An electrochemical DNA sensor based on an integrated and automated DNA walker

As an artificial nanomachine, a DNA walker demonstrates the potential for biosensing. In this study, a highly integrated, biostable, and autonomous electrochemical DNA walker sensor was rationally designed by a simple assembly of a Mn²⁺-dependent DNAzyme-powered DNA walker with nanoscale Mn²⁺ @MOFs containing free carboxylic acid groups UiO-66(Zr)-(COOH)₂. In this study, the release of Mn²⁺ from Mn²⁺@MOFs was exploited to drive the autonomous and progressive operation of the DNA walker, and the DNAzyme-driven DNA walker was constructed by the co-modification of walking strands and track strands onto the gold electrode (GE) surface. The walking strand was a single-stranded DNA containing a DNAzyme sequence, which was pre-silenced by the locking strand. The track strand was a specially designed DNA sequence that the target can hybridize with the locking strand; hence, the walking strand is unlocked, and the liberated DNAzyme catalyzes the cleavage of track strands to drive the DNA walker operation, shifting tetraferrocene away from the electrode and producing a significant signal change. A detection limit of 38 fM was obtained with our new system, exhibiting a wide linear range from 1.5625 × 10^-9 M to 1 × 10^-13 M. The proposed approach provided a novel means for constructing an highly integrated, automated, and DNAzyme-driven DNA walker for bioanalysis.