Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
  • A61L27/58—Materials at least partially resorbable by the body
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/70—Carbohydrates; Sugars; Derivatives thereof
  • A61K31/715—Polysaccharides, i.e. having more than five saccharide radicals attached to each other by glycosidic linkages; Derivatives thereof, e.g. ethers, esters
  • A61K31/716—Glucans
  • A61K31/722—Chitin, chitosan
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/02—Cosmetics or similar toiletry preparations characterised by special physical form
  • A61K8/0208—Tissues; Wipes; Patches
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/30—Cosmetics or similar toiletry preparations characterised by the composition containing organic compounds
  • A61K8/64—Proteins; Peptides; Derivatives or degradation products thereof
  • A61K8/65—Collagen; Gelatin; Keratin; Derivatives or degradation products thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/72—Cosmetics or similar toiletry preparations characterised by the composition containing organic macromolecular compounds
  • A61K8/73—Polysaccharides
  • A61K8/736—Chitin; Chitosan; Derivatives thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/14—Macromolecular materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P17/00—Drugs for dermatological disorders
  • A61P17/02—Drugs for dermatological disorders for treating wounds, ulcers, burns, scars, keloids, or the like
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q19/00—Preparations for care of the skin
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
  • C08B37/0024—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Glucans; (beta-1,3)-D-Glucans, e.g. paramylon, coriolan, sclerotan, pachyman, callose, scleroglucan, schizophyllan, laminaran, lentinan or curdlan; (beta-1,6)-D-Glucans, e.g. pustulan; (beta-1,4)-D-Glucans; (beta-1,3)(beta-1,4)-D-Glucans, e.g. lichenan; Derivatives thereof
  • C08B37/0027—2-Acetamido-2-deoxy-beta-glucans; Derivatives thereof
  • C08B37/003—Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
  • C08B37/0063—Glycosaminoglycans or mucopolysaccharides, e.g. keratan sulfate; Derivatives thereof, e.g. fucoidan
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
  • C08H1/00—Macromolecular products derived from proteins
  • C08H1/06—Macromolecular products derived from proteins derived from horn, hoofs, hair, skin or leather
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q19/00—Preparations for care of the skin
  • A61Q19/08—Anti-ageing preparations

Definitions

• BIODEGRADABLE POLYMERS PREPARATION THEREOF AND USE THEREOF IN THE MANUFACTURE OF BIOMATERIALS AND DRESSINGS
• the present invention relates to a new chemical process in aqueous medium for modifying biodegradable polymers.
• the method comprises a first aqueous reaction step between an amino acid, a peptide or a polypeptide with maleic anhydride to form a vinyl carboxylic acid which is in a second reaction step in contact with a biodegradable polymer having at least one primary amine function such as a glycosaminoglycan, such as chitosan, or a fibrous protein, such as collagen or elastin.
• the subject of the present invention is also the biodegradable modified polymers obtained according to the process and their use in the medical, pharmaceutical and cosmetic fields, particularly for the manufacture of biomaterials and dressings having biocompatibility and haemostatic properties. , bactericidal and / or healing.
• the adhesive power of the blood clot due to the presence of a polymerized fibrin network has been well known since 1909 when Bergel confirmed that fibrin can be used as a physiological bonding agent with healing properties.
• Ashton et al. report that conventional hemostatic gauze pads and the like, impregnated with a hemostatic material such as ferric chloride, thrombin, or the like, have been used in surgery for years to stop bleeding.
• a hemostatic material such as ferric chloride, thrombin, or the like
• these surgical haemostatic materials are criticized because they can not be left in situ in a closed wound because of the risk of neighboring tissues reacting to these foreign bodies.
• these materials are left inside a scarred wound, it will reopen the wound by breaking the formed blood clot involving new bleeding.
• Ashton et al therefore, mention that there is a vital need for hemostatic materials that could remain in a closed wound without causing serious reactions in the surrounding tissues.
• Ashton et al. propose the use of oxidized cellulose which not only has hemostatic properties but is also absorbable by animal tissues. Ashton et al. therefore propose hemostatic materials in oxidized cellulose having increased stability against deterioration during storage.
• the oxidized cellulose used comes from wood pulp, cotton, cotton linters, ramie, jute, paper or similar materials, and also regenerated cellulose or rayon produced by the "viscose" or Bemberg processes. This invention led to the commercialization of Surgicell TM by Johnson & Johnson.
• Glycosaminoglycans are thus long chains of unbranched polysaccharides made of the repetition of the same disaccharide unit.
• the disaccharides of this unit comprise a monosaccharide carrying a carboxylic group called galacturonic acid and a second saccharide carrying an N-acetylamine group called acetylglucosamine or N-acetylgalactosamine.
• These glycosaminoglycans are abundant in connective tissues, particularly in bone and cartilage tissue.
• the most used glycosaminoglycans are, for example, hyaluronic acid, chondroitin sulfate, dermatan, heparan sulphate or heparin.
• These same connective tissues also contain fibrous proteins of collagen and elastin structure, these two proteins also having very interesting medical applications in the field of wound healing.
• glycosaminoglycans are found in the carapaces of invertebrates: such as Chitin [ ⁇ - (1,4) -2-acetamido-2-diseoxy-D-glucose or poly N-acetyl-D-glycosamine].
• Chitin [ ⁇ -1,4) -2-acetamido-2-diseoxy-D-glucose or poly N-acetyl-D-glycosamine].
• the deacetylation of chitin leads to the formation of [( ⁇ -1,4) -2-amino-2-deoxy-D-glucose] chitosan.
• Chitin is the second most abundant natural polysaccharide after cellulose. It is well known that glycosaminoglycans and fibrous proteins have natural biocompatible, biodegradable, haemostatic and healing properties.
• biopolymers or biomaterials make it possible to classify them as biopolymers or biomaterials. Many medical or aesthetic applications have been developed with these biomaterials, especially in the field of wound healing. Each native biopolymer has its own biological and physicochemical properties, some have more fragile biomechanical properties or degrade in vivo faster than others. Depending on the desired use, much work on their chemical structural modification has been made to these biopolymers to obtain a biomaterial that is mechanically and chemically more robust, more absorbent or biochemically more active. Some modifications aim at modifying the volume or surface properties of the biopolymers so that these new biomaterials bring an exponential absorption of their thickness when they are in contact with the aqueous medium.
