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Proceedings Paper

Fluorophore conjugated silver nanoparticles: a time-resolved fluorescence correlation spectroscopic study
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Paper Abstract

Fluorescence detection is a central component in biological research. In recent years there has been a growing interest in the interactions of fluorophores with metallic surfaces or particles. A single-stranded oligonucleotide was chemically bound to a single 50 nm diameter silver particle and a Cy5-labeled complementary single-stranded oligonucleotide was hybridized with the particle-bound oligonucleotide. The bound Cy5 molecules on the silver particles were spatially separated from the silver surface by the hybridized DNA duplex chains, which were about 8 nm in length, to reduce the competitive quenching. We use fluorescence lifetime correlation spectroscopy (FLCS) with picosecond time-resolved detection to separate the fluorescence correlation spectroscopy (FCS) contributions from fluorophores and metal-conjugated fluorophores. The single Cy5-labeled 50 nm silver particles displayed a factor of 15-fold increase in emission signal and 5-fold decrease in emission lifetimes in solution relative to the Cy5-DNA in the absence of metal. Lifetime measurements support the near-field interaction mechanism between the fluorophore and silver nanoparticle. In this study, FLCS is being applied to a system where the brightness and the fluorescent lifetime of the emitting species are significantly different. Our measurements suggest that FLCS is a powerful method for investigating the metal-fluorophore interaction at the single molecule level and to separate two different species from a mixture solution emitting at the same wavelength. Additionally, the highly bright Cy5-DNA-Ag molecules offer to be excellent probes in high background biological samples.

Paper Details

Date Published: 24 February 2009
PDF: 7 pages
Proc. SPIE 7185, Single Molecule Spectroscopy and Imaging II, 71850C (24 February 2009); doi: 10.1117/12.808958
Show Author Affiliations
Krishanu Ray, Univ. of Maryland School of Medicine (United States)
Jian Zhang, Univ. of Maryland School of Medicine (United States)
Joseph R. Lakowicz, Univ. of Maryland School of Medicine (United States)

Published in SPIE Proceedings Vol. 7185:
Single Molecule Spectroscopy and Imaging II
Jörg Enderlein; Zygmunt Karol Gryczynski; Rainer Erdmann, Editor(s)

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