Branch-Migration based Fluorescent Probe for Highly Sensitive Detection of Mercury

Detection of heavy metals is of great importance for food safety and environmental analysis. Among various heavy metal ions, mercury ion is one of the most prevalent species. The methods for detection of mercury were numerous, and the T–Hg–T based assay was promising due to its simplicity and compatibility. However, traditional T–Hg–T based methods mainly relied on multiple T–Hg–T to produce enough conformational changes for further detection, which greatly restrained the limit of detection. Hence, we established a branch-migration based fluorescent probe and found that single T–Hg–T could produce strong signals. The sensing mechanism of our method in different reaction modes was explored, and the detection limits were determined to be 18.4 and 14.7 nM in first-order reaction mode and mixed reaction mode, respectively. Moreover, coupled with Endonuclease IV assisted signal amplification, the detection limit could be 1.2 nM, lower than most DNA based fluorometric assays. For practicability, the specificity...