• K. Park ef a /. Biodegradable Hydrogels for Drug Delivery- Technomic, Publishing Co., Inc. 1993, p. 107) have classified polysaccharides according to the following sources: i. Algae: Agar-agar, furcelleran, alginate, carrageenan; ii. Plants: plant extract (starch, pectin, cellulose), exudate gums (Arabian gum, tragacanth, karaya, ghatti) and seed gums (guar gum, locust bean gum) iii. Microbial: xanthan, pullulan, scleroglucan, curdlane, dextran, gellan. iv. Animal: Chitin and Chitosan, Chondroitin Sulfate, Dermatane Sulfate, Heparin, Keratane, Hyaluronic Acid.
• Synthetic polymers such as polyols and their derivatives, poly (vinylalcohols), polyvinylpyrrolidones, polyesters, or polyanhydrides are very well exploited for various pharmaceutical and medical applications. These polymers, considered as biodegradable materials, are often called "hydrogels".
• the biomaterials mentioned above can be made and used alone, taking into account their hemostatic properties or by incorporating coagulation proteins such as fibrinogen and thrombin, and proteins that promote healing. Pharmaceutically acceptable ingredients may also be added such as antibiotics, antibacterial agents, anti-cancer agents, etc.
• the first step of the process according to the invention for modifying the biodegradable polymers consists of a reaction between the maleic anhydride and an amino acid or one of its derivatives.
• Japanese Patent JP56012351 discloses the production of an N-acylamino acid by the reaction of a maleic or succinic anhydride with an amino acid in the presence of an inert organic solvent such as tetrahydrofuran ( THF) or dioxane, resulting for example in obtaining N- ⁇ -carboxypropionyl-DL- ⁇ -alanine.
• THF tetrahydrofuran
• the reaction is carried out at a temperature between 40 and 110 °, is used as an intermediate in the synthesis of organic compounds such as surfactants or in the extension of the chain of high molecular weight compounds such as polyamides or polyesters .
• Japanese Patent JP 59197459 (Itou Fumisaku et al., 1984) describes a method for obtaining polyamide materials resistant to impacts and fatigue due to bending from maleic anhydride grafted onto an elastomer which is then put into place. in reaction with an amino acid.
• US Pat. No. 5,665,693 (Kroner et al., 1997) describes a method for the preparation of detergents or cleaners containing a very low level of phosphate or in the absence of phosphate. This method involves reacting maleic anhydride, maleic acid and / or fumaric acid with hydrolysed proteins or proteins that have not passed the dipeptide stage. The reaction was carried out at a temperature of between 120 and 300 ° C. under high pressure and in a mixture of aqueous and organic solvents.
• Japanese Patent JP 2000319240 discloses a method for producing a maleinamic acid by reacting maleic anhydride with an amino carboxylic acid in the presence of an ammonium salt and in a hydrocarbon solvent non-polar.
• maleic anhydride reacts rapidly and especially with amino groups of proteins and peptides with formation of maleyl-proteins.
• the maleyl-amino group is very stable at neutral or alkaline pH but easily hydrolyzed at acidic pH. This characteristic makes it possible to block amine groups reversibly.
• the maleyl group could be removed because of the protonated forms of the free carboxylic groups that catalyze the hydrolysis of the amide linkages.
• De Wet PJ (Agroanimalia, (1975), 7 (4), pp. 101-104) describes the preparation of maleylmethionine by the reaction of maleic anhydride with L-methionine. according to the author, this compound is stable at pH 5.0 and 60% hydrolyzed at pH 2.20 after 8 hours. This reversibility of the reaction of maleic anhydride with an ⁇ -amino acid is proposed as a possible method for protection against ruminal deamination.
• the second step of the process according to the invention consists in modifying a biodegradable polymer and in particular collagen or chitosan.
• Fibrous proteins such as collagen, and glycosaminoglycans, such as chitosan, are often processed or polymerized to produce products with novel characteristics corresponding to new uses required or expected. These products have many applications in the medical, pharmaceutical, aesthetic or cosmetic fields.
• Collagen is a fibrous glycoprotein contained in connective and interstitial tissues. With its high molecular structure, it constitutes a very important element of the extracellular matrix of the human body. There are different types of collagen depending on their location with properties that allow it to be classified as one of the main essential elements of the skin, tendons, cartilage and bones. Collagen is inextensible and resists traction. It is particularly essential to the process of healing. Because of its haemostatic and healing properties, collagen has many interesting applications in the biomedical field. There are some major following applications of collagen:
• Gelatin only plays a passive role in topical hemostasis where bleeding is mechanically controlled by pressure on the wound or cut.
• the passive haemostatic effect of gelatin is only used for limited use where the need for a gelatin sponge to absorb abundant blood is necessary.
• These sponges are lyophilized products made from a purified and specially treated gelatin solution. Placed on the wound, they absorb a quantity of body fluid equivalent to several times their weight.
• Native collagen can not be used for all the applications mentioned above. The reason often evoked is its rapid degradation in vivo, its lack of elasticity which prevents it from adapting to the contour of wounds and also its low tensile force. This is why the authors cited below seek to change the natural state of collagen to find new applications.
• the collagen changes are often focused on the polymerization or grafting of other groups or other polymers of natural or chemical origin. In general, the change in the initial collagen structure greatly reduces the immunological response.
• collagens are of animal or human origin.
• collagen has biochemical and physicochemical characteristics that are relatively well suited for its use in biomaterials. These characteristics are in particular a good biocompatibility, a biodegradability and a remarkable hemostatic property.
• collagen has a mechanical pulling force that is too weak.
• Collagen-based products such as medical, surgical or cosmetic implants have encountered defects such as the difficulty of manual handling. Collagen is difficult to fold, it is difficult to follow the outline of an injury.
• the biodegradability of collagen for some application is considered too fast, for example the implant takes a long time to provide palliative and curative actions.
• collagen-based medical products must be chemically modified and often by coupling collagen to another chemical group.
