EP4232102A2

EP4232102A2 - Resorbable covering membrane for medical wound area treatment

Info

Publication number: EP4232102A2
Application number: EP21835198.9A
Authority: EP
Inventors: Heinrich Planck; Erhard Müller; Svenja Reimer; Christian PLANCK; Helmut Hierlemann
Original assignee: Polymedics Innovations GmbH
Current assignee: Polymedics Innovations GmbH
Priority date: 2020-12-03
Filing date: 2021-12-03
Publication date: 2023-08-30
Also published as: WO2022117840A3; KR20230116852A; JP2023551572A; DE102020215295A1; WO2022117840A2; US20230390453A1; PE20240364A1; MX2023006608A

Abstract

The invention relates to a covering membrane (10) for medical wound area treatment, in particular for burns or for preventing adhesion. The covering membrane (10) has a substrate layer (12) comprising a polymer material as well as collagen particles (14) which have a particle size I of more than 80 µm and are disposed in such a way as to be fixedly embedded in at least some portions of the polymer material of the substrate layer (12). The invention further relates to a process for manufacturing such a covering membrane (10).

Description

Resorbable cover membrane for medical treatment of wound surfaces

The present invention relates to an absorbable cover membrane for medical treatment of wound surfaces.

Such a cover membrane is known, for example, from EP 1 181 941 A2 and is marketed by Polymedics GmbH, Germany, under the name Suprathel®. The cover membrane is used in medical practice as a wound contact material, e.g. B. as a skin replacement material for burns or for the treatment of so-called decollements, d. H. of scouring wounds of the skin.

US Pat. No. 8,951,598 B2 discloses a cover membrane which has a biodegradable polymer carrier layer made from polylactic acid or polyglycolic acid has, which is doped with collagen nanoparticles. The polymer carrier layer can have, for example, a polylactide-glycolide copolymer (PLGA) with 10 to 40% by weight of nanoscale collagen particles.

The cover membrane mentioned at the outset offers pain-relieving and anti-infective effects in open wound surface treatment and allows largely undisturbed formation of granulation tissue with good mechanical properties at the same time. However, the haemostatic effect of the cover membranes is quite limited and the cover membrane shows only a slow ability to adsorb and absorb liquids on bloody wound surfaces or those wetted with exudate. It is well known that postoperative adhesions frequently occur in everyday clinical practice after operations in the abdomen. Such tissue adhesions can result in recurrent chronic pain, infertility and possibly even a mechanical blockage of the small intestine ( = ileus). It is known that even microscopically small peritoneal tissue lesions in connection with blood can cause adhesions. In this respect, additional prophylactic measures are useful, which promote accelerated postoperative healing and counteract such adhesions. Because of their slow capacity to adsorb and absorb liquids, the cover membranes mentioned are only conditionally suitable for intraperitoneal use for the purpose of adhesion prophylaxis.

It is therefore the object of the invention to specify a cover membrane which has improved haemostatic properties and allows an even broader spectrum of use. In addition, it is the object of the invention to specify a method for producing such a cover membrane.

The object relating to the cover membrane is achieved according to the invention by a cover membrane having the features specified in patent claim 1 . The manufacturing method according to the invention is specified in claim 13. Preferred developments of the invention are specified in the dependent claims and in the description. According to the invention, the cover membrane has collagen particles with a particle size of more than 80 μm, which are arranged and kept embedded at least in sections in the polymer material of the carrier layer. Due to the known swelling capacity of fibrillar collagen, ie collagen whose secondary or tertiary structure is intact, the binding of water to the cover membrane can be accelerated and the water-binding capacity of the cover membrane per unit area can be increased. In the present application, fibrillar or structurally intact collagen is understood to mean collagen whose α and β bands can be detected in the SDS-PAGE test.

Due to the fact that the collagen particles are anchored in the polymer material of the carrier layer, which is itself water-absorbent, the absorption of water by the polymer material of the carrier layer itself can also be promoted. When the cover membrane is applied to the wound surface, excess blood plasma and/or wound exudate can be removed from the wound surface more quickly and effectively. The swelling of the collagen particles increases the thickness of the cover membrane—at least locally—so that the distance between the cover membrane and the wound tissue supplied with it can increase, at least locally.

