A “turn on” fluorescent sensor for Hg2+ detection based on rolling circle amplification with DNA origami-assisted signal amplification strategy

As well as polluting the environment, mercury also causes diseases and poses a threat to human health. Thus, it is crucial to implement the rapid and sensitive determination of Hg2+. On the basis of assembling RCA (rolling circle amplification) scaffolds and complementary short chains to form ladder-nanoarrays based on the characteristics of RCA signal amplification, we have constructed a "turn on" fluorescence sensor with high selectivity and sensitivity for Hg2+ detection in environmental water samples. Nanoarray sensors assembled from DNA are biocompatible, programmable and addressable for target delivery and targeted detection, by labeling the thrombin-binding aptamer (TBA) exposed on the ladder with the FAM at the 5′ end and DABCYL labeling the quencher at the 3′ end, the fluorescence of FAM was weakened by fluorescence resonance energy transfer (FRET) when the two groups were close together. Upon addition of Hg2+, TBA combines with Hg2+ to form a hairpin structure to induce quencher release and fluorescence recovery. Consequently, the ladder-sensor performance is highly sensitive to Hg2+ in the concentration range of 1–1000 nM, with a limit detection (LOD) is 1.78 nM under the optimized conditions. In addition, fluorescence sensors built by combining DNA origami technology with aptamers has good optical performance, which opens up a new field for the identification of other biological samples.