A label-free fluorescence and naked-eye detection for ochratoxin A based on aptamer antiparallel G-quadruplex/crystal violet

Ochratoxin A (OTA) with high toxicity is widely present in agricultural products, posing an enormous threat to human and animal health. Thus, simple, rapid, sensitive and selective detection of OTA is highly necessary. Herein, we have developed a new label-free fluorescence and naked-eye detection platform for ochratoxin A based on the interaction between OTA-antiparallel G-quadruplex(G4)/crystal violet (CV). CV and OTA aptamer could form a G4 structure with high fluorescence intensity. When OTA was present in the G4/CV mixture, it replaced CV and bound to the OTA aptamer, and then the fluorescence of the mixture remarkedly quenched. The interaction among OTA and G4/CV had been revealed by fluorescence, ultraviolet and circular dichroism (CD) spectra. The detection process could be performed by naked-eye and could be completed within 10 min. The established method showed 0.1–1000 ng/mL linear detection range with 0.07 ng/mL limit of detection (LOD). The recovery rates in cereal samples were in the range of 76–105%. Compared with the classical ELISA, the recovery rates and the detected concentration of OTA in the naturally contaminated cereal samples were consistent. The new method can provide a simple, rapid and cost-effective, label-free and naked-eye detection of OTA with high specificity, good repeatability and high precision.