Studies On Amperometric And Potentiometric Immunosensors Based On Gold NanoParticles

Immunoassay was developed based on the principle of the specificity recognition of antigen and antibody. Electrochemical immunosensors based on the combination of electroanalysis and immunoassay, have been gained high recognition and application in clinical diagnosis, bioassay and environmental monitoring, owing to the advantages of their high sensitivity, fast analytical time, simple measurement, low-cost and high selectivity. The detection of the immunoassay based on the change in the amperometric or potentiometric response before and after antigen-antibody reaction.The immobilization of the anti-body of immunosensor was very important to its pefformance, so, the methods of immobilization of antibody to the electrode and retain their biocatalytic activities became most important for the pefformance of the immnosensor. In recent years, many kinds of immunosensors have been developed based on the nanophase materials as the carrier for the immobilization of antibody owing to their good biocompartibility and speciality adsorption, and so on . For these reasons, we have studied the immunosensors based on nano materials for the determination of antigen.Part 1. [AuCl₄]^- and Fe³⁺/[Fe(CN)₆]^3- ions-derivated immunosensing interface for electrochemical immunoassay of carcinoembryonic antigen in human serumA simple and sensitive electrochemical immunoassay for CEA was developed by using [AuCl₄]^- and Fe³⁺/[Fe(CN)₆]^3- ions-derivated immunosensing interface. [AuCl₄]^- was initially deposited by electrochemical reduction on a glassy carbon electrode (GCE) to form porous nanogold layer, then Prussian blue (PB) was electrodeposited onto the as-prepared nanogold layer, and then secondary nanogold particles were fabricated again on the PB surface by electrochemical reduction for the immobilization of anti-CEA antibodies. The presence of double-layer porous gold nanoparticles enhanced the immobilized amount of biomolecules, and improved the sensitivity of the immunoassay. PB, as a good redox probe, was facile to electrochemical analysis and measurement. Under optimal conditions, the developed immunoassay exhibited dynamic range from 3.0 to 80.0 ng/mL with a detection limit of 0.9 ng/mL CEA (S/N=3). Moreover, the selectivity, reproducibility and stability of the immunosensor were acceptable. Part2. Electrochemical immuno-bioanalysis for carcinoma antigen 15-3 based on tridimensional SiO₂@Au and electropolymerized thionine-modified gold electrodeA novel approach toward development of advanced immunosensors based on tridimensional SiO₂@Au nanoparticles and electropolymerized thionine (PTH) film on gold electrode was demonstrated in this paper, and the preparation, characterization, and measurement of relevant properties of the immunosensor useful for the detection of carcinoma antigen 15-3 (CA 15-3) were studied by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The immunosensor based on tridimensional SiO₂@Au nanoparticles provides more active sites and good adsorption properties for the attachment of the CA 15-3 antibody selective to CA 15-3. Under optimal conditions, the resulting immunosensor presents good linearity and specificity when it was evaluated on several standard serum samples and the working range was 1-8 and 8-250 U/mL with a detection limit of 0.42 U/mL(S/N=3). Importantly, the proposed methodology could be extended to the detection of other antigens or biocompounds.Part3. Studies on potentiometric immunosensor based on poly(vinyl chloride)-polyethyleneimine membrane electrodeA novel method for fabrication of a carcinoma antigen 125 (CA 125) potentiometric immunosensor has been developed by means of immobilizing CA 125 antibody (anti-CA 125) on gold nanoparticles (NG) and poly(vinyl chloride)-polyethyleneimine membrane electrode has been developed. Potentiometric technique was used to detect the performance of the resulting immunosensor and the conditions of this experimentation. At the optimized conditions, the resulting immunosensor exhibited a sigmoid curve with CA 125 concentration, high sensitivity, linear range from 0.090 to 12.612 U/mL with a detection limit of 0.28 U/mL, fast potentiometric response (<4 min), good reproduction and selection.