Aptasensor based on entropy-driven catalytic amplification system for the sensitive detection of acetamiprid in Chinese herbal medicine

The traditional method of acetamiprid residue detection is difficult to operate, time-consuming, laborious and requires high professional knowledge of the detection personnel, which cannot meet the requirement of on-field rapid detection. For this reason, a colorimetric aptasensor based on an entropy-catalyzed amplification system was developed for the ultrasensitive and selective determination of acetamiprid. In the absence of acetamiprid, the aptamer and cDNA form a double-stranded structure. The formed hemin/G-quadruplex mimicking DNAzyme can catalyze the substrate ABTS to generate the colored ion ABTS^- with the help of H₂O₂, and the solution turns blue-green. On the contrary, the presence of acetamiprid triggers the release of cDNA, which in turn initiates the entropy-driven system, resulting in the inability to form DNAzyme and therefore no blue-green color production in the solution. The quantity of acetamiprid determines the color. Under the optimal experimental conditions, the method showed a linear correlation (<i>R</i>² = 0.9837) for the detection of acetamiprid in the concentration range of 0.1-100 ng/mL, with a limit of detection of 0.06 ng/mL. The developed method was used for the determination of acetamiprid in spiked Coix lacryma and Bitter almond, with recoveries in the range of 90.3-110.3%. The proposed enzyme-free and label-free assay can be developed into a simple, sensitive and rapid detection platform.