title: UV-Light-Induced Improvement of Fluorescence Quantum Yield of DNA-Templated Gold Nanoclusters: Application to Ratiometric Fluorescent Sensing of Nucleic Acids.
abstract: The use of DNA as a template has been demonstrated as an effective method for synthesizing different-sized silver nanoclusters. Although DNA-templated silver nanoclusters show outstanding performance as fluorescent probes for chemical sensing and cellular imaging, the synthesis of DNA-stabilized gold nanoclusters (AuNCs) with high fluorescence intensity remains a challenge. Here a facile, reproducible, scalable, NaBH4-free, UV-light-assisted method was developed to prepare AuNCs using repeats of 30 adenosine nucleotides (A30). The maximal fluorescence of A30-stabilized AuNCs appeared at 475 nm with moderate quantum yield, two fluorescence lifetimes, and a small amount of Au(+) on the surface of the Au core. Results of size-exclusion chromatography revealed that A30-stabilized AuNCs were more compact than A30. A series of control experiments showed that UV light played a dual role in the reduction of gold-ion precursors and the decomposition of citrate ions. A30 also acted as a stabilizer to prevent the aggregation of AuNCs. In addition, single-stranded DNA (ssDNA) consisting of an AuNC-nucleation sequence and a hybridization sequence was utilized to develop a AuNC-based ratiometric fluorescent probe in the presence of the double-strand-chelating dye SYBR Green I (SG). Under conditions of single-wavelength excitation, the combination of AuNC/SG-bearing ssDNA and perfectly matched DNA emitted fluorescence at 475 and 525 nm, respectively. The formed AuNC/SG-bearing ssDNA enabled the sensitive, selective, and ratiometric detection of specific nucleic acid targets. Finally, the AuNC-based ratiometric probes were successfully applied to determine specific nucleic acid targets in human serum.
authors.affiliation: Department of Chemistry, National Sun Yat-sen University , 70 Lien-hai Road, Kaohsiung 804, Taiwan.
authors.forename: Zong-Yu
authors.initials: ZY
authors.lastname: Li
authors.affiliation: Department of Chemistry, National Sun Yat-sen University , 70 Lien-hai Road, Kaohsiung 804, Taiwan.
authors.forename: Yun-Tse
authors.initials: YT
authors.lastname: Wu
authors.affiliation: Department of Chemistry, National Sun Yat-sen University , 70 Lien-hai Road, Kaohsiung 804, Taiwan.|School of Pharmacy, College of Pharmacy, Kaohsiung Medical University , Kaohsiung 807, Taiwan.
authors.forename: Wei-Lung
authors.initials: WL
authors.lastname: Tseng
mesh_terms: D015374:Biosensing Techniques; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000302:isolation & purification; D005453:Fluorescence; D006046:Gold / Q000737:chemistry; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D009696:Nucleic Acids / Q000737:chemistry / Q000302:isolation & purification*; D045663:Quantum Dots / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014466:Ultraviolet Rays
chemical_list: D004277:DNA, Single-Stranded; D009696:Nucleic Acids; D006046:Gold
keywords: DNA; UV light; fluorescence; gold nanoclusters; ratiometric sensor