A ratiometric electrochemical aptasensor for sensitive detection of kanamycin in food based on entropy-driven strand displacement reaction

Kanamycin (KAN) has the potential to cause significant harm to human health, so the KAN residue present in food should be subject to strict regulation and control. Therefore, we constructed an enzyme-free ratiometric electrochemical aptasensor based on entropy-driven strand displacement reaction (ESDR) for sensitive detection of KAN in food. In the presence of KAN, it binds specifically to the aptamer, causing KAN-sensitive aptamer-tDNA (A-T) complex dissociation and the release of the tDNA, which triggers ESDR and results in an IFc/IMB maximum. In the absence of KAN, the release of the tDNA is not possible, leading to minimal IFc/IMB value. The aptasensor has a LOD of 74 fg/mL, enabling trace detection of KAN. In addition, the aptasensor demonstrated high specificity for KAN and remarkable reproducibility (RSD: 2.455%), which can be utilised for evaluating KAN concentrations in real samples. Moreover, the recovery rate of KAN in food samples ranged from 93.4% to 105.4%, suggesting that the ratiometric electrochemical aptasensor holds great potential in food safety detection.