A triple-signal strategy separated aptasensor for sensitive determination of aflatoxin B1 in peanut based on electrochemical and fluorescent dual-mode

It is necessary to develop accurate and sensitive AFB1 detection method due to its high toxicity of pathogenicity and carcinogenicity. The results of traditional single-mode AFB1 detection methods are easily affected by the test environment and human operation. Herein, an electrochemical and fluorescent dual-mode separated aptasensor was developed for detecting AFB1 with triple-signal readout. The AFB1 aptasensor was constructed by combining the Fc-labeled AFB1 aptamer with its complementary DNA (cDNA). Subsequently, the methylene blue (MB) was incorporated into dsDNA as another signal tag. In the presence of AFB1, the Fc tag approached to electrode surface, both of the cDNA and MB molecule released due to the interaction between AFB1 and its aptamer, resulting in "signal-on" and "signal-off" dual-signal strategy. There was a good linear relationship between the SWV electrochemical response signal and the logarithm of AFB1 concentration at 0.01-200 ng/mL (LOD 2.5 pg/ mL, S/N = 3). Meanwhile, the released cDNA was designed to trigger hybridization chain reaction (HCR), and the HCR product was served as template for the formation of fluorescent copper nanoparticles (CuNPs). There was a good linear relationship between the fluorescent intensity of CuNPs and the logarithm of AFB1 concentration at 0.001-200 ng/mL (LOD 0.28 pg/mL, S/N = 3). The separated fluorescent method showed broadened linear range and lower LOD compared with SWV method, both up to 10-folds, which improved the detection sensitivity. The constructed dual-mode AFB1 aptasensor showed satisfactory selectivity, stability and reproducibility, and the good recoveries of real peanut samples indicated its practical application in food detection.