Is there a clinical future for polymeric nanoparticles as brain-targeting drug delivery agents?

Injectable nanosized carriers (5-250 nm) are actively studied as anticancer drug delivery agents for targeted drug delivery to the brain. Among these, polymeric nanoparticles (Np) have been studied since 1995, but only five of them recently started Phase I clinical trials, and none of these targets brain pathologies. To date, clinical trials for brain drug delivery have started for macromolecular- and nanocarrier-based systems in the treatment of brain tumors. This review, on the basis of the results obtained so far from preclinical studies, will critically consider the possibilities that polymeric Np have to reach the clinic as drug delivery agents for the brain, in comparison with other platforms.