Preparation Of DNA Electrochemical Biosensors And Study For Atrazine's Detection

DNA electrochemical biosensor is noted widely in recent years for rapid development. It has been used in many fields such as food industry, disease diagnosis, pharmaceutical analysis and environmental monitoring due to the high sensitivity, better specificity, rapid response, easy handling, no pollution and low cost. DNA is the basic genetic material of organism, the interaction of some chemicals and DNA make the formation of DNA adducts, which can evaluate and predict potential carcinogenicity of pollutants because of reflecting the interaction condition between chemical pollutants and DNA. So DNA electrochemical biosensor holds some promise of a novel detection technique, and it has a broad prospect of application in the pollutant monitoring field.However, the method and material used to immobilize biomolecules is one of the crucial factors for improving the stability, selectivity and sensitivity of biosensor in the preparation, and the selection of appropriate indicator is also the key technology. Two new-typed DNA electrochemical biosensor was prepared, and the interaction between atrazine and Herring Sperm DNA was studied in this paper. The dissertation is divided into three main parts:(1) A novel DNA electrochemical biosensor was prepared by immobilizing the first generation polyamidoamine (G1 PAMAM) dendrimer on the glassy carbon electrode (GCE) surface by coupled activation agent, which was treated via electrochemical oxidation, then ssDNA was also immobilized through covalently action. Using methylene blue as the indicator, the DNA electrochemical biosensor was characterized by cyclic voltammetry and differential pulse voltammetry. The results indicated that the complementary ssDNA segment in the solution could be recognized and detected through mensurating the oxidation-deoxidation peaks current of embed methylene blue in dsDNA.(2) In order to explore the DNA damage effects induced by atrazine, ultraviolet absorption spectrometry, fluorescence spectrometry and cyclic voltammetry were used to study the the interaction between atrazine and Herring Sperm DNA. The results showed that a hypochromic effect and a slight red shift on the UV spectrogram of atrazine were observed after the interaction with Herring Sperm DNA, while the fluorescence increased obviously. Cyclic voltammetry indicated that the reductive potential of atrazine shifted positively with the peak current decreasing after the interaction with DNA. The above results proved that atrazine could be inserted into the double-helix of DNA and formed a stable DNA adduct.(3) The mixture of the fourth generation polyamidoamine (G4 PAMAM) dendrimer and chitosan with certain proportion was immobilized on the glassy carbon electrode (GCE) surface by the film forming properties of chitosan, then the amino group and the 5′-phosphate group of ssDNA had a covalently action by coupled activation agent of EDC. Using [Co(phen)3]3+ as the indicator, a new DNA electrochemical biosensor was prepared. The immobilization and hybridization of ssDNA was characterized by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Experiment results showed that the immobilized amount of DNA probe on modified layer increased, and the immobilized ssDNA kept a extension state, which was beneficial to the hybridization of DNA. Furthermore, this biosensor had a sensitive response for atrazine.