Chitosan-based materials: Preparation, modification and application

Chitosan is a natural biopolymer with a modifiable structure and abundant function groups, moreover, it can be processed into various shapes and sizes, making it suitable for various applications. This review analyzed and summarized the recent advances in chitosan-based materials, particularly focusing on the modification of chitosan by physical, chemical and biological methods, which provided plentiful information on the preparation, characterization and application of chitosan-based materials. In this review, various preparation and modification methods for improving chitosan performances, as well as the application of chitosan and its derivatives, were critically analyzed and summarized in detail. Chitosan-based materials can be fabricated into different shapes and sizes, such as nanofiber, nanoparticles, microspheres, membranes, and 3D printed scaffolds. In addition, chitosan can be modified through physical, chemical, and biological modifications, to obtain versatile chitosan-based materials. For physical modification, crosslinking and blending are commonly used., while chemical modification is based on chemical reactions (e.g. acylation, esterification, etherification, N-alkylation, graft copolymerization, and degradation), to prepare the corresponding derivatives (e.g. chemically cross-linked chitosan, grafted chitosan, low molecular weight chitosan, and oligo-chitosan) through crosslinking, grafting, and degradation. The biological modification is associated with various enzymes to realize the hydrolysis or grafting. With improved performances through modification, as well as various shapes and sizes, chitosan-based materials show promising applications in versatile fields, such as water treatment, food processing, pharmaceutical/biomedicine, textiles and agriculture. This review will deepen the understanding the state of the art of chitosan-based materials, including their preparation, characterization and application.