In addition, rapid contact of blood or wound exudate present on the wound surface can be made possible by the collagen particles. It is known that when collagen comes into contact with a wound, the binding of the von Willebrand factor (vWF) to the collagen and to the corresponding receptor of the thrombocyte membrane of thrombocytes and the adhesion of thrombocytes is promoted. The emptying of platelet granules (degranulation) can be increased and plasmatic blood coagulation (secondary hemostasis) can be triggered or increased. This is advantageous for accelerated and effective hemostasis and is not the case when using nanoscale collagen particles. Due to the particularly high bioavailability of collagen, the haemostatic properties of the cover membrane can be improved, and vascularization of the wound surface and thus wound healing can be accelerated. With an appropriately flexible, deformable design of the cover membrane, it can be easily adapted even to intraperitoneal surfaces that are difficult to cover three-dimensionally and to wound surfaces of the skin, for example in the area of joints.

The collagen particles preferably have a particle size in the range from 80 μm to 500 μm, particularly preferably in the range from 100 μm to 250 μm, very particularly preferably in the range from 100 μm to 150 μm. Surprisingly, it has been shown in practice that the haemostatic effect of the collagen in situ decreases beyond an average particle size of approximately 500 μm and the anchoring of the collagen in the carrier layer is no longer sufficiently stable with respect to the mechanical forces acting on the cover membrane during handling and application is. This can lead to an undesired shearing of the collagen particles from the carrier layer. Particularly reliable hemostasis can be achieved with a particle size between 100 μm and 150 μm.

According to a preferred development of the invention, the cover membrane has 0.4 to 80% by weight, preferably 0.5 to 25% by weight, of collagen particles. It should be noted that the improved haemostatic properties of the sheet material mediated by the collagen are already achieved with approximately 1% by weight of collagen. In this respect, the flat material can have in particular 0.4-2% by weight of collagen particles.

According to a preferred development of the invention, at least some of the collagen particles extend away from the carrier layer. The collagen particles thus form a collagen pole on the back and front of the carrier layer. Due to the size of the collagen particles alone, the cover membrane in the area of the collagen pole is more hydrophilic than without such a collagen pole. With this structure of the cover membrane, an immediate bioavailability of the collagen particles and thus an even faster onset of hemostatic effect of the cover membrane can be achieved. Alternatively or additionally, at least a portion of the collagen particles can bulge over the front or rear surface area of the carrier layer that encompasses or surrounds the respective collagen particle. In this case, the respective collagen particle is preferably kept completely embedded in the polymer material of the carrier layer.

According to the invention, the aforementioned collagen pole of the carrier layer has a structural height of more than 10%, preferably more than 20%, of the nominal thickness of the carrier layer. As a result, reliable contacting of the wound with the collagen particles can be achieved in a simplified manner, independently of the smallest possible bending radius of the cover membrane. This is advantageous for the liquid-absorbing and haemostatic effect of the cover membrane over its entire functional surface. In this way, the formation of unwanted accumulations of blood or wound fluid on the wound and also an associated risk of infection can be counteracted in a particularly reliable manner.

According to the invention, the carrier layer can have a collagen pole made of collagen fibers on both sides. On the one hand, this eliminates the risk of the cover membrane being applied the wrong way round on the wound surface to be treated with it. On the other hand, the collagen poles of the two sides of the carrier layer can differ from one another in terms of their nominal thickness, the average density of their collagen fibers per unit area of the cover membrane and/or the size of their collagen particles. As a result, one and the same cover membrane can be used for different wound management requirements, thus further expanding its range of application. In addition, when cover membrane sections are folded over, an undesired mutual adhesion of cover membrane sections can be counteracted.

The collagen pole on one side of the covering membrane can, for example, comprise collagen particles with an average particle size of 100 to 150 μm and the pole on the other side of the covering membrane can contain collagen particles with an average particle size between 250 and 500 μm. This can do that Swelling behavior of the collagen particles of the respective edging or pile of the carrier layer can be adapted to the respective wound area to be treated.

The collagen particles of the covering membrane can in particular be made from native type I and/or type III collagen, in particular bovine collagen. Such collagen is available on the market in sufficient quantities and in high purity.

According to the invention, the carrier layer can in particular comprise a copolymer based on the monomers lactide, glycolide, trimethylencarbonate, s-caprolactone and/or 1,4-dioxan-2-one or polyhydroxybutyrate (PHB) or mixtures of these polymers. As a result, the cover membrane can develop an anti-infective and pain-reducing effect, with complete hydrolytic and enzymatic degradability being fully retained.

