Generations of Chitosan: The Progress in Drug Delivery

The discovery of sulfhydryl-modified polymers named thiomers in the late twentieth century resulted in a reframing conceptualization of polymers and their pharmaceutical use. As it is well known, the mucosal barrier in the body has a high influence in drug delivery, leading to loss of drug or low bioavailability. Chitosan is a wide known polymer commonly used in the pharmaceutical and medical field due to its great properties. However, thiolated chitosan, as first generation, presents improvement in its mucoadhesive, as well as other properties compared to the native chitosan. S-protected or second generation of chitosan overcomes stability and oxidation problems. However, recent development of a third generation, less-reactive, chitosan changes the recent drug delivery field completely.