Fluorescence lifetime spectroscopy for pH sensing in scattering media

Area of Science:

• Biophotonics
• Analytical Chemistry
• Spectroscopy

Background:

• Scattering in biological tissues complicates optical measurements.
• Fluorescence lifetime spectroscopy offers potential for in-situ analyte detection.
• Developing robust methods for scattering media is crucial for biomedical applications.

Purpose of the Study:

• To demonstrate fluorescence lifetime spectroscopy for pH sensing in tissuelike scattering media.
• To validate the technique using a pH-sensitive dye (C-SNAFL-1) and Intralipid as a scatterer.
• To assess the method's robustness across varying scatterer concentrations.

Main Methods:

• Utilized phase and modulation ratio measurements as a function of modulation frequency.
• Employed the optical diffusion equation to model fluorescence propagation and generation.
• Measured average fluorescence lifetimes of C-SNAFL-1 in solutions with Intralipid scatterer at varying pH (5-9).

Main Results:

• Accurately determined average fluorescence lifetimes of C-SNAFL-1 across a pH range of 5-9.
• Lifetime values obtained in scattering media matched those from non-scattering measurements.
• The technique demonstrated robustness with Intralipid concentrations ranging from 1.5% to 3.0%.

Conclusions:

• Fluorescence lifetime spectroscopy is a viable analytical sensing approach in scattering media.
• The method accurately tracks analyte concentration changes via fluorescence lifetime kinetics.
• This technique shows promise for real-time monitoring in complex biological environments.