Preparation And Application Of Poly(pyridine-2,6-dicarbaldehyde) Film Electrode

The key step in the preparation of DNA biosensors is the immobilization of ssDNA at the electrode. Many methods have been employed for the immobilization of DNA, Including adsorption, self-assemblymonolayer, covalent binding, blending and electropolymerization. This paper focuses on fabricating novel electrochemical DNA biosensors by using an electropolymerization method. The paper is summarized as follows:In order to prepare a new electrochemical DNA biosensor, a thionine/Poly(pyri-dine -2,6-dicarbaldehyde) modified electrode (Th/PPy/GCE) was prepared by electropoly- merizing pyridine-2,6-dicarbaldehyde on a glassy carbon electrode, and covalently immobilizing thionine on the surface of poly(pyridine-2,6-dicarbaldehyde) film. The prepared process and electrochemical responses of Th/PPy/GCE were investigated by using electrochemical impedance spectroscopy and differential pulse voltammetry. The characteristic responses of Th/PPy/GCE for the dsDNA on the potential and current were found in favor of discrimination of the ssDNA and dsDNA. Under the optimum conditions, the current intensity was proportional to the logarithm of dsDNA concentration over the range from 1.0 to1.0×10-3mg/L mg/L with a correlation coefficient of 0.9988, and a 0.06 mg/L detection limit. The modified electrode was successfully applied to detect the oxidative damage to dsDNA mediated by Fenton reaction. The level of DNA damage can be distinctly showed by observing the change of current intensity and the shift of potential. The modified electrode also has a good stability, and the relative standard deviation is less than 4.83% for 5 electrode.On the basis of Th/PPy/GCE, the amino groups of thionine were used to covalently attach DNA probes mainly via the aid of glutaraldehyde cross-linking. The differential pulse voltammetry and electrochemical impedance spectroscopy were used to represent DNA immobilization and hybridization. The modified electrode was successfully applied to detect the concentration of cauliflower mosaic virus promoter fragment (CaMV35S) in many transgenic plants by the differential pulse voltammetry. The experimental results showed that the current intensity was proportional to the concentration of CaMV35S in the range of 1.00×10?10~1.00×10?6 molL?1, and the detection limit was 3.41×10?11molL?1.On the basis of Th/PPy/GCE, the gold nanoparticles were used to attach DNA probes. The ssDNA/Nano-Au/Th/PPy/GCE was applied to hybridizing DNA. The prepared process was investigated by using electrochemical impedance spectroscopy and differential pulse voltammetry. The modified electrode was more sensitive than that prepared by glutaraldehyde cross-linking. The differential pulse voltammetry was successfully applied to detect the concentration of the source PAT gene fragment of transgenic plants. The experimental results showed that the current intensity was proportional to the concentration of PAT gene fragment, the linear range is1.0×10?11 molL?1 to 1.0×10?6molL?1, and the detection limit is 3.36×10?12molL?1.