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

Area of Science:

• Biomedical imaging
• Molecular imaging
• Nanotechnology

Background:

• Fluorescently labeled Nanobodies (Nbs) offer advantages for molecular imaging, including speed and specificity.
• Dye properties significantly impact the performance of imaging tracers.
• Anti-EGFR Nbs are promising for targeting EGFR-expressing tumors.

Purpose of the Study:

• To evaluate three next-generation FNIR-Tag dyes conjugated to an anti-EGFR Nanobody (Nb) for molecular imaging.
• To assess the impact of different dye properties on tracer performance in vivo.
• To determine the suitability of these tracers for applications like fluorescence-guided surgery.

Main Methods:

• Conjugation of the anti-EGFR Nb 7D12 to FNIR-Tag-1.0, FNIR-Tag-766, and FNIR-Tag-804.
• In vitro characterization of the Nb-dye conjugates.
• In vivo imaging and biodistribution studies to evaluate pharmacokinetics, tumor uptake, and 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 fluorescence; distinct renal handling was observed for different dyes.

Conclusions:

• FNIR-Tag-labeled Nbs facilitate effective tumor visualization as early as 1 hour post-injection.
• While pharmacokinetics were similar, differences in tissue uptake, brightness, and optical compatibility influence detection sensitivity.
• Dye selection is crucial for optimizing sensitivity in clinical molecular imaging applications.