Blood-Brain Barrier
A highly selective semipermeable membrane formed by specialized endothelial cells that separates circulating blood from the brain and central nervous system.
The blood-brain barrier protects the brain from pathogens and fluctuations in blood chemistry, but it also limits which therapeutic compounds can reach the central nervous system. Most large molecules — including many peptides — cannot cross the BBB unaided, which is a central challenge in developing cognitive and neuroprotective peptide therapies.
Some research peptides are specifically engineered or selected for their ability to cross the BBB. Semax and Selank, for example, are intranasal peptides studied partly because the nasal route provides a pathway that partially bypasses the BBB, enabling CNS effects. Understanding BBB permeability is essential for evaluating any peptide intended to affect cognition, mood, or neurological function.