▎ 摘　　要

A sandwich-type photoelectrochemical immunoassay is described for the protein S100 ss which is an Alzheimer's disease biomarker found in the astrocytes of the brain. Antibody against S100 ss (anti-S100 ss) was labeled with CdS quantum dots and then acted as a secondary antibody. The labeled antibody was characterized by FTIR, ultraviolet-visible and fluorescence spectroscopy. An indium-tin oxide (ITO) electrode was modified with a nanocomposite prepared from reduced graphene oxide and gold nanoparticles. Then, a sol-gel film containing isocyanate functional groups (-N=C=O) was cast on the surface of the electrode. The NCO group reacts with amino groups of the labeled antibody to covalently bind them to the surface. The S100 was bound by the primary immobilized antibody on the rGO-Au/ITO electrode and then sandwiched with the labeled secondary antibody. Cyclic voltammetry and electrochemical impedance spectroscopy were applied to confirm the stepwise changes in the electrochemical properties of the electrode surface. The photoelectrochemical immunoassay, typically operated at a potential of +0.2V (vs. Ag|AgClsat) gives a signal that is related to the logarithm of the S100 concentration in the range from 0.25 to 10ng mL (-1) with a lower detection limit of 0.15pg mL (-1). The method was successfully applied to the determination of S100 in human serum samples.