Fabrication of a Biocompatible and Conductive Platform Based on a Single-Stranded DNA/Graphene Nanocomposite for Direct Electrochemistry and Electrocatalysis

A novel electrochemical platform was designed by combining the biocompatibility of single-stranded DNA (ss-DNA) and the excellent conductivity of graphene (GP). This nanocomposite (denoted as ss-DNA/GP) was first used as an electrode material for the immobilization and biosensing of redox enzymes. On the basis of electrostatic interactions, horseradish peroxidase (HRP) self-assembled with ss-DNA/GP on the surface of a glassy carbon (GC) electrode to form an HRP/ss-DNA/GP/GC electrode. UV/Vis and FTIR spectra were used to monitor the assembly process and indicated that the immobilized HRP on the ss-DNA/GP matrix retained its native structure well. A pair of stable and well-defined redox peaks of HRP with a formal potential of about -0.26 V (vs. Ag/AgCl) in a pH 7.0 phosphate buffer solution were obtained at the HRP/ss-DNA/GP/GC electrode; this demonstrates direct electron transfer between the immobilized HRP and the electrode. In addition, the modified electrode showed good electrocatalytic performance towards H2O2 with high sensitivity, wide linear range, and good stability. Accordingly, the ss-DNA/GP nanocomposite provides a novel and efficient platform for the immobilized redox enzyme to realize direct electrochemistry and has a promising application in the fabrication of third-generation electrochemical biosensors.