NL8301162A - ART SKIN. - Google Patents

Description

833035 / vdV / kd / dw

Short designation: Artificial skin.

The invention relates to an artificial skin, which can be used in particular in the treatment in humans or animals, of burns, skin diseases, of areas where the skin has been removed for transplantation or for covering the grafts themselves.

More particularly, the present invention relates to an artificial skin comprising two superimposed layers.

Such skins are already known from French patents 2,077,361, 2,377,206 and 2,332,863. These patents all relate to two-layer skins, one of which is called the outer layer, which. protects against external microorganisms, but is fully permeable to gases and other vapors, especially water, while the other layer in contact with the wound is spongy and cellular. The latter layer is bioresorbent into the skin according to French Pat. Nos. 2,377,205, while it is not in the other two patents mentioned above, while the layer according to French Pat. No. 2,077,361 serves primarily to absorb wound exudate residues .

In the manufacture of artificial skins according to the above-mentioned patents, an adhesive intermediate layer or an adhesive ribbon is generally used to unite the two layers, which have been prepared independently of each other. The independently pre-prepared layers can optionally be joined by thermoplastic fusion. All skins so produced have in particular the drawback that numerous operations are required for their manufacture. On the other hand, it has been found that certain artificial skins cannot be industrially satisfactorily manufactured by the above-mentioned methods, since the adhesion between the two layers is insufficient or because either layer is, by itself, too weak to be handled.

The invention now relates to an artificial skin which does not have the disadvantages of the known skins and can be obtained industrially by a simple method.

The invention more particularly relates to an artificial skin, the two layers of which can be obtained simultaneously.

830 1 1 6 2 1, -2- * »

The invention furthermore relates to an artificial skin which has improved mechanical properties and is therefore easy to handle.

In addition, the invention relates to an artificial skin 5 that is well tolerated by humans.

The invention also relates to an artificial skin that allows rapid healing of the wound.

The invention further relates to an artificial skin that can remain on the wound for several days, so that no daily renewals are required by the medical personnel. The skin of the present invention can therefore remain in contact with the wound throughout the healing period.

More particularly, according to a preferred embodiment, the present invention relates to an easily obtainable artificial skin, the layer of which is brought into contact with the wound is absorbent.

An artificial skin has now been found and this is the subject of the present invention, which is characterized in that it is obtained by simultaneously pouring, on a support, two polymer solutions onto each other which, after coagulation and release of the support, form two flexible and separate form layers joined together.

The invention is elucidated with reference to the annexed drawing, which schematically shows a preferred form for the industrial manufacture of an artificial skin according to the present invention.

To obtain an artificial skin according to the present invention, the following is done with reference to figure 1.

The endless belt (1), generally of a polished metal, advantageously stainless steel, is caused to move by, for example, the cylindrical motor (2), while the other cylinders (3) serve to return the angle at an angle. belt and make it possible to obtain the cycle shown in Figure 1. Obviously, this cycle can have a different shape. The belt (1) passes through a bath (4) located in / in a container (5), which bath for coagulation usually consists of water or water with a surfactant wetting agent and / or optionally a product such as acetic acid, in a amount less than 15 wt. When the belt (1) is in motion, pour on it using the casting heads (6 and 7) successively the poly- 830 1 1 6 2

* A

-3- additional solutions (8 and 9) which will form the two layers (10 and 11) of the artificial skin to be manufactured, the casting heads (6, 7) being placed such that the obtained layers (10, 11) are applied one above the other . More specifically, one of the casting heads (6 or 7) 5 is placed in front of the other (7 or 6). This is shown schematically, enlarged in Figure 2 which is a longitudinal section of the portion of the full cycle bounded by the mixed dotted lines (12 and 13). the thickness of the strip 1 not being shown in this cross-section. The casting heads (6 and 7) are of any known type and have a longitudinal slit in the portion near the belt (1), which slit is perpendicular to the direction of propagation of the belt (1), shown by the arrow. The slit width of each casting head (6 and 7) can determine the thickness of the layers (10 and 11) of the polymer solutions (8 and 9) applied to the belt. Optionally, the thickness of the layers (10 and 11) of the polymer solutions can be obtained by increasing the distance between the bottom end of the casting heads (6 and 7) and the belt 1.

