Table 1.
Purpose, Advantages and Disadvantages of Common Exosome Characterization Methods
| Methods | Purpose | Advantages | Disadvantages |
|---|---|---|---|
| Electron microscope (Scanning electron microscope SEM or Transmission electron microscope TEM) | Detection of exosomal morphology | Electron microscope can directly observe the morphological structure of exosomes, among which SEM can observe the surface structure, TEM can observe the internal structure and provide the information of particle size distribution.69 | Due to the complicated operation of TEM and higher requirements on sample preparation than SEM, it is not suitable for rapid measurement of a large number of samples.70 SEM’s resolution is lower than TEM. |
| Dynamic light scattering technology | Detecting the size of exosomes | The lower limit of measurement is 10 nm, which is suitable for the determination of monodisperse systems. | It is not suitable for measuring complex exosome samples with large size range, the concentration of exosomes cannot be detected, and it is difficult to distinguish contaminated proteins from exosomes. |
| Nanoparticle Tracking Analysis Technology (NTA) | Detecting the size and concentration of exosomes | The detection speed is fast and the exosomes can be observed in real time. The resolution is higher than the flow cytometer, and the lower limit of the measurement of fluorescent particles can reach 30–40nm. | The operation is complicated and it is difficult to distinguish contaminated proteins from exosomes. Camera levels and detection thresholds will affect the quantification of exosomes.71 |
| Western Blot (WB) |
Detection of the expression of exosomal marker proteins | As one of the classic methods, this technique is mature and can qualitatively and quantitatively analyze marker proteins. It is also easier to analyze exosomes from cell culture media. | The operation is complicated and time-consuming. The detection of marker proteins varies depending on the type of parental cell, and it is not suitable for the detection of exosomal marker proteins in biological fluids.10 |
| Enzyme-linked immunosorbent analysis (ELISA) | Detection of the expression of exosomal marker proteins | It has strong specificity and rapid detection, can qualitatively and quantitatively analyze marker proteins, and is suitable for high-throughput analysis.72 | The operation is complicated and time-consuming. The repeatability is not good and there are many interference factors. |
| Flow Cytometry | Detection of biomarkers of exosomes | This method is capable of high-throughput, multi-channel analysis, and the analysis speed is fast, and the required sample concentration is low. | This technique is time-consuming and laborious. The detection limit is 400nm, and the particle size of exosomes cannot be measured. In addition, due to the detection of optical signals, the accuracy and resolution are relatively low, and the characteristics of polydispersity and low refraction limit its application.73 |