Hydrogel based on hyaluronic acid

Hyaluronic acid (HA) is a natural, linear, polysaccharide, formed by repetitions of d-glucuronic acid and D-N-acetylglucosamine. It is the major component of extracellular matrix and essential for many tissues. Its derivatives are widely used in medicine, drug delivery, and tissue engineering thanks to their characteristics such as biocompatibility, biodegradability, nonimmunogenicity, and versatility. On the other hand, being the hydrogels constituted only by HA not stable, chemical modifications, covalent cross-linking, and gelling agents are needed in order to obtain their stability. Therefore, different strategies for obtaining physical and chemical HA hydrogels have been developed, such as click chemistry reactions, enzymatic and disulfide cross-linking, supramolecular assembly via inclusion complexation, and so on. HA-based hydrogels are so attractive and versatile materials for drug delivery, tissue engineering, regenerative medicine, cell therapy, and diagnostics. In particular, the overexpression of HA receptors on various tumor cells makes them promising drug delivery systems for targeted cancer therapy. In this context, the aim of the present chapter is to report the recent advances regarding the design of chemical and physical HA-based hydrogels and, particularly, their various applications for drug delivery and tissue engineering.