The casting heads can include a scraper to adjust the thickness of the layers. Advantageously, the polymer solution (8) constituting the very thin thickness layer (10) of the skin is first applied to the belt (1) in motion, the polymer solution (9) being applied to the layer (10). In that case, the pouring head (6) containing the polymer solution (8) is placed in front of the pouring head (7) containing the polymer solution (9). The two polymer solutions (8 and 9) are applied to the belt (1) before the latter penetrates into the coagulation bath. When the two layers (10 and 11) of the polymer solution penetrate into the bath (4), coagulation takes place. At the location of the cylinder (3a), the assembly (14) consisting of the two coagulated layers (10 and 11) releases from the belt (1) and is rolled up on the roll (15) as shown by the arrow . Thus, the artificial skin is obtained, and in general the thicknesses of the two layers (10 and 11) forming the assembly (14) are smaller than those of the layers (10 and 11) of the tape ( 1) applied polymer solutions. However, in the description, for the sake of simplicity, the same numbering is used to refer to either the layers (10, 11) of the polymer solutions applied to the belt (1), or the layers (10, 11) of the skin, i.e., of designate the assembly (14) obtained after coagulation in the bath (4).

It should be noted that the assembly (14) advantageously passes through washbasins (not shown) placed after tray (5) before being rolled up on a take-up roller. In addition, the polymer solution (9) advantageously contains a suspended pore-forming agent, in which case wash basins for this pore-forming agent, which may be, for example, sodium chloride, should be present at the outlet of the tray (5).

This pore-forming agent may preferably consist of calcium carbonate with well-defined grain size and the assembly (14) is then advantageously passed into trays containing dilute acetic acid (at a concentration generally between 0.1 and 15% by weight) * which increases the porosity and promotes the connection between the pores of this layer (11) when the calcium carbonate suspension reacts with acetic acid. Advantageously, the grain size of the calcium carbonate used is between 4 and 20 microns and is used in the polymer solution (9) in an amount corresponding to 2 to 20 times the weight amount of the polymer solution (9). Optionally, the assembly (14) can be rolled directly onto the cylinder (15) at the same time as a plastic net which is thus placed between the turns of the wound assembly (14) and can be washed by immersing the wound assembly in the acetic acid solutions and then wash with water. The skin 20 obtained by the above-described method comprises two flexible layers which are remotely joined together over their entire surface.

The thickness of the layers (10 and 11) applied to the belt (1) is chosen such that the obtained artificial skin has a first layer (11) which comes into contact with the skin, the thickness of which is between 25 100 and 2500 microns, preferably between 200 and 1500 microns and a second layer (10), which forms an external protection, the thickness of which is between 10 and 200 microns, preferably between 20 and 100 microns.

Generally, the polymer solutions (8 and 9) are applied to the belt (1) at a temperature between 1 and 50 ° C and preferably between 5 and 40 ° C. The temperature of the bath (4) is generally between 1 and 50 ° C and preferably between 5 and 40 ° C. Devices not shown in the figure make it possible, if necessary, to renew the bath continuously with stirring before homogenization.

Likewise, when the strap (1) leaves the bath (not shown), rub 55 rubber scrapers advantageously over the two surfaces to retain the bath liquid as much as possible and return it to the vessel (5). In the drive cylinder (2), the belt (1) is advantageously 83 0 1 1 6 2 -5- dried by any suitable device (not shown).

The polymer solutions (8 and 9) are chosen such that the obtained artificial skin contains a first layer (11), which is brought into contact with the wound, the structure of which is cellular and porous, the diameter of the pores generally being between 10 and 100 microns, where the porosity is between 70 and 95¾. The porosity is defined as the ratio (multiplied by 100) between the volume of the pores and the volume of the pores + the volume of the polymer of this first layer (11) of the artificial skin. Preferably, the polymer-10 solution (9) is chosen such that one can obtain an artificial skin, the layer (11) of which is bioresorbent during the healing of the wound. The polymer solution 8 is advantageously chosen such that the obtained artificial skin has a second layer 10 with a selective permeability which: - the removal of serum moisture while preserving proteins of the wound, the protection of the wound against external micro-organisms, such as microbes, viruses, yeasts or wild meat - promotes the maintenance of sufficient wound moisture to allow fiber renewal.

