Hyaluronic acid in ocular drug delivery

As a naturally-occurring polysaccharide which could be found in various ophthalmic tissues, hyaluronic acid (HA) has a wide range of applications in the eye, including treatment of dry eye, vitreous substitutes and ophthalmic viscosurgical devices. Besides that, HA can be used as an effective drug carrier for ocular disease treatment due to its excellent biocompatibility, biodegradability, bioadhesion properties, viscoelasticity and receptor interaction characteristic. This review summarizes recent advances in HA-based drug delivery systems for ocular disease treatment in which it could be used as drug-polymer conjugate, drug carrier substrates, and surface modifications of the carrier. To achieve the optimum drug delivery efficacy under varied ophthalmic diseases, the molecular weight (MW) and amount of HA should be selected rationally and applied to design diverse delivery systems.