Phosphorescent cationic iridium(iii) complexes dynamically bound to cyclodextrin vesicles: applications in live cell...

Area of Science:

• Supramolecular Chemistry
• Bioinorganic Chemistry
• Cellular Imaging

Background:

• Iridium(iii) complexes are known for their phosphorescent properties, useful in imaging.
• Cyclodextrin vesicles (CDV) can encapsulate molecules for targeted delivery.
• Functionalizing complexes for specific binding enhances their utility.

Purpose of the Study:

• To develop novel cationic iridium(iii) complexes for high-affinity binding to cyclodextrin vesicles (CDV).
• To investigate the photophysical properties of these complexes when bound to CDV.
• To evaluate the potential of these Ir(iii)-CDV conjugates for live cell imaging and mitochondrial staining.

Main Methods:

• Synthesis of cationic Ir(iii) complexes functionalized with adamantyl groups.
• Characterization of the binding affinity between Ir(iii) complexes and CDV using association constants (K_a).
• Spectroscopic analysis (emission spectra, quantum yields) of the complexes in solution and when bound to CDV.
• Cellular uptake studies and live cell imaging using fluorescence microscopy to visualize mitochondrial staining.

Main Results:

• Cationic Ir(iii) complexes functionalized with adamantyl groups exhibit high affinity (K_a = 1 × 10⁶ M^-1) for CDV.
• The emission of the Ir(iii)-CDV adducts is significantly enhanced and blue-shifted compared to free complexes.
• The enhanced emission is attributed to restricted mobility and a less polar environment at the vesicle surface.
• Ir(iii)-decorated CDV are efficiently internalized by cells.
• The complexes selectively stain mitochondria in live cells, demonstrating their utility in live cell imaging.

Conclusions:

• Adamantyl-functionalized cationic Ir(iii) complexes effectively bind to CDV, creating a robust host-guest system.
• The Ir(iii)-CDV conjugates display improved photoluminescent properties suitable for bioimaging.
• CDV serve as efficient carriers for delivering Ir(iii) complexes into cells for targeted mitochondrial visualization.