EV Flow Series | Edwin van der Pol - Size and refractive index of nanoparticles using Flow-SR

This video is part of the ISEV-ISAC-ISTH EV Flow Cytometry Working Group Seminar Series. Visit our website at http://www.evflowcytometry.org/ for more information. Subscribe to our seminar series and get access to our Slack channel to continue the discussion by completing this form: https://bit.ly/3eKmlNP Date: 20th May 2020 Topic: Educational Talk Title: Size and refractive index determination of sub-micrometer particles using the flow cytometry scatter ratio [Flow-SR] Moderators: Joshua Welsh [1], John Nolan [2] [1] National Institutes of Health, USA. [2] Scintillon Institute, La Jolla, USA Speaker: Edwin van der Pol, Amsterdam University Medical Centers, Netherlands Abstract: Flow cytometers measure light scattering signals in arbitrary units, which hampers data interpretation and comparison. Light scattering signals, however, contain valuable information about the size and composition of particles. This information can be assessed by calibration, which means conversion of arbitrary units to standardized measurement units, like diameter in nm. One scatter detector can be calibrated by measuring beads and describing the signals with Mie theory, taking into account the optical configuration of the flow cytometer and the sizes and refractive indices [RIs] of the beads. The RI is an intrinsic property of a particle that depends on the composition and that determines how efficient a particle scatters light. When the RI is known and one scatter detector is calibrated, Mie theory can be used to derive the diameter of extracellular vesicles [EVs] [1]. In this presentation, I will explain that by taking the ratio between side scatter and forward scatter signals, which we named the flow cytometry scatter ratio [Flow-SR], it becomes possible to determine both the diameter and RI of submicrometer particles [2]. Flow-SR enables label-free discrimination between EVs [RI < 1.42] and lipoprotein particles [RI > 1.45] in plasma and can be used to evaluate the specificity of antibody labels. We have automated Flow-SR and are applying it to analyze data in clinical research studies on EVs [next talk] [3]. [1] De Rond et al. Deriving extracellular vesicle size from scatter intensities measured by flow cytometry. Curr. Protoc. Cytom. e43, 1-14 [2018] [2] van der Pol et al. Absolute sizing and label-free identification of extracellular vesicles by flow cytometry. Nanomedicine 14, 801-10 [2018] [3] Gasecka et al. Ticagrelor attenuates the increase of extracellular vesicles concentrations in plasma after acute myocardial infarction compared to clopidogrel. J. Thromb. Haemost. 18[3], 609-623 [2020]