Gold Nanoparticle / Polypyrrole Dna Electrochemical Sensor Applications

The immobilization of the single-stranded DNA (ss-DNA) probes on the electrode is the key step in the preparation of DNA electrochemical biosensors. Its immobilization quantity and activity will directly affect the sensitivity of the sensor. In this paper, the ss-DNA is immobilized through self-assembly, combined with the application of nano-materials to prepare an electrochemical DNA biosensor. The papar can be summarized as follows:1. Conductive nano-polypyrrole films as the substrate are synthesized on the indium-tin oxide glass electrode (ITO) through constant potential method. Then, two electrochemical methods are used to synthesize nano-gold particles on the surface of the ITO/PPy modified electrode. The influence of the experimental parameters on the electrochemical properties of the electrodes is disscussed. The electrochemical performance and morphology of the films are characterized through electrochemical tests, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results reveal that the electrical singal of ITO/PPy/Au is much stronger; the size of Au_NP on ITO/PPy/Au is smaller, and the surface area of the same electrode is much larger than the ITO/Au electrode. These performances will help to build the functional sensitive membrane of DNA biosensor.2. The ss-DNA probe on ITO/PPy/Au modified electrode mentioned above has been constructed on the basis of [Fe(CN)₆]^3-/4- system. The optimal time and the best concentration of assembly are determined. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are applied to investigate the influence of ionic strength, pH value of the [Fe(CN)₆]^3-/4- solution, and the CV scan rate on the electrochemical properties. The detection condition of ss-DNA probe under the [Fe(CN)₆]^3-/4- system has been optimized. Moreover, the kinetic parameters of the ss-DNA modified electrode are analyzed in detail.3. A DNA electrochemical sensor based on [Fe(CN)₆]^3-/4- system has been fabricated. The hybridization time of complementary-DNA is optimized. The kinetic parameters of the double-stranded DNA modified electrode are analyzed. The linear range from 10^-8 to 10^-6 mol·L^-1 of target DNA is obtained by means of DPV and the detection limit of the DNA electrochemical sensor is 1.8×10^-10mol·L^-1. Moreover, the regeneration and the stability of the sensor are also studied.