The potential for nanoparticle-based drug delivery to the brain: overcoming the blood-brain barrier.

The development of blood-brain barrier (BBB)-targeting technologies is a very active field of research: targeting therapeutic actives to the central nervous system by means of systemic administration means crossing the BBB, and this is now one of the most challenging problems in drug development. The BBB is a unique regulatory system that protects the brain environment by separating it from direct contact with the circulating blood. In doing so, it impedes at the same time the access of a large number of diagnostic and therapeutic agents into the brain parenchyma. One of the possibilities of bypassing this barrier relies on specific properties of nanoparticulate vectors designed to interact with BBB-forming cells at a molecular level, as a result of which the transport of drugs or other molecules (such as nucleic acids, proteins or imaging agents) could be achieved without interfering with the normal function of the brain. This article summarises several recent example applications, presents emerging work and highlights the directions for further developments in this area.