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Biophys J, August 2002, p. 1165-1176, Vol. 83, No. 2

Fluorescence Lifetime Spectroscopy in Multiply Scattering Media with Dyes Exhibiting Multiexponential Decay Kinetics

Eddy Kuwana and Eva M. Sevick-Muraca

Departments of Chemistry and Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122 USA

To investigate fluorescence lifetime spectroscopy in tissue-like scattering, measurements of phase modulation as a function of modulation frequency were made using two fluorescent dyes exhibiting single exponential decay kinetics in a 2% intralipid solution. To experimentally simulate fluorescence multiexponential decay kinetics, we varied the concentration ratios of the two dyes, 3,3-diethylthiatricarbocyanine iodide and indocynanine green (ICG), which exhibit distinctly different lifetimes of 1.33 and 0.57 ns, respectively. The experimental results were then compared with values predicted using the optical diffusion equation incorporating 1) biexponential decay, 2) average of the biexponential decay, as well as 3) stretched exponential decay kinetic models to describe kinetics owing to independent and quenched relaxation of the two dyes. Our results show that while all kinetic models could describe phase-modulation data in nonscattering solution, when incorporated into the diffusion equation, the kinetic parameters failed to likewise predict phase-modulation data in scattering solutions. We attribute the results to the insensitivity of phase-modulation measurements in nonscattering solutions and the inaccuracy of the derived kinetic parameters. Our results suggest the high sensitivity of phase-modulation measurements in scattering solutions may provide greater opportunities for fluorescence lifetime spectroscopy.

Biophys J, August 2002, p. 1165-1176, Vol. 83, No. 2
© 2002 by the Biophysical Society   0006-3495/02/08/1165/12  $2.00


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M. Y. Berezin, H. Lee, W. Akers, and S. Achilefu
Near Infrared Dyes as Lifetime Solvatochromic Probes for Micropolarity Measurements of Biological Systems
Biophys. J., October 15, 2007; 93(8): 2892 - 2899.
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