A cross section of this layer (10) has a dense appearance under the microscope (magnification 200).

The polymer in the solution (9) is advantageously selected from the polymers based on polyamino acids. These polymers are therefore generally polymers or copolymers of van-amino acids and amino acids that contain another optionally esterified carboxyl group.

The preparation of such macromolecular substances is well known, for example, from "Synthetic Polypeptides" of Bamford, Elliot and Hauby, Academic Press, New York (1956) and from Advances in Protein Chemistry 13, 243 and following pages (1958). As esters of amino acids, it is possible in particular to use the alkyl esters, for example lower alkyl groups (methyl, ethyl). The amino acids are, for example, glutamic acid and aspartic acid.

The polymer in the solution (9) is preferably a copolymer of L-leucine and aspartic ester. The mole percentage of L-leucine is generally between 30 and 70% with the remainder of the copolymer containing the esterified diacid. Such copolymers advantageously have a specific viscosity reduced to 2 g / l, measured at 25 ° C in dichloroacetic acid, between 20 and 100 ml / gram and preferably between 30 and 70 ml / gram.

8301162 -6-

For the preparation of this copolymer, the N-carboxy anhydrides (NCA) of leucine and of the ester of the 0 (amino acid (with the COOH group at the 0 (position not esterified) are first prepared by the action of phosgene on the free amino acid groups) of these compounds The N-carboxy anhydrides are then allowed to copolymerize in the presence of a polymerization catalyst, for example, sodium hydride and / or triethylamine. replacing the benzyl group with methyl group It is also possible to hydrolyze all of the ester groups of the copolymer or a part thereof, since it contains aspartic acid groups in the macromolecular chain. to transesterification.

The solvents used to prepare the polymer solution (9) are advantageously organic solvents, or mixtures of solvents, selected in particular from dimethylformide (DMF) N-methylpyrrolidone (NMP), dimethyl acetamide (DMAC), and tetrahydrofuran (THF). The concentration of the polymer solution (9) is advantageously between 1 and 20 wt. %, preferably between 2 and 15¾ of the polymer.

The polymer of the solution (8) is non-bioresorbent and is selected, for example, from the homopolymers of acrylonitrile or from the polymers or mixtures of polymers which have repeating groups in their macromolecular chain from the polymerization of acrylonitrile and monomers containing sulfonic acid groups and / or of the polymerization of acrylonitrile and monomers containing quaternizable tertiary nitrogen atoms.

As polymers based on acrylonitrile and sulfonic acid monomer, there may be exemplified those obtained by copolymerizing acylonitrile with vinyl sulfonic acid, propene-1 sulfonic acid 1, allylsulfonic acid, methallylsulfonic acid, allyloxyethyl sulfonic acid, butene-2 and butene-3 sulfonic acid, hexene sulfonic acid in particular hexene-1-sulfonic acid; methylbutenesulfonic acid, methallyloxyethylsulfonic acid, allyloxy-3-propanol-2-sulfonic acid-1, allylthioethylsulfonic acid, allylthio-3-propanol-2-sulfonic acid-1; vinyl benzene sulfonic acids, for example, vinyl 3-benzene sulfonic acid-1; vinyl oxybenzene sulfonic acids, for example, vinyl oxy-2 and vinylloxy-4-benzenesulfonic acid-1; isopropenylbenzene sulfonic acids f 8301162 * ** -7- for example isopropenyl-2 and isopropenyl-4-sulfonic acid-1; bromovinyl-benzenesulfonic acids, for example bromo-2 and bromo-4-vinyl-3-benzenesulfonic acid-1; (A -methylstyrene sulfonic acids, -ethylstyrene sulfonic acids, isopropenylcumene sulfonic acids; mono, di- and trihydroxyvinylbenzene sulfonic acids; dichloro-2,5-vinylbenzenesulfonic acids-1, isopropenylnaphthalene sulfonic acids; - and p-methallylbenzene sulfonic acids; (o- and p-isopropenylphenyl) -4-n-butane sulfonic acids-1; vinyl chlorophenylethan sulfonic acids; o- and p-allyloxybenzene sulfonic acids; o- and p-metallyloxybenzene sulfonic acids; acids isopropyl-1-ethylene-sulfonic acid, (optionally converted into a salt).

