Electrochemical immunosensing of nanovesicles as biomarkers for breast cancer

Exosomes are nano-sized vesicles, which are currently under intensive study as potential diagnostic biomarkers for many health disorders, including cancer. This paper addresses the study of an electrochemical immunosensor in different formats for the characterization and quantification of exosomes derived from three breast cancer cell lines (MCF7, MDA-MB-231 and SKBR3). To achieve that, the exosomes were preconcentrated from cell-culture supernatant (and eventually in human serum) on magnetic particles modified with antibodies against the general tetraspanins CD9, CD63 and CD81, as well as specific receptors of cancer (CD24, CD44, CD54, CD326 and CD340). The electrochemical immunosensor is able to reach a limit of detection of 105 exosomes μL-1 directly in human serum, when performing the immunomagnetic separation with antiCD81 modified magnetic particles and the labeling based on CD24 and CD340 as cancer-related biomarker, avoiding the interference from free receptors in the serum matrix. Furthermore, the electrochemical immunosensor shows reliable results for the differentiation of healthy donors and breast cancer individuals based on specific epithelial biomarkers. This approach is a highly suitable alternative method for the detection of exosomes in scarce resource settings.