Studies On Formation And Biosensing Of Fluorescent Silver Nanoclusters Controled By DNA

In the past few years, highly luminescent noble metal nanoclusters (Au、Ag、 Pt)have emerged as a class of promising optical probes for the construction of high-performance opticalsensors because of their ultrasmall size (<2nm), strongluminescence, good photostability, excellent biocompatibility, and unique metal-coreligand-shell structure. Recently, DNA-templated silver nanoclusters (Ag NCs) have become emerging sets of fluorophores for wide applications such as biolabeling and biosensing/chemical sensing. In this article, many methods have been employed to investigate DNA single-nucleotide polymorphism (SNP) detection by DNA-templated fluorescent silver nanoclusters, the anion-polarizability-sensitized fluorescence indicates the role of anion electronic properties in tuning Ag NCs’ emission behavior, which should be seriously considered in designing Ag NCs-based sensors and devices, fluorescent Ag nanoclusters (Ag NCs) were employed as a useful inorganic fluorophore for this dinucleotide discrimination CpG to TpG. The main research contents are as follows:1. The Bulge site-containing DNAs (Bulge-DNAs) were employed as capping scaffolds for the formation of fluorescent Ag NCs using NaBH4as reductant to investigate the application of fluorescent silver nanoclusters for DNA single-nucleotide polymorphism (SNP) detection by the methods of fluorescence spectroscopy, UV-Vis spectroscopy and so on. Herein, we found that the bulge site in DNA duplex can be used to selectively grow fluorescent silver nanoclusters (Ag NCs). The as-prepared Ag NCs exhibit an emission behavior dependent on the base environment near the bulge site and can be in situ employed as readout for the specific bulge site recognition. We expect that the bulge site-determined Ag NCs’ formation is very likely to be developed into a simple method for the bulge site recognition with a high selectivity and sensitivity.2. In this work, Ag NCs that were size-selectively grown on DNAs were used to investigate the effect of electronic properties of halogen anions. Emission modulation of DNA-templated fluorescent silver nanoclusters were investigated by the methods of fluorescence spectroscopy, fluorescence lifetime, UV-Vis, TEM, XPS and so forth. We found that addition of halogen anions didn’t alter the Ag NCs’emission wavelength, however, the fluorescence intensity experienced an initial increase at low concentrations of Cl-, Br-, and I-, then following a gradual decrease at high concentrations. Less fluorescence sensitization occurred for the anion having high polarizability enough to form a covalent bond with Ag NCs. The anion-polarizability-sensitized fluorescence indicates the role of anion electronic properties in tuning Ag NCs’emission behavior, which should be seriously considered in designing Ag NCs-based sensors and devices.3.In this work, fluorescent Ag nanoclusters (Ag NCs) were employed as a useful inorganic fluorophore for this dinucleotide discrimination. CpG dinucleotide in DNA has a great potential of being easily mutated to TpG and this transition can induce some serious diseases. Therefore, there is much demand in developing efficient methods to selectively discriminate TpG from CpG. We use fluorescence spectroscopy, fluorescence lifetime, UV-Vis and so forth methods to detect the properties of the AgNCs. Here in, fluorescent Ag nanoclusters (Ag NCs) were employed as a useful inorganic fluorophore for this dinucleotide discrimination. We found that in contrast with CpG, GpG, and ApG dinucleotides, the unpaired T in TpG dinucleotide is much more efficient in growing fluorescent Ag NCs. Because the bulge site provides a constrained field for in situ growing fluorescent Ag NCs and the Ag+binding is strongly dependent on the DNA sequences around such field, mutation of CpG dinucleotide to TpG can be identified by a’turn-on’fluorescence response with a high selectivity. Additionally, the bulge site design was also compared with the abasic site structure in discrimination capacity of these dinucleotides. We expect that a practical method for the TpG recognition with a high selectivity can be developed using the bulge site-directed fluorescent Ag NCs as novel probes.