Studies On Au Nanocomposites And Microelectrodes For Immunosensing

Immunosensors can be applied to food assay, environmental monitoring, clinical assay, and so on. The electrochemical immunosensors with low cost, easy operation and capability for on-line monitoring have received increasing attention. With the advances of nanoscience and nanotechnology, nanomaterial-based electrochemical immunosensors has become the frontier of the research field. In this thesis, the recent progress of immunosensors is briefly reviewed. The studies are summarized as follows.1. A novel sandwich-type electrochemical immunosensor for human immunoglobulin G (hIgG) was developed using Au/SiO2 nanoparticles (NPs) with adsorbed horseradish peroxidase-anti-hIgG as the secondary antibody layer. The signal readout is based on the amperometric response to the catalytic reduction of H2O2 at an AuNPs-polythionine modified glassy carbon electrode. Under optimized conditions, the linear range for hIgG is from 0.1 to 200 ng mL-1, with a detection limit of 0.035 ng mL-1 (S/N=3).2. A novel label-free amperometric immunosensor for the determination of carcinoembryonic antigen (CEA) based on toluidine-nanogold-SiO2 nanocomposite has developed. The prepared nanocomposite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectrophotometry. Under optimal experimental conditions, the sensor can be used to determine trace CEA antigen, with a linear range from 1 to 80 ng mL-1 and a detection limit of 0.65 ng mL-1.3. A novel strategy for preparation of label-free AFP immunosensor based on Au microelectrode and nanoparticles has been developed. Firstly, a gold nanoparticle (AuNPs) monolayer was assembled on the Au wire microelectrode for antibody immobilization, the electrode modification process was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and AFM. It was found that the decrease of the electrode size can increase the detection sensitivity of the sensor. Under optimized conditions, the sensor can be used to determine sub-pg mL-1 AFP antigen.