Recent advances in extracellular vesicle-based organic nanotherapeutic drugs for precision cancer therapy

Due to the critical limitations of conventional antitumor agents, great efforts have been made to develop advanced drug delivery systems to enhance the therapeutic outcomes of antitumor drugs, reduce side effects, and overcome tumor drug resistance. In recent years, extracellular vesicles, especially exosomes, which are membrane-bound extracellular vesicles endogenously secreted by many types of human cells, have garnered increasing attention in biomedical applications. In particular, they are considered highly promising natural delivery nanocarriers for cancer therapy owing to their unique features, including nanoscale bilayer membrane, natural cell-to-cell communication, excellent biocompatibility, low toxicity and immunogenicity, prolonged circulation half-life, and good structural stability. This review provides essential knowledge of extracellular vesicles and highlights exosomes, small extracellular vesicles, as potential nanocarriers for drug delivery. In addition, recent developments of exosome-based organic nanotherapeutic agents for cancer treatment, mainly including chemotherapy, cancer phototherapy, and cancer sonodynamic therapy, are introduced. Finally, challenges and prospects are comprehensively discussed to provide further guidance for the future development of exosomal drug delivery systems. We believe that this review will spur the transition of exosome-based nanotherapeutic agents from bench to bedside for cancer therapeutics.