Engineering of structural and functional properties of nanotherapeutics and nanodiagnostics for intranasal brain targeting in Alzheimer's

Alzheimer's disease (AD) is the fifth leading cause of death on the planet. It hallmarks the presence of amyloid plaques and neurofibrillary tangles in geriatric patients. The condition witnesses early stages of mild dementia and learning inabilities. It progressively culminates into impaired behavioural functions, cognitive inability and impaired memory functions. Also, the COVID-19 pandemic has raised new concerns for AD patients as they are at higher risk of infection with COVID-19 than non-AD patients. The increasing toll of Alzheimer's patients is alarming a need for effective and safe therapeutics. This review discusses the various nanocarriers in delivering therapeutics for Alzheimer's via the intranasal route. Nanocarrier based therapeutic, diagnostic and theragnostic applications concerning AD have been covered. The review also discusses the nasal transport pathways and nanocarrier characteristics' role in cellular uptake mechanism. We have briefly discussed the potential biomarkers, imaging modalities, nano vaccines, advanced theragnostic probes, and related clinical studies. Lastly, we discussed the prospects concerning the development of intranasal nanodiagnostics and nanotherapeutics in Alzheimer's. Overall, this review summarizes various intranasal brain targeting strategies in AD.