title: Oligonucleotide-based fluorescence system for sensitive and selective detection of Ag(I) ions in aqueous solution.
abstract: In this letter, a new homogeneous assay with high sensitivity and selectivity was developed for the detection of silver ions in aqueous media at room temperature by using EvaGreen (EG), polycytosine oligonucleotide C₂₀ and single-walled carbon nanotubes (SWNTs). The fluorescence of EG is weak in the absence or presence of randomly coiled C₂₀ After C₂₀ interacted specifically with Ag(+) ions through C-Ag(+)-C bonding, C₂₀ would form a folded structure that preferentially binds to EG. As a result, the fluorescence of the mixture of C₂₀ and EG increased in the presence of Ag(+). As having a higher affinity with ssDNA and organic dye, SWNTs could easily form a complex with EG and C₂₀, which led to fluorescence quenching of the dye. Additionally, they can also effectively reduce background-signal fluorescence of the dye and greatly improve its specificity. Under the optimum conditions, the EG/C₂₀ probe exhibited a high selectivity towards Ag(+) over other metal ions. The detection limit was up to 7.4 nM (0.8 ppb). This method is low cost, label-free, and easy to use.
authors.affiliation: Department of Microbiology, College of Life Science, Hunan Normal University, Changsha, Hunan 410081, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.forename: Qizhi
authors.initials: Q
authors.lastname: He
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Xinghua
authors.initials: X
authors.lastname: Ding
authors.forename: Lingli
authors.initials: L
authors.lastname: Chen
authors.forename: Le
authors.initials: L
authors.lastname: Deng
mesh_terms: D004202:Disinfectants / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009841:Oligonucleotides / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D004202:Disinfectants; D005456:Fluorescent Dyes; D009841:Oligonucleotides; D014874:Water Pollutants, Chemical; D014867:Water; D012834:Silver