Table 1.

Methods for exosome quantification

Method	Label	Principle	Sensitivity	References
Particle-counting methods
NTA	No label	Analysis of the Brownian motion of particles by laser imaging	Isolated exosomes 1 × 107/mL	[69, 70]
TRPS	No label	Electrical detection of particles passing through nanopores		[71, 72]
Labeling methods
ELISA	Fluorescent, chemical luminescent	Enzyme-linked immunosorbent assay	ND [13]	[68, 73]
Flow cytometry with microbeads	Fluorescent	Exosomes captured by microbeads are labeled with fluorescently labeled antibodies for detection by flow cytometry	Serum 14 μL [13]	[62, 74]
nuclear magnetic resonance detection	Magnetic nanoparticle	Exosomes labeled with magnetic nanoparticles are detected by nuclear magnetic resonance	~10,000 exosomes	[75]
Nanoparticle capture by microfluidics	Fluorescent	Exosomes captured by magnetic nanoparticles are labeled with fluorescently labeled antibodies for detection by fluorescence microscopy	Plasma <50 μL	[76]
iNPS	Au nanoparticle	Exosomal proteins are captured around nanopores and labeled with Au nanoparticles to generate surface plasmon resonance for detection by spectroscopy	~10,000 exosomes	[77]
Hybrid method
ExoCounter	FG beads	Exosomes captured on an optical disc are labeled with FG beads for detection using an optical disc drive by diffraction	Serum 0.39 μL	[13]

ELISA enzyme-linked immunosorbent assay, iNPS intravesicular nanoplasmonic system, NTA nanoparticle tracking analysis, TRPS tunable resistive pulse sensing, ND not detected