A label-free electrochemical impedimetric DNA biosensor for genetically modified soybean detection based on gold carbon dots.

A label-free electrochemical impedimetric biosensor was constructed based on gold carbon dots (GCDs) modified screen-printed carbon electrode for the detection of genetic modified (GM) soybean. The structure and property of GCDs were investigated. The GCDs can directly bind to single-stranded DNA probes through Au-thiol interaction and boost electric conductivity for the DNA sensor construction. The quantification of target DNA was monitored by the change of electron-transfer resistance (Ret) upon the DNA hybridization on sensor surface. Under the optimal conditions, the Ret response (vs. Ag reference electrode) increased with the logarithm of target DNA concentrations in a wide linear range of 1.0 × 10-7 - 1.0 × 10-13 M with a detection limit of 3.1 × 10-14 M (S/N = 3). It was also demonstrated that the proposed DNA sensor possessed high specificity for discriminating target DNA from mismatched sequences. Moreover, the developed biosensor was applied to detect SHZD32-1 in actual samples, and the results showed a good consistency with those obtained from the gel electrophoresis method. Compared with the previous reports for DNA detection, the label-free biosensor showed a comparatively simple platform due to elimination of complicated DNA labeling. Therefore, the proposed method showed great potential to be an alternative device for simple, sensitive, specific, and portable DNA sensor.