College of Environmental Science and Engineering, Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China.
Anal Chem. 2013 Jan 15;85(2):1164-70. doi: 10.1021/ac303084d. Epub 2013 Jan 3.
An ultrasensitive "turn-on" fluorescent sensor was presented for determination of Hg(2+). This method is mainly based on Hg(2+)-induced conformational change of a thymine-rich single-stranded DNA. The water-soluble long-lifetime fluorescence quantum dot (Mn:CdS/ZnS) acted as the fluorophore, which was labeled on a 33-mer thymine-rich single-stranded DNA (strand A). The gold nanoparticles (GNPs) functionalized 10-mer single-stranded DNA (strand B) is selected as the quencher to quench the fluorescence of Mn:CdS/ZnS. Without Hg(2+) in the sample solution, strands A and B could form hybrid structures, resulting in the fluorescence of Mn:CdS/ZnS being decreased sharply. When Hg(2+) is present in the sample solution, Hg(2+)-mediated base pairs induced the folding of strand A into a hairpin structure, leading to the release of GNPs-tagged strand B from the hybrid structures. The fluorescence signal is then increased obviously compared with that without Hg(2+). The sensor exhibits two linear response ranges between fluorescence intensity and Hg(2+) concentration. Meanwhile, a detection limit of 0.18 nM is estimated based on 3α/slope. Selectivity experiments reveal that the fluorescent sensor is specific for Hg(2+) even with interference by high concentrations of other metal ions. This sensor is successfully applied to determination of Hg(2+) in tap water and lake water samples. This sensor offers additional advantage to efficiently reduce background noise using long-lifetime fluorescence quantum dots by a time-gated mode. With excellent sensitivity and selectivity, this sensor is potentially suitable for monitoring of Hg(2+) in environmental applications.
一种超灵敏的“开”式荧光传感器被提出用于测定 Hg(2+)。该方法主要基于 Hg(2+)诱导富含胸腺嘧啶的单链 DNA 的构象变化。水溶性长寿命荧光量子点（Mn:CdS/ZnS）作为荧光团标记在 33 个碱基富含胸腺嘧啶的单链 DNA（链 A）上。金纳米粒子（GNPs）功能化的 10 个碱基单链 DNA（链 B）被选为猝灭剂来猝灭 Mn:CdS/ZnS 的荧光。在样品溶液中没有 Hg(2+)时，链 A 和 B 可以形成杂交结构，导致 Mn:CdS/ZnS 的荧光急剧降低。当样品溶液中存在 Hg(2+)时，Hg(2+)-介导的碱基对诱导链 A 折叠成发夹结构，导致 GNPs 标记的链 B 从杂交结构中释放出来。与没有 Hg(2+)时相比，荧光信号明显增加。该传感器在荧光强度和 Hg(2+)浓度之间表现出两个线性响应范围。同时，根据 3α/slope 估计检测限为 0.18 nM。选择性实验表明，即使存在高浓度的其他金属离子干扰，荧光传感器也能特异性地检测 Hg(2+)。该传感器成功应用于自来水中和湖水样品中 Hg(2+)的测定。该传感器通过时间门控模式有效地利用长寿命荧光量子点来降低背景噪声，具有额外的优势。该传感器具有出色的灵敏度和选择性，有望适用于环境应用中 Hg(2+)的监测。
