Paper-based multicolor sensor for on-site quantitative detection of organophosphate pesticides based on acetylcholinesterase-mediated paper-based Au-etching of gold nanobipyramids and CIELab color space.

On-site quantitative detection of organophosphorus pesticides (OPs) is crucial for safeguarding food and public safety. This study presents a novel acetylcholinesterase (AChE)-mediated paper-based Au-etching of gold nanobipyramids (AuNBPs) system. The system employs a long-term storable AuNBPs-deposited nylon membrane embedded within a portable and temperature-controlled paper-based analytical device. This system, coupled with a colorimeter-based quantitative method, enables the development of a practical paper-based multicolor sensor (PMS) for on-site quantitative detection of three common OPs (paraoxon, dichlorvos, and trichlorfon). In the absence of OPs, AChE hydrolyzes acetylthiocholine to thiocholine, which reduces Au to Au. The presence of OPs inhibits AChE activity, thereby preserving Au to etch AuNBPs on nylon membranes, accompanied by multicolor changes. These color changes can be simply quantified by measuring the a∗ parameter of the CIELab color space using a portable colorimeter. Under optimal conditions, the PMS displayed eight OPs-corresponding color changes with a minimum detectable concentration of 1.0-10 μg/L (visual observation) and limits of detection of 0.8-7.2 μg/L (colorimeter) and 0.2-3.4 μg/L (UV-vis spectrometry). The PMS successfully determined the OPs in vegetable and rice samples with recoveries of 89.0-109 % and RSDs (n = 5) of <6 %. These results were consistent with those obtained using the HPLC-MS method. The PMS demonstrates excellent portability, AuNBPs stability, detection sensitivity, and reproducibility, making it a promising tool for the on-site quantitative detection of OPs residues in food. Furthermore, the paper-based etching system coupled with the colorimeter-based quantitative method provides a valuable reference to develop practical PMSs for various targets in diverse fields.