Being the most delicate organ of the body, the brain is protected against potentially toxic substances by the blood-brain barrier (BBB), which restricts the entry of most pharmaceuticals into the brain. The developmental process for new drugs for the treatment of CNS disorders has not kept pace with progress in molecular neurosciences because most of the new drugs discovered are unable to cross the BBB。The various strategies that have been explored to increase drug delivery into the brain include ① chemical delivery systems②biological delivery systems③disruption of the BBB④the use of molecular Trojan horses⑤Nanomaterials for drug delivery across the blood–brain barrier.