Mucoadhesive Micro-/Nano Carriers in Ophthalmic Drug Delivery: an Overview

Abstract

The eye is a challenging organ for ophthalmic drug delivery due to the barriers associated with the anterior and posterior segments like nasolacrimal drainage, blinking, induced lacrimation, impermeability of corneal epithelial membrane, and blood-ocular barrier. Although there are conventional approaches, such as eye drop, ointment, suspension, implants, and injection, they suffer from limitations of low bioavailability, poor patient compliance (due to invasive approach and repeated dosing), and potential for several side effects. This review explored the various mucoadhesive polymers, derivatized polymers, and different modification methods for such polymer derivatization (via carboxymethylation, thiolation, and quaternization) for their effective drug delivery toward ophthalmic application. Various types of micro and nanoparticulate systems of such derivatized mucoadhesive polymer-based carriers have been also exemplified and discussed here for their improved medicinal efficacy. To address the issues associated with conventional ophthalmic formulations, mucoadhesive drug delivery has been proposed. The emerging technologies play an important role in the development of more efficient mucoadhesive carriers obtained by derivatization or modification of core polymers with various functional groups such as carboxymethyl, amine, and new generation thiols. Mucoadhesive polymers form bonding with mucin (hydrogen, covalent, electrostatic bonding, etc.) and enhance corneal residence time and cellular uptake of the drug. Mucoadhesive carriers are designed to associate with the micro and nanoparticulate systems to overcome the ocular barriers with improved therapeutic efficacy.