Application of nanoparticles in ocular drug delivery systems

Application of a drug in the form of eye drops represents easiest, safest and, at the moment, the most common non-invasive method of ocular drug application. Other conventional ophthalmic formulations in the form of aqueous and oily solutions, ointments, suspensions and emulsions were established to increase bioavailability, solubility and pericorneal retention time of a drug, compared to eye drops. But in the last few decades, nanotechnology-based ophthalmic formulations have been intensively analysed in the area of drug delivery to anterior and posterior parts of the eye. Systems based on nanotechnology with adequate nanoparticle size can be formed to achieve lower irritation and inflammation and better bioavailability and interaction of a drug with ocular tissue. The nanocarrier-based approach led to the development of nanoparticles, nanosuspensions, nanoemulsions, liposomes, nanomicelles, niosomes, nanocrystals and dendrimers for ocular drug delivery. These systems have significant advancements compared to conventional systems, particularly if they are observed as systems for drug delivery to the posterior eye part. Besides advantages, the nanoparticle use in these circumstances could be a reason for concern, because of certain toxic effects noticed in some studies. In this article, we aim to provide an overview of the potential of incorporating an active pharmaceutical ingredient into nanoparticles investigated in the therapy of anterior and posterior eye segment conditions. We will discuss the most important improvements that have been accomplished in the development of nanoparticle-based formulations for the treatment of glaucoma, autoimmune uveitis, age-associated macular degeneration and corneal and choroidal neovascularization.