An Approach for Measuring Extracellular Vesicle Size Using the Attenuation-Velocity Change Ratio of SH-SAW Biosensors

Large EVs (lEVs) and small EVs (sEVs) are distinct extracellular vesicles (EVs) found in physiological fluids with different size ranges, biogenesis pathways, and biomarker cargoes. This study introduces a novel approach using a shear horizontal surface acoustic wave (SH-SAW) biosensor to estimate the lEV composition independently of EV concentration and interfering agents. A layer parameter, corresponding to the ratio of amplitude attenuation to velocity fractional change, is shown to be linearly correlated with the median EV size. To further discriminate lEVs from sEVs, separate pull-downs with the sEV marker CD9 and the generic sEV/lEV marker GPC1 are used. Wharton's jelly mesenchymal stem cell-derived EVs are shown to contain 2.5 times more lEVs in composition than those derived from adipose stem cells. Our results suggest that elevated lEV expression can be quantitatively detected using SH-SAW-based liquid biopsy in age-related diseases.