Analysis of bacteria-derived outer membrane vesicles using tunable resistive pulse sensing

Accurate characterization of submicron particles within biological fluids presents a major challenge for a wide range of biomedical research. Detection, characterization and classification are difficult due to the presence of particles and debris ranging from single molecules up to particles slightly smaller than cells. Especial interest arises from extracellular vesicles (EVs) which are known to play a pivotal role in cell-signaling in multicellular organisms. Tunable resistive pulse sensing (TRPS) is increasingly proving to be a useful tool for high throughput particle-by-particle analysis of EVs and other submicron particles. This study examines the capability of TRPS for characterization of EVs derived from bacteria, also called outer membrane vesicles (OMVs). Measurement of a size distribution (124 ± 3 nm modal diameter) and concentration (lower bound 7.4 x 10 9 mL -1 ) are demonstrated using OMVs derived from uropathogenic Escherichia coli . Important aspects of measurement are discussed, including sample preparation and size selection. Application of TRPS to study EVs could assist the development of these particles in clinical diagnostics and therapeutics.