Engineering exosomes for targeted neurodegenerative therapy: innovations in biogenesis, drug loading, and clinical translation.

Neurodegenerative diseases (NDDs), including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD) and multiple sclerosis (MS), are characterized by progressive neuronal dysfunction and limited therapeutic options, largely due to the restrictive nature of the blood-brain barrier (BBB). Exosomes, naturally occurring extracellular vesicles (EVs), have gained attention as innovative drug delivery vehicles owing to their intrinsic ability to cross the BBB, minimal immunogenicity, high biocompatibility, and capability to carry diverse therapeutic cargos such as proteins, nucleic acids, and small molecules. Furthermore, exosomes can be bioengineered to enhance drug-loading efficiency and targeting specificity, positioning them as a versatile and effective platform for treating NDDs. In this review, we summarize recent advances in exosome biogenesis, secretion, and engineering, with an emphasis on innovative strategies for exosome isolation, drug loading, and surface modification. We further explore their roles in modulating neuroinflammation, promoting neural regeneration, and enabling precise therapeutic delivery. Critical challenges associated with large-scale production, quality control, and regulatory compliance under Good Manufacturing Practices (GMP) are also discussed. Collectively, these developments underscore the transformative potential of engineered exosomes in advancing precision therapies for neurodegenerative disorders and offer strategic insights into their clinical translation.