A Label Free Immunosensor For AFB₁ Based On Gold 3DNEEs With SpA Orientation

In this thesis, the research status and progress on aflatoxin electrochemical immunosensor, nanoelectrode ensembles and modified electrodes were summarized. The gold 3DNEEs was fabricated by an electroless procedure using polycarbonate membrane as the template. The three chemically modified electrodes Po PD/3DNEEs, Cys/3DNEEs and Sp A/3DNEEs were obtained with different approaches. The AFB1 immunosensors based on such chemically modified electrodes were constructed and performed well in quantitative analysis for AFB1.The cyclic voltammetry was employed for Po PD electropolymerization on 3DNEEs. The cyclic voltammograms agreed well with the theoretical analysis of the initial stages of the electropolymerization process of o PD. The PAN-Like structure of Po PD prepared was demonstrated by infrared spectroscopy. The AFB1 immunosensor BSA/Anti-AFB1/Sp A/GA/Po PD/3DNEEs was constructed and the parameters of its fabrication were optimized. The equivalent circuit was built to simulate the impedance spectra. The immunosensor was proved to possess wide detection range between 4.0×10-11~8.0×10-9 g/m L and low detection limit of 3.4×10-12 g/m L(S/N=3). The immunosensor was superior to the correlative immunosensors fabricated by other researchers.Based on cysteamine self-assembling on MGE and 3DNEEs, the BSA/Anti-AFB1/GA/Cys/MGE, BSA/Anti-AFB1/GA/Cys/3DNEEs and BSA/Anti-AFB1/Sp A/GA/Cys/3DNEEs were constructed. Optimization was performed for cysteamine self-assembling, time and p H for cross linking, as well as detection system. The detection limits of the three immunosensors by EIS were 2.0×10-11 g/m L(S/N=3), 9.0×10-12 g/m L(S/N=3) and 1.4×10-11 g/m L(S/N=3) respectively. The detection limits of BSA/Anti-AFB1/GA/Cys/MGE and BSA/Anti-AFB1/Sp A/GA/Cys/3DNEEs by SWV were 6.5×10-11 g/m L(S/N=3) and 5.7×10-12 g/m L(S/N=3) separately.The Sp A/3DNEEs was obtained by directly modification of Sp A on 3DNEEs. The XPS spectroscopy of Sp A/MGE proved that the m odification was based on the formation of Au-S bond. The immunosensor BSA/Anti-AFB1/Sp A/3DNEEs was constructed. The time for Sp A and antibody immobilization were optimized. The immunosensor was proved to possess the detection limit of 1.9×10-11 g/m L(S/N=3) with the detection range between 2.0×10-11~1.0×10-8 g/m L.