检测痕量Hg~(2+)的DNA电化学生物传感器

通过自组装方法将修饰有二茂铁基团的富T序列DNA分子(DNA-Fc)固定在金电极表面,得到了一种基于DNA修饰电极的电化学汞离子(Hg2+)传感器.当溶液中有Hg2+存在时,Hg2+可与修饰电极上DNA的T碱基发生较强的特异结合,形成T-Hg2+-T发卡结构,使DNA分子构象发生改变,其末端具有电化学活性的二茂铁基团远离电极表面,电化学响应随之发生变化.示差脉冲伏安法(DPV)结果显示:DNA末端二茂铁基团的还原峰在0.26V(vs饱和甘汞电极(SCE))附近,峰电流随溶液中Hg2+浓度的增加而降低;Hg2+浓度范围在0.1nmol·L-1-1μmol·L-1时,电流相对变化率与Hg2+浓度的对数呈现良好的线性关系.该修饰电极对Hg2+的检测限为0.1nmol·L-1,可作为痕量Hg2+检测的电化学生物传感器.干扰实验也表明,该传感器对Hg2+具有良好的特异性与灵敏度.

DNA Electrochemical Biosensor for Trace Hg2+ Detection

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.