Targeting specific cells in the brain with nanomedicines for CNS therapies

Treatment of Central Nervous System (CNS) disorders still remains a major clinical challenge. The Blood-Brain Barrier (BBB), known as the major hindrance, greatly limits therapeutics penetration into the brain. Moreover, even though some therapeutics can cross BBB based on their intrinsic properties or via the use of proper nanoscale delivery vehicles, their therapeutic efficacy is still often limited without the specific uptake of drugs by the cancer or disease-associated cells. As more studies have started to elucidate the pathological roles of major cells in the CNS (for example, microglia, neurons, and astrocytes) for different disorders, nanomedicines that can enable targeting of specific cells in these diseases may provide great potential to boost efficacy. In this review, we aim to briefly cover the pathological roles of endothelial cells, microglia, tumor-associated microglia/macrophage, neurons, astrocytes, and glioma in CNS disorders and to highlight the recent advances in nanomedicines that can target specific disease-associated cells. Furthermore, we summarized some strategies employed in nanomedicine to achieve specific cell targeting or to enhance the drug neuroprotective effects in the CNS. The specific targeting at the cellular level by nanotherapy can be a more precise and effective means not only to enhance the drug availability but also to reduce side effects.