Hairpin oligonucleotides anchored terbium ion: a fluorescent probe to specifically detect lead(ii) at sub-nM levelsElectronic supplementary information (ESI) available: Kinetics of terbium ions coordinated to GH5, photo-bleaching of Tb-GH5 probe, fluorescence of Tb-GH5 probe plotted with respect to probe concentration, and fluorescence of Tb-GH5 probe (with other metal ions) with respect to Pb2+ concentration. See DOI: 10.1039/c3an36795a

• Main Authors: Wei, Yueteng, Liu, Ru, Wang, Yaling, Zhao, Yuliang, Cai, Zhifang, Gao, Xueyun
• Format: Journal Article
• Language: English
• Published: 18.03.2013
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c3an36795a

A terbium based fluorescent probe was synthesized by coordinating terbium ions with a designed oligonucleotides (5′-ATATGGGGGATAT-3′, termed GH5). GH5 improved the fluorescence of terbium ions by four orders of magnitude. The fluorescence enhancement of terbium ions by different oligonucleotides sequences indicated that the polyguanine loop of the hairpin GH5 is key to enhance terbium ion emission. The quantum yield of Tb-GH5 probe was 10.5% and the probe was photo-stable. The result of conductivity titration indicated that the stoichiometry of the probe is 3.5 Tb: 1 GH5, which is confirmed by fluorescence titration. This probe had high sensitivity and specificity for the detection of lead ions. The fluorescence intensity of this probe was linear with respect to lead concentration over a range 0.3-2.1 nM ( R 2 = 0.99). The limit of detection for lead ions was 0.1 nM at a signal-to-noise ratio of 3. Tb-GH5 (GH5: designed oligonucleotides with hairpin structure) probe emits bright, sharp fluorescence. Lead ions compete with terbium ions causing the terbium ions to depart from GH5 decreasing fluorescence.