Engineering of a magnetic dual-signal SERS aptasensor for the ratiometric detection of acetamiprid in tea samples

Acetamiprid (AP) is commonly used in combination to control pests and diseases and increase crop yield. However, as a systemic pesticide, its residue does not easily degrade and is toxic to the human body. Therefore, it is urgent to establish a sensitive and rapid method for detecting AP. Here, a novel magnetic SERS aptasensor with dual signal was designed through capture probes (Fe 3 O 4 @Au@4-MBN@Ag-aptamer) and signal probes (Au@4-MPY@Ag-cDNA) for the ratiometric detection of AP. The capture probes can hybridize signal probes with via complementary base pairing to form composite probes. Based on the magnetic separation of capture probes and aptamer-target recognition, the composite probes dissociate during AP detection, which would contribute to the release of a large amount of signal probes, resulting in regular changes in signal output of 4-MBN and 4-MPY. Analysis reveals that the SERS intensity ratio of 4-MBN to 4-MPY was inversely correlated with the concentration of AP, enabling the detection of AP. Under the optimal conditions, the developed aptasensor exhibited a good linear relationship in the range from 10 −4 M-10 −9 M between the SERS intensity ratio and the concentration of AP, and the limit of detection (LOD) was as low as 4.75 μg/kg. Furthermore, the SERS aptasensor had good reproducibility, long-term stability, and superior specificity. Compared with conventional HPLC method, the proposed SERS aptasensor exhibited high detection accuracy and satisfactory recovery rate in real tea samples, serving as a detection model for other pesticides and showing promising applications in food safety.