CHITOSAN AND ITS MODIFIED FORMS: PREPARATION, PROPERTIES, APPLICATION. REVIEW

Over the past decades, increased interest has been shown to macromolecular materials, the raw materials of which are renewable resources. In this context, polysaccharides are a common, biodegradable and inexpensive natural resource. So one of the most common polysaccharides after cellulose is chitosan, which is obtained from chitin. The use of chitosan, a natural polymer, has recently increased due to its antimicrobial and antifungal properties, zero toxicity, biocompatibility, and ability to form biofilms and hydrogels. Applications and research areas include biomedicine, pharmaceuticals, biomaterials, water purification, and hair and skin care products. However, the use of chitosan is limited due to the complexity of modifying its structure and poor solubility in water. Among the main chemical modifications for the functionalization of the chitosan structure are N-substitution, O-substitution (with or without protection of chitosan reaction centers) and crosslinking with other compounds. These chemical modifications make it possible to improve its chemical and physical properties. Taking into account the current importance of using chitosan with chemical modification, this review examines the structure, production methods, physicochemical properties, ways of chemical modification and application of chitosan, as well as the individual properties of chitosan, which make it possible to create innovative new materials with special characteristics revealing its adaptability and bio-value. Special attention is paid to the methods of modification of chitosan by various methods and functional components, which allow varying its qualitative, quantitative and biological characteristics. Approaches to the production of guanidine-containing chitosan and the properties of such composite materials, as well as a wide range of applications, are discussed.