• Enzymatically modified collagen has been prepared and tested by Rubin and Stenzel [Rubin, AL and Stenzel, KH, in Biomaterials (Stark, L. and Aggarwal, G., Eds.), Plenum Press, NY (1969)] which show that the treatment does not cause an immune response compared to unmodified collagen. This difference in behavior is explained by the fact that the enzyme used effectively removes telopeptides from collagen without destroying the initial molecular structure.
• U.S. Patent 4,488,911 discloses a method for preparing collagen in solution (CIS), wherein native collagen is extracted from animal tissue and diluted in an aqueous acidic solution, and then digested with an enzyme such as pepsin, trypsin or Pronase TM. Enzymatic digestion removes the telopetide portions of the collagen molecules, and isolates atelopeptide collagen in solution. The atelopeptide collagen thus obtained is substantially non-immunogenic and substantially uncrosslinked due to removal of the major crosslinked regions. Collagen in solution can then be precipitated by dialysis in a moderate shear environment to produce collagen fibers that look like native collagen fibers.
• an enzyme such as pepsin, trypsin or Pronase TM. Enzymatic digestion removes the telopetide portions of the collagen molecules, and isolates atelopeptide collagen in solution.
• the atelopeptide collagen thus obtained is substantially non-immunogenic and substantially uncrosslinked due to removal
• the precipitated and reconstituted fibers may also be crosslinked by heating or radiation in the presence of a chemical crosslinking agent such as for example an aldehyde such as formaldehyde or glutaraldehyde.
• a chemical crosslinking agent such as for example an aldehyde such as formaldehyde or glutaraldehyde.
• the products obtained can be used as medical implants because of their biocompatibility and their reduced immunogenicity.
• telopeptide collagen Despite the unchanged protein structure after purification, purified collagen or atelopeptide collagen degrades more rapidly in vivo when implanted in mammals. For this reason, the polymerized atelopeptide collagen has been cross-linked or grafted with chemical radicals to increase its fiber network and allow the modified product to resist longer in vivo biodegradability, increase its tensile strength or solution viscosity.
• the first group uses a crosslinking or polymerizing agent which forms a bridge between the same molecules or through this bridge other molecules could be grafted onto this bridge.
• US Pat. No. 3,823,212 (Chvapil et al., 1974) describes a method for obtaining membranes or sponges based on crosslinked collagen by treating collagen with glutaraldehyde at low temperature, from -5 to -40 ° C. and lasting from one day to 30 days. Antibiotics may be added to the collagen during its preparation.
• the products obtained have found medical applications such as the treatment of burns or abrasions of the skin (where large affected surfaces must be covered to prevent wound infections), assist wound healing by providing active therapeutic compounds, or prevent maceration of wounds and slow absorption of exudations.
• U.S. 4,060,081 discloses the use of collagen and mucopolysaccharides as synthetic skin, crosslinked using glutaraldehyde. Another use of glutardialdehyde to crosslink collagen has been described in US Pat. No. 4,131,650 (Braumer et al., 1978). The authors describe a treatment of the skin by applying to it a water-based paste on which is placed a sheet containing at least 3% by weight of water-soluble collagen having a permeability to the skin. water of more than about 0.1 g / dm 2 / min, the collagen being transported through the dough and absorbed by the skin.
• the sheet has a thickness of about 0.01 to 0.03 mm and has a degree of crosslinking corresponding to that obtained for about 0.1-0.5% by weight of glutardialdehyde used in an acid medium.
• the leaflet may also contain an active cosmetic agent such as amino acid, peptide, protein, hormone, placental extract, phosphatide, tissue extract, fresh cells and vitamins.
• the dough can be dried by heating, producing a retraction of the leaflet to increase contact with the skin.
• U.S. Patent 4,424,208 discloses an improved collagen formulation suitable for use in soft tissue augmentation.
• the Wallace formulation comprises reconstituted atelopeptide fibrillar collagen (such as, for example, Zyderm ® ) in combination with crosslinked atelopeptide collagen particles dispersed in an aqueous medium.
• the addition of cross-linked collagen particles improves the persistence of the implant or its ability to resist retraction after implantation.
• the crosslinking agent used is glutaraldehyde.
• US Patent 4,582,640 (Smestad et al., 1986) describes the preparation of a gluturaledehyde-crosslinked atelopeptide CIS (GAX) for use in medical implants.
• Collagen is crosslinked under conditions favoring fibers rather than inter-fibers and the product obtained has a greater persistence than a non-crosslinked atelopeptide collagen.
• the product is marketed by Collagen Corporation under the trademark Zyplast ® .
• US Patent 4,597,762 discloses a method for the preparation of type I collagen and the polymerization thereof with glutaric dialdehyde in the presence of ficin and L-cysteine.
• the product obtained is for use in human and veterinary medicine.
• cross-linked collagen A major disadvantage to the use of cross-linked collagen is the negative biological reaction due to the release of aldehyde, a reagent often used to polymerize collagen and make it insoluble in several applications. Detachment of the cross-linked collagen-bound aldehyde demonstrates cell cytotoxicity, specifically for the fibroblast (Speer et al., J. Biomedical Materials Research 1980, 14, p.753, Cook et al., British J. Exp. 64: 172).
• glutaraldehyde polymers unlike glutaraldehyde in monomeric form, form lattice bonds between collagen molecules and that these bonds can rearrange to release glutaraldehyde and glutaraldehyde polymers (Cheung, DT and Nimni, MD, Connective Tissue Research 10, 187-217, 1982).
• Collagen coupling agents used to prevent secondary and parasitic reaction due to free aldehydes constitute the second coupling group.
• new coupling agents are:
• anhydride dicarboxylic compounds
• US Patents 4,703,108 and US 4,970,298 Teach the preparation of a collagen matrix, sponge or film by contacting the collagen with a crosslinking agent selected from a carbodiimide and an active ester is derived from N-hydroxysuccinimide followed by high dehydration.
• US Patent 4,713,446 discloses a chemically modified collagen prepared by reacting native collagen with di- or tri-carboxylic acid derivatives such as halides, sulfonyls, anhydrides or esters as than coupling agents. This reaction is controlled so as to limit the degree of crosslinking.
• the reaction takes place at the level of the residual amine functions of the lysine found on the collagen.
• the product obtained is dissolved in a physiological buffer thus giving a viscoelastic solution having various therapeutic applications in the surgical field and particularly in ophthalmology.
