Fluorescence and Colorimetric Dual-Signal Aptamer Sensor Based on Aptamer-Functionalized Fe₃O₄ Nanoparticles Decorated with Au and Pt Nanoparticles Combined with Fluorescently Labeled Aptamer Complementary Chain-Functionalized SiO₂ Nanoparticles for Detecting the Insecticide Acetamiprid

Acetamiprid (ACE) is a nicotinic chloride insecticide with certain genotoxicity and cytotoxicity that poses a threat to human health. Therefore, it is necessary to establish a rapid and sensitive method for the detection of ACE in agricultural products. In this study, Au and Pt nanoparticles with enzyme-catalyzing and fluorescence-quenching ability were coated on the surface of Fe 3 O 4 nanoparticles to obtain Fe 3 O 4 –Au/Pt. Simultaneously, SiO 2 nanoparticles were synthesized. Aptamer (Apt)-functionalized Fe 3 O 4 –Au/Pt (Fe 3 O 4 –Au/Pt-Apt) and fluorescently labeled aptamers with complementary chain-functionalized SiO 2 (SiO 2 -cDNA-FAM) were used as identification probes. Based on the specific recognition of Apts to ACE, the enzymatic activity of Fe 3 O 4 –Au/Pt, and its fluorescence quenching effect, combined with magnetic separation, a fluorescence and colorimetric dual-signal aptamer sensor for ACE detection was constructed. Based on the optimal conditions, ACE in the concentration of 0.5–6 μg/mL presents a good linear correlation with Δ F (Δ F = F – F 0, F and F 0 are fluorescence intensities in the presence or absence of ACE) and absorbance value ( A ). The standard curve of the fluorescence signal was Δ F = 233.68 C + 34.48. R 2 = 0.9937, and the limit of detection (LOD) was 0.42 μg/mL. The standard curve of the colorimetric signal was A = 0.0385 C + 0.0486, with R 2 = 0.9966, and the LOD was 0.39 μg/mL. The method had no cross-reaction with thiamethoxam (THI), nitenpyram (NIT), imidacloprid (IMI), and thiamethoxam (CLO). The average recoveries of ACE in actual samples (Chinese cabbage and cucumber) were 92.69%–102.54% (CV < 3.67%) and 85.59%–97.52% (CV < 3.54%) for fluorescence and colorimetric signals, respectively. The above results show that the sensor has good specificity and can be used for actual sample detection. Meanwhile, this study provides technical support for pesticide residue detection.