According to the invention, the carrier layer can contain 20% by weight to 99.6% by weight of copolymer and/or polyhydroxybutyrate and 0.4% by weight to 80% by weight of collagen particles with a particle size >80 μm, preferably 0.8% by weight. to 25% by weight of the collagen particles.

According to the invention, the carrier layer can in particular comprise a terpolymer of 65 to 87% by weight of lactide, 5 to 20% by weight of trimethylene carbonate and 5 to 20% by weight of E-caprolactone. The monomers lactide, trimethylene carbonate and s-caprolactone can be present in the terpolymer in particular in the range from 85/10/5 to 70/20/10% by weight.

The carrier layer of the cover membrane preferably has a nominal thickness d of 50 to 3000 μm, preferably 80 to 500 μm or 800 to 2500 μm.

The method according to the invention for producing the cover membrane explained above comprises the following steps: • comminuting provided and preferably dried native collagen to form collagen particles with an average particle size greater than 80 μm, preferably greater than 100 μm;

• Production of a polymer solution from an absorbable polymer and a suitable solvent;

• a) Suspending the collagen particles in the polymer solution and applying the collagen suspension thus obtained with the collagen particles suspended therein to a flat carrier; or b) application of the polymer solution to a planar support after the support has previously been sprinkled with the collagen particles and/or with subsequent sprinkling of the polymer solution with the collagen particles; and

• Removal of the solvent by drying, in particular by freeze drying.

The suspension/dispersion of the collagen particles in the polymer solution has to be carried out very carefully in order not to further damage the collagen particles directly or through shearing forces, in particular to further comminute them. Very finely divided collagen (< 50 μm) degrades very quickly to gelatine in the polymer solution, so that the fibrils of the collagen particles with their original helical shape are destroyed. It is therefore procedurally necessary to maintain the particle size greater than 80 µm to preserve the integrity and desired function of the collagen in vivo. It is therefore necessary to focus on a size and structure-preserving suspension/dispersion of the collagen particles. According to the invention, this is preferably achieved in that the collagen particles are dispersed or suspended in the polymer solution by stirring for a maximum of two minutes, preferably for a maximum of one minute.

It is also possible to suspend/disperse the collagen particles by stirring in the pure solvent for a maximum of two minutes, preferably one minute, and then carefully stirring the collagen suspension with the polymer solution. Drying stabilizes the carrier layer of the cover membrane. Longitudinal segments of the collagen particles arranged outside the carrier layer can partially stand up during drying or when the cover membrane is detached from the planar carrier. If the flat support is in the form of a plate, in particular a glass plate, with a completely flat surface, the back of the dried cover membrane is correspondingly smooth, ie in particular without collagen particles extending away from the back of the support material. If the cover membrane is to have a collagen pole on both sides, a glass plate with micro-indentations or, alternatively, a carrier with a microporous coating can be used as the planar carrier.

If the collagen particles are scattered onto the carrier or onto the polymer solution/collagen suspension applied to the carrier, this can be done solely by gravity or also forced by means of a compressed gas/compressed air. In this way, the collagen particles can be anchored particularly reliably in the polymer solution or the collagen suspension.

According to the invention, the native collagen is preferably dried before it is comminuted, or the comminuted collagen particles are dried before they are suspended in the solution. In the former case, a particularly efficient comminution of the collagen and in the latter case a particularly efficient suspension of the collagen particles in the solution can be achieved.

Further advantages of the invention result from the description and the drawing. Likewise, the features mentioned above and those detailed below can be used according to the invention individually or collectively in any combination. The exemplary embodiments described below are not to be understood as an exhaustive list, but rather have an exemplary character for the description of the invention.

Show in the drawing: 1 shows a cover membrane with a carrier layer, in which collagen particles with a particle size of more than 80 μm are anchored, in a schematic sectional view;

2 shows a cover membrane in a side view;

3 shows the cover membrane according to FIG. 2 in a plan view showing a collagen particle which is completely embedded in the polymer material of the carrier layer and protrudes over the (planar) surface area of the carrier layer surrounding the collagen particle.

FIG. 4 shows the cover membrane according to FIG. 2 after swelling in water at 37° Celsius for several hours;

5 shows a block diagram of a method according to the invention for producing a cover membrane according to the invention; and

6 shows an SDS-PAGE test for detecting an undesired degradation of collagen particles as a function of the mixing time when mixing the collagen particles with a polymer solution.

