Polymeric Nanoparticles for Nasal Drug Delivery to the Brain: Relevance to Alzheimer's Disease

Currently, Alzheimer's disease (AD) accounts for more than half of all dementia cases. Although genetics, age, and environmental factors affect the disease, the cause of AD is not yet fully known. Various drugs have been proposed for the prevention and treatment of AD, but the delivery of these therapeutic agents to the brain is difficult. The blood–brain barrier prevents systemic drugs from accessing the central nervous system and designing a suitable system to overcome this barrier has attracted much attention. The intranasal pathway, given its proximity to the brain, provides a great opportunity for drug delivery. Understanding the physiological characteristics of the nose can be useful in selecting the appropriate carrier and material. Some of the emerging vehicles used for nose-to-brain delivery of anti-AD drugs are natural (such as chitosan) and polymeric (such as poly(lactic-co-glycolic acid) and polyethylene glycol) nanoparticles (NPs). This review discusses the hypotheses for AD pathogenesis and highlights recent advances in the applications of natural and polymeric NPs for treatment. The fundamental and applied aspects of this approach for nasal drug delivery to the brain are reviewed here with thoughts on what is needed for the field to mature also provided.