Modulation sensing of fluorophores in tissue: a new approach to drug compliance monitoring

Omoefe O. Abugo; Zygmunt Gryczynski; Joseph R. Lakowicz

doi:10.1117/1.429956

1 October 1999 Modulation sensing of fluorophores in tissue: a new approach to drug compliance monitoring

Omoefe O. Abugo, Zygmunt Gryczynski, Joseph R. Lakowicz

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Journal of Biomedical Optics, Vol. 4, Issue 4, (October 1999). https://doi.org/10.1117/1.429956

We describe a method to detect the presence of fluorophores in scattering media, including intralipid suspensions and chicken muscle covered with skin. The fluorophores were rhodamine 800 (Rh800) and indocyanine green (IcG), both of which can be excited at long wavelengths where there is minimal absorption by tissues. These fluorophores were dissolved in intralipid or in chicken muscle under skin. A method to approximate the fluorophore concentration in such samples was developed using a long lifetime reference fluorophore in a polymer film placed immediately on the illuminated surface of the sample. Because of the long lifetime of the reference film, the modulation of its emission at low frequencies near 2 MHz is near zero. Since the lifetime of Rh800 and IcG are below 2 ns the modulation of the combined emission is a measure of the intensity of the fluorophore (Rh800 or IcG) relative to the long lifetime reference. Using this method we were able to measure the concentration-dependent intensities of Rh800 and IcG in an intralipid suspension. Additionally, micromolar concentrations of these probes could be detected in chicken muscles, even when the muscle was covered with a layer of chicken skin. The presence of an India ink absorber in the intralipid had only a moderate effect on the modulation values. We suggest the use of this transdermal detection of longwavelength fluorophores as a noninvasive method to monitor patient compliance when taking medicines used for treatment of chronic diseases such as AIDS or tuberculosis.

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Omoefe O. Abugo, Zygmunt Gryczynski, and Joseph R. Lakowicz "Modulation sensing of fluorophores in tissue: a new approach to drug compliance monitoring," Journal of Biomedical Optics 4(4), (1 October 1999). https://doi.org/10.1117/1.429956

Published: 1 October 1999

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KEYWORDS

Modulation

Tissues

Ruthenium

Skin

Phase shift keying

Indocyanine green

Rhodamine

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