• the crosslinking agents are, in particular, amino succinic, succinic chloride, phthalic amine or glutanic.
• No. 5,412,076 discloses a crosslinked modified collagen soluble in water or in an aprotic and polar organic solvent, the free thiol groups belonging to the cysteine residues or its analogs are crosslinked by the formation of disulfide bridges and to give gels or crosslinked products in the presence of mild oxidizing agents, this method allows excellent control of the reaction rate and degree of crosslinking.
• the various applications are in the field of adhesives, biomaterials for the formation of prostheses, implants or other medical articles.
• U.S. Patent No. 5,874,537 discloses collagen-based compositions for uses as adhesives or sealants for medical use. Prior to polymerization, soluble or partially fibril collagen monomers for solution are chemically modified with an acylating agent, a sulfonating agent for a combination of both.
• the collagen compositions thus prepared can be used as medical adhesives for bonding soft tissues or as sealant films having a variety of medical uses such as wound closure or tendon coating to prevent adhesion formation. after a surgical operation.
• US Pat. Nos. 5,866,165 and 5,972,385 (Liu et al., 1999) describe the preparation and use of a support matrix for the production of tissues such as bone, cartilage or soft tissue.
• a polysaccharide is reacted with an oxidizing agent to open the polyssacharide sugar rings and thereby form aldehyde groups that react to form covalent bonds in the collagen.
• the polysaccharide used is hyaluronic acid.
• US Patent 6,165,488 discloses a similar method using a naturally occurring polyaldehyde macromolecule obtained by crosslinking collagen with periodate for uses as biocompatible, bioabsorbable and nontoxic materials for medical use or therapeutic.
• US Patent 6,309,670 discloses a method of treating bone tumors comprising administering a matrix composed of a collagen, a polysaccharide and a differentiation factor. The polysaccharide reacts with an oxidizing agent to open the sugar rings thereby forming aldehyde groups which as previously discussed react to form covalent binders in the collagen.
• the polysaccharides used are hyaluronic acid, dextran or dextran sulfate.
• US Patent 6,127,143 discloses the use of a phosphorylaton method to obtain a biocompatible product from a purified collagen that is produced using two proteolytic enzyme treatments and a reducing agent. Prior to phosphorylation, the purified collagen is delipidated and then processed by compression, dehydration, dispersions and drying to form collagen fibers. Purified and biocompatible collagen can be used in transplantation or hemostasis and can be combined with compounds such as antibiotics, antivirals, growth factors or other compounds useful for biomedical uses.
• US Pat. No. 6,335,007 discloses a collagen gel which is obtained by crosslinking a polyanion with a carbodiimide.
• the polyanions used are alginic acid, gum arabic, polyglutamic acid, polyacrylic acid, polyaspartic acid, polymalic acid, carbomethylcellulosetel and a carboxylated amino and water-soluble carbodiimides such as 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide.
• the claimed product consists of a kit for producing the collagen gel comprising an aqueous solution of collagen, a aqueous solution of polyanion and an aqueous solution of carbodiimide.
• Patents 6,969,400 and 6,911,496 disclose a composition of a crosslinked polymer comprising a first synthetic polymer containing multiple nucleophilic groups covalently attached to a second synthetic polymer containing a multitude of electrophysical groups.
• the first synthetic polymer is preferably a polypeptide or polyethylene glycol that has been modified to contain several nucleophilic groups such as primary amines or thiols.
• the second synthetic polymer may be a hydrophilic or hydrophobic polymer containing or having been modified to contain one or more electrophilic groups such as succinimidyl groups.
• Compositions may also contain other compounds such as natural polysaccharides or proteins such as glycosaminoglycans or collagens and / or biological agents.
• This patent also teaches methods for using the crosslinked polymer compositions to improve adhesion between first and second surfaces; tissue augmentation to prevent the formation of surgical adhesion or to cover the surfaces of synthetic implants.
• U.S. Patent 6,962,979 discloses crosslinked biomaterial compositions which are prepared using hydrophobic polymers and a crosslinking agent.
• the hydrophobic polymers used are mainly those containing two or more succinimidyl reactive groups including disuccinimidyl suberate, bis (sulfosuccinimidyl) suberate and dithiobis (succinimidylpropionate).
• the crosslinked biomaterial compositions prepared using mixtures of hydrophobic compounds and hydrophilic crosslinking agents are also taught in this patent. The compositions can be used to prepare implants for various medical uses. US Pat. No.
• 6,916,909 (Nicolas et al., 2005) describes new peptide collagens which are modified by grafting free or substituted thiol functions contained in the mercaptoamine radicals.
• the essence of this invention is to obtain thiol collagens which can be crosslinked in a sufficient and controlled manner by forming sulfur bridges and which are also biocompatible.
• US Patent 6,790,438 discloses a peptide modified collagen to prevent postoperative adhesions.
• the peptide collagen is modified by the grafting of the thiol functions present on the mercaptoamine radicals which are exclusively grafted onto the aspartic and glutamic acids of the collagen chains in formation of amine bonds.
• the third group relates to copolymerization reactions between the collagen and a polymer by a covalent bond giving a more or less cross conformation.
• the polymers most associated with collagen are acrylic derivatives, acrylonitriles, styrenes, polyurethanes, polyalcohols and silicones.
• US Patent 4,452,925 discloses hydrogels prepared by polymerization of a mixture comprising a significant amount of an organic monomer having a polymerizable ethylenic group such as N 1 N-dimethylacrylamide, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate or methoxytriethylene glycol methacrylate, and a small amount of solubilized collagen.
• the reagents used are at least partially soluble in the aqueous reaction medium.
• the hydrogels thus prepared constitute articles of new shape that are useful in the medical and cosmetic fields.
• the fourth collagen coupling group consists in producing a dense network by creating covalent bonds only between the collagen molecules without incorporation of other groups of molecules.
• This group includes: ultraviolet, beta or gamma irradiation produces deamination and thus allows coupling at the imine and aldol bonds or free radicals released by these ray sources, which form structures with the covalent bridges.
