Evaluating tartrazine as an optical clearing agent for fluorescence lifetime imaging

Area of Science:

• Biomedical Optics
• Fluorescence Imaging
• Tissue Optics

Background:

• Fluorescence lifetime imaging (FLI) provides molecular and functional insights into tissues.
• Deep tissue imaging is hindered by scattering and absorption, reducing signal and complicating interpretation.

Purpose of the Study:

• To investigate tartrazine (FD&C Yellow 5) as a biocompatible optical clearing agent for deep tissue FLI.
• To assess tartrazine's ability to improve signal recovery and data accuracy in scattering media.

Main Methods:

• Utilized tartrazine, an FDA-approved food dye, as an optical clearing agent.
• Employed lifetime-based unmixing to separate tartrazine's short fluorescence lifetime from longer-lived probes.
• Optimized tartrazine concentration (≤ 0.6 M) to reduce scattering and improve signal recovery.
• Validated the method using multi-depth tissue phantoms for deep tissue imaging ( > 1 cm).

Main Results:

• Tartrazine significantly reduced the reduced scattering coefficient (μs') by over 90% at optimal concentrations.
• Effective separation of tartrazine's ultrashort intrinsic lifetime (∼0.10 ns) from conventional NIR probes (>0.50 ns) was achieved.
• Accurate recovery of fluorescence signals and lifetimes from targets >1 cm deep was demonstrated.
• Results were comparable to low-scattering controls, showcasing enhanced imaging depth and accuracy.

Conclusions:

• Tartrazine is a practical and effective optical clearing agent for deep tissue FLI.
• This approach enhances imaging depth, resolution, and quantitative accuracy in highly scattering media.
• The findings support the use of tartrazine in preclinical imaging studies requiring deep tissue visualization.