An overview of carboxymethyl derivatives of chitosan: Their use as biomaterials and drug delivery systems.

Chitin is one of the most abundant natural polymers in the world and is used for the production of chitosan by deacetylation. Chitosan is nontoxic and biodegradable and, therefore, can be used as a biomaterial and for the construction of drug delivery systems. Nevertheless, the poor solubility of chitosan in neutral or alkalinized media has restricted its applications in the pharmaceutical and biomedical fields. Chitosan can be easily carboxymethylated to improve its solubility in aqueous media while its biodegradability and biocompatibility are preserved. Carboxymethyl chitosans show improved solubility in aqueous media, which makes them an attractive alternative source for producing biomaterials and drug delivery systems as well as for designing nanotechnology-based systems. Thus, carboxymethyl chitosan-based materials have a wide applicability and good potential in the development of biomedical nanodevices and controlled release drug formulations. This review summarizes preparations and properties of hydrophilic chitosan-based materials such as nanoparticles, microparticles, tablets, and films as well as procedures related to various practical applications.