The Electrochemical DNA Sensor Based-on Graphene Nanocompisite Film

Many scientists have focused on the graphene/polymer composite in the biosensing and electrochemical field because of its high electro-conductivity and rich conjugated structure. In this paper, the nanocomposite film based-on graphene was constructed by electrochemical method and chemical method. The film realized the detection of DNA. The details of the work can be summarized as follows:(1) A novel one-step electrochemical synthesis of the reduced graphene oxide and poly(m-aminobenzenesulfonic acid, ABSA) nanocomposite (PABSA-rGNO) via pulse potentiostatic method (PPM) for direct and freely switchable detection of target genes is presented. The PABSA-rGNO presents excellent electrochemical activity and thermal stability even in neutral environment. The immobilization of the probe DNA was successfully conducted via noncovalent method due to π-π interaction between conjugated nanocomposite and DNA bases, resulting in electrochemical self-signals decrease. However, when the probe modified eletrode hybridized with target DNA sequences, the resulted dsDNA released from conjugated nanocomposite, accompanied with the regeneration of self-signals. The synergistic effect of graphene-based nanocomposite and the application of sensitive electrochemical impedance spectroscopic detection method (EIS) improved the sensitivity for the target DNA detection.(2) We reported a simple and low-cost method to prepare large-area, wavy graphene oxide (GNO) nanowalls intercalated by sulfonated polyaniline (SPAN, a copolymer of aniline and m-aminobenzenesulfonic acid). The strong π-π*stacking between the backbones of SPAN and the GNO basal planes, and the electrostatic repulsion between the negatively charged SPAN and graphene oxide sheets yield a unique free-standing, three-dimensional interconnected nanowall structure. Through ultrasonication of the mixed dispersion of graphite oxide (GO) and SPAN, the negatively charged SPAN ceaselessly diffused, was adsorbed and intercalated into the simultaneously resulting GNO layers to form nanowall. The unique morphology owned larger specific surface area and presented good electrochemical response for [Fe(CN)6]3-/4-,which is widely adopted to monitor the immobilization and hybridization of DNA. At the same time, because the negative charge and rich conjugated nanostructure of nanocomposite can prompt the adsorption of the positively charged guanine and adenine via strong n-n*interactions or electrostatic adsorption, the hybrid was also adopted as an excellent electrocatalytic platform for simultaneous determination of guanine and adenine.