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Proceedings Paper

Metal-enhanced intrinsic fluorescence of proteins and label-free bioassays
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Paper Abstract

Most of the applications of fluorescence require the use of labeled drugs and labeled biomolecules. Due to the need of labeling biomolecules with extrinsic fluorophores, there is a rapidly growing interest in methods which provide label-free detection (LFD). Proteins are highly fluorescent, which is due primarily to tryptophan residues. However, since most proteins contain tryptophan, this emission is not specific for proteins of interest in a biological sample. This is one of the reasons of not utilizing intrinsic tryptophan emission from proteins to detect specific proteins. Here, we present the intrinsic fluorescence for several proteins bound to the silver or aluminum metal nanostructured surfaces. We demonstrate the metal enhanced fluorescence (MEF) of proteins with different numbers of tryptophan residues. Large increases in fluorescence intensity and decreases in lifetime provide the means of direct detection of bound protein without separation from the unbound. We present specific detection of individual types of proteins and measure the binding kinetics of proteins such as IgG and streptavidin. Additionally, specific detection of IgG and streptavidin has been accomplished in the presence of large concentrations of other proteins in sample solutions. These results will allow design of surface-based assays with biorecognitive layer that specifically bind the protein of interest and thus enhance its intrinsic fluorescence. The present study demonstrates the occurrence of MEF in the UV region and thus opens new possibilities to study tryptophan-containing proteins without labeling with longer wavelength fluorophores and provides an approach to label-free detection of biomolecules.

Paper Details

Date Published: 3 March 2010
PDF: 7 pages
Proc. SPIE 7577, Plasmonics in Biology and Medicine VII, 75770K (3 March 2010); doi: 10.1117/12.840412
Show Author Affiliations
Krishanu Ray, Ctr. for Fluorescence Spectroscopy, Univ. of Maryland School of Medicine (United States)
Henryk Szmacinski, Ctr. for Fluorescence Spectroscopy, Univ. of Maryland School of Medicine (United States)
Mustafa H. Chowdhury, Ctr. for Fluorescence Spectroscopy, Univ. of Maryland School of Medicine (United States)
Joseph R. Lakowicz, Ctr. for Fluorescence Spectroscopy, Univ. of Maryland School of Medicine (United States)


Published in SPIE Proceedings Vol. 7577:
Plasmonics in Biology and Medicine VII
Tuan Vo-Dinh; Joseph R. Lakowicz, Editor(s)

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