Endonuclease-driven DNA walking for constructing a novel colorimetric and electrochemical dual-mode biosensing method.

The development of methods to realize the on-site analysis of antibiotic pollutants is of great importance for food quality control and environmental monitoring. Herein, we designed a magnetic bead (MB)-based DNA walker and utilized its target-triggered and endonuclease-driven walking reaction to develop a novel colorimetric and electrochemical dual-mode biosensing method for the convenient detection of kanamycin (Kana) antibiotic. The colorimetric signal transduction strategy of the method was constructed on the telomerase extension of the DNA walking-released telomeric primer into G-quadruplex/hemin DNAzymes. Due to the DNA walking and telomerase dual signal amplification, a good linear relationship from 0.1 pg mL to 1 ng mL was obtained for this strategy with a detection limit of 22 fg mL. Meanwhile, the MB complex produced through the above DNA walking reaction was also used as a multipedal DNA walker to develop an electrochemical signal transduction strategy. By utilizing it to trigger another endonuclease-driven DNA walking at a DNA hairpin-modified electrode, ferrocene labels were quantitatively released from this electrode to cause the electrochemical signal decrease. Because of the dual endonuclease-driven DNA walking for signal amplification, a five-order of magnitude wide linear relationship from 0.01 pg mL to 1 ng mL was obtained with an ultralow detection limit of 8.4 fg mL. As the two strategies did not involve complicated manipulations and the requirement of expensive instruments, this biosensing method exhibits a high application value for the on-site semiquantitative screening and accurate analysis of antibiotic residues.