In these polymers, the amount of the groups derived from acrylonitrile is generally between 40 and 99%, and preferably between 60 and 96% (weight percent to the total weight of the copolymer). As typical examples of such copolymers, the copolymers of acrylonitrile with methallylsulfonic acid or its salts can be mentioned, the preparation of which is described in French patent 2,076,854.

As polymers on the basis of acrylonitrile and a monomer with a tertiary nitrogen atom, mention may be made, which are obtained by copolymerization of acrylonitrile with vinyl dimethyl amine, allyldimethylamine / dimethylamino-1-propene, 2-dimethylamino-1-propylene, -dimethylamino-2-butene, 4-dimethylamino-1-butene, 3-dimethyl-amino-1-butene-3-dimethylamino-2-methyl-1 'propene, methyl ethyl allyl amine, vinyl diethylamine, 5-dimethylamino-1 pentene, 4- dimethylaminc, 3-methyl-1-butene, -x methyl-propyl-allylamine, allyldiethylamine, / methyl-amino-2-hexene, ethylvinylbutylamine, allyldiisopropylamine, / methyl-1-amino-2-propyl-1-pentene, allyldibutylamine, dialkylaminostrene especially dimethylamino styrene and diethylaminostyrene, vinyl pyridines 2-3, especially N-vinyl pyridine / vinyl pyridine / vinyl pyridine, methyl pyridine or their substitution derivatives such as methyl 2-vinyl pyridine / ethyl-2 vinyl- pyridine / Inethyl vinyl pyridine / dilnethy 1- 2- vinyl pyridine, N-vinyl carbazole, / vinyl pyrimidine, / vinyl benz midazole.

In these polymers, the amount of groups derived from acrylonitrile is generally between 40 and 99%, and preferably between 60 and 96% by weight (percent by weight, based on the total weight of the copolymer).

ft 8301162 * -8-

The quaternizing agents for the tertiary amino groups as well as the treatment conditions have been described in the literature.

In general, esters of inorganic acids are used, such as the alkyl halides, cycloalkyl halides or aralkyl halides. Preferably, the alkyl, cycloalkyl and aralkyl groups contain at most 14 carbon atoms. As examples of such quaternizing agents, the methyl, ethyl, propyl, cyclohexyl or benzyl chlorides, bromides, and iodides, dimethyl or diethyl sulfate can be mentioned.

The copolymers with sulfonic acid groups or with quaternary ammonium groups described above are insoluble in water (solubility generally less than 1 wt%) at room temperature while being soluble in organic solvents or solvent mixtures. The solvents used to prepare the polymer solution (8) are therefore organic solvents or mixtures of organic solvents, which are preferably polar and aprotic, in particular are selected from dimethylformamide, N-methylpyrrolidone and dimethylacetamide.

The concentration of the polymer solution (8) is generally between 1 and 50¾ of the copolymer, and preferably between 5 and 40¾.

The polymer solution (8) may additionally contain a mixture of a polymer which has groups in the macromolecular chain from the copolymerization of acrylonitrile and a monomer with sulfonic acid group and from a polymer in the macromolecular chain which has groups from copolymerization of acrylonitrile and a monomer with tertiary nitrogen which can be quaternized, such as those described above. Such bi-ionic polymers are described in French Patent No. 2,144,922.

The artificial skin according to the present invention is advantageously cut into pieces of practical dimensions for clinical use and is generally kept in a moist state after being treated with a hydrophilic additive such as eg glycerol or preferably polyethylene glycol with a molecular weight which is, for example, between 300 and 1000. This impregnation treatment with a hydrophilic additive can take place, for example, in trays just before the skin (14) is rolled onto the take-up roller (15).

EXAMPLE

830 1 1 6 2 -9-

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An artificial skin is continuously produced using the device described above with reference to the figures.

