A ruthenium-rhodamine complex as an activatable fluorescent probe.

Area of Science:

• Coordination Chemistry
• Photochemistry
• Biomedical Imaging

Background:

• Ruthenium-bipyridyl complexes are widely studied for their photophysical properties.
• Rhodamine dyes are known for their strong fluorescence but can suffer from photobleaching and aggregation.
• Developing light-activated probes with enhanced fluorescence and low toxicity is crucial for biological applications.

Purpose of the Study:

• To synthesize and characterize a novel ruthenium-bipyridyl complex with a rhodamine-based fluorescent ligand.
• To investigate the light-induced release of rhodamine and subsequent fluorescence enhancement.
• To evaluate the potential of this complex as a biologically friendly caged fluorescent probe for imaging and flow analysis.

Main Methods:

• Synthesis of a ruthenium-bipyridyl complex incorporating a rhodamine moiety.
• Photophysical characterization including fluorescence spectroscopy and quantum yield measurements.
• Demonstration of visible-light activation and rhodamine release.
• Application studies as a neuronal marker and flow profiler in model systems.

Main Results:

• A novel ruthenium-bipyridyl complex with a rhodamine ligand was successfully synthesized and characterized.
• The complex exhibited weak fluorescence due to rhodamine quenching, which increased nearly 6-fold upon visible-light irradiation.
• A fast and clean heterolytic reaction was observed, releasing the rhodamine fluorophore.
• The probe demonstrated low toxicity and was successfully used for neuronal marking and flow profiling.

Conclusions:

• This work presents the first visible-light activatable fluorophore based on transition metal chemistry.
• The developed probe is biologically friendly, non-toxic, and suitable for caged fluorescence applications.
• The probe shows promise for advanced applications in neuronal imaging and flow analysis techniques like flow injection analysis (FIA).