A label-free dual-mode aptasensor for detecting zearalenone based on exonuclease I cascaded PtNWs/MXene nanozyme

Zearalenone (ZEN) is a common mycotoxin widely present in food and agricultural products, posing a serious threat to human health. This work developed a fluorescent/smartphone-assisted colorimetric dual-mode aptasensor for detecting ZEN. Platinum nanowires-supported MXene (PtNWs/MXene) composites exhibit peroxidase-like (POD) activity, which can be inhibited by the adsorbed ZEN-specific DNA aptamers. In the presence of ZEN, the specific binding between ZEN and the aptamer triggers desorption of the aptamer from the PtNWs/MXene surface, thus restoring the POD activity of composites. With hydrogen peroxide introduced, PtNWs/MXene catalyzes the oxidation of colorless o-phenylenediamine into colored 2,3-diaminophenazines, simultaneously generating a fluorescent signal. Exonuclease I mediates target cycling to achieve signal amplification, further boosting the detection sensitivity. The smartphone-based colorimetric mode shows a linear detection range of 10 ~ 900 ng/mL with a limit of detection (LOD) of 6.57 ng/mL, while the fluorescence mode presents a linear range of 1 ~ 1000 ng/mL and a LOD as low as 0.74 ng/mL. This sensing platform can accurately distinguish ZEN-positive and ZEN-negative samples, and the detection results are highly consistent with those of ELISA. It provides an efficient and reliable new solution for highly sensitive on-site ZEN detection, demonstrating significant application potential in food safety monitoring.