Fabrication of DNA/graphene/polyaniline nanocomplex for label-free voltammetric detection of DNA hybridization

A novel DNA electrochemical biosensor was described for the detection of specific gene sequences. Electrochemically reduced graphene oxide (ERGNO) was prepared on polyaniline (PAN) nanofibers modified glassy carbon electrode (GCE). Compared with the electrochemical reduction of graphene oxide directly on bare GCE (reduction potential: ca. −1.3 V), more positive reduction potential (ca. −1 V) for graphene oxide was observed with the PAN membrane existing. The formed ERGNO/PAN nanocomposites were applied to bind ssDNA probe via the non-covalent assembly. The surface density of ssDNA was calculated by voltammetric studies of redox cations ([Ru(NH3)6]3+), which were bound to the surface via electrostatic interaction with negative charged phosphate backbone of the DNA. After the hybridization of ssDNA probe with complementary DNA, the response of surface-bound [Ru(NH3)6]3+ changed obviously, which could been adopted to recognize the DNA hybridization. Under optimal conditions, the dynamic range of the DNA biosensor for detecting the sequence-specific DNA of cauliflower mosaic virus (CaMV35S) gene was from 1.0 × 10−13 to 1.0 × 10−7 mol L−1, with a detection limit of 3.2 × 10−14 mol L−1. This biosensor also showed a high degree of selectivity.