Exosomes as Advanced Nanocarriers: Overcoming the Blood-Brain Barrier for Targeted Therapeutic Delivery in Neurodegenerative Diseases

INTRODUCTION: Exosomes, nanosized extracellular vesicles secreted by diverse cell types, have emerged as promising natural nanocarriers for therapeutic delivery. Their intrinsic ability to cross the Blood-Brain Barrier (BBB) positions them as valuable tools for treating neurodegenerative diseases. This review critically examines exosome biology, transport mechanisms, engineering strategies, and their clinical potential as drug-delivery platforms for the Central Nervous System (CNS). METHODS: We analyzed recent experimental, translational, and clinical studies on exosomes and engineered derivatives, focusing on BBB penetration, therapeutic cargo delivery, and applications in brain disorders. Key advances and landmark preclinical studies were synthesized to provide a comprehensive perspective. RESULTS: Exosomes cross the BBB through receptor-mediated transcytosis, lipid raft-associated uptake, and macropinocytosis, enabling bidirectional transport between circulation and brain. Their intrinsic cargo, including proteins, nucleic acids, and lipids, can reflect disease states and serve as predictive biomarkers. Engineered exosomes further enhance delivery potential, as surface functionalization and optimized cargo loading improve brain specificity and therapeutic efficacy in preclinical models. Collectively, both native and engineered exosomes surpass many synthetic carriers in stability, targeting, and BBB penetration. DISCUSSION: Versus previous reviews, this manuscript integrates exosome composition, engineering, isolation technologies, and administration routes, while also addressing patent and clinical translation challenges. Importantly, it highlights quantitative and mechanistic insights into BBB transport, offering a distinct framework for advancing exosome-based CNS therapies. CONCLUSION: Exosomes constitute a versatile platform for BBB-crossing drug delivery. By consolidating mechanistic, preclinical, and translational evidence, this review highlights their transformative potential in neurodegenerative disease therapy while outlining limitations and future directions.