A ratiometric sensor for DNA based on a dual emission Ru(dppz) light-switch complex

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Photochemistry

Background:

• Ruthenium complexes are explored for their photophysical properties and potential biological applications.
• Understanding DNA-metal complex interactions is crucial for developing novel diagnostic and therapeutic agents.
• Dual emission properties in metal complexes offer unique sensing capabilities.

Purpose of the Study:

• To synthesize and characterize novel water-soluble ruthenium complexes.
• To investigate the DNA binding modes and affinities of these complexes.
• To explore the potential of these complexes as DNA sensors based on their emission changes.

Main Methods:

• Synthesis and characterization of ruthenium complexes.
• Spectroscopic techniques (UV-Vis absorption, emission spectroscopy) to study DNA binding.
• Computational modeling to understand excited states and binding interactions.
• Affinity measurements using fluorescence titration.

Main Results:

• Both ruthenium complexes exhibit dual emission from metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT) excited states.
• One complex shows groove binding, while the second exhibits both groove binding and intercalation into duplex DNA.
• Both complexes bind DNA with high affinity.
• The intercalating complex displays a significant increase in MLCT emission upon DNA binding, while LLCT emission remains unchanged, enabling ratiometric sensing.

Conclusions:

• The studied ruthenium complexes possess favorable DNA binding properties and unique photophysical characteristics.
• The complex with an intercalating Ru(II)(dppz) moiety serves as the first ratiometric sensor for DNA.
• These findings open avenues for developing advanced DNA-responsive luminescent probes.