Advances in extracellular vesicle isolation methods: a path towards cell-type specific EV isolation

Extracellular vesicles are small, heterogenous, phospholipid-rich vesicles that are secreted by all cells into the extracellular space. They play a key role in intercellular communication because they can transport a variety of biomolecules such as proteins, lipids, and nucleic acids between cells. As categorized by the International Society of Extracellular Vesicles (ISEV), the term EV encompasses different sub-types, including exosomes, microvesicles, and apoptotic bodies, which differ in their size, origin, and cargo. EVs can be isolated from biological fluids such as blood, urine, and cerebrospinal fluid, and their biomolecular content can be analyzed to monitor the progression of certain diseases. Therefore, EVs can be used as a new source of liquid biomarkers for advancing novel diagnostic and therapeutic tools. Isolating and analyzing EVs can be challenging due to their nanoscopic size and low abundance. Several techniques have been developed for the isolation and characterization of EVs, including ultracentrifugation, density gradient separation, size-exclusion chromatography, microfluidics, and magnetic beadbased/affinity methods. This review highlights advances in EV isolation techniques in the last decade and provides a perspective on their advantages, limitations, and potential application to cell-type specific EV isolation in the future.