Classifications

• • 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
  • C08B37/0072—Hyaluronic acid, i.e. HA or hyaluronan; Derivatives thereof, e.g. crosslinked hyaluronic acid (hylan) or hyaluronates
• • 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
  • A61L27/20—Polysaccharides
• • 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
  • A61L27/52—Hydrogels or hydrocolloids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2203/00—Applications
  • C08L2203/02—Applications for biomedical use

Definitions

• the present invention refers to soluble, bio-compatible gels consisting of hyaluronic acid cross-linked with bi-functional L-aminoacids or L-aminoesters, or mixtures thereof, to a process for their preparation and to their use in the pharmaceutical, cosmetic surgical and medical fields.
• Hyaluronic acid is a mucopolysaccharide consisting of alternated units of D- glucuronic acid and N-acetyl-glucosamine, bound together by ⁇ 1-3 and ⁇ -4 bindings.
• Hyaluronic acid is found in nature in the synovial liquid of articular joints, in the vitreous humour of eyes, in the umbilical cordon and in the connective tissues.
• Hyaluronic acid can be obtained by extraction from animal tissues like cockscombs or umbilical cordons, or can be recovered from the fermenting broth of specific Streptococci.
• the present invention allows to overcome the above said problem by making available gels soluble in water and bio-compatible prepared by cross-linking hyaluronic acid with bi-functional L-aminoacids or L-aminoesters or their mixtures.
• the characteristics of the compounds according to the invention make them ideal products for use in various fields from pharmaceutical to medical.
• the product in the form of film or gel, can for example be used as anti-adherent material in surgery (in abdomen, spinal surgery etc); in this case the material forms a barrier separating the damaged tissues and is absorbed after a time which allows the formation of the new tissues.
• the products according to the present invention can be also used as substrate for tissue engineering (derma, epidermis tissue, bones, fat cells, etc.) and can be used in ophthalmology, dermatology, in the osteoartritis field etc.
• the compounds according to the invention can be prepared in water or in a mixture water/organic solvents as DMF or DMSO depending on their use.
• the reaction is carried out in two subsequent steps: firstly the hyaluronic acid is activated and thereafter the binding between hyaluronic acid a cross-linking agent is performed.
• the activation of hyaluronic acid takes place in the presence of a carbodiimide soluble in water according to known processes (see for example Tomihata, J. Biomed. Mater. Res., 1997, 37(2), 243-251; Danishefsky, Carbohydrate Res., 1971, 16, 199-205).
• a carbodiimide soluble in water the N-3-dimethylamino-propylethylcarbodiimide hydrochloride is particularly preferred.
• the cross-linking agents are bi-functional ⁇ L- amino acids, i.e. having a second functional group besides the amino acid group, or their esters or mixtures thereof.
• Particularly preferred are L-lysine, L-serine, L- lysine ethylester di-hydrochloride, L-lysine methylester di-hydrochloride, L-serine methylester hydrochloride, L-serine ethylester hydrochloride or mixtures thereof.
• the use of amino esters instead of amino acids allows the protection of the carboxylic functions of the amino acids in respect of their possible activation and their involvement in secondary reactions.
• the reaction is carried out in a reactor equipped with a stirring system and a temperature controller.
• the hyaluronic acid sodium salt is dissolved in water in a concentration comprised between 0.5 and 2.5% according to the desired characteristics of the final product, the preferred concentration is 1 - 1.5%.
• the reaction temperature is one of the essential condition for obtaining the products of the invention and it must be comprised between 0°C and 25°C, preferably between 0°C and 10°C.
• the pH is brought at 3 - 6, preferably 4-5, for example by adding diluted HCl.
