Chitosan biopolymer, its derivatives and potential applications in nano-therapeutics: A comprehensive review

[Display omitted] •Chitosan (CS) is a degradable and biocompatible polymer commonly exploited in drug delivery.•Different chitosan derivatives are being synthesized to enhance the surface chemistry and organ targeting efficiency.•This review focuses on different nanostructures of CS and derivatives for various routes of administration.•CS vaccine carriers are also discussed along with functionalization of CS nanostructures.•Few clinical trials are mentioned together with marketed products. Chitosan (CS) is a natural biopolymer used frequently in drug delivery because of its biodegradability and biocompatibility. Several derivatives of CS have also been synthesized to improve the mucoadhesion and solubility of the nascent CS. The nano and micro particles are reported to have enhanced drug bioavailability, solubility and permeation. Recently, there is an advancement in the active targeted drug and gene delivery using CS because of its tunable surface modifications. This review focuses on CS and its chemically modified structures along with their different nanostructures with examples from the most exploited routes of administration. Herein, the functionalization of CS nanoparticles has also been enlisted along with the use of CS in the immunotherapy as vaccine carriers. Beside, few patents, ongoing clinical trials and already marketed CS-based products are also enlisted.