1 shows a covering membrane 10 for the medical treatment of wound surfaces, which is also particularly suitable for intraperitoneal adhesion prophylaxis. The cover membrane 10 comprises a carrier layer 12 with a front side and a back side 12a, 12b. The carrier layer 12 is structurally formed here by a copolymer based on the monomers lactide, trimethylene carbonate, E-caprolactone and/or 1,4-dioxan-2-one, or polyhydroxybutyrate (PHB) or mixtures of these polymers. The carrier layer 12 is therefore biocompatible and hydrolytically and/or degradable by endogenous enzymes and completely resorbable.

The carrier layer has a nominal thickness d which, depending on the mechanical application requirements placed on the cover membrane 10, can be from 50 to 3000 μm, preferably from 80 to 500 μm or from 1000 to 2500 μm. For improved hemostasis or faster absorption of blood and wound fluid, collagen particles 14 are embedded in the material of the carrier layer 12, at least in sections. In other words, the collagen particles 14 are anchored in the material of the carrier layer 12 . The collagen particles 14 can be kept embedded in the polymer material of the carrier layer and, according to FIG. 1, at least partially extend away from the carrier layer 12 or bulge over the front side, as explained below in connection with FIG. If the collagen particles 14 extend away from the carrier layer, they can together form a collagen pole 16 of the carrier layer 12 . When the cover membrane 10 is ready for use, the structural height h of the collagen pole 16 can be more than 10%, preferably more than 20%, of the nominal thickness d of the carrier layer 12.

The collagen particles 14 all consist of comminuted native collagen, for example type I and/or type III collagen, and can in particular be of bovine, murine or porcine origin. The collagen particles 14 have a particle size I of more than 80 μm, preferably between 100 μm and 500 μm, particularly preferably between 100 μm and 250 μm.

Due to the collagen pole 16, the cover membrane 10 has two different useful sides 18, 20 in the exemplary embodiment shown in FIG. If the cover membrane 10 is applied with its pole-side useful side 18 to a wound surface (not shown), direct contact with the wound surface by the collagen particles 14 is made possible. This ensures a particularly high bioavailability of the collagen and its functional advantages in the treatment of wound surfaces are fully exploited at an early stage. These include, in particular, the known haemostatic properties of fibrillar collagen, its swelling capacity due to a pronounced absorption capacity of blood and wound exudate, and its favorable effects with regard to rapid vascularization of the wound surface and wound healing. In practice it has been shown that even small mass fractions of the collagen particles 14 promote the aforementioned effects. In this respect, the cover membrane 10 can comprise between 0.5 to 80% by weight of collagen particles 14, preferably between 0.8 to 25% by weight of collagen particles 14. In practice, the cover membrane 10 can be folded and respective folding sections (not shown), e.g. B. with their mutually facing back 12b, are superimposed. Particularly in the case of adhesion prophylaxis, this offers the advantage of a particularly large liquid absorption capacity in relation to the surface unit 22 of the folded cover membrane 10 in contact with the wound surface. In addition, laparoscopic application of the cover membrane can be facilitated as a result.

According to an embodiment not shown in the drawing, the cover membrane 10 can also have a collagen pole 16 made of collagen particles 14 on both sides. In practice, this can on the one hand counteract an inadvertent laterally inverted application of the covering membrane 10 and provide a usable collagen surface 20 on both sides. At the same time, when the cover membrane is applied to a wound, an annoying sticking of the cover membrane 10 to itself can be counteracted. It should be noted that the collagen poles 16 on the front and back sides 12a, 12b of the carrier layer 12 can differ from one another in terms of the average density of their collagen particles 14 per unit area 22 of the cover membrane 10 and/or the size of their collagen particles 14 or their structural height h . As a result, a cover membrane 10 with different collagen useful sides 18, 20 can be provided and the possible range of uses of the cover membrane 10 in treating wound surfaces can thus be expanded.

In the figs. 2 to 4 another cover membrane 10 is shown in its ready-to-use state. This cover membrane differs from the exemplary embodiment explained above in connection with FIG. 1 essentially in that the collagen particles 14 are arranged and kept completely embedded in the polymer material of the carrier layer 12 . In other words, the collagen particles 14 are here completely surrounded or enveloped by the polymer material of the carrier layer. 2 shows a side view of the cover membrane, in which the nominal thickness d of the carrier layer can be clearly seen. 3 shows the ready-to-use cover membrane 10 in the area of a collagen particle 14 in a microscopic plan view and with a height profile along the measuring section marked S. The collagen particle 14 bulges together with the polymer material (locally limited) over the surface area 24 of the front side 12a of the carrier layer 12 surrounding the collagen particle 14 . The surface area 24 of the carrier layer 12 is planar or essentially planar.

