A metal ion-triggered and DNA-fueled molecular machine for amplified and sensitive fluorescent detection of Hg2+

Hg 2+ ions are highly toxic and bioaccumulative pollutant that can lead to adverse toxicological effects on environment and human health, and the establishment of simple and sensitive methods for the detection of trace Hg 2+ ions is thus of great significance. On the basis of a new metal ion-triggered and DNA-fueled molecular machine strategy, we have established a sensitive and convenient approach for detecting Hg 2+ in different water samples without involving in any enzymes or nanomaterials for signal enhancement. The target Hg 2+ ions associate with the DNA complex probes through the formation of specific thymine-Hg 2+ -thymine (T-Hg 2+ -T) mismatched base pairing, which results in the release of the fluorescently quenched ssDNA from the complex probes to expose the pre-blocked toeholds. Subsequently, the fuel DNA further binds to the toeholds and triggers the operation of the molecular machine via strand displacement reactions to recycle the target ions, leading to the release of many fluorescently quenched ssDNAs for amplified monitoring of Hg 2+ within the dynamic range of 0.1–100 nM with a detection limit of 65 pM. Besides, with specific T-Hg 2+ -T coordination, the established approach shows high selectivity to the target ions and can be employed to detect Hg 2+ in tap and river water samples.