Reproducible extracellular vesicle size and concentration determination with tunable resistive pulse sensing

Abstract

Daily measurements with a fixed stretch and voltage (n=102) on a standard urine sample show a minimum detected vesicle diameter of 128±19 nm [mean±standard deviation; coefficient of variation (CV) 14.8%]. The vesicle concentration was 2.4·109±3.8·109 vesicles/mL (range 1.4·108-1.8·1010). When we compared setting a fixed stretch and voltage to setting a fixed blockade height on 3 different pores, we found a minimum detected vesicle diameter of 118 nm (CV 15.5%, stretch), and 123 nm (CV 4.5%, blockade height). The detected vesicle concentration was 3.2-8.2·108 vesicles/mL with fixed stretch and 6.4-7.8·108 vesicles/mL with fixed blockade height. Summary/conclusion: Pore-to-pore variability is the cause of the variation in minimum detected size when setting a fixed stretch and voltage. The reproducibility of the minimum detectable diameter is much improved by setting a fixed blockade height.