt material, and lasts for less than two weeks in an in vitro physiological solution maintained at 37°C.

41. The medical patch according to claim 39, wherein the dried hydrogel precursor layer comprises multiple layers of a blend of the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor, or a stack of one or more sublayers of the PEG-electrophilic hydrogel precursor and one or more sublayers of the PEG-nucleophilic hydrogel precursor, wherein adjacent sublayers are in direct contact with each other, and the medical patch independently has a width and length of 1 cm to 15 cm and a thickness of 0.5 mm to 5 mm.

42. The medical patch according to claim 39, wherein the PEG-electrophilic hydrogel precursor and the PEG-nucleophilic hydrogel precursor independently have a molecular weight of 10 K Da to 25 K Da and 4 to 8 arms, and the reactive electrophile comprises an ester.

43. A wound filling composition comprising a certain amount of shredded material from a patch according to any one of claims 39 to 42.

Images