If the cover membrane 10 shown in Fig. 3 is placed in water and then analyzed by measurement, there is increased swelling of the cover membrane 10 in the area of a collagen particle 14, i.e. locally limited, compared to collagen-free carrier layer sections of the cover membrane or the collagen particle 14 surrounded 4 shows a microscope image of the cover membrane 10 after a water bath at 37° C. for 22 hours. The nominal thickness d (cf. FIG. 1) of the cover membrane 10 is approximately 250 μm on average according to the height profile image, with the collagen particle 14 shown (cf. FIG. 1) being approximately 350 μm over the surface region 24 of the carrier layer 12 (cf. FIG. 1) that encompasses the collagen particle 14 collagen particle-free carrier layer section) protrudes.

Water contacting the cover membrane 10 diffuses through the polymer material of the support layer covering the collagen particles 14 and is absorbed by the collagen particles 14 . In this way, the collagen particles 14 withdraw water from a bleeding wound and thus accelerate the cessation of bleeding. The combination of the collagen particles 14 and the synthetic resorbable polymer (e.g. polylactide-caprolactone-trimethylene carbonate) combines the positive properties of both materials. The resorbable polymer material of the carrier layer 12 is in direct contact with the wound (eg a burn wound) and can improve wound healing through the enzymatic release of lactic acid and develop a pain-relieving and anti-infective effect. production method

In the following exemplary embodiments of a method 100 for producing the cover membrane 10 according to the invention, reference is also made to the block diagram shown in FIG. 5 with individual method steps of the method 100 .

The method 100 has the following method steps:

In a first step 102, provided and preferably dried native collagen 200 is comminuted to form collagen particles 14 with a particle size greater than 80 μm, preferably greater than 100 μm.

In a subsequent optional step 104, the collagen particles 14 can be suspended in an organic solvent 202, for example dimethyl sulfoxide (DMSO), to form a collagen stock suspension 204. Surprisingly, the collagen particles 14 are stable or largely stable in pure DMSO, so that the collagen particles 14 suspended in DMSO do not degrade.

In a further step 106, a polymer solution 206 is produced from an absorbable polymer 208 and a suitable solvent 210.

In step 108 the collagen particles 14 or the collagen particles 14 contained in the collagen stock suspension 204 are suspended/dispersed in the polymer solution 206 so that a collagen suspension 212 is obtained.

Here it must be ensured that the size and functionality of the collagen particles 14 (ie structural integrity with detectability of o and ß bands in the SDS-PAGE test) are retained. It has surprisingly been shown that the collagen particles 14 are not stable, for example in a solution 206 of a statistical terpolymer of D,L-lactide-trimethylene carbonate-caprolactone, and can degrade over time to form collagen particles 14 with a grain size of <50 μm. In that regard, on the one hand, a speedy processing of Collagen Suspension 212 displayed. In addition, when mixing the collagen particles 14 with the polymer solution 206, extremely gentle stirring, in particular for a limited period of time, is indicated in order not to further comminute or destroy the collagen particles 14 directly or through shearing. For example, a dispersing device from the Ultra Turrax® series from IKA®-Werke GmbH & CO. KG, Germany.

6 shows the result of an SDS-PAGE test (sodium dodecyl sulfate polyacrylamide gel electrophoresis test) of the collagen suspension 212 as a function of the stirring time using an aforementioned Ultra Turrax® stirrer. In the first (left) lane, a protein marker PM (protein marker: "Precision Plus Protein Standard" from BioRad with defined molecular weights between 10 - 250 kDa; 10 μl sample volume) was applied. The reference bands typical of the protein marker PM are shown A solution containing native bovine collagen (sample volume 4 μl) was applied to the second lane. In lanes 7 to 10, a sample (sample volume 33 μl) of the collagen suspension 212 was applied with a stirring time of 2×15 s (lane 7), 2× 30 s (lane 8), 2 x 60 s (lane 9) and 2 x 5 min (lane 10).

