Label-free surface protein profiling of extracellular vesicles by an electrokinetic sensor.

Small extracellular vesicles (sEVs) generated from the endolysosomal system, often referred to as exosomes, have attracted interest as a suitable biomarker for cancer diagnostics, as they carry valuable biological information and reflect their cells of origin. Herein, we propose a simple and inexpensive electrical method for label-free detection and profiling of sEVs in the size range of exosomes. The detection method is based on the electrokinetic principle, where the change in the streaming current is monitored as the surface markers of the sEVs interact with the affinity reagents immobilized on the inner surface of a silica micro-capillary. As a proof-of-concept, we detected sEVs derived from the non-small cell lung cancer (NSCLC) cell line H1975 for a set of representative surface markers, such as epidermal growth factor receptor (EGFR), CD9 and CD63. The detection sensitivity was estimated to be ~175000 sEVs, which represents a sensor surface coverage of only 0.04%. We further validated the ability o...