Gel formation in polymeric composites for modification of fibrous materials

Abstract

The possibility of using oxidized nucleotides and nuclosides as cross-linking reagents for preparing chitosan hydrogels with a broad range of applications was examined. It was found that the ratio of dialdehyde to chitosan amine and the reaction medium pH affected gel formation in aqueous acetic acid solutions of chitosan in the presence of the cross-linking reagents glutaraldehyde and oxidized nucleic acid derivatives. IR spectra of chitosan and its derivatives were recorded and characterized. Immobilization of the proteolytic enzyme trypsin in chitosan films on fibrous materials was studied. Fibrous materials are modified by hydrogels based on biocompatible polymers in order to produce new materials for medicine, pharmacology, biotechnology, and ecology [1, 2]. Hydrogels are polymeric systems that are capable of retaining up to several thousand percent of water but have lost the ability to flow. Covalent cross-linking of polymers in aqueous solution by bifunctional reagents forms a continuous gel network that provides strength and simultaneously free diffusion of water. The properties of hydrogels can be used to create new materials for biotechnology (cell cultivation), biomedicine (tissue engineering), pharmacology (controlled release drug systems), and medicine (wound dressings) [3]. One of the most promising polymers for creating such materials is the biocompatible and biodegradable polysaccharide chitosan, which contains reactive groups in almost every elementary unit. Glutaraldehyde (GA) is used as a cross-linking reagent and is capable of reacting with chitosan amines by forming azomethine bonds. However, because GA can undergo aldol and crotonic condensation [4], the products of its reaction with chitosan contain C=C double bonds and carbonyls that can be toxic upon contact with living tissues. Herein the possibility of cross-linking chitosan with oxidized nucleic acid derivatives such as nuclosides consisting of ribose and a purine or pyrimidine base and nucleotides containing also a phosphate was studied in order to prepare