Extracellular vesicle-based drug delivery system boosts phytochemicals' therapeutic effect for neurodegenerative diseases

Neurodegenerative diseases (NDs) are a major threat to the elderly, and efficient therapy is rarely available. A group of phytochemicals has been shown to ameliorate NDs; however, poor stability, low bioavailability, and reduced drug accumulation in brain tissue limit their application in NDs. Therefore, a targeted drug delivery system is a feasible treatment strategy for NDs. Extracellular vesicles (EVs) possess many favorable bioactivities and are excellent carriers for targeting brain tissue. This review summarizes EVs as novel phytochemical carriers in ND therapy. First, we discuss the current challenges of ND therapy and the therapeutic effects of phytochemicals for NDs. Second, we highlight the ability of EVs to cross the blood-brain barrier and act as drug carriers to enhance the therapeutic efficacy of drugs for NDs. Finally, encapsulation strategies for phytochemicals in EVs are particularly reviewed, as they are critical for obtaining high loading efficacy and stable drug delivery systems. This review provides new insights into EV-based drug delivery systems for improving the therapeutic effect of phytochemicals for ND treatment. Therefore, the release rate and pharmacokinetics of phytochemicals should be well controlled to ensure the therapeutic efficacy of phytochemical-loaded EVs in the brain.