Electrochemical stripping analysis of nanogold label-induced silver deposition for ultrasensitive multiplexed detection of tumor markers.

A multiplexed electrochemical immunoassay method was developed for simultaneous ultrasensitive measurement of tumor markers based on electrochemical stripping analysis of silver nanoparticles (Ag NPs). The Ag NPs were deposited on a disposable immunosensor array with a reduction reaction catalyzed by nanogold labels. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. Through a sandwich-type immunoreaction, antibody-functionalized Au NPs were captured onto immunosensor surface to induce the silver deposition from a silver enhancer solution. The deposited Ag NPs could be directly measured by anodic stripping analysis in KCl solution. The catalytic deposition enhanced the analytical sensitivity for detection of protein markers. The interference of dissolved oxygen could be avoided as the detection was performed with positive stripping potential range. Using carcinoembryonic antigen and α-fetoprotein as model analytes, the proposed multiplexed immunoassay method showed wide linear ranges of three orders of magnitude with the detection limits down to 3.5 and 3.9 pg mL(-1), respectively. The localized silver deposition, as well as the stripping detection process, eliminated completely the electrochemical cross talk between adjacent immunosensors. The immunosensor array exhibited acceptable reproducibility, stability and accuracy, showing a promising potential in multianalyte determination for clinical application.