▎ 摘　　要

In this paper, zirconia (ZrO2) and graphene (GR) nanocomposite was electrodeposited on the surface of carbon ionic liquid electrode (CILE), which was used to construct an electrochemical DNA biosensor. GR was electroreduced from graphene oxide by potentiostatic method, and ZrO2 nanoparticle was further electrodeposited on GR/CILE by cycling voltammetric scan in a ZrOCl2 solution. The presence of GR on the electrode surface can provide a highly conductive interface with large surface area for the loading of ZrO2 nanoparticles. Single-stranded DNA (ssDNA) probe sequences with phosphate group at the 5' end could be easily immobilized on the surface of ZrO2/GR/CILE due to the strong affinity between ZrO2 and phosphate groups. The ssDNA/ZrO2/GR/CILE was applied to hybridize with the target ssDNA sequence, and methylene blue (MB) was used as the electrochemical indicator. Due to the different binding models of MB with double-stranded DNA and ssDNA on the electrode surface, electrochemical response of MB was decreased after the hybridization reaction. Under the optimal conditions, the reduction peak current of MB was proportional to the concentration of Staphylococcus aureus nuc gene sequence in the range from 1.0 x 10(-13) to 1.0 x 10(-6) mol L-1 with the detection limit of 3.23 x 10(-14) mol L-1 (3 sigma). The electrochemical DNA sensor exhibited good selectivity to various mismatched ssDNA sequences, and the polymerase chain reaction amplification products of S. aureus nuc gene sequence were further detected with satisfactory results. Therefore, this electrochemical DNA sensor with ZrO2 nanoparticles and GR nanosheet modified electrode could be used for the detection of specific ssDNA sequence in real biological samples.