The Research On Enzyme-Catalyzed Precipitation And Nanomaterial Functionalized Interface Biosensors

In this paper,we developed three novel immunosensors and a mediator-free enzyme sensor, based on efficient immobilization of biomolecule and signal-amplified methods to improve detection sensitivity and decrease the detection limit. The detailed materials are shown as follows:(1) An amplified immunosensor with highly sensitivity has been proposed based on precipitation of an insoluble product on functionalized electrode (in Chapter 2). Anti-hIgG was immobilized onto the surface of gold electrode modified with 1,6- hexanedithiol and colloidal Au interface. It was proved that the amount of immobilized antibody and the immunoactivity of bound antibodies could be well improved by colloidal Au. HRP labeled antibody reacted with antigen, then HRP biocatalyzed DAB (3,3'-diaminobenzidine) in the presence of H₂O₂, resulting in an insoluble product onto the electrode surface, to achieve an obviously decreased frequency. The results show that this method can greatly improve the detection sensitivity of hIgG in human serum. The immunosensor can be used to quantitatively determine hIgG in the range of 1.6×10^-8～1.0×10^-4 g mL^-1. The detection limit is 1.0×10^-8 g mL^-1.(2) An amplified immunoassay with improved sensitivity has been proposed based on two-step amplification procedures of enzyme-catalyzed precipitation and biotin-streptavidin binding system (in Chapter 3). Anti-IgG antibody was immobilized onto the surface of gold electrode modified with a thin layer of protein A.Biotin labeled anti-IgG antibody and HRP-streptavidin were premixed to form network complex to be used as probes for amplifying the sensing response of antibody-antigen interaction. HRP biocatalyzed DAB (3,3'-diaminobenzidine) in the presence of H2O2, resulting in an insoluble product on the electrode surface, to achieve an enhanced electron-transfer resistance on the electrode surface as well as a decreased frequency. The results show that this method can greatly improve the detection sensitivity of hIgG in human serum with concentration as low as 1.0×10^-8 g mL-1. We employed Faradaic impedance spectroscopy and quartz crystal microbalance (QCM) to follow the stepwise assembly of the systems and investigate immunosensing properties.(3) A new piezoelectric quartz crystal immunosensor for hCG detection was constructed. The anti-hCG antibody was deposited on the gold electrode's surface of 9...