The blood-brain barrier (BBB) is a protection barrier which regulates the passage of compounds from the blood to the brain. It protects the brain and contributes to its homeostasis.Ballabh, P., Braun, A. and Nedergaard, M., 2004. The blood–brain barrier: an overview: structure, regulation, and clinical implications. Neurobiology of disease, 16(1), pp.1-13. Weiss, N., Miller, F., Cazaubon, S. and Couraud, P.O., 2009. The blood-brain barrier in brain homeostasis and neurological diseases. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1788(4), pp.842-857.