, Dunnan Li,

We report a versatile strategy for electrochemical and optical signal-on/off immunosensing, on the basis of enzyme-mediated growing Au nanoparticles. By applying antibody and enzyme (glucose oxidase or catalase) conjungated Au nanoparticles as secondary antibodies, the sandwich-type immunosensor can achieve either a “signal-on ” or a “signal-off ” electrochemical / optical detection. Scanning electron microscope, electrochemical, and spectral studies revealed that the AuNPs growth is dependent on H2O2 concentration, which is mediated by glucose oxidase or catalase. More AuNPs lead to larger electrochemical and optical signals, and vice versa. As a proof-of-concept, the immunosensor platform was used to detect immunoglobulin G in human serum