A Review of the Therapeutic Potential of Stem Cell‐Derived Nanocarriers to Treat Neurological Disorders

Neurological disorders (NDs) are characterized by substantial loss of specific neurons, with Alzheimer's and Parkinson's diseases being the most frequent NDs and nearly 99% of all "foreign substances" are prohibited from entering the brain by the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (CFB). These barriers, while crucial for brain protection, pose significant challenges for drug delivery, as they restrict the entry of many therapeutic agents into the brain, and this represents the primary manifestation of the absence of pathogenesis-targeting therapeutics. With significant success across multiple cell transplantation research efforts, stem cell therapy has been utilized for decades to treat neurological disorders. They work by replacing injured or lost cells directly, releasing proliferation and neurotrophic factors through autocrine and paracrine actions, suppressing neurological inflammation, and activation of endogenous brain progenitor cells. Nanocarriers derived from stem cells represent an innovative and promising therapeutic strategy for combating neurological diseases, combining faculties of regeneration of stem cells with the precision of nanotechnology. These nanocarriers possess natural biocompatibility and can efficiently cross the BBB to transport the therapeutic agents directly to affected neural tissues, thereby promoting enhanced treatment efficacy while reducing off-target effects. However, key challenges remain in large-scale production, standardization, and long-term safety. Thus, this review has examined the potential applications of stem cell extracellular vesicle (EV)-nanocarriers, mainly exosomes and recent development in the treatment of neurological diseases.