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.