Method for detection of Hg2+ based on the specific thymine–Hg2+–thymine interaction in the DNA hybridization on the surface of quartz crystal microbalance

A simple and sensitive method was developed for the detection of mercury ions with quartz crystal microbalance (QCM), based on the specific thymine–Hg2+–thymine (T–Hg2+–T) interaction and gold nanoparticle-mediated signal amplification. To enhance the sensitivity of detection a sandwich hybridization approach was adopted in this work. The QCM gold surface was modified with the probe SH-oligonucleotides (Oligo-1) and 6-Mercapto-1-hexanol to form an active surface for the hybridization of a longer ss-DNA (Oligo-2), and then Oligo-3 hybridazated with an excess and matching part of Oligo-2. In all oligonucleotides, there existed T bases. In the presence of Hg2+ ions, special T–Hg2+–T reaction greatly enhanced the hybridization of oligonucleotides and detection sensitivity. The gold nanoparticle (Au NPs) amplifier method further increased the sensitivity of detection. A detection sensitivity of 5 nM Hg2+ was obtained in the QCM system, whereas other coexisting metal ions (such as Ni2+, Mg2+, Co2+, Cr3+, Pb2+, Cd2+, Mn2+, Ba2+) had no significant interference. This method reveals a new approach for the manufacture of a kind of simple and low cost sensors for the Hg2+ detection.