Multifunctional role of microRNAs in mesenchymal stem cell-derived exosomes in treatment of diseases

Table 1 Exosome isolation methods

Isolation method	Principle	Advantages	Limitations
Ultracentrifugation	Exosomes are purified by physical centrifugation according to their size and specific gravity	(1) The most common method; (2) Bulk extractability; and (3) Low cost	(1) The operation is complex and time-consuming; (2) Increased impurities; (3) Loss due to adsorption on the tube wall; and (4) Expensive equipment is needed[158]
Ultrafiltration	According to the size of exosomes, exosomes are separated by filter membrane	(1) Simple operation; (2) Rapid process; and (3) High yield	(1) Low-purity; and (2) Stress and shear forces can cause exosome damage
Size exclusion chromatography	The biofluid dissolves in the mobile phase and passes through the stationary phase, in which the various components of the mixture move at different speeds and are separated[159]	(1) High recovery rate; and (2) The structural integrity of exosomes is maintained	(1) Time-consuming; and (2) Low-purity
Precipitation[160,161]	By chemical extraction, the exosome liquid is combined with the liquid in the kit, and eventually the exosomes are deposited.	(1) Simple operation; (2) Rapid process; (3) No need for special equipment	Increased impurities
Immune affinity capture	Immune isolation is performed by magnetic bead-specific adsorption of exosome surface antigens	(1) Easy operation; (2) Rapid process; (3) High purity; and (4) High yield	(1) Does not apply to large-volume cell supernatant; and (2) High cost
Microfluidic technologies (ExoChip)	A microfluidic platform based on nano-acoustic filters, viscoelastic fluid separation, lateral displacement, and immune affinity separates exosomes from biological fluids	(1) Rapid separation; (2) High purity; and (3) Saving the sample	The research is not sufficient and is not widely used at present