Volume 29, Issue 4 pp. 152-161
Research Article
Free to Read

Fluorescence Quenching by Colloidal Heavy Metals Nanoparticles: Implications for Correlative Fluorescence and Electron Microscopy Studies

Irawati K. Kandela

Corresponding Author

Irawati K. Kandela

Department of Pharmaceutical Sciences, 777 Highland Avenue, Madison, WI 53705, USA

1675 Observatory Drive Madison, WI 53706 USA.Search for more papers by this author
Ralph M. Albrecht

Ralph M. Albrecht

Department of Pharmaceutical Sciences, 777 Highland Avenue, Madison, WI 53705, USA

Department of Animal Science, 1675 Observatory Drive, Madison, WI 53706, USA

Search for more papers by this author
First published: 03 May 2007
Citations: 35

Abstract

Labels for correlative immunolabeling in light (LM) and electron microscopy (EM) employing colloidal metal nanoparticles (gold or palladium) and fluorescent dyes (Alexa Fluor, AF) were investigated. The fluorescence signals from direct conjugates (cAu-IgG-AF) and from an indirect label system (cAu-IgG-anti IgG-AF) were studied using scanning spectrofluorometry and fluorescence light microscopy.

Direct conjugation of protein—AF, IgG-AF or FGN-AF to 18 and 5 nm colloidal gold (cAu18 and cAu5) or 12 nm colloidal palladium particles (cPd12) resulted in nearly completely quenched fluorescence signals (>99 %) at excitation wavelengths of 488, 546 and 594 nm. In contrast, indirect conjugation, when colloidal metal particles and AF were conjugated to primary or secondary antibody, respectively (cAu-IgG-antiIgG-AF), sufficient fluorescence signal was detected.

Commercially available conjugates, consisting of IgG-AF-cAu5 and IgG-AF-cAu10, were also tested and proved to be a mixture of IgG-AF (unbound to cAu) and cAu-IgG-AF. SCANNING 29: 000-V000, 2007. © 2007 Wiley Periodicals, Inc.

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