检测痕量Hg^2＋的DNA电化学生物传感器

DNA Electrochemical Biosensor for Trace Hg^(2+) Detection

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.

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 Hg^2＋, the single strand DNA on the electrode surface turned to a thymine-Hg^2＋-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 show a 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 Hg^2＋.The rate of current change is linear with regards to lgcHg^2＋ over a concentration range from 0.1 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 Hg^2＋ detection.