An electro-optical platform for the ultrasensitive detection of small extracellular vesicle sub-types and their protein epitope counts.

Methods for detecting proteins in small extracellular vesicles (sEVs) lack sensitivity and quantitative accuracy, missing clues about health and disease. Our study introduces the Nano-Extracellular Omics Sensing (NEXOS) platform, merging electrical (E-NEXOS) and optical detection (O-NEXOS). E-NEXOS determines the concentration of target sEV sub-types, and O-NEXOS quantifies the concentration of target protein epitopes (TEPs) on those TEVs. In this work, both technologies were compared to several sEV detection tools, showing superior detection limits for CD9CD81 and CD9HER2 sEVs. Furthermore, the additional information on TEVs and TEPs from bulk sEV samples, provided new phenotyping capabilities. We determined the average number of CD81 and HER2 proteins on CD9 sEVs, a number which was later validated on spiked human plasma. These results highlight the compatibility of NEXOS with complex biofluids and, as importantly, hint at its many potential applications, ranging from basic research to the anticipated clinical translation of sEVs.