Ultrasensitive and selective detection of mercury(II) in aqueous solution by polymerase assisted fluorescence...

A new label-free Hg(2+) ions assay with polymerase assisted fluorescence amplification was developed. In this approach, a single strand template probe containing a mercury ion recognition sequence (MRS) which is composed of two thymine (T)-rich functional areas separated by a spacer of random bases was designed. In this sensing system, upon addition of Hg(2+) ions, the complexation of Hg(2+) ions with the MRS yielded a hairpin complex through T-Hg(2+)-T base pairs. The formation of the hairpin structure initiated the replication of the template probe in the presence of the polymerase/dNTPs. Then the replication products of long duplex DNA probes were stained with a sensitive reagent SYBR Green I (SG). As a result, SG integrated with the duplex DNA probes and induced a distinguishable fluorescence enhancement in response to Hg(2+) ions triggered replication reaction. Due to the fluorescence amplification step, this method exerted substantial enhancement in sensitivity and could be used for rapid and selective detection of low picomolar Hg(2+) ions. It is expected that this cost-effective fluorescence sensor might hold considerable potential in the detection of Hg(2+) ions in real environmental samples.