Water-soluble, deep-red fluorescent squaraine rotaxanes

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Biomedical Imaging

Background:

• Fluorescent tracers are essential tools in biological research and medical diagnostics.
• Developing stable, water-soluble, and highly emissive deep-red fluorophores remains a challenge.
• Rotaxanes offer unique structural properties for designing novel molecular probes.

Purpose of the Study:

• To synthesize and characterize novel fluorescent squaraine rotaxanes.
• To evaluate their chemical stability and performance as water-soluble fluorescent tracers.
• To assess their suitability for in vivo imaging applications.

Main Methods:

• Synthesis of eight distinct fluorescent squaraine rotaxanes.
• Spectroscopic analysis to determine absorption and emission properties.
• Chemical stability assays.
• In vivo studies in living mice to evaluate biodistribution and clearance.

Main Results:

• Successfully prepared eight fluorescent squaraine rotaxanes with deep-red emission.
• Identified squaraine rotaxanes with four large stopper groups exhibiting enhanced chemical stability.
• Demonstrated that two specific compounds possess high fluorescence, rapid renal clearance, and minimal tissue uptake in mice.
• Confirmed their suitability as water-soluble, fluorescent tracers.

Conclusions:

• Squaraine rotaxanes with appropriate structural modifications can serve as effective deep-red fluorescent tracers.
• The presence of large stopper groups is crucial for enhancing chemical stability.
• These optimized squaraine rotaxanes show significant potential for in vivo imaging applications due to favorable pharmacokinetic properties.