EXPLORING THE POTENTIAL OF CYCLOMETALATED IRIDIUM COMPLEXES IN IMAGING AND OTHER APPLICATIONS

Asst. Prof. Filip Kielar
Lecture of Institute guest
18.10.2024 10:30, Lecture room A

Cyclometalated iridium complexes are interesting compounds with intriguing photophysical properties. They exhibit facile emission wavelength tunability, large Stokes shifts, and long luminescence lifetimes. This makes these compounds interesting for use in biological imaging, sensing, lighting, catalysis, and other applications. Inspired by their properties and their limited utilization in imaging, we focused our efforts on tris-cyclometalated iridium complexes derived from the archetypal structure [Ir(ppy)3]. Initially, we have demonstrated the utility of these tris-cyclometalated iridium complexes carrying an aminoalkyl substituent on one of the ppy ligand in fluorescence microscopy. Furthermore, we have also investigated a tris-cyclometalated iridium complex equipped with a dpa chelator as a potential metal ion sensor. More recently, we focused our attention on designing multifunctional imaging probes for biological imaging based on a polymeric system containing such a tris-cyclometalated iridium emitter. The system was constructed using copolymers of N-(2-hydroxypropyl)methacrylate (HMPA), which offer the possibility to include several functional components in a single molecule. We have constructed such a system (iBody) using an iridium based luminescent probe, glutamate carboxypeptidase II (GCPII) targeting ligand, and a biotin affinity tag. The synthesized macromolecular probes differed in the structure of the polymer and content of the iridium complex. The applicability of the synthesized probes has been tested in flow cytometry (FACS) based assay, laser confocal microscopy, and fluorescence lifetime imaging (FLIM). The combined results from these investigations have shown that the targeted iBodies labelled with the iridium luminophore exhibit selective labelling of GCPII expressing cells. Particularly, the FLIM experiment has shown that the iBodies with the iridium label exhibit a lifetime greater than 100 ns, which distinguishes them from typically used systems labelled with organic fluorophores exhibiting short fluorescence lifetimes. Therefore, our results indicate that the synthesized probe exhibits interesting properties, which supports the development of additional biological tools utilizing the key components (iridium complexes, iBody concept) used in this system.

The lecture is presented in English