Graphene-modified electrode for DNA detection via PNA–DNA hybridization

We describe the fabrication of a novel electrochemical deoxyribonucleic acid (DNA) biosensor based on electrochemical reduced graphene oxide (ERGO) and peptide nucleic acid (PNA)–DNA hybridization. Primarily, the ERGO-modified electrode was achieved by one-step electrodeposition technique on the glassy carbon electrode (GCE) through cyclic voltammetric (CV) reduction of a graphene oxide colloidal solution. Subsequently, PNA was immobilized onto the surface of the ERGO through a linker (1-pyrenebutanoic acid succinimidyl ester, PASE), and then the PNA-functionalized electrochemical biosensor was used to detect DNA via PNA–DNA hybridization. Differential pulse voltammetry (DPV) was employed to monitor the hybridization event by using methylene blue (MB) as the electrochemical indicator. It was found that the peak currents of MB were linear with the logarithm of the complementary target DNA concentrations, and the dynamic detection range for the target DNA was from 1.0 × 10−7 to 1.0 × 10−12 mol L−1 with a detection limit of 5.45 × 10−13 mol L−1 (3σ/S). Furthermore, the fabricated biosensor could successfully discriminate the one base mismatched and non-complementary DNA sequences from the complementary DNA sequence.