Development of sensitive colorimetric aptasensor based on short DNA aptamer and its application to screening for paraquat residues in agricultural soil.

Paraquat is a widely used herbicide for controlling weeds and grasses in agriculture, and its contaminated residues in agricultural areas are of increasing concern. This work reports the development of the sensitive and easy-to-use colorimetric aptasensor for screening paraquat residues in agricultural soil. The short DNA fragments derived from the original aptamer were analyzed for their capability to interact with paraquat by molecular dynamic simulation. The paraquat-aptasensor was developed using the selected DNA fragment and gold nanoparticles. Its limit of detection (LOD) for paraquat is 2.76 nM, which is more sensitive than the aptasensor with long-length aptamer (LOD = 12.98 nM). The developed aptasensor shows the selectivity to paraquat, but not to other tested herbicides; ametryn, atrazine, difenzoquat, 2,4-D-dimethyl ammonium, and glufosinate. The recovery rates of paraquat detection in the spiked soil samples were in a range of 99.5%-105.1%, with relative standard deviation values of <4%. The developed aptasensor was used to screen for paraquat residues in agricultural soils, and three out of 23 soil samples were tested positive for paraquat, which was confirmed by a high-performance liquid chromatography analysis. These results suggested the potential application of the developed aptasensor to detect paraquat residues in agricultural sites.