Detection of membrane antigens of extracellular vesicles by surface plasmon resonance

Extracellular vesicles (EVs) are membrane-bound vesicles released from cells to the extracellular milieu, playing an important role in the biological processes, including intercellular communications (1). EVs can be generally divided into exosomes, microvesicles (MVs), and apoptotic bodies largely by their size, despite debate about their definition (2). Recently, the application of EVs as a tool for non-invasive liquid biopsy in tumor specimens has been investigated in prostate cancer (3), glioblastoma (4), and pancreatic cancer (5). Therefore, it is important to develop a better detection technique for the surface antigen of EVs, leading to the discovery of a precise biomarker for the diagnosis and prognosis of tumor. Currently, there are several techniques being used for the detection and characterization of EVs, including nanoparticle tracking analysis, dynamic light scattering analysis, zeta potential analysis, tunable resistive pulse sensing, Raman spectroscopy, electron microscopy, enzyme-linked immunosorbent assay, western blot, and “omics” such as proteomics and RNA-seq (6). In addition, surface plasmon resonance (SPR) sensing has emerged as a widespread biophysical sensing tool for the analysis of membrane molecules, including surface proteins and carbohydrates.