Size, surface charge, and shape determine therapeutic effects of nanoparticles on brain and retinal diseases.

Nanoparticles can be valuable therapeutic options to overcome physical barriers to reach central nervous system. Systemically administered nanoparticles can pass through blood-neural barriers; whereas, locally injected nanoparticles directly reach neuronal and perineuronal cells. In this review, we highlight the importance of size, surface charge, and shape of nanoparticles in determining therapeutic effects on brain and retinal diseases. These features affect overall processes of delivery of nanoparticles: in vivo stability in blood and other body fluids, clearance via mononuclear phagocyte system, attachment with target cells, and penetration into target cells. Furthermore, they are also determinants of nano-bio interfaces: they determine corona formation with proteins in body fluids. Taken together, we emphasize the importance of considerations on characteristics of nanoparticles more suitable for the treatment of brain and retinal diseases in the development of nanoparticle-based therapeutics. FROM THE CLINICAL EDITOR: The central nervous system (CNS) remains an area where drug access and delivery are difficult clinically due to the blood brain barrier. With advances in nanotechnology, many researchers have designed and produced nanoparticle-based systems in an attempt to solve this problem. In this concise review, the authors described the current status of drug delivery to the CNS, based on particle size and shape. This article should stimulate more research to be done on future drug design.