Study And Application Of Nano-composite Materials To Build The Combination Of Photochemical And Electrochemical Biosensors

In recent years, electrochemical immunoassay has been combined with the rapid development, is moving in the direction of a highly sensitive, high-throughput technologies and applications with a variety of development. Various types of nano-materials used in the construction of the immune sensors, in particular made some encouraging progress in the analysis of electrochemiluminescence and photoelectrochemical methods. In this dissertation, a series of electrochemiluminescence and photoelectrochemical systems were developed. By coupling, new bioanalytical and biosensing strategies were construeted with good performance.This dissertation includes the following four parts:(1) In this work, gold nanoparticles functionalized nitrogen-doped graphene composite Au-NG composite nanoparticles were prepared, the composite could combine the advantages of gold nanoparticles and nitrogen-doped graphene. The Au-NG-Ru(bpy)32+were used to label the second antibody, a high sensitivity electroluminescence immunosensor was constructed with sandwich-typy method. The primary antibody was first immobilized on the Au-NG modified electrode due to the covalent conjugation, then the antigen and the Au-NG-Ru(bpy)32+ composite nanoparticles labeled secondary antibody was conjugated successively to form a sandwich-type immunocomplex through the specific interaction. Accordingly, through the electroluminescence response of Au-NG-Ru(bpy)32+and triethanolamine, a strong electroluminescence signal was obtained and an amplification analysis of protein reaction was achieved, which led to an increase of the immunosensor sensitivity. In the optimal experimental conditions, the immunsensor performed high sensitivity and wide liner for detection HIgG in the range of 0.01-500 ng/mL and the limit detection was 5 pg/mL.(2) The Ru(bpy)32+ and luminol were chosen as the electroluminescence signal probe and respectively encapsulated in Au-NG as immune label. Relative to the Au-NG-Ru(bpy)32+ as the label of anti-CEA, the Au-NG-luminol was used to label the anti-AFP.The they were orderly subjected the sandwich immunoassay on one electrode surface. The cathodal and anodic electroluminescence scans were executed synchronously at the potential scope of-1.3-1.0 V. And the electroluminescence responses appeared at 0.9 V for the AFP antigen and at -1.2 V for the CEA. The immunosensor showed liner ranges of 0.01-35 ng/mL for AFP and 0.01-60 ng/mL for CEA. This result testifies that the multiplexed assay can be realized in the electroluminescence.(3) Semiconductor nanomaterials (or quantum dots) have been extensively developed because of its unique fluorescence characteristics and good biocompatibility. In this study, ochratoxin A was used as the analyte, a highly sensitive label-free electroluminescence immunosensor based on CdS-Fe3O4 composite nanoparticles was developed. The CdS-Fe3O4 composite nanoparticles were prepared in this experiment, was used to lable antibodies. The CdS-Fe3O4 composite nanoparticles not only provided a large surface areas and biocompatible environment for adsorption of biomolecules, but also exhibited high electroluminescence intensity and good conductivity. The modified electrodes were evaluated by means of EIS and ECL. Under the optimal conditions, a linear relationship between the electroluminescence intensity and OTA concentration was obtained in the range of 0.01 ng/mL to 100 ng/mL with a detection limit of 6 pg/mL. This approach offered obvious advantages of simple, high sensitively and good selectivity, which possessed great potential for mycotoxin detection in food safety.(4) Based on CdS-Fe3O4 nanocomposite constructed photoelectrochemical immune sensing technology. The immunosensor was prepared by covalently immobilizing capture antibodies on CdS-Fe3O4 nanocomposite modified screen-printed carbon electrodes. After immunoreactions, Aflatoxin B1 was detected. The immunosensor exhibited a wide linear range and low detection limit, linear range 0.01-70 ng/mL, the detection limit of 5 pg/mL. The newly designed strategy avoided background interference for the electrochemical immunoassay and, thus, provided a promising potential in practical application.