Improving the transport of chemotherapeutic drugs across the blood-brain barrier.

The successful treatment of brain tumors or metastases in the brain is still hampered by the very efficient blood-brain barrier, which prevents the cerebral accumulation of a pharmacologically sufficient amount of a drug. Beside the possibility of disintegrating the functionality of this effective working barrier, a nanocarrier-mediated transport is presently an interesting and promising method to increase the drug concentration in the brain. Nanocarriers are small vesicles (<200 nm) and can be prepared by polymerization, resulting in nanoparticles, or by producing superficial lipid structures to incorporate the drug. In this context, liposomes are of importance owing to their ability to adapt their properties to the pharmacological requirements. In this article, we will give an overview of current possibilities of enhancing anticancer drug transport across the blood-brain barrier, based on its structure and functionality. Special consideration will be given to recent liposomal approaches that use active targeting for receptor-mediated transport across this physiological barrier.