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  Chemical Sensors 2013, 3: 16
  Research Article
Electrochemical DNA biosensor based on single-walled carbon nanotubes-pyrenebutyric acid complex
  Cai Xilia, Gao Fenga, Li Fuxiaoa, Wang Xiaa, Zhang Xuana, Gao Feia, Jiang Shulianb, Wang Qingxianga  
a Department of Chemistry and Environment Science, Zhangzhou Normal University, Zhangzhou, P. R. China
b Zhangzhou Product Quality Supervision and Inspection Institute, Zhangzhou 363000, P. R. China

  A sensitive electrochemical DNA biosensor was constructed using the inorganic-organic nanocomposite consisting of single-walled carbon nanotubes (SWNTs) and 1-pyrenebutyric acid (PBA) as the sensing platform. Dispersity experiments showed the presence of PBA can greatly improve the solubility and stability of SWNTs. The dispersion was then dropped on a gold electrode surface for dryness to get the nanocomposite modified electrode (SWNTs-PBA/Au), and the amino modified 18-mer oligonucleotides from CaMV35S promoter gene were further covalently grafted on SWNTs-PBA/Au by a facile carboxyl-amino condensation reaction. The step-by-step assembly process was electrochemically characterized by cyclic voltammetry using [Fe(CN)6]3-/4- ions as the electroactive probe. The results illustrated that the sensing interface of SWNTs-PBA/Au has large DNA loading amount and high electric conductivity due to the nanosized effect of SWNTs in the modified film. Furthermore, the analytical performance of the biosensor was evaluated using methylene blue (MB) as the electroactive hybridization indicator. It was obtained that when the complementary sequences were detected, and the peak currents of MB varied linearly with the logarithm values of the concentrations of the complementary sequences in the range from 1.0×10-15 to 5.0×10-13 mol L-1. The detection limit was estimated to be of 2.9×10-16 mol L-1 based on 3S/N characteristic. The hybridization selectivity experiments showed that the sensing system can accurately discriminate complementary sequences from the base-mismatched and the non-complementary sequences.
  DNA biosensor; Single-walled carbon nanotubes; 1-Pyrenbutyric acid; Hybridization  

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