Freezing-driven assembly of DNA walking machine facilitate G4 nanowires growth for electrochemical detection of kanamycin

The traditional nucleic acid-modified electrode in room-temperature manner suffers from the drawback of time-consuming and uneven distribution. In this work, we adopted the freeze-thawing method to construct a nicking enzyme-powered DNA walking machine on the gold electrode. In the absence of kanamycin, the intact substrate strand can trigger the self-assembly and form G4 nanowires on the electrode surface. After adding hemin, a significant catalytic current of the TMB oxidization can be observed. By contrast, once the specific binding between aptamer and kanamycin occurs, the activated walking strand processes a consecutive binding-cleavage cycle with the substrate strand on the electrode surface. The residue substrate fragment is unable to trigger the subsequent G-quadruplex assembly, resulting in a decrease in catalytic current. Under optimal experimental conditions, a linear relationship between the kanamycin concentration and current decrease was obtained in the range from 5 to 100 pM, and the limit of detection was 1.44 pM. This method has also demonstrated practical performance in the spiked milk and honey with satisfactory recoveries of 107.1 % to 114.3 % and 94.3 % to 101.5 %, respectively.