The collagen bands (o, ß and y regions) typical of collagen particles 14 can be clearly seen with an Ultra Turrax® mixing time of 2×15 s (lane 7). Even with a mixing time of 2 x 30 s and 2 x 60 s, the intensity of the bands in the y and ß region decreases increasingly. With a mixing time of 2 x 5 min, the bands in the y-region are almost no longer recognizable and the bands in the o- and ß-region are clearly less pronounced. Astonishingly, the reduction in the intensity of the o, ß and y regions shows a clear degradation of the collagen even after stirring for 5 minutes. With even longer stirring, the alpha and beta bands in the collagen suspension 212 can also no longer be recognized (not shown). For the aforementioned reasons, the collagen particles 14 are preferably dispersed/suspended in the respective polymer solution 206 for less than 2 minutes, very particularly preferably for a maximum of 1 minute. The collagen suspension 212 obtained in this way is applied to a flat carrier 216 in step 110, preferably by means of a doctor blade 214. In particular, a glass plate can be used as the flat carrier 216 .

In a final step 112, the collagen suspension 212 is dried, in particular freeze-dried, and the solvent 210 is thereby removed.

Alternatively or in addition to steps 104 and 108, the collagen particles 14 in step 114 can also be applied to the flat carrier 210 before the solution 206 or the collagen stock suspension 212 is applied to the flat carrier 210 or after the application of the solution 206/collagen suspension 212 be applied or scattered onto the planar carrier 210 onto the solution 206/collagen suspension 212. In the latter case, this can be done by means of a compressed gas or by means of compressed air in order to introduce the collagen particles 14 into the solution 206 or the collagen suspension 212 at least in sections.

example 1

In step 102, 0.5 g of dried bovine collagen 200 is comminuted into collagen particles 14 with a grain size>80 μm. The collagen particles 14 are subsequently dispersed in an organic solvent 202 in step 104 to obtain a collagen stock suspension 204 . For this purpose, the collagen particles 14 are added, for example, to 49.5 g of dimethyl sulfoxide (DMSO) and gently dispersed therein for 15 seconds. This gives a 1% collagen stock suspension 204.

In the subsequent step 106, a 150 g example of a 23% solution 206 of a statistical terpolymer of D,L-lactide-trimethylene carbonate-caprolactone in a solvent 208 is provided.

Subsequently, in step 108, a total of 50 g of 1% DMSO collagen stock suspension 204 is mixed with 150 g of 23% solution of a random terpolymer of D,L-lactide-trimethylene carbonate-caprolactone Mixed collagen suspension 212 and homogenized twice for 15 seconds each time by stirring.

In step 110, the collagen suspension 212 is squeegeed onto the carrier 216, for example a glass plate, using a squeegee 214 with a squeegee gap of 250 μm, and then in step 112 freeze-dried. This creates a cover membrane 10 with a nominal thickness d of approx. 120 μm, consisting of 98.6% lactide-trimethylene carbonate-caprolactone terpolymer and 1.4% bovine collagen particles 14.

example 2

In step 108, a total of 1.15 g of ground collagen particles 14 with a particle size >80 μm are added to 100 ml of a 23% polymer solution 206 of a statistical terpolymer of D,L-lactide trimethylene carbonate-caprolactone in DMSO and stirred gently to form the collagen suspension 212 .

The collagen suspension 212 is then squeegeed onto the flat carrier 216 in step 110 using a squeegee 214 with a squeegee gap of 500 μm. Finally, the solvent 210 of the collagen suspension 212 is removed by freeze-drying the collagen suspension 212 . This creates an approximately 100-250 μm thick cover membrane in the form of a collagen composite membrane made from 95% of a random terpolymer of lactide-trimethylene carbonate-caprolactone and 5% collagen particles 14 with a grain size>80 μm.

Example 3

If a total of 4.6 g of collagen particles 14 with a particle size >80 μm are alternatively suspended in the polymer solution 206 according to example 2, a cover membrane 10 of about 100-250 μm thick and made of 80% of a random terpolymer is obtained with otherwise unchanged further process steps from D,L-lactide - trimethylene carbonate caprolactone and 20% bovine collagen particles 14 with a grain size of over 80 pm. Example 4:

In the first step 102, native cattle collagen is comminuted into collagen particles 14 with an average particle size of >80 μm. Then, in step 104, 0.25 g of the dried collagen particles 14 are added to 49.5 g DMSO and gently dispersed for 15 seconds. This gives a 1% collagen stock suspension 204.

