‘Turn-on’ detection ofHg2+ ion using a peroxidase-like split G-quadruplex–hemin DNAzyme

Abstract

A highly sensitive and selective Hg²⁺ detection method was developed based on the Hg²⁺-mediated formation of split G-quadruplex–hemin DNAzymes. In this method, two label-free oligonucleotides are used. In the presence of Hg²⁺, the two oligonucleotides hybridize to each other to form a duplex, in which T–T mismatches are stabilized by T–Hg²⁺–T base pair. As a result, the G-rich sequences of the two oligonucleotides can associate to form a split G-quadruplex, which is able to bind hemin to form the catalytically active G-quadruplex–hemin DNAzymes. This can be reflected by an absorbance increase when monitored in the H₂O₂–ABTS (2,2′-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid) reaction system by using UV-vis absorption spectroscopy. This ‘turn-on’ process allows the detection of aqueous Hg²⁺ at concentrations as low as 19 nM using a simple colorimetric technique. With the development of the studies on metal–base pairs, this Hg²⁺-sensing method can be easily extended to the analysis of other metal ions.