A T-Hg2+-T metallo-base pair-mediated dual amplification fluorescent strategy for the selective and sensitive detection of Hg2+

摘要

The mercuric ion is a highly toxic contaminant and causes severe harm to the environment and human health. Herein, a T-Hg2+-T metallo-base pair-mediated dual amplification fluorescent strategy was proposed for the selective and sensitive detection of Hg2+ based on a target cycle and DNAzyme cycle. First, Hg2+ selectively bound with T-T mismatches in H-DNA and A-DNA to form stable T-Hg2+-T metallo-base pairs. This initiated the strand displacement between H-DNA and A-DNA to obtain the Hg2+-mediated partial double-stranded structure, with a blunt 3'-terminus of the opened H-DNA (donated as the Hg-complex). Next, under the action of Exo III, the Hg-complex was digested to release DNAzyme, A-DNA and Hg2+. The released Hg2+ could bind with another A-DNA and H-DNA, and the target cycle started anew, eventually generating numerous DNAzymes. DNAzymes then catalyzed the cleavage of a molecular beacon (MB) to generate free fluorophores. Upon cleavage, DNAzymes were released and continuously hybridized with another MB to trigger a second DNAzyme cycle. Finally, numerous fluorophores were liberated, resulting in a significantly amplified signal. The strategy showed a good linear relationship in the range from 2.0 x 10(-10) mol L-1 to 1.0 x 10(-8) mol L-1, with a detection limit of 7.2 x 10(-11) mol L-1. The proposed strategy exhibited remarkable selectivity towards Hg2+ against other metal ions. Furthermore, this strategy was successfully applied to detect Hg2+ in real water samples. The proposed strategy provided a reliably quantitative candidate for potential application in environmental monitoring and biotoxicity analysis.