Table 1.

Comparison of different isolation techniques.

Classification	Isolation technique	Process time		Advantages	Disadvantages	References
Centrifugation techniques	Ultracentrifugation	3-6h		Simplicity of operator Single processing sample is large Most commonly used separation techniques	Low purity Time-consuming	(45, 47, 48, 59)
Size-based techniques	Density gradient centrifugation	24h		Higher purity compared to differential centrifuges	Long incubation time leads to destruction of sEV	(48, 60, 61)
	Ultrafiltration	1-3h		Wide range of application Suitable for primary screening	Low purity Not suitable for plasma	(49, 50)
Capture-based techniques	Size exclusion chromatography	0.5-2h		The obtained exosomes have high activity High purity	Complicated operation High cost and expensive instruments	(52–54)
	Magnetic beads and immunoaffinity capture	4h		High purity High resolution high recoveries	Low yield Bound antibodies are not easily removed	(48, 51, 62, 63)
Polymer-based techniques	Commercial kits	0.5-3h		No special equipment required Easy operation Short time-consuming	Low production High cost Laboratory only	(47, 57 ,58)
Microfluidics-based techniques	Size-based microfluidics	0.5-1h		Label-free, fast, highly reproducible, highly recoverable and high resolution	Not able to separate sEVs that have the same size	(64–66)
	Immunoaffinity-based microfluidic separation	0.5-1h		Low cost, small size, speed, sensitivity, labeling-free, and high recoveries	Bound antibodies are not easily removed	(57, 66, 67)
	Dynamic microfluidics	0.5-1h		High rate, purity Simple microchannel structure Controllable process	High demands on the manipulator	(66, 68–70)