Key Laboratory for Analytical Science of Food Safety and Biology, MOE, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian, 350116, China.
Mikrochim Acta. 2017 Dec 20;185(1):72. doi: 10.1007/s00604-017-2536-1.
An ultrasensitive conformation-dependent colorimetric assay has been developed for the detection of mercury(II) ions. It is based on the use of exonuclease III (Exo III)-assisted target recycling and gold nanoparticles (AuNPs). In the absence of Hg(II), the hairpin-shaped DNA probe (H-DNA) binds to AuNPs and stabilizes them in solutions of high ionic strength. In the presence of Hg(II), on the other hand, the sticky termini of the H-DNA form a rigid DNA duplex stem with a blunt 3'-terminus. Thus, Exo III is activated as a biocatalyst for selective and stepwise removal of mononucleotides from the 3'-terminus of the H-DNA. As a result, Hg(II) is released from the T-Hg(II)-T complexes. The guanine-rich sequences released from the H-DNA are then self-assembled with potassium ion to form a stable G-quadruplex conformation. In solutions of high ionic strength, this results in aggregation of AuNPs and a color change from red to blue which can be seen with bare eyes. The method is highly sensitive and selective. It has a linear response in the 10 pM to 100 nM Hg(II) concentration range, and the detection limit is as low as 3.2 pM (at an S/N ratio of 3). The relative standard deviation at a level of 0.5 nM of Hg(II) is 4.9% (for n = 10). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 92% to 106%. Graphical abstract A conformation-dependent colorimetric system was fabricated for label-free detection of mercury(II) by utilizing exonuclease III(Exo III)-assisted target recycling and gold nanoparticles (AuNPs).
一种基于外切酶 III（Exo III）辅助目标循环和金纳米粒子（AuNPs）的用于检测汞（II）离子的超灵敏构象依赖比色测定法已经被开发出来。在不存在 Hg(II) 的情况下，发夹状 DNA 探针（H-DNA）与 AuNPs 结合并在高离子强度溶液中稳定它们。另一方面，在存在 Hg(II) 的情况下，H-DNA 的粘性末端形成具有钝 3'-末端的刚性 DNA 双链茎。因此，Exo III 被激活为生物催化剂，用于从 H-DNA 的 3'-末端选择性地和逐步去除单核苷酸。结果，Hg(II)从 T-Hg(II)-T 复合物中释放出来。从 H-DNA 释放出的富含鸟嘌呤的序列随后与钾离子自组装形成稳定的 G-四链体构象。在高离子强度溶液中，这导致 AuNPs 聚集并且颜色从红色变为蓝色，肉眼可以看到。该方法具有高度的灵敏度和选择性。它在 10 pM 至 100 nM Hg(II)浓度范围内具有线性响应，检测限低至 3.2 pM（信噪比为 3）。在 0.5 nM Hg(II)水平下的相对标准偏差为 4.9%（n=10）。该方法已应用于加标环境水样中 Hg(II)的检测，回收率在 92%至 106%之间。
