Quantifying the concentration of evs in urine or plasma through confocal microscopy
It is possible to measure the number of extracellular vesicle in urine or plasma by following a protocol for immobilizing EV's in non-denaturing polyacrylamide gel. EV's are labeled (either specifically or non specifically) and then imaged with a confocal microscope[@hartjes2020EVQuant; high-throughput quantification and characterization of extracellular vesicle (sub)populations].
This method is much more straightforward than nanoparticle tracking analysis and it requires less sample preparation. It essentially boils down to finding bright spots in 3D and counting them. The protocol is nicknamed EVQuant.
To measure absolute concentration it is crucial to calibrate the observation volume[@hartjes2020EVQuant; high-throughput quantification and characterization of extracellular vesicle (sub)populations]. With this approach, the maximum concentration of particles that can be detected is around 10E11 pcles/ml, and the minimum is 5E8 pcles/ml. Although it is not clear why is there a minimum (perhaps it is given by the total observed volume)? This is not far from what the Dispertech device offers.
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