Table 3.

Methods of exosome isolation

Isolation	Principle	Advantages	Disadvantages	References
Ultracentrifugation	Density, size and shape based sequential separations of particulate constituents and solutes. Consists of several centrifugation steps aiming to remove cells and debris, followed by exosomes	Reduced cost and contamination risks Large sample capacity Yields large amounts of exosomes	High equipment cost, long run time, labour intensive, low portability High speed centrifugation can damage exosomes	[43]
Ultrafiltration	Based on size differences between exosomes and other particulates. The exosome population will be concentrated on the pore containing membrane	Fast, does not require special equipment, good portability	Moderate purity of isolated exosomes, shear stress induced deterioration, possibility of clogging and vesicles trapping, exosome loss due to attaching to membranes	[44]
Size exclusion chromatography	Separates macromolecules on the basis of their size, applying fluid on a column packed with porous, polymeric beads	Precise separation of large and small molecules Exosome structure is not affected by shearing force	Long runtime	[45]
Precipitation	Altering the solubility or dispersibility of exosomes by using water-excluding polymers	Easy to use, does not require specialized equipment, large and scalable sample capacity Mild effect on isolated exosomes	Co-precipitation of other non-exosomal contaminants like proteins and polymeric materials Long runtime	[46, 47]
Immunoaffinity-based capture	Exosome fishing based on specific interactions between membrane-bound antigens (receptors) of exosomes and immobilized antibodies (ligands)	Highly purified exosomes High possibility of subtyping	High reagent costs, exosome tags must be known, low capacity and low yields, antigenic epitopes may be blocked or masked Isolated exosomes may lose their functional capacity	[48]
Microfluidic technologies	Manipulates small amounts of fluids using channels with dimensions of micrometres using capillary forces	Small volume sample is required, simple, time-saving and low cost, real time process control	Less sensitive	[49, 50]