Label-Free Ag+ Detection by Enhancing DNA Sensitized Tb3+ Luminescence
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Date
2016-08-26
Authors
Kleinke, Kimberly
Saran, Runjhun
Liu, Juewen
Journal Title
Journal ISSN
Volume Title
Publisher
Multidisciplinary Digital Publishing Institute
Abstract
In this work, the effect of Ag+ on DNA sensitized Tb3+ luminescence was studied initially using the Ag+-specific RNA-cleaving DNAzyme, Ag10c. While we expected to observe luminescence quenching by Ag+, a significant enhancement was produced. Based on this observation, simple DNA oligonucleotide homopolymers were used with systematically varied sequence and length. We discovered that both poly-G and poly-T DNA have a significant emission enhancement by Ag+, while the absolute intensity is stronger with the poly-G DNA, indicating that a G-quadruplex DNA is not required for this enhancement. Using the optimized length of the G7 DNA (an oligo constituted with seven guanines), Ag+ was measured with a detection limit of 57.6 nM. The signaling kinetics, G7 DNA conformation, and the binding affinity of Tb3+ to the DNA in the presence or absence of Ag+ are also studied to reveal the mechanism of emission enhancement. This observation is useful not only for label-free detection of Ag+, but also interesting for the rational design of new biosensors using Tb3+ luminescence.
Description
Keywords
Coordination Polymers, Silver Nanoparticles, Metal-Ions, Binding, Fluorescence, Sequence, Dnazyme, Nanoclusters, Molecules, Duplexes