Highly sensitive oligonucleotide-based fluorometric detection of mercury(II) in aqueous media

This paper describes a highly sensitive and selective Hg2+ sensor using a label free Hg2+ specific probe (5′-18T-3′) and an intercalation dye SYBR Green I (SG). The Hg2+ specific probe is composed of thymines (T) and readily forms T–Hg2+–T complexes in the presence of Hg2+. This specific T–Hg2+–T formation affects the hybridization of the Hg2+ specific probe and the intercalation of SG. Upon treatment of 1 nM 5′-18T-3′ with different amount of Hg2+ (0.1–10 nM), which is followed by hybridization with 1 nM 5′-18T-3′ and incubation with 1 μL of SG, the solution fluorescence gave a linear response (R = 0.996) to the concentration of Hg2+. The detection limit for Hg2+ was 0.5 nM (0.1 ppb). The overall test only takes few minutes and very little interference is observed from non-specific metal ions. This approach may find potential applications in monitoring the Hg2+ concentration in drinking water.