In step 108, 50 g of the 1% DMSO collagen stock suspension 204 are mixed with 150 g of a 12.5% solution of a random terpolymer of D,L-lactide-trimethylene carbonate-caprolactone and homogenized 2×15 seconds by stirring. The collagen suspension 212 obtained in this way is squeegeed onto the flat carrier 216 using a squeegee 214 with a squeegee gap of 600 μm.

In step 112, the collagen suspension 212 is freeze-dried, so that a cover membrane with a nominal thickness of approximately 180 μm d made of 98.6% lactide-trimethylene carbonate-caprolactone terpolymer and 1.4% bovine collagen particles 14 with a grain size>80 μm is obtained.

Claims

Cover membrane (10) for medical treatment of wound surfaces, in particular burns or for adhesion prophylaxis, with a carrier layer (12) comprising an absorbable polymer material and with collagen particles (14) with a particle size I > 80 μm, which are present in the polymer material of the carrier layer (12) at least in sections are arranged held embedded. Cover membrane (10) according to Claim 1, characterized in that the collagen particles (14) have an average particle size I in the range between 80 μm and 500 μm, preferably in the range between 100 μm and 250 μm, very particularly preferably in the range between 100 μm and 150 μm pm, exhibit. Cover membrane (10) according to claim 1 or 2, characterized in that the cover membrane (10) between 0.4 and

80% by weight, preferably between 0.4 and 25% by weight, very particularly preferably between 0.4 and 2%, of collagen particles (14). Cover membrane (10) according to one of the preceding claims, characterized in that at least some of the collagen particles (14) bulge over the surface area of the carrier layer (12) surrounding the respective collagen particle (14) or with the formation of a collagen pole (16) of the carrier layer (12) stretched away. Cover membrane (10) according to Claim 4, characterized in that the collagen pole (16) when the cover membrane (10) is ready for use has a structural height h of more than 10%, preferably more than 20% of the nominal thickness d of the carrier layer (12) having. Cover membrane (10) according to Claim 4 or 5, characterized in that the carrier layer (12) has a collagen pole (16) on both sides. Cover membrane (10) according to one of the preceding claims, characterized in that the collagen particles (14) are made from native, in particular bovine, collagen of type I and/or type III. Cover membrane (10) according to one of the preceding claims, characterized in that the carrier layer (12)

• a copolymer based on the monomers lactide, trimethylene carbonate, glycolide, s-caprolactone and/or l,4-dioxan-2-one, or polyhydroxybutyrate (PHB) or

• Includes mixtures of these polymers. Cover membrane (10) according to Claim 8, characterized in that the carrier layer (12) comprises a terpolymer of 65 to 87% by weight lactide, 5 to 20% by weight trimethylene carbonate and 5 to 20% by weight E-caprolactone. The cover membrane (10) of claim 9, wherein the monomers lactide, trimethylene carbonate and s-caprolactone are present in the terpolymer in the range of 87/8/5 to 70/20/10% by weight. Cover membrane (10) according to one of the preceding claims, wherein the carrier layer (12) has a nominal thickness d of 50 μm to 3000 μm, preferably of 80 μm to 500 μm or of 1000 μm to 2500 μm. Method (100) for producing a cover membrane (10) according to one of the preceding claims, comprising the steps:

• Crushing (102) provided and preferably dried native collagen (200) into collagen particles (14) with an average particle size greater than 80 μm, preferably greater than 100 μm;

• Production (106) of a polymer solution (206) from an absorbable polymer (208) and a suitable solvent (210);

• a) suspending (108) the collagen particles (14) in the polymer solution (206) and applying (104) the collagen suspension (212) thus obtained with the collagen particles (14) suspended therein to a flat carrier (216); or b) applying (104) the polymer solution (204) to a flat carrier (216) after previously sprinkling (114) the carrier (216) with the collagen particles (16) or with subsequent sprinkling (114) of the polymer solution (206) with the collagen particles (14); and

• Removal (112) of the solvent (210) by drying, in particular by freeze drying. Process according to Claim 12, characterized in that a copolymer based on the monomers lactide, trimethylene carbonate, glycolide, E-caprolactone and/or 1,4-dioxan-2-one or polyhydroxybutyrate (PHB) or mixtures of these polymers is used. Method according to Claim 12 or 13, characterized in that the collagen particles (14) are dispersed in the polymer solution (206) by stirring for a maximum of two minutes, preferably for a maximum of one minute.