The polymer solution applied in the casting head (6) is a solution of 19.6¾ acrylonitrile-sodium metallylsulfonate copolymer 5 in dimethylformamide, which contains 0.6 equivalent of SO 2 groups / kg and of which at 5 g / l in the dimethylformamide (4.25 g per liter of sodium nitrate contains a reduced specific viscosity at 25 ° C of 200 ml / g.

This copolymer contains 90.5 wt. Groups derived from acrylonitrile.

10 The polymer solution (9) introduced into the pouring head (7) contains: - 8 g of a poluce condensate of leucein and the methyl ester of aspartic acid (molar ratio 62/38, of which at 25 ° C in dichloroacetic acid at 2 g / 1 reduced specific viscosity is 50 ml / g).

- 15 g of N-methylpyrrolidone, - 132 g of tetrahydrofuran, - 80 g of calcium carbonate (grain size 12 microns).

With the casting head (6) one can deposit a layer (10) with a thickness of 100 microns on the strip (1), of 0.5 mm thickness, while the casting head (7) ) on the layer (10), can deposit a layer (11) with a thickness of 400 microns. The location of the pouring head (7) is such that the two layers (10,11) 12 sec. before they are immersed in the coagulation bath (4).

The length of the belt is 20 cm and the length of the layers 25 <Ί0 and 11) is 16 cm, which corresponds to the length of the gap of the casting heads ^ 6 and 7).

The coagulation bath (4) is a solution with 1¾ (volume / volume) acetic acid and 0.2¾ (volume / volume) "Decon 90" which is kept at 20 ° C.

"Decon 90" is marketed by PR0LAB0 (No. 23 280 30 in the catalog 1975) and is an aqueous solution of potassium hydroxide, triethanolamine, sodium citrate, sodium lauryl ethoxysulfate, polyoxyethylenated alkyl phenol and alkyl benzene sulfonic acid.

The polymer solutions (8 and 9) have a temperature of 20 ° C in the casting heads (6.7).

The length of the tape (1) immersed in the bath (4) is 1 meter, the propagation speed of the tape is regulated at 0.25 meters / minute so that the coagulation time is sufficient.

8301162 -10- / The assembly (14) is collected on the cylinder (15) at the exit of the coagulation bath after it has been released from the support band in (3a).

The assembly (14) is then rolled onto cylinder (15) 5 and three. immersed in the same solution as that of the coagulation bath described above (4) for hours.

The assembly (14) is then washed for two hours with distilled water.

The assembly (14) is then divided into elements with a length of 20 cm and a width of 14 cm and impregnated with an 80/20 (volume) mixture of polyethylene glycol with molecular weight 300 and solution PBS / nrv 83501 from the BI0MERIEUX catalog. PBS is an aqueous solution containing the following ingredients: - NaCl 8 g / 1 15 - KCl 0.2 g / 1 - CaCl2, 2H20 0.132 g / 1 - MgCl2, 6H20 0.100 g / 1 - Na2HP04, 2H20 1.441 g / 1 - HK2P04 0.2 g / l. The final product is advantageously presented in an impermeable, heat-sealed and sterilized bag (2.5 megarad) sterilized.

The artificial skin thus obtained contains an outer layer (10) of acrylonitrile copolymer, the thickness of which is 65 microns, the appearance of which is closed under the microscope (magnification 200) and a bio-resorbing layer (11), the thickness of which is 280 microns and whose pore diameter ranges from 20 to 60 microns.

The artificial skin thus produced has a permeability to water vapor of 1.35 l / µm (at 22 ° C, humidity 60 °) and a flow rate to water under a differential pressure of 2 bar of 1,150 l / µm.

Samples of this sterilized artificial skin have been applied to areas where the skin was removed for transplantation from the same patient in 49 patients. These clinical trials show that the tolerability is very good and in particular no allergic reaction has been observed. The artificial skin was left on each patient throughout the healing period from the site where the graft was taken. At the end of the healing period, it was observed that the bioresorbant layer (11) had completely disappeared. The researchers emphasize the fact that the areas where the grafts were removed in a few hours, according to the invention, were no longer painful in contrast to what usually takes place. In the two series of patients examined, most patients observed a reduction of 3 to 4 days in the average time usually required for healing. After healing, an area of good quality and very satisfactory appearance was obtained.

