Extracellular vesicles (EVs) or exosomes are small membrane vesicles of endocytic origin that are released by many cell types, e.g., T cells, B cells, dendritic cells, platelets, neurons, and epithelial cells. Depending on the originating cell, exosomes are loaded with a specific set of proteins, lipids, and nucleic acids. EVs are involved in various biological processes, including immune surveillance, blood coagulation, neuronal communication, stem cell maintenance, and tissue repair. Their impact on tumor progression, neurodegeneration, autoimmune disorders, and other diseases is under investigation as is their diagnostic potential from liquid biopsies such as blood plasma and urine.

Detection of EVs by flow cytometry has historically presented challenges due to their small size (30-100um) and aggregation.

We have developed a multiplex bead-based capture method using beads labelled with 39 different exosome surface markers and detected using a cocktail of antibodies against the tetraspanins (CD9, CD63, CD81) binding to exosomes. These complexes can then be analysed based on the fluorescence characteristics of both the bead and detection antibody.

We show results from a number of studies demonstrating rapid assessment of exosome composition from a variety of cancer cell lines and plasma.