A novel breast cancer screening platform: An epitope-based biomarker coupled to electrochemical sensor.

9 Background: The subtractive proteomic selection technology called Phage Display (PD) has been extensively used by our group in the discovery of high affinity ligands to target tissues and molecules. We have selected specific ligands against IgG purified from BC tissues, which was successfully coupled to an electrochemical sensor to detect the tumor-specific immune response. Methods: After PD selections, all immunoreactive peptide ligands were further characterized by DNA sequencing, in vitro translated and submitted to bioinformatic analyses. Further validations were performed by ELISA. We then used one synthetic peptide (SF4) for the construction of an immunosensor, which was applied to patients and control samples for final validation. Electrochemical impedance spectroscopy (EIS) was performed. Results: We have selected the F4 peptide for final validation and sensor construction due to its capability of detecting IgG in the peripheral blood and the excellent ELISA ratio BC:BBD, discriminating more than 70% of BC patients. The synthetic peptide reached a good precision in BC diagnosis (68%), but surprisingly, the selected F4 clone presented the highest sensitivity and specificity, (77.8% and 85.7%, respectively), suggesting that it can be used as a diagnostic reagent for early BC screening prior to imaging and pathological analyses. The electrochemical sensor that was built with the epitope-based peptide discriminated all IgG from BC and healthy individuals. Results with the EIS sensor demonstrated that the presence of (SF4) peptide IgG generated higher resistivity (-Z ') compared to the system containing only the peptide or the control sera. This is justified by the fact that with the immobilized biological peptide layer was correctly conjugated with the IgG forming an antigen: antibody complex that led to an increased resistance to the charge transfer system, producing a decrease in electron transfer between the iron-coupled / ferricyanide redox and the electrode surface. Conclusions: An electrochemical sensor using an epitope-based biomarker was developed, which allows for the first time BC screening using a very simple platform that could be an important auxiliary tool to mammography imaging.