Design And Application Of Electrochemistry Biosensor Based On Electroactive And Biocompatible Materials

Biosensor is a very active research and engineering technical field. Wherein, electrochemical biosensors have valuable applications in clinical diagnosis, environmental monitoring, food and pharmacy industries because of its excellent selectivity, high sensitivity, rapid response, low cost, continuous detection, easy to be miniaturized.In the design and fabrication of electrochemical biosensors, the crucial step is how to develop a simple and effective strategy for the construction of sensitive membrane. Aimed at the problems existed in immobilization technique of biosensors, the main work of this paper is focus on the development of new immobilization strategies of biomaterials for the purpose of improving the performance and long-term stability of biosensors. The details, are summarized as follows:1. A simple and controllable electrodeposition approach was proposed for one-step construction of glucose biosensors by in situ codeposition of ferrocene-branched chitosan (CS-Fc), multiwalled carbon nanotubes (MWNTs), and glucose oxidase (GOD) onto electrode surface. The formation of CS-Fc could not only effectively prevent the leakage of Fc and retain its electrochemical activity, but also provide a biocompatible microenvironment for retaining the native activity of the immobilized biomolecules. Moreover, MWNTs act as an electron relay in the biocomposite system significantly improved electronic conductivity of the biocomposite and facilitated electron transfer between the GOD and the electrode for the electrocatalysis of glucose. Thus, the present biosensor exhibited fast response, high sensitivity, excellent stability and reproducibility towards the quantification of glucose.2. In this work, a new biomolecular immobilization strategy based on redox based on redox-active ferrocene-branched chitosan/multiwalled carbon nanotubes (CS-Fc/MWNTs) and gold nanoparticles (Au NPs) was used to develop a highly sensitive amperometric immunosensor. The formation of CS-Fc/MWNTs composite film effectively avoids the leakage of Fc and retains its electrochemical activity. Further adsorption of Au NPs into the CS matrix provides both the interactive sites for the immobilization of HBsAb and a favorable microenvironment to maintain the activity of the HBsAb, and in addition prevents leakage of HBsAb molecules from the CS-Fc/MWNTs/Au NPs/HBsAb film structure efficiently. After the immunosensor was incubated with sample solution containing HBsAg, the current response of Fc decreased with an increasing HBsAg concentration. The developed immunosensor exhibits a specific response to HBsAg in the range of 1.0-420 ng mL-1 with a detection limit of 0.28 ng mL-1 (S/N= 3). The prepared method is simplified, economical and efficient, and the resulting immunosensor exhibits high sensitivity and selectivity, long-term stability and good reproducibility.3. In this part, layer-by-layer self-assembly (LBL) technology was used to design a new nontoxic electrochemical biomimetic interface for immobilization of biomolecule. Firstly, a stable{CS-Fc/MWNTs/Au NPs}n multilayer films with excellent redox activity and good biocompatibility was prepared by alternate adsorption of oppositely charged CS-Fc/MWNTs and Au NPs. Subsequently, HBsAb used as a model antibody was assembled onto the surface of Au NPs for the detection of HBsAg. Through LBL self-assembly of CS-Fc/MWNTs and Au NPs, the constructed three-dimensional mutilayer network structure could provide more stereo sites and ideal platform for further immobilization of biomolecules without loss their activity and efficiently prevent the leakage of biomolecules from the sensing electrode surface. The resulted immunosensor exhibits a high sensitivity, good reproducibility, and long-term stability, indicating the method to be a promising alternative for clinical diagnosis.4. This paper introduced assembles the positively charged chitosan-ferrocene on 3-mercaptopropanesulfonic sodium salt (MPS) modified electrode, using the adsorption between positively charged amino and Au NPs, the Au NPs was immobilized on the electrode surface. Then using intense adsorption between Au NPs and the antibody, realizes the immobilization of antibody on the electrode surfarce to prepare immune sensing interface. As a-fetoprotein (AFP) a model antibody, combined with surface plasmon resonance (SPR) detection technology and use the advantages of magnetic Fe3O4@Au to sensitively detection AFP with sandwich immunoassay. The electrode surface modified by different material was characterized by SPR, cyclic voltammetry (CV), and impedance (EIS). The nanometer Fe3O4@Au compound particle can not only effectively link with the secondary antibody, but also separate and concentrate samples and amplify the SPR detection signal. Compared to the tradition of immunosensor, the immunosensor with low detection limit (0.65ng mL-1), high sensitivity, good stability, it can meet the requirements of the actual measure.