RU2099352C1 - Method for production of hydrogel-forming agent of chitosan - Google Patents

Abstract

FIELD: food industry, cosmetics, medicine and other branches of industry. SUBSTANCE: method involves interaction of chitosan with glutaric aldehyde followed by reduction of reaction product with the help of sodium boron hydride. Then isolation of hydrogel-forming agent by its filtering, washing and drying are carried out. Mentioned above interaction of chitosan with glutaric aldehyde takes place in acetate buffer at pH 3.5-5.5 and at ionic strength of the solution 0.1-0.5, molar ratio of glutaric aldehyde and chitosan being 1:6-15. Desired hydrogel-forming agent is colorless, together with water it produces highly viscous hydrogels having concentration less than 0.15 %. EFFECT: improved efficiency of the method.

Description

 The invention relates to chemical technology, specifically to a method for producing a hydrogel former from chitosan, and in particular to a method for cross-linking chitosan macromolecules to obtain a highly effective gel former, and can be used to produce highly viscous hydrogels with water contents up to 99.85% and higher, used in food, cosmetic and other industries.

 A known method for producing cross-linked gels based on chitosan by the interaction of chitosan in solution with dialdehyde, followed by reduction with sodium borohydride / 1 /. Known methods for producing chitosan gels by crosslinking chitosan molecules with glutaraldehyde / 2, 3 /.

 The closest known solution to a similar problem is a method of producing a hydrogel former from chitosan by reaction of the latter with glutaraldehyde followed by reduction of NaF, NaBr or NaSCN / 4 / in the electrolyte medium.

 However, in all of the above studies, only the formation of dark brown gelatinous substances was observed under various conditions, and no attempt was even made to isolate a purified, stable chitosan product from the resulting mixtures that could produce hydrogels when mixed with water, that is, outside the reaction of chitosan with glutaraldehyde.

 The aim of the present invention is to obtain a highly effective colorless chitosan gelling agent in dry form, capable of producing hydrogels when mixed with water, that is, outside the reaction of chitosan with glutaraldehyde.

 To achieve this goal, the present method is proposed for producing a hydrogel former from chitosan by reacting chitosan with glutaraldehyde in acetate buffer at pH 3.5 5.5, the ionic strength of the solution 0.1 0.5 and the molar ratio of glutaraldehyde and chitosan equal to 1 6 15, recovery of the reaction product with sodium borohydride, followed by isolation of the hydrogel former by filtration, washing and drying.

 Distinctive features of this method are the reaction of chitosan with glutaraldehyde under the above conditions, the restoration of the reaction product with sodium borohydride and the isolation of the hydrogel former in dry form as a result of filtration, washing and drying.

 The proposed method allows to obtain a highly effective chitosan hydrogel without the use of special equipment due to the fact that a solution of chitosan in acetate buffer at pH 3.5 5.5, ionic strength of the solution 0.1 0.5 and molar is introduced into the reaction with glutaraldehyde at room temperature the ratio of glutaraldehyde chitosan 1 6 15. The transparent colorless hydrogel formed in 2 4 hours is treated with a solution of sodium borohydride, followed by separation of the dry hydrogel forming, filtering, washing and drying. The resulting product forms in water at a concentration of 0.15% and less highly viscous hydrogels with a dynamic viscosity of 15 25 P.

 Proposed in the invention, the reaction conditions of glutaraldehyde with chitosan exclude the formation of intensely colored compounds, discussed in the analogues, and allow to obtain a pure colorless product, which is the condition for its use in cosmetics, medicine and the food industry.

 The proposed method for producing a chitosan-based hydrogel-forming agent makes it possible to produce gels cheaper and more effective than the currently widely used pectin or polyacrylamide gels.

 The following examples illustrate the present invention.

Example 1. In a glass cup with a capacity of 2 l, 8.5 g (45.33 mmol in terms of 100% degree of deacetylation) of chitosan (humidity 8%, molecular weight 500,000 1,000,000, degree of deacetylation of 73% obtained from the crab shell) are placed, 715 ml of water and 60 ml of 100% acetic acid are added, stirred until completely dissolved (2 2.5 hours), 10.9 g of sodium acetate trihydrate are introduced, after dissolution of which 3.02 ml of a 25% solution are added to the mixture (7.555 mmol) of glutaraldehyde in water. After these procedures, in solution at a molar ratio of glutaraldehyde chitosan 1 6 pH is 3.5, and the ionic strength is 0.1. The mixture is stirred vigorously for 20-30 minutes and left at room temperature for 5 hours. 600 ml of water are added to the resulting gelatinous mass, stirred vigorously until complete homogenization, and the resulting gel is reduced with a solution of 10 g of sodium borohydride in 500 ml of water for 3 hours. The precipitate is filtered off, washed with water, dried in vacuo at 40 ^° -50 ^{° C.} and a dry colorless gelling agent is obtained in quantitative yield. The 0.15% hydrogel prepared from it is completely homogeneous and has a dynamic viscosity of 16 P.

Example 2. 8.5 g (46.31 mmol in terms of 100% degree of deacetylation) of chitosan (humidity 10% molecular weight 350,000 700,000, degree of deacetylation 90% obtained from the crab-shear carapace) are placed in a 2 L glass glass. 730 ml of water and 3.66 ml of 100% acetic acid are added, stirred until complete dissolution (16 to 20 hours), 54.4 g of sodium acetate trihydrate are added, after dissolution of which 1.235 ml of a 25% solution are added to the mixture ( 3.087 mmol) of glutaraldehyde in water. After these procedures, in a solution with a molar ratio of glutaraldehyde chitosan 1 15, the pH is 5.5, and the ionic strength is 0.5. The mixture is stirred vigorously for 20-30 minutes and left at room temperature for 5 hours. 600 ml of water are added to the resulting gelatinous mass, stirred vigorously until complete homogenization, and the resulting gel is reduced with a solution of 10 g of sodium borohydride in 500 ml of water for 3 hours. The precipitate is filtered off, washed with water, dried in vacuo at 40 ^° -50 ^{° C.} and a dry colorless gelling agent is obtained in quantitative yield. The 0.12% hydrogel prepared from it is completely homogeneous and has a dynamic viscosity of 22 P.

 Sources of information taken into account when preparing the application.

 1. Masri M. Chemical modifications unsoluble polymers, Polymer. Prepr. 1975, v. 16, N 2, p. 70.

 2. R. A.A. Muzzarelly, G. Barontini, R. Rocehetti. Cross-linked modification of chitosan with glutaraldehyde, Biotechnol. Bioeng. 18, 1445, 1976.

 3. G.K. Moore, G.A.F. Robert. The study of chitosan gelation by its reaction with glutaraldehyde, Int. J. Biol. Macromol. 2, 78, 1980.

 2 4. G. A. F. Roberts, K. E. Taylor. The formation of gels by reaction of chitosan with glutaraldehyde, Macromol. Chem. 190, 951, 1989.

Claims (1)

 A method of producing a hydrogel former from chitosan by reacting the latter with glutaraldehyde followed by reduction, characterized in that the reaction of chitosan with glutaraldehyde is carried out in acetate buffer at pH 3.5 5.5, the ionic strength of the solution is 0.1 0.5 and the molar ratio of glutaraldehyde chitosan 1 6 15, the reaction product is reduced with sodium borohydride, followed by isolation of the hydrogel former by filtration, washing and drying.