• This coupling method can only be performed with a low energy source; the use of a high energy source leading to hydrolysis or denaturation of collagen;
• Carbodiimides such as cyanamide and dicyclohexylcarbodiimide are reagents used in this process;
• U.S. Patent 4,614,794 (Easton et al., 1986) discloses obtaining a biomaterial from a mixture of collagen and sodium alginate. After a lyophilization step, these compounds are converted into a coupled dehydrothermal complex by heating at 115 ° C. under vacuum for 48 hours.
• US Pat. No. 4,931,546 (Tardy et al., 1990) describes the coupling between the collagen molecules, at neutral or basic pH, by means of aldehyde functions formed by the action of a periodic acid or its salts. of sodium with the collagen molecule.
• US Patent 4,958,008 (Petite et al., 1990) describes a method for obtaining a biomaterial for the preparation of a collagen-based bioprosthesis that has been coupled through the formation of an azide-collagen group. and amine of the collagen lysine terminal giving an amide bond. This formation gives an internal coupling reaction of the collagen network.
• Chitosan derived from deacetylated chitin is a polysaccharide composed of the random distribution of ⁇ - (1-4) -linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Due to its haemostatic properties and its affinity for lipids, chitosan has become for more than two decades a highly exploited substance for its applications in the medical, pharmaceutical, cosmetic and dietary fields. Medical applications are also based on the characteristics of chitosan, such as its biocompatibility (minimizes inflammatory reactions), its bioabsorbability and biodegradability.
• chitosan is well known to be a good substrate for cell colonization thereby stimulating cell growth and increasing the rate of wound healing by stimulating immune response and tissue reconstruction, preventing microbial infections, and absorbing the exudate.
• chistosane also has antibacterial and antimicrobial properties.
• U.S. 4,031,025 (Vanlerberghe et al., 1977) describes the method of acylating chitosan with a saturated or unsaturated diacid anhydride.
• the product obtained is used in the cosmetic preparation as a moisturizing agent for the skin.
• the saturated anhydrides used are succinic anhydride, acetoxysuccinic anhydride, methylsuccinic anhydride, diacetyltartaric anhydride and diglycolic anhydride.
• the unsaturated anhydrides are maleic anhydride, itaconic anhydride or citraconic anhydride.
• chitosan derivatives obtained therefore carry an acid group corresponding to the anhydride used by the formation of a covalent bond with the amines of chitosan.
• US Pat. No. 4,424,346 (Hall et al., 1984) describes the production of chitin and chitosan derivatives for their use in metal chelation, in the pharmaceutical and cosmetic formulation, in chromatographic separation, in the immobilization of enzymes. etc.
• These derivatives are obtained by a modification of the amine residues on polyglucosamine with formation of groups:
• the modification must allow an improvement and not the opposite of the physical properties of the biodegradable polymer to be modified, such as the traction force and the workability.
• the polymers once modified must remain biocompatible and biodegradable biomaterials. If the polymer used is a biomaterial, it must remain after its modification. The chemical reactions of modifications generally take place in an organic medium that can prematurely damage the chain. polymer or weaken it. In aqueous media, the chemical compounds used such as EDC OR NHS can also be trapped in the material and make it toxic and therefore not biocompatible.
• the coupling agent used to modify the polymer must not cause parasitic cross-linking reactions of the polymer chains, and this again to avoid the denaturation of the biodegradable polymer used and thus retain its initial properties.
• the present invention aims to meet the needs mentioned above.
• a first object of the present invention is a process for preparing a modified biodegradable polymer comprising:
• step (b) A second aqueous reaction step between the vinyl carboxylic acid obtained in step (a) and a biodegradable polymer having at least one primary amine function to obtain the desired modified biodegradable polymer.
• a second object of the present invention is the modified biodegradable polymer obtained by the method described above and its use for the production of biomaterials having biocompatible, haemostatic and healing properties.
• Another object of the present invention is a dressing comprising the biomaterial as defined above.
• the hemostatic dressing according to the invention is biocompatible and has haemostatic and healing properties
• the present invention addresses the difficulties encountered in the field of biomaterials and makes it possible to achieve very simply biomaterials for use in the manufacture of biological dressing, skin substitute, prosthesis and / or implant.
• biomaterials have both hemostatic, healing and antiseptic properties, and are also biocompatible, cytocompatible and biodegradable.
• the advantages of the present invention are essentially due to the use during the polymer modification process of an aqueous medium to retain the initial properties of the polymer and limit the presence of residual chemical compounds in the material making it unsuitable to its use as a biomaterial.
• an unsaturated dicarboxylic acid to modify an amine biodegradable polymer makes it possible to avoid the cross-linking reactions of these polymers.
• the subject of the present invention is a process for preparing a modified biodegradable polymer.
• the method generally comprises a first aqueous reaction step (a) between an amino acid, a peptide or a polypeptide and maleic anhydride (also known as but-2-enanoic anhydride) to form a vinyl carboxylic acid.
• a reaction in aqueous medium takes place between the vinyl-carboxylic acid obtained in step (a) and a biodegradable polymer.
• the biodegradable polymer used must have at least one primary amine function which reacts with the double bond of the vinyl carboxylic acid.
• the modified biodegradable polymer is obtained.
• step a) of the process according to the invention can be represented as follows:
• R represents an amino acid, peptide or polypeptide residue of the general formula (I) HOOC-R-NH 2 .
• the residue R can be chosen so that the general formula (I) preferably represents an essential amino acid. More preferably, the essential amino acid is selected from glycine, L-alanine, valine, leucine, isoleucine, phenylalanine, methionine, tryptophan, serine, threonine, asparagine, glutamine , aspartic acid, glutamic acid, cysteine, tyrosine, histidine, lysine and arginine.
• the essential amino acid is selected from glycine, L-alanine, valine, leucine, isoleucine, phenylalanine, methionine, tryptophan, serine, threonine, asparagine, glutamine , aspartic acid, glutamic acid, cysteine, tyrosine, histidine, lysine and arginine.
• the R residue may also be chosen so that the general formula (I) represents a non-essential amino acid.
• the non-essential amino acid is chosen from the residues presented in Table 1 below:
• the R residue may also be chosen so that formula (I) represents a peptide or a polypeptide.
• residue R can also be chosen so that formula (I) represents an aromatic molecule, provided that the compounds of formula (I) aromatic are soluble in water.
