DNA Eelectrochemical Biosensor Based On Gold Nanoparticles/Graphene/Polyaniline

Graphene/Polyaniline (GE/PANI) nanocomposites which were characterised by XRD, Raman were synthesised through in suit polymerization in this paper. The optimal condition of the DNA fixed and hybrid was confirmed by electrochemical characterization (CV, DPV, EIS) compared with different material modified electrode. The electrode modified with SH-DNA probe was prepared through covalent bonding of Au-S, using [Fe(CN)6]3-/4- as direct electrical activity indicator and CPZ as indirect electrical activity indicator, which is used to identify and detect the target DNA sequences.The prepared probe DNA electrochemical biosensor can effectively identify complementary ssDNA fragment and has a good sensitivity, selectivity, stability and reproducibility. The paper is divided into four chapters:The first chapter gives an overview of design principle and classification of the DNA electrochemical biosensor, and introduces simply some nanocomposites as electrochemical biosensor carrier.We synthesised GE/PANI nanocomposits with graphite and aniline monomer as the raw material in the second chapter. Then the morphology of the nanocomposites was characterized by TEM, XRD, Raman. Through electrochemical characterization (CV, DPV), the suitable electrode material which possessed good stability and high catalytic activity for [Fe(CN)6]3-/4- was chosed. Through the electrochemical test, we optimized the composition of the electrode materials and pH of the electrolyte, which provided a high performance material for DNA electrochemical biosensors.The third chapter optimized the condition of single-stranded DNA(ssDNA) fixed and dsDNA through DNA hybridization modified electrode with CV, DPV tests. We fixed SH-ssDNA on the modified electrode surface using covalent bonding then prepared DNA electrochemical biosensor. Through the performance detection of DNA electrochemical biosensor, we found a good linear relationship from 10-6 to 10-12mol/L range between the DPV peak current (ip) and the concentration of complementary strand. In this concentration range, DNA can be quantitative detected, and the detection limit is 1.0×1013 mol/L. The study also found that the biological sensors had good selectivity, stability and reproducibility. An indicator type of a high performance DNA electrochemical biosensor was prepared by the reciprocity between chlorpromazine hydrochloride and DNA in the fouth chapter. The results of pulse voltammetry indicated that the biosensor has good selectivity,stability and reproducibility. The linear range of the biosensor was determined between 1.0×10-11 and 1.0×10-12mol/L. In this concentration range, DNA can be quantitative detected, and the detection limit is 4.034×10-13mol/L.