Blood-Brain Barrier & Drug Delivery
The blood-brain barrier (BBB) is a highly selective, protective membrane that regulates the exchange of substances between the bloodstream and the central nervous system (CNS). It plays a crucial role in maintaining brain homeostasis, shielding the brain from harmful toxins, pathogens, and fluctuations in blood composition. However, this protective function also poses a significant challenge in drug delivery, as it restricts the passage of most therapeutic compounds, including those intended for treating neurological disorders such as Alzheimer’s disease, Parkinson’s disease, brain tumors, and epilepsy. Overcoming the BBB remains one of the greatest hurdles in neuropharmacology and drug development. The BBB is primarily composed of endothelial cells, which form tight junctions that prevent the free diffusion of molecules. These endothelial cells are supported by astrocytes, pericytes, and microglia, which collectively help maintain the barrier’s integrity and regulate transport mechanisms. The BBB selectively allows the passage of essential nutrients, such as glucose and amino acids, through specialized transporters while blocking large or hydrophilic molecules. Most conventional drugs fail to penetrate the BBB due to their size, polarity, or lack of specific transport mechanisms.