Chitosan-based systems for oral drug delivery applications

Chitosan (CS) is a versatile cationic polysaccharide, isolated from chitin via alkaline deacetylation. It is a biocompatible and biodegradable natural polymer, considered safe, and acts as an effective intestinal absorption enhancer of therapeutic agents, due to its intrinsic mucoadhesive characteristics and ability to restrain the integration of epithelial tight junctions in a reversible manner. Various studies have been established regarding the protective effect of CS-based drug delivery systems against acidic denaturation and enzymatic degradation. Additionally, of CS-based drug delivery systems have prolonged residence time of loaded therapeutic agents in intestinal region and also enhanced their absorption through the intestinal epithelium. Further, CS has discrete chemical/functional groups which could be altered to attain definite objectives and fabricate a targeted delivery system; it makes it a polymer with a wide range of applications in pharmaceuticals and biomedical field. These properties make CS and modified CS as potential candidates for the establishment of novel gastrointestinal (GI) and oral drug delivery systems. The CS-based delivery systems have been reported for numerous biomedical applications through GI and oral delivery of various therapeutic agents like antiinfective, anticancer, proteins and peptides, gene and nucleic acids, and vaccines, which is further explored in this review.