Silicon Flavylium Polymethine Dyes for Shortwave Infrared Imaging

Area of Science:

• Materials Science
• Biomedical Imaging
• Organic Chemistry

Background:

• Shortwave infrared (SWIR) imaging (1000-2000 nm) offers advantages for in vivo studies, such as reduced scattering and deep-tissue penetration.
• Developing bright small-molecule fluorophores emitting above 1100 nm for SWIR imaging remains a significant challenge.

Purpose of the Study:

• To introduce a new class of silicon-containing flavylium (SiliFlav) polymethine dyes.
• To address the limitations of current fluorophores for deep-tissue SWIR imaging.
• To demonstrate the utility of SiliFlav dyes for in vivo fluorescence imaging.

Main Methods:

• Synthesis of silicon-containing flavylium (SiliFlav) polymethine dyes.
• Characterization of photophysical properties, including emission spectra and quantum yields.
• Formulation of the lead fluorophore (SiliFlav5) into canola oil nanoemulsions.
• In vivo fluorescence imaging in mice to visualize vasculature and spleen.

Main Results:

• Achieved unprecedented bathochromic shifts in emission up to 200 nm by incorporating a silicon heteroatom.
• Maintained respectable fluorescence quantum yields (up to 0.30%).
• Demonstrated bright SWIR emission above 1300 nm with SiliFlav5 nanoemulsions.
• Obtained high-resolution in vivo imaging of mouse vasculature and spleen.

Conclusions:

• SiliFlav polymethine dyes represent a new class of fluorophores for SWIR imaging.
• These dyes overcome key limitations, offering bright emission and deep-tissue penetration.
• SiliFlav dyes provide a promising platform for advanced in vivo deep-tissue SWIR imaging applications.