Highly Sensitive Voltammetric Immunosensing of Cancer Biomarkers HER2 and CA125 Using Gold Nanoparticles Anchored Reduced Graphene Oxide Enzyme-Free Nanolabel

Sandwich type voltammetric immunosensors were developed for the quantitative determination of cancer biomarkers, HER2 (human epidermal growth factor receptor 2), and CA125 (cancer antigen 125). Specific antibodies were immobilized on the gold electrodes by using a self-assembled monolayer of mercaptoundecanoic acid (MUA) activated by EDC-NHS ((1-ethyl-3-(3-dimethylamino propyl) carbodiimide and N -hydroxysuccinimide). Antibody conjugated gold nanoparticles decorated reduced graphene oxide (anti-HER2-Au/rGO and anti-CA125-Au/rGO) were used as enzyme-free nano labels for signal amplification. The sensors were characterized thoroughly by spectroscopic, microscopic, and electrochemical methods. Differential pulse voltammetric (DPV) studies in the presence of thionine revealed that the current signal produced is directly related to the biomarker concentration. A linear range of 0.2 pg ml −1 to 100 ng ml −1 was obtained, which indicated the immunosensors to be highly sensitive in lower concentrations of cancer biomarkers. Finally, the fabricated immunosensors were tested with serum samples spiked with HER2 and CA125. The results obtained from the test confirmed the data collected from clinical labs.