Magnetic DNA walker mediated in-situ deposition of polyaniline for the electrochemical detection of kanamycin

Enzyme-powered DNA walker suffers from limited loading capacity of substrate strand and incompatible recognition and enzymatic catalysis environments. To improve the sensitivity, AuNPs@Fe 3 O 4 was employed as track interface to construct an enzyme-driven DNA walker, which features magnetic separation characteristic and high specific surface area. Upon recognition of kanamycin, a large amount enzymatic cleavage fragment presented in the supernatant after consecutive cleavage of substrate strand by activated walking strand. To further amplify the signal, these enzymatic cleavage products mediated an in-situ deposition of polyaniline (PANI) on the tetrahedral DNA nanostructure (TDNA) modified electrode enables a label-free detection of kanamycin. Owing to the introduction of magnetic separation, the background signal was substantially reduced compared with that obtained using DNA-AuNPs, resulting in approximately 2.5-fold enhancement in the signal-to-noise ratio (S/N). Under optimal experimental conditions, a good linear relationship was observed between the logarithmic concentration of kanamycin and the current signal difference in the range of 5–100 pM and the limit of detection was 1.1 pM. Furthermore, the practical performance of the proposed method had been well-demonstrated through real sample validation in spiked milk samples, with recoveries ranging from 92.0% to 102%, confirming its practical application capability