Preparation Of Oligonucleotide-Stabilized Silver Nanocluster And Feasibility Research As Fluorescent Probe

Silver Nanoclusters (Ag NCs) is a kind of Core/Shell molecular aggregate. Monolayers or biomolecules are play the role of Shell and Core is often composed by several or dozens of silver atoms. Template Stabilized method and Monolayer Protected method, with different structures and functions, are synthesis approaches of Ag NCs classified by blocking group. Ag NCs provide biology analysis and medical diagnosis with new labeling methods and open up new applications for its good biocompatibility and photostability with no power-low blinking on all relevant time scales. The preparation processes and physical and chemical properties of Ag NCs, utilized oligonucleotide with loop-stem structure as template, were described in this paper. The optimal conditions for preparation were studied in detail. Moreover, the Ag NCs-probe was prepared with Ag NCs and the feasibility in application as fluorescent probes were analyzed and studied.1. Photoluminescent Ag NCs was prepared with oligonucleotide. The as-prepared Ag NCs present pink and bright red colour under visible light and 365 nm UV-light, respectively. They have an absorption maximum (λmax) of 262 nm and excitation and emission maximum of 295 and 660 nm, respectively. Quantum yield (QY) is 0.105. Ag NCs present good dispersivity under the Fluorescence microscope. The Ag NCs are composed of at least two components possessing 6 to 8 atoms with a diameter of about 0.9 nm, indicate through polyacrylamide gel electrophoresis. The maximum and minimum migration rates of clusters are 1.74 and 1.37, and the migration rate of oligonucleotide is 1.67.2. Optimal conditions of Ag NCs in preparation and application. Ag NCs are able to be prepared under pH6.5-7.5 and stored in the temperatures no high than 60℃keeping strong fluorescence. Ag+, Na+,K+,Zn2+, Ba2+, Ca2+, Mg2+, Co2+, Bi3+, Sr2+, Al3+, Pb2+, Fe3+ F-, Br-,Cl-, CH3COO-,B4O72-,SO32-,SO42-,C2O42- and IO3-make less or no influence to the fluorescence of Ag NCs. except Cu2+, Hg2+. IO4- and S2O32+. which quenches the Ag NCs seriously.3. Ag NCs were designed as optical sensor for sensitive detection of Cu2+ and Hg3+ for their serious quenching effect to fluorescence of Ag NCs, and the working curves were plotted. The detection limits for Cu2+ and Hg2+ were calculated to be 6.0 nmol/L and 9.3 nmol/L respectively, following the IUPAC criterion. Quenching mechanisms were discussed. EDTA can recover the fluorescence of Ag NCs partly after quenched by Cu2+ and Hg2+, and the recovery rates are 70% and 40%, respectively.4. Ag NCs were designed as optical sensor for sensitive detection of IO4- and S2O32-, for their serious quenching effect to fluorescence of Ag NCs, and the working curves were plotted. The detection limits for IO4- and S2O32-were calculated to be 8.8 nmol/L and 15.7 nmol/L, respectively, following the IUPAC criterion. Quenching mechanisms were discussed.5. Ag NCs-probe was prepared with the oligonucleotide-stabled Ag NCs and probe sequence. The as-prepared Ag NCs-probe presents salmon pink fluorescence under UV light (365 nm). It has fluorescence spectra from 300-400 nm and 500-800 nm. The maximum emission peak shifts to 645 nm, narrows the emission spectra, increases the fluorescence intensity with 16.5% after adding 30%-70% methanamide solutions. The fluorescence intensity of Ag NCs-probe decreases with 80% and 90% methanamide solutions.6. Specific sequence of O157:H7 was detected by fluorescent Ag NCs-probe. The Oligonucleotide microarrays were prepared and then hybrized with the as-prepared Ag NCs-probe, and detected the sequence of O157:H7. It proved to be feasible in biological detection after measuring the fluorescence signal.