Chitosan-based hydrogel for intranasal drug delivery; current advances in the brain diseases treatment.

Neurodegenerative diseases represent a growing health concern that is projected to become more prevalent and affect more people in the upcoming decades. One of the most complicated components of recent neurodegenerative disease therapies is the penetration and delivery of therapeutics to the central nervous system (CNS), which are hindered via the blood-brain barrier (BBB). In response, innovative treatment approaches leveraging noninvasive techniques including nanosized drug delivery systems and intranasal (IN) administration with higher treatment efficacy and patient satisfaction are developing as potential options. IN administration delivers medications directly to the brain through both the olfactory and trigeminal pathways, with the olfactory pathway representing the primary route for nose-to-brain transport. Among various IN platforms, chitosan (CS)-based hydrogels have attracted considerable attention because of their excellent biocompatibility, biodegradability, mucoadhesive properties, and ability to enhance drug permeation by prolonging nasal residence time and transiently modulating epithelial tight junctions. This review critically summarizes recent advances in CS-based hydrogels for IN drug delivery for the treatment of brain diseases including Alzheimer's disease (AD), Parkinson's disease (PD), depressive manifestations, ischemia,brain tumors,epilepsy, seizures, and schizophrenia. In addition, the review discusses the relationships between hydrogel design and therapeutic performance, highlights current translational challenges, and outlines future perspectives for the clinical development of CS-based IN hydrogel systems.