Highly sensitive and selective detection of Hg2+ using mismatched DNA and a molecular light switch complex in aqueous solution.

A novel "signal-on" assay for sensitive and selective detection of Hg(2+) in aqueous solution based on mismatched DNA and a molecular light switch complex, Ru(phen)(2)(dppz), was reported in the present work. This Hg(2+) specific sensor system composed of two label-free DNA probes with eight T-T mismatches, which could form stable DNA duplexes by thymine-Hg(2+)-thymine (T-Hg(2+)-T) in the presence of Hg(2+). The luminescence of Ru(phen)(2)(dppz) is very weak in aqueous solution, and significant luminescence can be observed when intercalating into DNA duplexes. By monitoring Hg(2+)-dependent luminescence intensity enhancement, highly sensitive and selective determination of Hg(2+) has been achieved. Under the optimum conditions, the luminescence intensity was proportional to the concentration of Hg(2+) in the range of 1.0x10(-9)-1.5x10(-7) M. A detection limit of 3.5x10(-10) M Hg(2+) was achieved using 3sigma. The presence of other metal ions did not interfere with the detection of Hg(2+) even at high concentrations. This approach is simple and rapid, which can be used to monitor the Hg(2+) concentration in drinking water and natural media within 30 min.