A fluorescent aptasensor based on gold nanoparticles quenching the fluorescence of rhodamine B to detect acetamiprid

Pesticide residue detection is one of the main safety issues in the utilization of medicinal plants. In this work, a highly selective and sensitive aptasensor for acetamiprid determination was designed. The mechanism of the proposed method is based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and rhodamine B (RB). Aptamers protect AuNPs from salt-induced aggregation, which causes fluorescence quenching of RB by the AuNPs via surface energy transfer. In the absence of acetamiprid, AuNPs were coated with aptamers on the surface and dispersed in NaCl solution. At this time, the dispersed AuNPs could perfectly quench the fluorescence intensity of RB. In contrast, in the presence of acetamiprid, aptamers specifically combine with acetamiprid to form a complex. With a high salt concentration, AuNPs would be aggregated without aptamer protection, weakening the RB quenching effect. Therefore, the concentration of acetamiprid could be obtained from the change in fluorescence intensity in the system. A fluorescent sensing method was established with a linear range from 0.1 to 3 μg mL^-1, and the LOD was 0.0285 μg mL^-1. The recoveries of acetamiprid in traditional Chinese medicine (TCM) samples were 96.23-105.75%. This method has great application value for the detection of acetamiprid in a complex sample matrix.