Design Of Electrochemistry Immunosensor Based On Biocompatible Hybrid Nanomaterials

Electrochemical immunosensor is a kind of biosensor combined electrochemical analysis method with immunology technology and developed to have fast, sensitive, easy operation, high selectivity etc. Immunosensor mainly composed of biological recognition system (receptor) and transducer. Fixing antigen or antibody molecules onto a transducer called construction of the sensor sensitive interface. In the research and exploitation of immunosensors, the most important and crucial work is how to develop a simple and effective strategy for the immobilization of immunocomponent and keep its good biological activity. The main work of this paper is focus on the preparation of functional composite nanomaterials, construction of sensitive sensor interface and novel signal enhancement strategy of the immunosensor. The details are summarized as follows:1. Covalently synthesized poly(allylamine)-branched ferrocene (PAA-Fc) redox polymer. A stable PAA-Fc composite film with good film forming property was first formed on the electrode surface. Subsequently, Au NPs were adsorbed onto the PAA-Fc film surface through the well-developed interaction between Au NPs and amino groups of PAA, which provided reactive sites for further antibody immobilization. Then the PAA-Fc/Au NPs/HBsAb immunosensor was fabricated for the detection of HBsAg. The fabricated immunosensor provided good microenvironment for antibody immobilization, and realized the immobilization of the electron-mediator stable on the electrode surface, moreover the absorbed Au NPs acted as a conducting "wire", which increased the electron-transfer efficiency, improved sensitivity of the immunosensor, and realized the high sensitive label-free detection to hepatitis B surface antigen. We also doped MWNTs into PAA-Fc membrane. The existence of MWNTs not only increased immobilized Au NPs on the electrode surface, which further dramatically increased fixed antibody molecule density, but also provided the electronic transmission channel between the electrode and electrolyte, accelerated the electron-transfer efficiency between Fc in the composite film and electrode surface, improved the sensitivity of PAA-Fc/MWNTs/Au NPs/HBsAb immunosensor. Compared to the immunosensor without MWNTs, the immunosensor doped with MWNTs presented high sensitivity, low detection limit, good application prospect.2. In this part, a novel amperometric immunosensor for the detection of carcinoembryonic antigen based on CS-Fc/GO nanocomposite as a sensor platform and combined redox cycling reaction to amplify the signal. Covalently synthesized CS-Fc composite, and then mixed with GO through electrostatic interaction to prepare CS-Fc/GO nanocomposite film, thereby graphene with a large surface area, good biocompatibility, and rich carboxyl could immobilized a lot of antibodies. In addition, using Fe3O4/Au NPs as a secondary antibody label which can catalyze redox cycle reaction can fabricate immunosensor with high sensitivity. Energy-dispersive X-ray spectrometer (EDS) and scanning electron microscopy (SEM) was used to characterize the synthesized Fe3O4/Au NPs composite nanoparticles, electrochemistry of the nanocomposite film were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The properties of the immunosensor were studied in detail. Linear range of the immunosensor was 0.001-30.0 ng mL-1, the linear correlation coefficient was 0.9976, and the detection limit was 0.39 pg mL-1.3. This paper introduced a novel CEA immunosensor based on the surface of gold nanoparticles in situ electron mediators. Crosslinking primary antibodies on polyethylene imide (PEI) modified ITO surface, and then incubate with different concentrations of antigen, and then incubate with gold nanoparticles labeled secondary antibody, and finally dip the modified electrode in potassium ferricyanide the solution, under certain conditions prussian blue can be generated in situ on the surface of gold nanoparticles. Prussian blue not only has a sensitive electrochemical performance, but also has good optical properties. This paper using carcinoembryonic antigen as model antibody investigated by cyclic voltammetry (CV) and ultraviolet spectrophotometry (UV-Vis) for the quantitative detection, and the performance of the immunosensor were studied in detail. The linear range of detection of optical immunosensors is 2.0-120 ng mL-1, the detection limit was 1.3 ng mL-1. The linear range of detection of electrochemical immunosensors is 1.6—10 ng mL-1 and 10-160 ng mL-1, the detection limit was 0.82 ng mL-1. The results showed that the developed versatile immunosensor prepared by proposed strategy was easy, convenience, disposable, to be a promising alternative for clinical diagnosis.