基于DNA双链电荷转移的Hg2+电化学生物传感器的研究

基于DNA双链电荷转移原理,利用胸腺嘧啶(thymine)与Hg2的特异性识别和计时电量法构建了一种高灵敏检测水溶液中Hg2的电化学生物传感器.该传感器将含有1个T-T碱基错配对的DNA互补双链通过Au-S键自组装在金电极表面,运用计时电量法在含有亚甲基蓝的铁氰化钾溶液中进行测定.T-T错配阻断了DNA双链内部电荷转移,而Hg2通过T-Hg2-T配位作用与双链DNA特异性结合并形成DNA双链内部电荷转移通路,引起电极表面计时电量的变化.计时电量测定结果显示:在亚甲基蓝的还原峰电位(-380mV)附近,计时电量随着溶液中的Hg2+浓度的增大而增加,Hg2+浓度在1.0 nmol/L～ 104 nmol/L范围内,计时电量的变化量与Hg2浓度的对数呈良好的线性关系,线性相关系数(R2)为0.997,检测限为0.5 nmol/L(S/N=3).干扰实验表明,该传感器对Hg2具有良好的特异性和选择性.

Electrochemical biosensor based on charge transfer of DNA duplexs for the detection of Hg2+

In this paper,combined Hg2+ specific recognition of thymine with chronocoulometry,we constructed a highly sensitive electrochemical biosensor based on DNA-mediated charge transport for the detection of Hg2+ in aqueous solution.DNA duplexs with one T-T base mismatch were assembled onto a gold electrode surface through Au-S bond.Chronocoulometry was used to detect Hg2+ in 2 mmol/L Fe(CN)6] 3-(0.1 M KCl,pH 7.4) containing 2.0 μmol/L MB.T-T mismatch blocked the internal charge transfer of the DNA duplexs.In the presence of Hg2+,the DNA on the electrode surface specifically recognized Hg2+ and formed thymine-Hg2+-thymine complexs.Thus,internal charge transfer path in dsDNA was formed,significantly improving charge transport onto the gold electrode surface.The results showed the chronocoulometry of DNA-modified gold electrode increased with the increase of Hg2+ concentration at the reduction peak of methylene blue (-380 mV).The change of chronocoulometry was linear with regard to lgcHg2+ over a concentration range from 1.0 n to 104 nmol/L (R2 =0.997) and with a detection limit of 0.5 nmol/L (S/N =3).A test for a series of interference metal ions showed that this biosensor based on DNA-mediated charge transport is highly specific and selective toward Hg2+.