Application of graphene-pyrenebutyric acid nanocomposite as probe oligonucleotide immobilization platform in a DNA biosensor.

A stable and uniform organic-inorganic nanocomposite that consists of graphene (GR) and pyrenebutyric acid (PBA) was obtained by ultrasonication, which was characterized by scanning electron microscopy (SEM) and UV-vis absorption spectra. The dispersion was dropped onto a gold electrode surface to obtain GR-PBA modified electrode (GR-PBA/Au). Electrochemical behaviors of the modified electrode were characterized by cyclic voltammetry and electrochemical impedance spectroscopy using [Fe(CN)6](3-/4-) as the electroactive probe. A novel DNA biosensor was constructed based on the covalent coupling of amino modified oligonucleotides with the carboxylic group on PBA. By using methylene blue (MB) as a redox-active hybridization indicator, the biosensor was applied to electrochemically detect the complementary sequence, and the results suggested that the peak currents of MB showed a good linear relationship with the logarithm values of target DNA concentrations in the range from 1.0×10(-15) to 5.0×10(-12) M with a detection limit of 3.8×10(-16) M. The selectivity experiment also showed that the biosensor can well distinguish the target DNA from the non-complementary sequences.