Although the synthetic skin described above has been obtained by directly pouring the polymer solution (8) onto the support (1), ie onto the moving metal belt, it is of course not outside the scope of the invention when the polymer solution (8) is poured onto a fabric ribbon. or a non-woven porous ribbon, which has the same propagation speed and almost the same width as the belt (1). This ribbon of very small thickness (about 20 to 60 microns) can consist of polypropylene, polyester or in particular polyamide. It is carried by the belt (1) 20 during the deposition of the polymer solutions (8 and 9) and forms an integral whole with the obtained artificial skin after the latter has been released from the belt (1) at the point indicated by (3a) . Advantageously, this ribbon is only on the second layer (10) of the obtained skin, of which it strengthens the mechanical resistance.

On the other hand, optionally, the polymer solution (8) can be poured onto a film which rests on the belt (1) and thereby moves (at the same speed), which film is then separated from the obtained artificial skin (14).

An advantageous variant of the method, the skin (14) is not rolled on a receiving roller (15) and the coagulation, immersion, washing and impregnation treatments are continuously carried out in successive bins, followed by (after the bins) cutting and conditioning the skin.

8301162

Claims (10)

Artificial skin, which can be used in particular in the treatment of burns and conditions, characterized in that it is obtained by simultaneously pouring two polymer solutions (8 and 9) on a support (1) on top of each other which, after coagulation in a bath (4) and releasing the support (1), form two flexible and separate bonded layers (10, 11). Artificial skin according to claim 1, characterized in that the polymer solutions are chosen such that the skin consists of: - a first layer (11) which is brought into contact with the wound, resor-10 residing in the organism, biodegradable, cell-shaped, hygroscopic, containing interconnected cells, spongy and permeable to liquids, - a second layer (10), which forms an external protection, permeable to gases, but maintains sufficient moisture and 15 external pathogenic micro organisms. Artificial skin according to claim 2, characterized in that: - the polymer solution (9), with which the first layer (11) can be obtained, mainly consists of a polymer or a copolymer of 20 Cl amino acids, - the polymer solution (8), with which the second layer (10) can be obtained, mainly consisting of a polymer selected from the homopolymers of acrylonitrile or from the polymers or mixture of polymers which repeat in their macromolecular chain groups derived from the polymerization of acrylonitrile and monomers containing sulfonic acid groups and / or from the polymerization of acrylonitrile and monomers containing quaternizable tertiary nitrogen atoms. Artificial skin according to claim 3, characterized in that the polymer solution (9) with which the first layer (11) is obtained contains a polycondensate of leucine and aspartic acid, the carboxyl group furthest from the amino group, at least in part, is esterified with a methyl group, and the polymer solution (8), by which the second layer (10) can be obtained, contains a polymer obtained by copolymerization of acrylonitrile and sodium methyl-35-sulfonate. 8301162 -13- Artificial skin according to claim. 2-4, characterized in that the polymer solution (8) with which the layer (10) can be obtained contains a polymer of which the amount of groups originating from acrylonitrile exceeds 40 wt. 5o, relative to the total weight of the polymer. Artificial skin according to claims 2-5, characterized in that the polymer solution (9) with which the first layer (11) can be obtained contains a pore-forming agent in an amount corresponding to 2-20 times the weight of the polymer of this solution. Artificial skin according to one or more of the preceding claims, characterized in that the polymer solution (9) as pore-forming agent contains calcium carbonate and the coagulation bath (4) is an aqueous solution containing between 0.1 and 15 wt. % acetic acid. Artificial skin according to one or more of the preceding claims, characterized in that the polymer solutions (8 and 9) are cast on an endless moving belt (1). Artificial skin according to claims 2-8, characterized in that the polymer solution (8) has 1 to 50 wt. % polymer, the polymer solution (9) 1-20 wt. % polymer, the solution (8) from which the outer layer (10) of the skin can be formed is poured onto the support (1) and the solution (9) is poured onto the layer (10) which is deposited on the support (1). Artificial skin according to one or more of the preceding claims, characterized in that the polymer solutions (8 and 9) are cast on a reinforcement tape applied to the support (1), which tape forms a whole with the obtained skin after it has been released. of the carrier (1). 8301162