Pre-Assembly of Near-Infrared Fluorescent Multivalent Molecular Probes for Biological Imaging

Area of Science:

• Chemical Biology
• Molecular Imaging
• Materials Science

Background:

• Development of advanced molecular probes is crucial for sensitive biological imaging.
• Near-infrared (NIR) fluorescent probes offer advantages for deep tissue penetration and reduced autofluorescence.
• Multivalency and tunable binding properties are key for enhancing probe efficacy and specificity.

Purpose of the Study:

• To describe a programmable pre-assembly method for creating NIR fluorescent molecular probes.
• To demonstrate tunable multivalent binding properties of these probes.
• To evaluate their utility in fluorescence microscopy and in vivo imaging, particularly for bone targeting.

Main Methods:

• A modular assembly process involving threading macrocycles onto a fluorescent PEGylated squaraine scaffold.
• Incorporation of multiple targeting ligands onto the macrocycle periphery.
• Characterization using spectrometric methods and gel electrophoresis.
• Evaluation of spectral features like red-shift and energy transfer for diagnostics.
• Testing of bone-targeting probes in a mouse model.

Main Results:

• Successful synthesis of high-purity threaded complexes with tunable multivalent binding.
• Demonstrated effectiveness of probes in fluorescence microscopy and in vivo imaging.
• Enhanced bone accumulation observed with a probe featuring 12 bone-targeting ligands compared to one with six.
• High mechanical and chemical stability of probes confirmed by 24-hour fluorescence retention at the bone target site.
• Versatility of the pre-assembly method for generating probe libraries.

Conclusions:

• The described pre-assembly method provides a versatile platform for creating NIR fluorescent molecular probes.
• Tunable multivalency and high stability are achievable, enhancing imaging and diagnostic capabilities.
• This method enables combinatorial production of probe libraries for diverse applications in molecular imaging and diagnostics.