In vivo Fluorescent Molecular Imaging Using Nanobodies Labeled with Next-Generation FNIR-Tag-Dyes

Area of Science:

• Molecular imaging
• Nanotechnology
• Bioconjugation chemistry

Background:

• Fluorescently labeled Nanobodies (Nbs) offer high-contrast molecular imaging for applications like fluorescence-guided surgery.
• Dye properties significantly impact the performance of imaging tracers.

Purpose of the Study:

• Evaluate three next-generation FNIR-Tag dyes conjugated to an anti-EGFR Nanobody (Nb) for molecular imaging.
• Assess the impact of different dye properties on tracer performance in vivo.

Main Methods:

• Conjugated anti-EGFR Nb 7D12 to FNIR-Tag-1.0, FNIR-Tag-766, and FNIR-Tag-804.
• Performed in vitro characterization and in vivo imaging and biodistribution studies.
• Assessed pharmacokinetics, tumor uptake, tumor-to-background ratios, contrast-to-noise ratios, and renal clearance.

Main Results:

• All Nb-based tracers showed rapid tumor accumulation and clearance from blood and non-target tissues, with predominant renal elimination.
• 7D12-FNIR-Tag-1.0 had higher tumor uptake; 7D12-FNIR-Tag-766 showed improved tumor-to-background and contrast-to-noise ratios.
• 7D12-FNIR-Tag-804 had lower tumor signal but comparable contrast due to reduced background; distinct renal handling was observed between dyes.

Conclusions:

• FNIR-Tag labeled Nbs facilitate effective tumor visualization as early as 1 hour post-injection.
• While overall biodistribution was similar, differences in tissue uptake, brightness, and system compatibility influence detection sensitivity.
• Careful dye selection is crucial for optimizing detection sensitivity in clinical imaging applications.