G-Quadruplex DNA for Fluorescent and Colorimetric Detection of Thallium(I)

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• 作者：Michael Hoang ; Po-Jung Jimmy Huang ; Juewen Liu
• 刊名：ACS Sensor
• 出版年：2016
• 出版时间：February 26, 2016
• 年：2016
• 卷：1
• 期：2
• 页码：137-143
• 全文大小：604K
• ISSN：2379-3694

文摘

Thallium is a highly toxic heavy metal, but its sensing is underexplored compared to its neighboring elements in the periodic table: lead and mercury. Thallium has two oxidation states. A DNAzyme-based biosensor for Tl³⁺ was reported recently, representing the first work in this area. However, the most environmentally abundant thallium is monovalent Tl⁺, which is the focus of this work. Since Tl⁺ is similar to K⁺ in terms of size and charge, G-quadruplex DNAs are herein tested for Tl⁺ detection. First, nine dual fluorophore labeled DNA probes are screened. Among them, a DNA designated PS2.M has the largest increase in fluorescence resonance energy transfer (FRET) efficiency upon Tl⁺ addition. This FRET-based assay is directly used as a biosensor yielding a detection limit of 59 μM Tl⁺. In comparison, K⁺ had a much lower response and the other tested monovalent metals do not produce a significant signal increase. In addition, a colorimetric sensor was developed based on DNA protected gold nanoparticles. When folded by Tl⁺, the nonlabeled PS2.M DNA cannot effectively adsorb onto gold nanoparticles. This leads to a color change from red to blue upon salt addition. The detection limit is 4.6 μM Tl⁺, and Tl⁺ spiked in a lake water sample can also be detected. CD spectroscopy is used to further understand Tl⁺ binding to PS2.M. This study demonstrates that DNA can also be used for detecting Tl⁺, and this work gives rise to a highly effective probe for this purpose.