Homogeneous modification of chitin and chitosan based on an alkali/urea soluble system and their applications in biomedical engineering

Abstract

Resource shortage and environmental degradation have forced people to pay attention to the development and application of environmentally friendly production methods. Alkali/urea is a green water-based solvent for chitin and chitosan, and has been widely used in structural analysis and functional material preparation in recent years. This review systematically summarizes the discovery, improvement and promotion of alkali-soluble systems and expounds its dissolution mechanism for chitin and chitosan in the first section. As the core content, we focused on the application of alkali/urea dissolution systems such as NaOH/urea, KOH/urea and KOH/LiOH/urea in the homogeneous chemical modification of chitin and chitosan. The dissolved chitosan and chitin ensure the uniformity and high efficiency of the chemical modification reaction and avoid the need for high temperature, organic dispersants, alkali swelling and other auxiliary reaction conditions. Moreover, the prepared alkylation, quaternization, carboxylation, acrylamidation derivatives exhibit novel structures and functional characteristics and have been applied in antibacterial, tissue engineering repair, drug delivery, 3D cell culture, bioimaging, wastewater remediation and other fields. We envision that this review will provide new inspiration and ideas for the improvement of the alkali/urea dissolution system and its application in other fields.