EXOSOMES AS BIOLOGICAL COURIERS: BRIDGING INTERCELLULAR COMMUNICATION, PRECISION DIAGNOSTICS, AND NEXT-GENERATION DRUG DELIVERY

Exosomes are nanoscale, membrane-bound extracellular vesicles that mediate intercellular communication by shuttling proteins, lipids, nucleic acids, and other bioactive molecules from cell to cell. Considerable interest in the use of exosomes as disease biomarkers, monitoring tools, vehicles for regenerative medicine, and drug delivery systems is fueled by their ability to mirror the molecular composition of their parental cell. Originally considered as "garbage bags" of cells, exosome research has grown to include extricated coding and noncoding RNA, and the construction and operation of cellular communication networks that control immunity, inflammation, neoplastic invasion, and tissue repair. This review covers exosome biogenesis, composition, functions, isolation, and characterization methods, diagnostic applications, and emerging therapeutic applications, particularly their potential as drug-delivery vehicles including loading of therapeutic cargoes and vesicle surface modifications. Although exosomes have shown tremendous promise in preclinical studies, the adoption of exosomes in clinical practice remains limited due to the heterogeneity of vesicles, the myriad of isolation methods, limited standardization, unstable biodistribution data, manufacturing hurdles, and safety issues. Rigorously reproducible extracellular-vesicle nomenclature, orthogonal characterization techniques, and well-designed functional studies can hopefully steer future research toward credible clinical applications. High yields of scalable, cGMP-compatible preparations, robust potency assays, quality controls, and carefully planned clinical trials are critical for realizing exosomes' true potential as drug-delivery systems.