Sensitivity programmable ratiometric electrochemical aptasensor based on signal engineering for the detection of...

Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (I_Fc), while the current intensity of THI (I_THI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (I_THI/I_Fc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of I_THI/I_Fc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to I_THI/I_Fc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05-20 ng mL^-1 and a detection limit of 0.016 ng mL^-1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.