Table 1.

The current isolation techniques for sEVs.

Isolation technique	Isolation principle	Potential advantage	Potential disadvantage
Ultracentrifugation-based technique	Particulates in suspension will be sedimented according to their density, size, and shape when subjected to a centrifugal force	Easy to operate, need no special reagent, large sample capacity and yield large amounts of sEVs	Protein aggregates contamination, high shear force may induce the aggregation and rupture of sEVs, high equipment cost, instruments consume a great deal of space, long run time
Size-based technique	Based on the size difference between sEVs and other particulates in suspension	Ultrafiltration: need no special reagent, fast, low cost; SEC: harvest highly purified sEVs	Ultrafiltration: moderate purity, high shear force may induce rupture of sEVs, decrease yield when sEVs attached to filter; SEC: need special and customized equipment, time-consuming
Precipitation	Altering the solubility or dispersibility of sEVs with water-excluding polymers	Easy to operate, large sample capacity, need no special equipment	Protein aggregates contamination, take a long time to precipitation
Immunoaffinity capture-based technique	Specific binding between antigen tags of sEVs and immobilized antibodies	Simple and convenient strategy, harvest highly purified sEV subtyping, short run time	High reagent cost, only a portion of the sEVs can be separated (low yields), antigen tags were blocked by reagents, which affects the biological behaviors of the isolated sEVs
Microfluidic-based technique	Immunoaffinity, size, or density were integrated into the microfluidic chip	Microscale isolation and need little amount of body fluid samples (dozens of microliters), integrate separation and detection into a single chip, fast and easy automation	Low sample capacity, need special and customized regents, lack of standardization tests on clinical samples

SEC size exclusion chromatography.