Extracellular vesicles (EVs) are released from various cells and play an important role in cellular communications relating to various diseases . EVs can be used as biomarkers for diagnosis, prognosis, and determining the cell state. Although proteomics or genomics of EVs have been extensively studied, little is known about details of surface glycans on EVs. We report that comprehensive glycan patterns on intact exosomes can be analysed using an evanescent field fluorescence-assisted (EFF) lectin array system . This lectin array system is simple, sensitive, and real-time detection of surface glycan patterns on intact EVs without the destruction of EVs.
EVs were isolated from various kinds of mouse and human cells including cancer cells, undifferentiated and differentiated MSCs, and immune cells by differential ultracentrifugation. Cy3-labeled EVs and their originating cell membranes (CMs) were applied to a glass slide with 45 lectins and fluorescence intensities were detected using an evanescent-field fluorescence scanner without washing. Hierarchical clustering analysis and principal component analysis were performed to evaluate whether surface glycans on EVs have their cell specific patterns. The results indicated that glycan profiling of EVs can be used to classify cell types (normal or cancer) and they can be further divided into each type of cancer, MSC sources, and cell lineages. Sialic acids–coaded EV (sialic acids were highly enriched on the surface of EVs analyzed by the lectin array) specifically interacted with cells expressing sialic acid-binding immunoglobulin (Ig)-like lectins (siglecs), such as HeLa cell in vitro and antigen-presenting cells in vivo.
In conclusion, EFF-lectin array method is a powerful tool for comprehensively glycan analysis of EVs towards functional analysis of glycan on EV surface and also biomarker discovery.
 N. Seo, et al. Nature Communications, 9, 435(2018),  A. Shimoda, et al. Biochem. Biophys. Res. Commun., 491, 701(2017)