Ligand-cascading nano-delivery devices to enable multiscale targeting of anti-neurodegenerative therapeutics

Neurodegenerative diseases are a debilitating set of conditions that affect a significant fraction of the world's population, and this fraction is expected to increase as the population ages. Many therapeutic strategies have been explored to treat the pathological mechanisms of neurodegenerative diseases, but multiple sequential hurdles to central nervous system (CNS) delivery, including the blood-brain barrier (BBB), diseased neuronal membranes, and the organelle barrier, make drug delivery challenging and necessitate the use of innovative strategies to target and cross each barrier. Advances in drug delivery technology have the potential to improve the standard of treatment for neurodegenerative diseases by enhancing local drug concentration at the pathologically relevant cells and organelles. Furthermore, ligand-cascading nano-delivery devices could address these issues by sequentially presenting targeting ligands for crossing each of the aforementioned hurdles. In this review, we provide an overview of ligand technologies that enable BBB transcytosis, localization to or internalization in diseased neuronal cells, and localization at the organelle of interest. We summarize recent strategies for sequentially presenting pertinent ligands at each hurdle to CNS delivery. These ligand-cascade strategies will enable rational design of nano-delivery devices for multiscale targeting of anti-neurodegenerative therapeutics.