Simple and label-free detection of DNA hybridization on a modified graphene nanosheets electrode

In this study, an effective method was devised to synthesize amelogenin genes in solution and to amplify electrical detection of DNA hybridization based on graphene nanosheets (GNs) modified glassy carbon electrode (GCE). GNs are well known as effective biocompatible and conductive materials that can provide large surface area and a sufficient numbers of binding points for DNA immobilization. The biosensor fabrication processes and the electrochemical responses of probe immobilization and hybridization with target DNA were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) using [Fe(CN)6](3-/4-) as an electrochemical redox. Due to minimum nonspecific DNA adsorption, a very high specificity of DNA hybridization was achieved, and the hybridization rate of the target DNA in optimum conditions was increased significantly. With this approach, the target DNA could be quantified in a linear range from 1.0×10(-20) to 1.0×10(-14) mol L(-1) for the first segment and from 1.0×10(-13) to 1.0×10(-6) mol L(-1) for the second segment, with a detection limit of 7.1×10(-21) mol L(-1) by 3s(b). In addition, the biosensor exhibited a high level of stability and repeatability, even for the determination of DNA sequences in real samples without amplification.