Smartphone-assisted colorimetric aptasensor for detecting acetamiprid residue in food based on the enhanced laccase-mimic activity of spherical Ag2O nanoparticles

Acetamiprid (ACE), a neonicotinoid pesticide broadly used in agricultural production, can accumulate in the food chain due to excessive or incorrect use, thereby posing a threat to human health. In this manuscript , a colorimetric aptasensor assisted by a smartphone was established, relying on the S-18 aptamer-mediated amplification of the laccase-mimic activity of spherical Ag 2 O nanoparticles (NPs). The S-18 aptamer strengthens the interaction and facilitates electron transfer between the Ag 2 O NPs and oxidative substrates, which significantly improves the laccase-mimic activity of the Ag 2 O NPs. When acetamiprid is present, the S-18 aptamer preferentially binds to the target molecule, forming a steady aptamer-acetamiprid complex. This binding interaction prevents the aptamer from promoting the catalytic behavior of the Ag 2 O NPs, producing a distinct and quantifiable color variation in the reaction system. Monitoring the concentration-dependent colorimetric response enables the quick and accurate identification of acetamiprid. The colorimetric aptasensor achieved a limit of detection (LOD) of 8.69 μg∙L −1 markedly lower than the maximum residue limits defined by the national standard (GB 2763–2019) for acetamiprid in fruits and vegetables. Furthermore, the aptasensor demonstrates satisfactory recovery rates in actual samples analyses of cabbage, apple, and tomato, confirming its practical potential for on-site food safety oversight.