The dissociation of the walking strand from the track gives rise to decreased efficiency and long reaction time of DNA walkers. In this work, we constructed a DNA walker combining the introduction of a wedge segment with a bimetallic metal–organic framework (MOF) electrocatalyst to solve this problem. The target methylated DNA acted as a single-legged walker, and the immobilization probe assembled on the track contained a wedge segment that was complementary to the target methylated DNA persistently, inhibiting its dissociation from the track. The fuel strand modified with a bimetallic MOF would drive the target strand to conduct branch migration and move processively along the track. The stepwise movement of the target strand resulted in the loading of numerous bimetallic MOF catalysts to reduce H2O2 at the electrode interface, thereby a significantly increased current response would be obtained for the detection of methylated DNA. This DNA walker achieved a detection limit of 200 aM within 20 min and effectively distinguished DNA with different methylation statuses, which would pave a way for rapid and sensitive monitoring of DNA methylation.
The fragments of molecular motors can be transported and operated autonomously along a track. Most molecular walker systems are assembled from DNA building modules, exhibiting great potential applications in biocomputing, drug transport, sensing, etc. Hereby, we report a DNA walker driven by endonuclease Nt.BbvC I that can autonomously induce “signal off” sensing platform for highly sensitive detection of tumor cells. DNA density and trajectory conformation can affect DNA walker properties. Molybdenum selenide@gold nanoparticles (MoSe 2 @AuNPs) are modified on the electrode surface as a scaffold to accommodate more hairpin probe (H1) and provide a good interface for DNA walking. Magnetic beads are used to enrich target tumor cells, release single-stranded DNA (S1) and trigger DNA walker-based amplification strategy. Upon addition of tumor cells, more DNA-methylene blue (DNA-MB) is cracked from the electrode surface. Benefiting from efficient electrode modification, magnetic enrichment, DNA walker and enzyme-assisted amplification, an ultra-high sensitivity electrochemical cell analysis is realized, with a detection limit of 2 cells mL −1 . More importantly, this DNA walker strategy is available for tumor cell analysis in clinical samples, suggesting the potential diagnostic applications.
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