The Blood-Brain Barrier (BBB) is a highly selective permeability barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system (CNS).

The BBB allows the passage of water, some gases, and lipid soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function.

The BBB is the gateway to the CNS: all drugs targeting the brain must pass through it. BBB alterations are also proper of several neurodegenerative diseases as ALS. Moreover, chronic inflammatory states, as those typically occurring in aging diseases, lead to tissue degeneration and membrane permeability, thus favouring immune cell crosstalk within the central nervous system. This crosstalk is crucial in the onset of neuroinflammatory events which characterize the early steps of neuronal degeneration.