Nano and microtechnologies for ophthalmic administration. An overview

Abstract

Ocular drug delivery is one of the most challenging fields of pharmaceutical research. They are generally employed to overcome the static (different layers of cornea, sclera, and retina including blood aqueous and blood-retinal barriers) and dynamic barriers (choroidal and conjunctival blood flow, lymphatic clearance, and tear dilution) of the eye. Ophthalmic formulations must be sterile, and the biomaterials used in the preparation of pharmaceutical systems completely compatible and extremely well tolerated by ocular tissues. The location of the target tissue in the eye will determine the route of administration. Ophthalmic administration systems are intended for topical, intraocular and periocular administration. In this review we describe the main pharmaceutical nano- and microsystems currently under study to administrate drugs in the eye, covering microparticles, nanoparticles, liposomes, microemulsions, niosomes and dendrimers. We have performed the corresponding revision of the published scientific literature always emphasizing the technological aspects. The review discusses also the biomaterials used in the preparation of the nano and microsystems of ophthalmic drug delivery, fabrication techniques, therapeutic significances, and future possibilities in the field.