To sustain homeostasis and other critical processes, the brain is a very sensitive and delicate neuronal organ system that requires a steady supply of fuels, gases, and nutrients. The blood-brain barrier (BBB) has proven to be a significant obstacle to drug delivery to the brain. The BBB in a healthy brain serves as a diffusion barrier that prevents most compounds from passing from the bloodstream to the brain, allowing only small molecules to pass through. Since the population of seniors and patients with CNS problems is growing, global drug development for brain diseases will have to rise substantially in the next 20 years. However, when compared to other therapeutic domains, drug development for brain diseases has the lowest success rates.