Stimuli sensitive ocular drug delivery systems

This chapter will focus on some new representative areas of ophthalmic drug delivery research: the use of pharmaceutical nanosystems, and especially smart polymers. Stimuli-sensitive hydrogel systems show markedly reversible sol-gel phase transitions in response to physiological stimuli (temperature, pH, and presence of ions in organism fluids or enzyme substrate) or other external stimuli (electric current, light). This kind of material can improve drug bioavailability by increasing the residence time of the formulation in the eye surface. Furthermore, hydrogels can be combined with other carrier systems, such as nanoparticles, niosomes, liposomes, polymeric micelles, dendrimers, or cyclodextrins to enhance their permanence on the surface and to overcome the static barrier, allowing a specific local delivery with minimal systemic effects.