A novel label-free electrochemical aptamer sensor based on base mismatch and strand displacement for detection of kanamycin

Misuse of kanamycin in animal husbandry has led to serious food safety issues. In this study, a label-free electrochemical aptasensor based on the base mismatch and strand displacement was developed for detection of kanamycin residue in agricultural products. A novel ferrocene-naphthalimide derivative was employed as the electroactive indicator. The effects of complementary DNA (cDNA) probe length, position and number of mismatched bases in aptamer-cDNA duplex on the performance of displacement-based aptasensor were systematically investigated. The experimental results were in well accordance with the molecular simulation results. Under optimal conditions, the aptasensor exhibited good reproducibility, stability, selectivity, and a wide linear range of 1.0 × 10 −10 –1.0 × 10 −4  g/mL, with a LOD of 1.1 × 10 −11  g/mL (S/N = 3). The proposed aptasensor was used to detect kanamycin residues in milk and chicken liver. Satisfactory recoveries and relative standard deviations indicated that the aptasensor was competent for detection of kanamycin residues in agricultural products.