Recent development in nanocrystal based drug delivery for neurodegenerative diseases: Scope, challenges, current and future prospects

Nanocrystals (NCs) are defined as pure solid particles, with less than 1 mu m in mean diameter, having crystalline characteristic, mainly composed of 100% pure drug with stabilizers surrounding the particles. Fabrication into nanocrystals can improve the solubility of drugs under Biopharmaceutics Classification System (BCS) Class II to IV by enhancing the bioavailability to increase the therapeutic efficacy. This could offer a new opportunity in developing new potential therapy for neurodegenerative diseases, owing to their small size that could cross over blood brain barrier (BBB) exhibiting sustained release properties. To date, there are no FDA-approved nanocrystals for neurodegenerative diseases but there are a few potential candidates that have been developed to potentially combat Alzheimer's disease, Parkinson's disease and cerebral ischemia injury. These nanocrystals are discussed in this review with regard to their fabricating methods, stabilizers of choice, pharmacokinetic parameters, and challenges. The current prospective of nanocrystals in neurodegenerative diseases are also presented here. It is hoped that this review would shed some light in understanding the role of nanocrystals in neurodegenerative diseases and the challenges in developing them.