Recent advances in brain delivery of synthetic and natural nano therapeutics: Reviving hope for Alzheimer's disease patients

As the globe's population increases, the incidences of Alzheimer's disease (AD) are steadily increasing. AD represents the most common neurological disorder and constitutes 60-70% of all dementia cases. The accumulation of amyloid plaques, intraneuronal fibrillary tangles, the decrease in choline acetyltransferase, and the loss of cholinergic neurons are considered the hallmarks of AD. The current FDA-approved anti-AD drugs can only inhibit AD symptoms for a limited time without stopping or reversing the progression of the disease. In addition, their clinical applications are hindered by their partial ability to cross the blood-brain barrier (BBB), poor bioavailability, and systemic adverse effects. Nevertheless, the nanoformulation of synthetic and natural drugs into advanced nanodelivery systems has been utilized for their efficient brain delivery. In addition to a brief introduction to AD, its pathology, and current treatment options, this review sheds light on the novel nanodelivery systems used recently for the brain delivery of various therapeutic agents.