Electrochemical DNA Sensor Based on Chitosan-Graphene and Electrodeposited Gold Nanoparticle Modified Electrode for the Detection of Staphylococcus aureus nuc Gene Sequence

Background: Electrochemical DNA sensor is a convenient and sensitive method for the detection of target ssDNA sequence. The developments of nanomaterials modified electrodes provide more opportunity for the enhancement of the analytical performances. Objective: The aim of this paper is to construct a new electrochemical DNA sensor for the detection of Staphylococcus aureus nuc gene sequence with a chitosan-graphene (CTS-GR) and gold nanoparticles (AuNPs) modified electrode. Methods: Electrodeposition was used to synthesize AuNPs directly on carbon ionic liquid electrode (CILE) to obtain AuNPs/CILE. Then CTS-GR nanocomposite was dropped on the surface of AuNPs/CILE to obtain CTS-GR/AuNPs/CILE. The nanocomposite on the electrode was suitable for immobilization of probe ssDNA sequence with electrostatic attraction. Hybridization took place with the complementary ssDNA sequences and assessed with methylene blue (MB) as electrochemical indicator. Results: Due to the synergistic effects of CTS-GR and AuNPs, the modified electrode exhibited excellent electrochemical performances. The reduction peak currents of MB were in line with the concentration of the specific nuc gene sequences from 1.00-13 to 1.00-6 mol L-1 with a detection limit of 3.330-14 mol L-1 (3δ). This electrochemical DNA sensor displayed prominent selectivity to distinct different mismatched ssDNA sequences. Conclusion: This electrochemical DNA biosensor exhibited properties such as higher sensitivity, wider linear range and lower detection limit, which were further applied to the PCR product detection with favorable results.