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 mu L 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. (C) 2008 Elsevier B.V. All rights reserved.