August 10, 2021 – Publication highlight: Measuring extracellular vesicles (EVs) in biofluids
In this post we highlight a recent publication from researchers in the Faculty of Medicine (AMC) at the University of Amsterdam, in which a standard method was developed for analyzing extracellular vesicles (EVs) in biofluids using Spectradyne’s Microfluidic Resistive Pulse Sensing (MRPS).
M. Cimorelli, R. Nieuwland, Z. Varga, E. van der Pol, “Standardized procedure to measure the size distribution of extracellular vesicles together with other particles in biofluids with microfluidic resistive pulse sensing,” PLOS One 16, e0249603 (2021)
DOI link to publication
The study details standard operating procedures (SOPs) and protocols for using the nCS1 to quantify particles directly in human plasma, urine, and conditioned cell culture medium. Method development techniques for determining appropriate dilution factors for these samples that optimize sample flow, limit of detection, reproducibility and agreement over different size ranges are reported. Here are a few highlights from the authors’ findings:
- Particle size distributions are highly reproducible, even for such complex biological samples.
- The measured particle size distributions are independent of sample dilution, as expected.
- Size distributions from cartridges with overlapping detection ranges agree well with one another in the overlapping region.
- The particle concentration in these samples spanned 5 orders of magnitude over the measured size range, underscoring the value of MRPS’s broad measurement dynamic range.
One final recommendation from the paper warrants some additional discussion: From parallel flow cytometry experiments the authors conclude that the optimal diluent for measuring vesicles in biofluids by MRPS is 0.1% bovine serum albumin (BSA). However, the discussion also includes the caveat that EV detection by flow cytometry relied on fluorescent antibody labeling, and that the labeling itself may have been disrupted by the Tween and led to an apparent decrease in EV concentration in the measurements. More broadly, several other papers studying the stability of EVs in buffer containing detergents have concluded that Tween does not affect the stability of vesicles (e.g., Arab et al. (2021), Osteikoetxea et al. (2015)), a conclusion that Spectradyne finds in agreement with the majority of its customers’ applications.
We would like to thank the authors of this paper for performing such a thorough characterization of Spectradyne’s technology, and for laying the groundwork of standardization for MRPS measurements of extracellular vesicles in biofluids!