Nanoparticles in Ocular Drug Delivery Systems for Topical Administration: Promises and Challenges

The majority of pharmaceutical formulations for the treatment of ocular pathologies are for topical administration. However, this kind of ophthalmic formulations has disadvantages such as low bioavailability and, consequently, a reduced therapeutic effect. This happens due to the anatomical and physiological specificity of the eyeball (tissues with different characteristics, the presence of different defense mechanisms, etc.) effects, reducing the residence time of formulation in contact with the ocular surface and consequently fall dramatically the penetration ability of the formulation through the ocular tissues. The repeated administration of this type of ophthalmic formulations with the aim to produce the desired therapeutic effect leads to the appearance of side effects due to its systemic absorption. In order to overcome the weaknesses of this type of therapy is necessary to use different strategies. In this review article, we discuss some of these different strategies, with particular emphasis on the application of colloidal dispersions in ophthalmic formulations, particularly, the use of polymeric and lipid nanoparticles. In fact, the results of the published scientific research has demonstrated that the use of this type of strategy not only promotes the increase in the precorneal residence time of the ophthalmic formulation, but also the ability to penetrate through the ocular tissues, enhancing the drug bioavailability and the therapeutic efficacy of ophthalmic formulations. Finally, it is also given emphasis not only to the current state of the scientific research in this area, but also to the existing patents and the followed procedure to place on the market an ophthalmic formulation based on nanoparticles.