Ultrasensitive and selective colorimetric detection of acetamiprid pesticide based on the enhanced peroxidase-like activity of gold nanoparticles

Abstract

This paper reports a new colorimetric aptasensor for the detection of acetamiprid pesticides with high sensitivity and selectivity based on the enhanced peroxidase-like activity of gold nanoparticles (AuNPs). The aptasensor employs an S-18 aptamer as the target specific recognition molecule and the enhanced peroxidase-like activity of AuNPs as the signal transmission element. In the absence of acetamiprid, S-18 aptamer sequences can adsorb on the surface of AuNPs and enhance their negative charge density because of the attached negatively charged DNA backbone, which will inhibit the peroxidase catalytic activity of the AuNPs, thus inhibiting the oxidation of the substance 2,2′-azino-bis(3-ethyl benzothiazoline-6-sulfonic acid) (ABTS). In the presence of acetamiprid, aptamer sequences can specifically bind with pesticide molecules to form an acetamiprid–aptamer complex which can interact with the AuNPs’ surface through the adsorption energy of the nucleobases. Thus, the surface active sites of the AuNPs are activated and their catalytic activity is enhanced greatly, which enables the AuNPs to catalyze the oxidation of ABTS to generate green oxidation products with a characteristic absorption peak at 735 nm. The color variation is relevant to the concentration of acetamiprid, which can be determined using a UV-Vis spectrometer or even by the naked eye. The present colorimetric aptasensor has a dynamic range of 10–160 μg L⁻¹ with a limit of detection as low as 1.02 μg L⁻¹ and high selectivity against other competitive pesticides. Moreover, the proposed aptasensor can accurately and efficiently screen out acetamiprid in representative actual samples that contain trace levels of pesticides, suggesting that it has more advantages than traditional methods for the detection of trace pesticide residues. Such an ultrasensitive aptasensor will play a prominent part in agricultural product and environmental detection.