• the advantage of using maleic acid lies in the formation of the vinyl carboxylic acid compound of formula (II) having a double bond located at the ⁇ of a dicarboxylic acid function. Accordingly, the double bond is activated and will react, preferably in acidic aqueous medium, with the amino function (s) of the biodegradable polymer to be modified in step (b) of the process.
• the amino function will not react under these conditions with the acid functions of the molecule of formula (II), thus avoiding any crosslinking reaction between several polymer chains. Accordingly, the amino acid, peptide or polypeptide portion of the molecule of formula II will remain free once it is grafted onto the biodegradable polymer.
• step (a) is preferably carried out in an aqueous medium and at a temperature of between approximately 20 and 100 ° C., preferably between approximately 20 and 80 ° C. and more preferably between approximately 20 and 60 ° C.
• the process according to the present invention is the use of water as a reaction solvent, thus avoiding premature polymer chain destruction due to the use of an organic solvent.
• maleic anhydride reacts in water to return to its hydrated state. Because of this hydrolysis reaction of the anhydride in an aqueous medium, the molar ratio between the maleic anhydride and the amino-carboxylic acid (I) used in step (a) is between about 1/1 and 2/1, more preferably this ratio is between 1, 2/1 and 2/1, and even more preferably the molar ratio between maleic anhydride and amino-carboxylic acid (I) is about 1, 5 / 1.
• the compound of formula (I) used in step a) of the process according to the invention is preferably present in the reaction medium so that its concentration is very high. More preferentially, the reaction medium is saturated with the compound of formula (I). Depending on the degree of solvation of the compound of formula (I), heating may be applied to facilitate its dissolution and to accelerate the coupling reaction.
• the formation of the vinyl carboxylic acid (II) (or coupling product) is instantaneous in the form of fine powders.
• the coupling product is recovered by vacuum filtration and washed several times with water to remove the maleic acid formed by the hydrolysis of maleic anhydride.
• the washing water is preferably cooled to about 4 to 10 0 C to prevent the loss of coupling product.
• the coupling product is then dried in air. It should be noted that the yield obtained decreases when the steric hindrance of the radical R increases.
• the unsaturated dicarboxylic acid of general formula (II) is reacted with a biodegradable natural polymer having at least one amino function present on its molecular structure.
• the number of amine functions of the biodegradable polymer is variable and depends on the nature of the biodegradable polymer chosen.
• the double bond of the vinyl-carboxylic acid is activated by the presence of the carboxylic acid function and reacts, preferably in acidic aqueous medium, with the function or functions amines of the biodegradable polymer.
• the biodegradable natural polymer used is a fibrous protein or a glycosaminoglycan.
• the rate of modification (or grafting rate) of a fibrous protein or a glycosaminoglycan is complex.
• this rate of change can be determined by physicochemical methods such as viscosity measurements of the solutions of the modified polymers (see the article Durand A. et al, Biomacromolecules, 2006, vol 7 (3), pp 958 -64, relating to preparation of hydrophobically modified polysaccharides).
• the fibrous protein used is collagen or elastin. Even more preferentially, the fibrous protein used is collagen.
• step b) of the process comprises a covalently coupling reaction between the vinyl-carboxylic acid of formula (II) on collagen molecules.
• the source of collagen may be prepared from tendons, ligaments, skins or any other sources containing collagen and well known to those skilled in the art.
• the source of collagen sources can be selected from terrestrial animals: horses, pigs, cattle, reptiles including birds and sailors.
• the placenta of human origin can be used to isolate human collagen.
• all sources and all types of collagen can be used to carry out their coupling with the vinyl-carboxylic acid of general formula (II) obtained according to step (a) of the process described above.
• the collagen used may be native or crude, or enzymatically treated with pepsin or ficin or papain to remove the telopeptide.
• Collagen can also be purified or chemically pre-modified.
• the collagen used in step (b) of the process is of volatile origin such as chicken, goose, duck or other types of birds.
• the selected bird is a chicken aged about 6 to 10 weeks from which the legs are removed.
• the legs are recovered after slaughter and used within 24 hours or can be stored at -20 0 C for later use.
• the legs are washed with demineralized water, then disinfected with a 70% ethanol solution, then split longitudinally along the metatarsals and fingers, and are soaked in a sterile solution of sodium chloride at a concentration of between 2 and 4 M (mol / L), preferably 2 M, for 1 to 4 weeks at a temperature of between about 2 and 8 ° C.
• the scales surrounding the legs are removed and the tendons, ligaments and skin are removed from the bones and then cut into small pieces.
• Tris (hydroxymethyl) aminomethane commonly called Tris
• w / v weight / volume
• sodium citrate at 2.40% (w / v)
• pH 7.30-7.50
• ambient temperature is meant a temperature of the part to which the operator works and being generally between 15 and 3O 0 C.
• the materials are milled using a domestic blender for a period of at least one (1) minute (min.), Preferably in four (4) times fifteen (15) second (s), or until obtaining a pasty consistency.
• the collagen solution thus obtained is added with a second volume of 0.5M acetic acid (or 3% v / v) and the stirring continues for 4 hours at room temperature.
• a solution of pepsin (Sigma) in 0.5M acetic acid (or 3% v / v) is added to the collagen solution for purifying the collagen without the telopeptides.
• the solution is stirred at room temperature for at least 24 hours, preferably between 24 to 72 hours.
• the solution is then centrifuged. The residue is thus removed and the solution containing the collagen is recovered.
• the collagen solution is cooled to a temperature between about 0 and 2 ° C and then its pH is adjusted to about 9 with a solution of NaOH (1ON and 1 N) previously cooled to a temperature of about 0 to 2 ° C to deactivate the excess pepsin.
• the temperature of the solution should be constantly maintained at between about 0 and 2 ° C during pH adjustment.
• This solution is then centrifuged at low temperature between about 0 and 2 ° C at a rotation speed of about 4200 rpm (round per minute) for one hour.
• the supernatant containing the purified, highly viscous collagen is recovered.
• the residue containing the deactivated pepsin and the telopeptides is removed.
• the purified collagen is isolated by adding solid NaCl with stirring to a final concentration of 2.5 M per liter of collagen solution or by addition of a 1 M solution of sodium acetate.
