Nanoparticles with naturally occurring biodegradable polymers have emerged as potential carriers of various therapeutic agents. Chitosan, a cationic polysaccharide, is one of such biodegradable polymers, which has been extensively exploited for the preparation of nanoparticles with several therapeutic agents. In recent years, the area of focus has shifted from chitosan to chitosan derivatized polymers due to its vastly improved properties such as better drug retention capability, improved permeation, enhanced mucoadhesion, and sustained release of therapeutic agents. Chitosan derivatized polymers are primarily the quaternized chitosan derivatives, chitosan cyclodextrin complexes, thiolated chitosan, pegylated chitosan, chitosan combined with sugar ligands, chitosan with cholanic acid, chitosan-linolenic acid and chitosan-DTPA. This review article covers the various modifications of chitosan, their preparation procedures and various works done with them.
