基于DNA双链电荷转移的Hg^(2+)电化学生物传感器的研究

Electrochemical biosensor based on charge transfer of DNA duplexs for the detection of Hg^(2+)

基于DNA双链电荷转移原理,利用胸腺嘧啶(thymine)与Hg^(2+)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Hg^(2+)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Hg^(2+)通过T-Hg^(2+)-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(-380m V)附近,计时电量随着溶液中的Hg^(2+)浓度的增大而增加,Hg^(2+)浓度在1.0 nmol/L^104nmol/L范围内,计时电量的变化量与Hg^(2+)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Hg^(2+)具有良好的特异性和选择性。

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,p H 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 ds DNA 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 m V）. 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. 5nmol / L（ S / N = 3）. A test for a series of interference metal ions showed that this biosensor based on DNAmediated charge transport is highly specific and selective toward Hg2＋.