• the precipitated collagen is recovered by centrifugation, solubilized again in a solution of acetic acid at 0.5 M (or 3% v / v) and reprecipitated again in a solution of NaCl (1M) or sodium acetate ( 1 M).
• the collagen recovered by centrifugation is washed twice with a 0.3M NaCl solution.
• the purified atelopeptide collagen is dissolved in 1% (v / v) acetic acid and ready to be coupled with the unsaturated carboxylic acid. .
• the atelopeptide collagen recovered after the last wash may be dehydrated with ethanol or acetone, dried and stored for later use.
• Collagen such as atelopeptide collagen obtained according to the method described above, is dissolved in an approximately 1% (v / v) solution of acetic acid.
• the vinyl carboxylic acid of general formula (II) (which is also hereinafter referred to as the coupling agent) is added to the collagen solution with stirring for one hour.
• the solution becomes viscous and is heated at 37 ° C for 15 minutes or until complete dissolution of the coupling agent.
• the coupled collagen solution becomes more fluid and the stirring is maintained for about one to four hours at about 20 ° C.
• the coupled collagen is precipitated by adding an equivalence of 1 M solid NaCl or 1 M sodium acetate per liter of collagen solution.
• the precipitate is recovered by centrifugation for 45 minutes at a rotation speed of about 4200 rpm and at a temperature of about 2 to 4 ° C.
• the coupled collagen is dissolved again in a 1% (w / v) solution of acetic acid, and the collagen is precipitated for a second time by adding a solution of 0.8M NaCl or 1M acetate acetate. sodium with stirring. Stirring is maintained for about one to four hours to complete the precipitation.
• the biodegradable natural polymer used in step b) of the process according to the invention is a glycosaminoglycan.
• glycosaminoglycan used is chitosan derived from chitin.
• the chitosan used must contain at least 75% of amino groups (NH 2 -), which amounts to chitin deacetylated at a rate of at least 75%.
• the chitosan used is commercial chitosan from crab shells with a deacetylation level of greater than 85% (Chitosan referenced C3646 in Sigma).
• the chitosan is dissolved in acetic acid at 3% w / v.
• the vinyl carboxylic acid is added to the powder with vigorous stirring.
• the mixture is heated to about 60 0 C and this temperature is maintained until the total dissolution of the acid.
• the heating is then cut off and stirring is maintained for about two (2) hours.
• the coupled chitosan is precipitated by addition of a 1 M solution of NaCl or 1 M sodium acetate per liter of chitosan solution.
• the precipitate is recovered by centrifugation or filtration and washed at least twice with pure water.
• the washed precipitate is finally recovered by centrifugation or filtration and dehydrated with ethanol or acetone and dried in air and at about 20-25 ° C.
• the present invention also relates to the modified biodegradable polymer obtained by the method described above and the use of this polymer in the manufacture of biomaterials.
• the biomaterials obtained can be used especially in the field of medicine and more particularly in surgery, pharmacy, dermatology, aesthetics and cosmetics.
• the biomaterials according to the present invention are biocompatible. Indeed, the presence of amino acids, peptides or polypeptides grafted along the polymer chain provides or enhances the biocompatibility properties. The biomaterial will thus be tolerated by the tissues, which will make it possible to accentuate the haemostatic and healing properties of the original biodegradable polymer.
• a preferred embodiment of the invention relates to the use of the modified polymer according to the invention to produce a dressing with haemostatic and healing properties.
• the dressing according to the invention may be manufactured in the form of powder, sponge, gel, film or cream.
• the sponge may be manufactured by the freeze-drying method known in the art.
• the dressing according to the invention may also contain a certain amount of biodegradable but unmodified polymers used in step (b) of the process according to the invention which have not reacted.
• the transparent film can be made by ventilating drying at a temperature of between about 20 and 25 ° C.
• the drying time mentioned above varies according to the volume and thickness of the film or sponge.
• the powder, the sponge, the film, the cream or the gel can be individually packaged in polypropylene bottles or aluminum bags and ready to be sterilized by gamma radiation, a sterilization technique also well known in the art.
• Pharmaceutically acceptable ingredients soluble in the same medium as collagen, such as antibiotics, antiseptics, anti-cancer agents or mixtures thereof, are incorporated before filtration and lyophilization.
• the biodegradable polymer by the modification made to its structure after coupling with the vinyl-carboxylic acid of formula (II) influences the structure of the network of the constituent polymer chains of the material manufactured.
• the resulting polymer network is denser.
• the phenomenon of crushing the meshes (or collapse) during the drying of the films prepared with this compound can be avoided, resulting in a maintenance of the mesh size (without shrinkage) during air drying or by cold and under vacuum (lyophilization) and a notable increase in the following properties:
• the polymer according to the invention there are products prepared for use in medicine such as tissues or artificial organs replacement such as skin (burn treatment), bones (prostheses and implants) , ligaments or tendons (implants).
• tissues or artificial organs replacement such as skin (burn treatment), bones (prostheses and implants) , ligaments or tendons (implants).
• Hemostatic dressings according to the invention allow a faster healing of wounds and thus reduces residual scars.
• the biomaterials according to the invention can be used in aesthetics and cosmetology, to fight against aging of the skin (wrinkles), accidental residual scars, acne or burns.
• biomaterials according to the invention can be encapsulated in the form of microbeads, microcapsules or implants for controlled release in vivo.
• tendons, ligaments and skins are brought into contact with stirring in 1 L of acetic acid (0.5 M or 3% (v / v)) for 2 hours at room temperature, then are ground using a domestic mixer. The grinding lasts a total of 1 minute (4 x 15 seconds) or until a pasty consistency is achieved.
• the collagen solution is supplemented with a second volume (1 L) of acetic acid (0.5 M or 3%) and the stirring continues for 4 hours at room temperature.2.25 g of pepsin of porcine origin mucosa (Sigma) or 3% by weight with respect to the chicken pieces (according to US Pat. No. 6,448,378) are dissolved in 10 ml of 0.5M acetic acid.
• the solution was allowed to stand at about 0-2 0 C for 16 hours and then centrifuged at 4200 rpm (Beckman J6-MC) for 1 hour and at 2-4 ° C. Two parts are separated, the clear and very viscous part containing the atelopeptide collagen is transferred into a beaker and kept at 0-2 ° C, the rise of the temperature beyond 6 ° C leads to the formation of collagen gels. The residue containing pepsin and telopeptides is removed.
