Nano-vectors for the Ocular Delivery of Nucleic Acid-based Therapeutics.

Nucleic acid-based therapeutics have gained a lot of interest for the treatment of diverse ophthalmic pathologies. The first to enter in clinic has been an oligonucleotide, Vitravene(®) for the treatment of cytomegalovirus infection. More recently, research on aptamers for the treatment of age related macular degeneration has led to the development of Macugen(®). Despite intense potential, effective ocular delivery of nucleic acids is a major challenge since therapeutic targets for nucleic acid-based drugs are mainly located in the posterior eye segment, requiring repeated invasive administration. Of late, nanotechnology-based nano-vectors have been developed in order to overcome the drawbacks of viral and other non-viral vectors. The diversity of nano-vectors allows for ease of use, flexibility in application, low-cost of production, higher transfection efficiency and enhanced genomic safety. Using nano-vector strategies, nucleic acids can be delivered either encapsulated or complexed with cationic lipids, polymers or peptides forming sustained release systems, which can be tailored according to the ocular tissue being targeted. The present review focuses on developments and advances in various nano-vectors for the ocular delivery of nucleic acid-based therapeutics, the barriers that such delivery systems face and methods to overcome them.