Rapid bacteria electrochemical sensor based on cascade amplification of 3D DNA walking machine and toehold-mediated strand displacement

The foodborne pathogens have caused many life-threatening diseases. Herein, a new electrochemical platform was developed for detection, using 3D walking machine and enzyme-free toehold-mediated strand displacement. High-variable region of 16S rDNA fragment of Escherichia coli ( E. coli ) was used as the target to verify the approach. In presence of target, Exonuclease III (Exo III)-powered hairpin-loaded Au nanoparticles ( [email protected] ) was aroused, which emerged large amounts of 3D toehold-loaded AuNPs ( [email protected] ) walking machine. The “legs” of the walking machine hybridized with hairpin2 (HP2) tracks probe modified on surface of electrode and exposed toehold region of HP2 probe. The toehold-mediated strand displacement triggered rolling of AuNPs along the electrode, through the interaction of hairpin3-F c (HP3-F c ) probe with toehold region of HP2 probe. Thus large amounts of F c were closed to the electrode and led to significant current responses for E. coli detection. The method could continuously recycle low-concentration targets. Furthermore, due to the increase of “legs” and decrease of the derailment of leg DNA , which was beneficial to shorten detection time and amplify response. The detection limits (LOD) was 20 CFU/mL, the detection time was less than 1.5 h. This method was promising to be applied in early diagnosis of foodborne pathogen.