• the collagen solution thus obtained can be directly subjected to coupling with the selected vinyl carboxylic acid.
• the washing solution is removed by centrifugation at 4200 rpm for 1 hour and at 0-2 0 C and the precipitate is dehydrated with pure ethanol and dried at 20-25 ° C.
• the mass of collagen obtained is 9.40 g.
• the solution is heated at 37 ° C for at least 30 minutes or until the total dissolution of the acid.
• the temperature is allowed to drop to 20 ° C. with stirring for an additional time of 2 to 4 hours.
• the coupled collagen is precipitated by adding to the solution with stirring an equivalence of 2.5 M NaCl or 1 M solid sodium acetate in the solution. A fine precipitate appears.
• the coupled collagen is recovered by centrifugation at 4200 rpm for 1 hour and at 0-2 ° C.
• the precipitate is then dissolved again in an equal volume before the first precipitation with a solution of acetic acid at 1% (v / v ).
• a second precipitation of the coupled collagen was made by adding to the solution with stirring an equivalence of 0.8 M NaCl or 1 M solid sodium acetate.
• the coupled collagen is purified again and is again recovered by centrifugation at 4200 rpm for 1 hour and at about 0-2 ° C.
• the washing solution is removed by centrifugation at 4200 rpm for 1 hour and at 0-2 ° C. and the precipitate is dehydrated with pure ethanol and dried at 20-25 ° C.
• the mass of modified collagen obtained is 8 20 g.
• the precipitate is then redissolved in an equal volume before the first precipitation with a solution of acetic acid at 1% (v / v).
• a second precipitation of the coupled collagen was made by adding to the stirred solution an equivalence of 0.8 M NaCl or 1 M solid sodium acetate.
• the washing solution is removed by centrifugation at 4200 rpm for 1 hour and at 0-2 ° C. and the precipitate is dehydrated with pure ethanol and dried at 20-25 ° C.
• the mass of modified collagen obtained is 7. , 02 g.
• the second compound used in this invention is commercial chitosan from 85% deacetylated crab shells (Sigma C3646).
• HOOC-CH 2 -NH-CO-CH CH-COOH are added to the chitosan solution with stirring and at room temperature, the pH of the mixture of about 3.50.
• the mixture is heated at 55-60 ° C. for at least 1 hour or until the total dissolution of the coupling agent.
• the temperature is lowered to 20 0 C with stirring, and then the coupled chitosan is precipitated by adding to the stirred solution for at least 1 hour 1 M NaCl or 1 M of solid sodium acetate.
• the mixture is centrifuged at 4200 rpm for 1 hour at 0-2 0 C (Beckman J6-MC) to recover the coupled chitosan.
• the precipitate is washed twice with pure water and finally the coupled chitosan is recovered by centrifugation at 4200 rpm for 1 hour at about 0-2 ° C.
• the chitosan is dehydrated with ethanol and dried at room temperature. .
• the mass of chitosan obtained is 9.55 g. 5.7 Preparation of biomaterials and hemostatic dressings.
• the solution thus prepared is a biomaterial that can be used either directly in the medical, biomedical, pharmaceutical or cosmetic field, or for the manufacture of dressings.
• Acceptable pharmaceutical ingredients such as antibiotics, bactericides, or anticancer agents may be incorporated into this biomaterial in liquid form prior to performing a dressing.
• the dressing may be prepared in different forms such as a sponge, a film, a powder, a gel or a cream.
• the shape will be chosen according to the intended use for this dressing.
• the solution prepared above is poured into nonstick molds.
• the volume of the solution is determined according to the size of the mold and the thickness of the dressing.
• the molds are placed on the shelves of a freeze dryer at 20 ° C (FTS System) programmed to lower the temperature of the tablets at 0 ° C., at a rate of 1 ° C. per minute.
• the temperature is maintained at 0 0 C for "1 hour, then the temperature continues to descend at -20 0 C and maintained for 1 hour. After this time, the temperature drops to -40 0 C and maintained for 1 hour for the ice formation either very homogeneous without formation of crystals on the surface.
• a vacuum of 200 mtorr is then made after this time and at the same time the temperature of the tablets back to 20 0 C at 0.02 ° C per minute.
• the vacuum is lowered to 20 mTorr and the temperature continues to rise to 30 ° C and maintained another 2 hours before the end of the lyophilization cycle.
• Freeze-dried sponges or dressings are taken out of their mold and packaged individually in aluminum bags. These sachets are sterilized with gamma radiation.
• the solution prepared above is poured into polycrystal, polycarbonate or polystyrene molds.
• the volume of the solution is determined according to the size of the mold and the thickness of the films.
• the molds are then placed under the laminar flow hood. Drying takes about 48 to 60 hours at room temperature.
• the films are peeled off their mold and packaged individually in aluminum bags. These sachets are sterilized with gamma radiation.
• Coupled collagen or coupled chitosan obtained according to the method described is ground to obtain a very fine powder.
• This powder is packaged in polypropylene bottles closed with a stopper. These flasks are sterilized with gamma radiation.
• Acceptable pharmaceutical ingredients such as antibiotics, bactericides or anticancer agents may be incorporated into the powder.
• Tests of the haemostatic effect of dressings obtained in sponge form were performed on rabbits in the liver.
• the dressings tested are prepared with modified collagen and modified chitosan according to the method described above.
• Each dressing has an area of about 5 cm by 3 cm and a thickness of about 0.4 cm.
• the control used is a compress folded in 4 thicknesses to obtain a thickness equivalent to that of the hemostatic sponges.
• the rabbits are anesthetized and incised longitudinally in the abdomen, the exposed liver is cut at the end of the lobe of a piece of about 2cm x 0.5cm. Sponges are applied directly to wounds by hand holding without applying strong pressure. Higher manual pressure is applied with the compress. Hemostasis is observed every 30 seconds until complete bleeding stops.
• Hemostatic sponges have also been applied to accidental cuts in the human epidermis.
• the application of the sponge resulted in a rapid (but not quantified) arrest of bleeding and accelerated healing of the wound with no residual scarring.

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