Real-time fluorescence detection of Hg2+ ions with high sensitivity by exponentially isothermal oligonucleotide amplification

A new sensitive assay for Hg2+ ions has been demonstrated in this work based on isothermal exponential amplification reaction (EXPAR). In the presence of Hg2+ ions, a thymine (T)-rich oligonucleotide probe will firstly combine with a T-rich template through Hg2+-mediated T–Hg2+–T interaction and subsequently trigger the EXPAR reaction. EXPAR is a simple, fast and highly efficient amplification technique, which can provides 106–109 fold amplification under isothermal conditions within minutes. Therefore, with real-time fluorescent detection of EXPAR products triggered by Hg2+ ions, high sensitivity is achieved and as low as 100 pM Hg2+ ions can be accurately determined in a 10 μL reaction system. Furthermore, due to the specific binding between Hg2+ and thymine, even 10–100 fold excess of other metal ions do not interfere with the detection of Hg2+ ions, showing high specificity of this proposed assay.