Copper-enhanced gold nanoparticle tags for electrochemical stripping detection of human IgG

We demonstrate herein a novel electrochemical protocol for quantification of human IgG based on the precipitation of copper on gold nanoparticle tags and a subsequent electrochemical stripping detection of the dissolved copper. The immunoassay was conducted by following the typical procedure for sandwich-type immunoreaction. Goat anti-human IgG was immobilized on the wells of microtiter plates. The human IgG analyte was first captured by the primary antibody and then sandwiched by secondary antibody labeled with gold nanoparticles. The copper enhancer solution was then added to deposite copper on the gold nanoparticle tags. After dissolved with HNO3, the released copper ions were then quantified by ASV. The detection limit is 0.5 ng/mL by 3σ-rule. In order to investigate the feasibility of the newly developed technique to be applied for clinical analysis, several standard human IgG serum specimens were also examined by the method. To our knowledge, the copper enhancing procedure is the first time to be developed for immunoassay. The new strategy of using copper-enhanced gold nanoparticle tags for electrochemical stripping detection holds great promise for immunoassay and DNA detection.