Extracellular vesicle separation and isolation: conventional and microfluidics-integrated hybrid approaches

Extracellular vesicles (EVs) are gaining attention as important biomarkers for disease diagnosis, treatment, and prognosis.Before analyzing EVs, it is most important to separate (isolate) EVs from biological fluids, and researchers have developed various EV separation technologies.Existing typical EV separation methods (differential ultracentrifugation, density gradient ultracentrifugation, size-exclusion chromatography, ultrafiltration, and dielectrophoresis) have different mechanisms and advantages and disadvantages; thus, it is necessary to clearly understand the differences.Recently, hybrid EV separation methods that apply existing EV methods to microfluidic platforms to precisely process samples and automate multiple steps by integrating them into a single fluidic chip have attracted great interest, and among them, filtration and dielectrophoresis are in the spotlight.In this paper, we first review the basic principles and limitations of existing EV separation methods, and then review the recent trends in ultrafiltration-microfluidic and dielectrophoresis-microfluidic hybrid EV separation.