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

A new label-free Hg2+ 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 Hg2+ ions, the complexation of Hg2+ ions with the MRS yielded a hairpin complex through T-Hg2+-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 Hg2+ 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 Hg2+ ions. It is expected that this cost-effective fluorescence sensor might hold considerable potential in the detection of Hg2+ ions in real environmental samples. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.