A label-free and signal-on supersandwich fluorescent platform for Hg2+ sensing

A label-free supersandwich fluorescent assay was demonstrated for the first time by taking Hg(2+) as a detection candidate. The principle of the proposed supersandwich fluorescent platform is based on the formation of supersandwich structure by T-Hg(2+)-T coordination and the fluorescence enhancement of the intercalated Genefinder (GF) in double strand DNA (dsDNA). Such supersandwich fluorescent DNA sensor exhibits a linear range of 10-300 nM for the detection of Hg(2+), with a detection limit of 2.5 nM on the basis of the 3σ/slope (σ represents the standard deviation of the blank samples), which is well below the permit of the U.S. Environmental Protection Agency (<10 nM). The detection can be fulfilled in less than 10 min. The proposed mix-and-detect fluorescent platform exhibits excellent sensitivity, selectivity, and convenient manipulation. The assay was successfully used to detect Hg(2+) in the lake water samples, which suggested its potential in practical samples.