Kitosan

Kitosan, commonly referred to as chitosan, is a natural biopolymer derived from chitin, the structural polymer found in crustacean shells and some fungal cells. It is produced by partial deacetylation of chitin, forming poly(N-glucosamine). The degree of deacetylation and molecular weight influence solubility, charge density, and mechanical properties.

In dilute acidic solutions, kitosan carries positive charges on protonated amino groups, making it soluble, while it is insoluble at neutral or basic pH. It can form films, hydrogels, and fibers and is biodegradable and generally biocompatible. Its cationic nature supports antimicrobial activity and metal ion chelation, and it can interact with negatively charged surfaces and polymers.

Production sources include crustacean shells and, to a lesser extent, fungal cell walls. Processing typically involves demineralization, deproteination, and deacetylation with alkali, followed by purification. The product is characterized by the degree of deacetylation and molecular weight, which can be adjusted to suit applications.

Applications are diverse: water treatment for flocculation and metal adsorption; agriculture as seed coatings and biostimulants; and biomedicine for wound dressings, drug delivery systems, and scaffolds. Regulatory status varies by region; medical-grade kitosan requires high purity to meet safety standards. Limitations include poor solubility at neutral pH, batch variability, and the need for crosslinking to improve mechanical strength.