CD44 and cancer: Doldan et al. employed amperometry for detecting surfacelocated exosomal proteins using an immunosensor.42 Amperometry was also adopted for the iMEX device, whichsuccessfully profiled exosomal membrane proteins, including CD63,from cancer patients.43 More recently,Moura et al. applied amperometry for cancer-specific exosome markers(CD24, CD44, CD54, CD326).44 All threemethods use direct or indirect labeling of the exosomal protein, orresponse amplification through enzymatic digestion.