TY - JOUR
T1 - Intensity measurements in scattering media
AU - Lakowicz, Joseph R.
AU - Dattelbaum, Jonathan D.
AU - Gryczynski, Ignacy
N1 - Funding Information:
This work was supported by a grant from the National Institutes of Health National Center for Research Resources RR-08119.
PY - 1999/11/2
Y1 - 1999/11/2
N2 - We describe a new method which allows quantitative measurements of fluorescence intensity in highly scattering media. The measurement principle is based on observing the emission from both the fluorophore of interest with a nanosecond decay time and of a reference fluorophore which displays a much longer microsecond lifetime. The reference fluorophore is placed on rather than in the sample to mimic a sensing device with the long lifetime reference held against the skin. The amplitude modulation of the emission is observed using the standard method of frequency-domain (FD) fluorometry. At an intermediate modulation frequency, the modulation is equivalent to the fractional intensity of the nanosecond fluorophore. The method was tested in 0.5% intralipid, which is more highly scattering than skin. Quantitative intensity measurements were obtained for various concentrations of fluorescein in intralipid, and of the pH sensor 6-carboxyfluorescein (6-GF). Low frequency modulation measurements provide a general method for quantitative measurements in the presence of factors which preclude direct intensity measurements.
AB - We describe a new method which allows quantitative measurements of fluorescence intensity in highly scattering media. The measurement principle is based on observing the emission from both the fluorophore of interest with a nanosecond decay time and of a reference fluorophore which displays a much longer microsecond lifetime. The reference fluorophore is placed on rather than in the sample to mimic a sensing device with the long lifetime reference held against the skin. The amplitude modulation of the emission is observed using the standard method of frequency-domain (FD) fluorometry. At an intermediate modulation frequency, the modulation is equivalent to the fractional intensity of the nanosecond fluorophore. The method was tested in 0.5% intralipid, which is more highly scattering than skin. Quantitative intensity measurements were obtained for various concentrations of fluorescein in intralipid, and of the pH sensor 6-carboxyfluorescein (6-GF). Low frequency modulation measurements provide a general method for quantitative measurements in the presence of factors which preclude direct intensity measurements.
UR - http://www.scopus.com/inward/record.url?scp=0033361582&partnerID=8YFLogxK
U2 - 10.1016/S0925-4005(99)00234-8
DO - 10.1016/S0925-4005(99)00234-8
M3 - Article
AN - SCOPUS:0033361582
SN - 0925-4005
VL - 60
SP - 1
EP - 7
JO - Sensors and Actuators, B: Chemical
JF - Sensors and Actuators, B: Chemical
IS - 1
ER -