State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, College of Chemistry & Chemical Engineering, Hunan University, Changsha 410082, PR China.
Talanta. 2012 May 30;94:178-83. doi: 10.1016/j.talanta.2012.03.014. Epub 2012 Mar 10.
We report here a highly sensitive electrochemical sensing platform for Ag(+) detection based on Ag(+)-induced conformational change of cytosine-rich single stranded DNA C-rich ssDNA probe and the controlled assembly of MWCNTs. In the protocol, the gold electrode was first modified with a dense 16-mercaptohexadecanoic acid self-assembled monolayer (MHA/SAM). The hydrophobic MHA/SAM isolated the electrode from the electroactive indicator in the aqueous solution, which resulted in the electronic transmission blocking. It was eT OFF state. In the presence of Ag(+), C-Ag(+)-C coordination induced the conformational change of C-rich ssDNA probe from random-coil structure to fold into a hairpin structure, which cannot wrap on the surface of the MWCNTs. Then the "naked" MWCNTs can be assembled on the MHA/SAM gold electrode, mediating the electron transfer between the electrode and the electroactive indicator. It generated measurable electrochemical signals (eT ON). The resulting change in electron transfer efficiency was readily measured by differential pulse voltammetry at target Ag(+) concentrations as low as 1.3 nM. The linear response range for Ag(+) detection was from 10 to 500 nM. This method dose not need of electroactive molecules labeling on the C-rich ssDNA probe. Moreover, it has good selectivity to other environmentally relevant metal ions. Therefore, the developed electrochemical assay is an ideal method for Ag(+) detection with some advantages including sensitivity, selectivity, simplicity, low-cost, and no requirement for probe label preparation. We expect that this strategy could be a generalized platform for DNA-based sensing.
我们在此报告了一种基于 Ag(+)诱导富含胞嘧啶的单链 DNA (C-rich ssDNA)探针构象变化和 MWCNTs 可控组装的高灵敏电化学传感平台用于 Ag(+)检测。在该方案中，首先将金电极用密集的 16-巯基十六烷酸自组装单层 (MHA/SAM) 修饰。疏水性的 MHA/SAM 将电极与水溶液中的电化学指示剂隔离开来，从而导致电子传递阻断。此时处于电子传输关闭 (eT OFF) 状态。在存在 Ag(+)的情况下，C-Ag(+)-C 配位诱导富含胞嘧啶的 ssDNA 探针从无规线团结构构象变化为发夹结构，从而无法缠绕在 MWCNTs 表面。然后，“裸露”的 MWCNTs 可以组装在 MHA/SAM 金电极上，介导电极和电化学指示剂之间的电子转移。这会产生可测量的电化学信号 (eT ON)。通过差分脉冲伏安法在目标 Ag(+)浓度低至 1.3 nM 时，很容易测量到电子转移效率的变化。Ag(+)检测的线性响应范围为 10 至 500 nM。该方法不需要对富含胞嘧啶的 ssDNA 探针进行电化学活性分子标记。此外，它对其他环境相关金属离子具有良好的选择性。因此，所开发的电化学分析方法是一种用于 Ag(+)检测的理想方法，具有灵敏度高、选择性好、简单、成本低、无需探针标记制备等优点。我们期望这种策略可以成为一种基于 DNA 的传感的通用平台。
