Aptamer based simple plastic lab-on-a-chip for rapid on-site monitoring of paraquat herbicide residue in soils

Abstract

In this study, an aptamer-based lab-on-a-plastic-chip was developed for paraquat (PQ) herbicide detection. The acrylic chip with a 1.8 × 5.3 cm size, fabricated by engraving, had two parts: a sample chamber and a reaction channel. The assay on chip combined an aptamer-specific PQ binding and a colorimetric signal detection using gold nanoparticles. When PQ was present, particle aggregation brought on by aptamer binding resulted in a purple color change. But in the absence of PQ, the aptamer prevented the salt-induced aggregation, leaving a red color. These changes could be seen with the naked eye. The chip showed great specificity (100 %) and sensitivity (96 %) and could detect PQ in less than 45 minutes with a limit of detection of 100 ppb. The determination PQ residue in field revealed 2 out of 25 samples contaminated with residue, providing info for further management. This work demonstrated a rapid and low-cost platform, suitable for rapid detection applications.