A regenerative ratiometric electrochemical biosensor for selective detecting Hg2+ based on Y-shaped/hairpin DNA transformation.

Inspired by dual-signaling ratiometric mechanism which could reduce the influence of the environmental change, a novel, convenient, and reliable method for the detection of mercury ions (Hg 2+ ) based on Y-shaped DNA (Y-DNA) was developed. Firstly, the Y-DNA was formed via the simple annealing way of using two different redox probes simultaneously, omitting the multiple operation steps on the electrode. The Y-DNA was immobilized on the gold electrode surface and then an obvious ferrocene (Fc) signal and a weak methylene blue (MB) signal were observed. Upon addition of Hg 2+ , the Y-DNA structure was transformed to hairpin structure based on the formation of T-Hg 2+ -T complex. During the transformation, the redox MB gets close to and the redox Fc gets far away from the electrode surface, respectively. This special design allows a reliable Hg 2+ detection with a detection range from 1 nM to 5 μM and a low detection limit down to 0.094 nM. Furthermore, this biosensor exhibits good selectivity and repeatability, and can be easily regenerated by using l -cysteine. This study offers a simple and effective method for designing ratiometric biosensors for detecting other ions and biomolecules. [ABSTRACT FROM AUTHOR]