Recent progress in nanocarriers for direct nose to brain drug delivery

Nose to brain drug delivery is considered as a viable option to deliver various therapeutic agents with low cerebral bioavailability bypass blood-brain barrier (BBB). The drug absorbed from the olfactory region through nerve fibers and the vascular pathway is the underlying mechanism for the nose to brain drug delivery. Drug-loaded nanocarriers intended for the nose to brain delivery have numerous advantages in addition to overcoming the biological barriers (BBB, first-pass metabolism and intestinal degradation), more patient compliance (in comparison to injection), rapid drug absorption, and enhanced bioavailability (especially for lipophilic drugs) also provided. This review summarizes advances of drug-loaded nanocarriers such as nanoemulsions, microemulsions, lipid nanoparticles, transfersomes, liposomes and polymeric micelles that have been reported for an effective nose to brain drug delivery and the various methods to overcome the mucociliary clearance, the lower brain-blood ratio and the limited amount of the drug that can be incorporated which are the most common drawbacks for the nanocarriers delivery via the nose to the brain. Major considerations in the development of nose-to-brain drug delivery systems and their toxicity are also discussed.