• activating agent/hyaluronic acid sodium salt Another essential factor for obtaining the products according to the invention it is the ratio: activating agent/hyaluronic acid sodium salt; the activating agent must be added in quantities comprised between 0.05 - 0.5 equivalents for equivalent of monomer unit of hyaluronic acid, preferably between 0.1 and 0.2 equivalents. If higher quantities of activating agent are used irreversible binding between hyaluronic acid and activating agent takes place instead of the wanted binding hyaluronic acid/cross-linking agent which causes the formation of undesired products which are insoluble or partially insoluble in water and having bio- compatibility and purity characteristics which are different from those of the presently described products. Finally the cross-linking agent is added in quantities comprised between 0.1 - 1 equivalents for equivalent of monomer unit of starting hyaluronic acid.
• reaction mixture is kept at the fixed temperature and under stirring for 15 minutes - 4 hours, preferably 30 minutes - 2 hours.
• a solution of NaCl 1 M is added and a buffer solution at pH 7 - 8 (preferably 7.5) then the mixture is purified according to known techniques as dialysis and/or diafiltration on ultrafiltration membrane and/or precipitation with an organic solvent and/or evaporation under vacuum and/or freeze drying.
• the preferred methods are diafiltration on membrane having a cutoff of 30 KDa and freeze drying.
• the solid product can be solved in water or in physiologic solution in various concentrations in order to obtain viscous solutions or transparent gels, it is also possible to obtain thin films, membranes according to the wanted use.
• the product can be sterilised for example by filtration at 0.2 ⁇ .
• the reciprocal quantities hyaluronic acid/activating agent/cross-linking agent have an effect on the cross-linking grade and therefore they will be chosen according to the wanted viscoelastic properties. Obviously the final characteristics will also be a consequence of the hyaluronic acid used as starting product.
• hyaluronic acid having higher molecular weight will result in a liquid more viscous and compact compared to the one obtained with a hyaluronic acid having lower molecular weight.
• hyaluronic acid having a molecular weight comprised between 100.000 and 2.000.000 is used and the final products will have a molecular weight comprised between 200.000 and 2.500.000.
• the final products have a cross-linking degree of 2 - 40%.
• hyaluronic acid sodium salt (MW 1.550.000) (2.5 mmol) are dissolved in 100 ml of demineralised water. The temperature is maintained at 5°C and the pH value is brought to 4.5 by addition of diluted HCl. 0.048 g (0.1 eq) of N-3-dimethylamino- propylethylcarbodiimide hydrochloride and 0.31 g (0.5 eq) of L-lysine ethylesterdi- hydrochloride are added.
• hyaluronic acid sodium salt (MW 1.550.000) (2.5 mmol) are dissolved in 100 ml of demineralised water. The temperature is maintained at 5°C and the pH value is brought to 4.5 by addition of diluted HCl. 0.096 g (0.2 eq) of N-3-dimethylamino- propylethylcarbodiimide hydrochloride and 0.31 g (0.5 eq) of L-lysine ethylesterdi- hydrochloride are added.
• hyaluronic acid sodium salt (MW 750.000) (2.5 mmol) are dissolved in 100 ml of demineralised water. The temperature is maintained at 5°C and the pH value is brought to 4.5 by addition of diluted HCl. 0.048 g (0.1 eq) of N-3-dimethylamino- propylethylcarbodiimide hydrochloride and 0.20 g (0.5 eq) of L-serine methylester hydrochloride are added.
• hyaluronic acid sodium salt (MW 750.000) (2.5 mmol) are dissolved in 100 ml of demineralised water. The temperature is maintained at 5°C and the pH value is brought to 4.5 by addition of diluted HCl. 0.096 g (0.2 eq) of N-3-dimethylamino- propylethylcarbodiimide hydrochloride and 0.20 g (0.5 eq) of L-serine methylester hydrochloride are added.
• hyaluronic acid sodium salt (MW 1.600.000) (2.5 mmol) are dissolved in 100 ml of demineralised water. The temperature is maintained at 5°C and the pH value is brought to 4.5 by addition of diluted HCl. 0.048 g (0.1 eq) of N-3-dimethylamino- propylethylcarbodiimide hydrochloride and 0.18 g (0.5 eq) of L-lysine are added.
• Example 1 The solid obtained in Example 1 is dissolved in water in a concentration of 3-4g/l and filtered, under sterile condition, at 0.2 microns.
• the filtered gel is sterile and has a content of endotoxines lower than 0.2

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• 2003
  • 2003-01-31 WO PCT/IB2003/000321 patent/WO2004067575A1/en not_active Application Discontinuation
  • 2003-01-31 AU AU2003303820A patent/AU2003303820A1/en not_active Abandoned
  • 2003-01-31 EP EP03815561A patent/EP1592715A1/de not_active Withdrawn

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