title: Sodium Green as a potential probe for intracellular sodium imaging based on fluorescence lifetime.
abstract: We characterized the use of the fluorescent probe Sodium Green for measurements of intracellular free sodium using frequency-domain, phase-modulation fluorometry. The intensity decays were found to be strongly Na+ dependent, with mean lifetime increasing from 1.13 ns in the absence of Na+ to 2.39 ns in the presence of 140 mM Na+. Detailed analysis of the intensity decays in the presence of Na+ and K+ in the concentration range from 0 to 500 mM is provided. Sodium sensing using data measured at a single modulation frequency is described. Phase and modulation data showed high sensitivity to Na+ and substantially lower sensitivity to K+. Additionally, exposure of Sodium Green to intense illumination indicated that Sodium Green is much more photostable than its precursor, fluorescein. These results indicate that lifetime-based measurements with Sodium Green can be used for imaging of intracellular free [Na+] in the range from about 0.5 to 50 mM with high accuracy.
authors.affiliation: Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: H
authors.initials: H
authors.lastname: Szmacinski
authors.forename: J R
authors.initials: JR
authors.lastname: Lakowicz
mesh_terms: D005434:Flow Cytometry / Q000379:methods; D005456:Fluorescent Dyes / Q000737:chemistry*; D009930:Organic Chemicals; D012964:Sodium / Q000032:analysis*
chemical_list: D005456:Fluorescent Dyes; D009930:Organic Chemicals; C098118:sodium green; D012964:Sodium