Upconversion nanoparticle-based strategy for crossing the blood-brain barrier to treat the central nervous system disease

The blood-brain barrier (BBB) is a major challenge for the treatment of central nervous system (CNS) diseases. The BBB strictly regulates the movement of molecules into and out of the brain, and therefore protects the brain from noxious agents. However, for this reason the BBB also acts as a major obstacle that prevents most therapeutic molecules from getting into the target site of the brain. Therefore, it is essential to develop an efficient and general approach to overcome the BBB and transport the drug to the targeted region. Nanoparticle-based drug delivery systems are emerging as a promising drug delivery platform, due to their distinct advantages of tunable biophysical properties such as surface chemistry, size, and shape leading to various biological actions (like clearance, biodistribution, and biocompatibility) in the body. Therefore, it was hypothesized that the surface and shape of nanoparticles will influence their BBB permeation efficiency. Here, we describe a series of upconversion nanoparticles with different surfaces (oleic acid-free, DNA-modified, Silica coating, and PEG-encapsulated), PEGylated UCNPs with various shapes were generated (including sphere and rod). The cellular uptake ability, biodistribution, and BBB penetration of those UCNPs were assessed in cultured cells (NSC-34 neuron- like cells) and in vivo (zebrafish models).