Nanoparticles: Important Tools to Overcome the Blood-Brain Barrier and Their Use for Brain Imaging

Nanoparticles are important tools for brain disease diagnoses and treatment. In both cases, either used for imaging or for the transfer of drugs, they have to cross the blood-brain or the blood-cerebrospinal fluid (CSF) barrier in order to reach the brain parenchyma. The endothelial cells of the cerebral microvessels form the so-called blood-brain barrier (BBB). The BBB is located within the cerebral capillaries and is formed by the endothelial cells lining the vessel wall. Different neuroinvasive strategies have been applied to enhance the brain uptake of therapeutic drugs, including direct injection into the parenchyma, implantation of drug-loaded polymeric matrices, polymeric wafers, and microcapsules with controlled release. Nanoparticles may be classified by their chemical nature into organic and inorganic carriers. For brain disease imaging, magnetic resonance imaging (MRI) is one of the primary imaging modalities used in the clinic for providing high spatial and temporal resolution.