Advances in optical imaging of drug delivery across the blood-brain barrier

The blood-brain barrier (BBB) is a unique interface between the cerebral circulation and the brain. It plays crucial roles in facilitating the brain nutrient uptake and waste removal, maintaining the stability of the micro-environment in the central nervous system (CNS), and protecting the CNS under physiological and pathological conditions. On the other hand, the BBB also hinders drug delivery to the brain. Various strategies have been explored for enhancing drug delivery across the BBB to the brain, and a variety of smart nano-drugs and biomaterials have been designed to pass the BBB to achieve targeted therapy of neurological and brain diseases. Meanwhile, to observe, assess, and quantify drug delivery across the BBB as well as the efficacy of drugs for the treatment of brain diseases, multiple optical imaging techniques and platforms have been developed. In this chapter, we systematically review the progresses and applications of optical imaging techniques for drug delivery to the brain.