Small extracellular vesicles isolation and separation: Current techniques, pending questions and clinical applications

Extracellular vesicles, especially small extracellular vesicles (sEVs) are now accepted as important messengers in cell-to-cell communication and as a promising drug delivery platform. They are involved in nearly all physiological and pathological processes and are involved in disease diagnosis and therapy. However, their heterogeneity of physicochemical properties and functions is not fully understood, which hinders further clinical applications. To obtain highly bioactive sEVs with both high yield and purity, will certainly facilitate their future study and application. This review informs up-to-date research on frequently-used and cutting-edge technologies of sEVs isolation and makes a deep comparison and analysis of different methods, including their advantages, limitations and applications. Pending questions about the inherent property of these small vesicles as well as isolation strategies are discussed. Additionally, an overview of their applications in disease diagnosis and treatment, including some of the on-going clinical trials, are also reviewed.