Screening and identification of a DNA aptamer to construct the label-free fluorescent aptasensor for ultrasensitive and selective detection of clothianidin residue in agricultural products

Clothianidin pesticide not only pollutes the ecological environment, but also poses a potential threat to human health. Thus, it is of great importance to develop efficient and accurate methods to recognize and detect clo-thianidin residues in agricultural products. Aptamer has the advantages of easy modification, high affinity and good stability, which is particularly suitable as a recognition biomolecule for pesticide detection. However, the aptamer against clothianidin has not been reported. Herein, the aptamer (named CLO-1) had good selectivity and strong affinity (Kd = 40.66 +/- 3.47 nM) to clothianidin pesticide, which was screened for the first time by Capture-SELEX strategy. The binding effect of CLO-1 aptamer to clothianidin was further studied by circular dichroism (CD) spectroscopy and molecular docking technique. Finally, the CLO-1 aptamer was used as the recognition molecule to construct a label-free fluorescent aptasensor using GeneGreen dye as sensing signal for the highly sensitive detection of clothianidin pesticide. The constructed fluorescent aptasensor had the limit of detection (LOD) as low as 5.527 mu g L-1 for clothianidin, and displayed good selectivity against other competitive pesticides. The aptasensor was applied to detect the clothianidin spiked in tomatoes, pears and cabbages, and the recovery rate was good in the range of 81.99%-106.64%. This study provides a good application prospect for the recognition and detection of clothianidin.