Highly selective detection of mercury (II) using a G-rich oligonucleotide-based fluorescence quenching method

We provide a highly sensitive and selective assay to detect Hg2+ in aqueous solutions using single fluorescence-labeled G-quadruplex at room temperature. The mechanism is that AS1411 converted to G-quadruplex in the presence of potassium ion, and then, by this technique utilizing the high binding capacity of T–Hg2+–T makes the fluorescence dye come closer to GGG of AS1411 to causing fluorescence signal quenching by photoinduced electron transfer energy transfer. At physiological pH, the detection limit can be as low as 10 nM, with high selectivity toward Hg2+ ions over a lot of metal ions. The linear correlation existed between the fluorescence intensity and the concentration of Hg2+ over the range of 0–250 nM (R = 0.9920) in real sample. Accordingly, we expect this G-quadruplex-based sensor will be a potential application for detection of environmentally toxic mercury.