Abstract:

In this paper we demonstrated a novel type of electrochemical Hg2+ biosensor based on a DNA-modified electrode. Ferrocenyl-modified T-rich DNA (DNA-Fc) molecules were synthesized for use as electrochemical probes. We then fixed these DNA-Fc probes onto a gold electrode surface by self-assembly. In the presence of Hg2+, the single strand DNA on the electrode surface turned to a thymine-Hg2+-thymine (T-Hg2+-T) hairpin structure. The ferrocenyl groups were kept away from the surface of the electrode, and this could be measured sensitively by differential pulse voltammetry (DPV). The results showa reduction peak of ferrocene at 0.26 V (vs saturated calomel electrode (SCE)) and the peak current of DPV decreased with increasing the concentration of Hg2+. The rate of current change is linear with regards to lgcHg2+ over a concentration range from0.1 nmol·L-1 to 1 μmol·L-1 and with a detection limit of 0.1 nmol·L-1. A test for interference metal ions showed that this electrochemical biosensor based on a DNA modified electrode is highly sensitive and selective, and it can be widely used for trace Hg2+ detection.

Key words: Biosensor, Hg2+, DNA, Conformational change, Differential pulse voltammetry, Electrochemical impedance spectroscopy