Accumulated evidence has indicated that exosomes play a vital role in many biological processes such as intercellular communication, antigen presentation, and waste management. Since the fingerprints of exosomes resemble their parental cells, they are widely recognized as next generation biomarkers for disease diagnosis, prognosis, and therapy. Being endogenous in nature, exosomes also present themselves as an exquisite vehicle for the delivery of therapeutic cargoes because of their immunological inertness and exceptional ability to elicit potent cellular responses. Therefore, the quantification of exosomes is crucial in facilitating exosome research and application.
Researchers from the National University of Singapore summarize the progress in exosome quantification techniques with representative examples to illustrate their working principles with some discussion on challenges and prospects.
Schematic representation of iMEX and its exosome sensing mechanism
The workflow of the iMEX is as follows: exosomes in cell-free body fluids such as serum, plasma, and urine are first selectively captured by magnetic beads coated with an exosome-specific antibody – antitetraspanin transmembrane protein antibody. A signal unit – a secondary antibody tagged with HRP – is introduced to the captured exosomes after the magnetic beads are held on the sensing units and a quick washing. Amplified electrochemical detection is realized through the electroreduction of enzymatically oxidized 3,3′,5,5′-tetramethylbenzidine.