The Extracellular Vesicles: Current Definitions and Biological Functions

Abstract Extracellular vesicles (EVs) are membrane-bound nanoparticles released by cells that mediate intercellular communication in physiological and pathological conditions. EVs include exosomes, microvesicles, and apoptotic bodies, which differ in size and biogenesis. Exosomes originate from multivesicular bodies within the endosomal pathway, whereas microvesicles form through outward budding of the plasma membrane. Advances in EV research have improved understanding of their formation, cargo sorting, and release mechanisms. Analytical techniques such as ultracentrifugation, size-exclusion chromatography, nanoparticle tracking analysis, electron microscopy, and flow cytometry have enhanced EV characterisation, including size, morphology, and molecular composition. EVs have gained significant attention as potential disease biomarkers, mediators of immune regulation, and natural carriers for therapeutic delivery of proteins, nucleic acids, and drugs. However, challenges remain in standardising isolation and analytical methods and in understanding EV heterogeneity. Further studies are essential to support the clinical translation of EV-based diagnostics and therapeutics. This paper provides a comprehensive review of the fundamental concepts and diverse applications of EVs, integrated with the latest updates on classification standards and current clinical research.