A multi-parameter and simultaneous study of energy metabolism, oxygenation and intracellular pH using metabolic FLIM and PLIM of novel iridium phosphorescent complexes (SIMOPI)

• Applicant: Dr. Angelika Rück
• Subject Area: Medical Physics, Biomedical Technology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449775525

The development of metabolic disorders causes significant changes in the energy metabolism and mitochondrial respiration of cells. This can have an adverse influence on other factors such as cellular pH level and/or oxygen tension. Glycolytic metabolic pathways, reverse pH gradient and hypoxic status are often combined. Therefore, a parallel study is desired showing the influence of different oxygenation on the alteration of energy metabolism, followed by possible induction of abnormal cellular acidic or alkaline stress that finally inhibits cellular respiration. Our project is an agreed collaboration between the University of Ulm and the St. Petersburg State University that performs simultaneous studies demonstrating the relationship between mitochondrial energy metabolism, intracellular and mitochondrial pH and oxygen levels in both normal and cancer cells using time resolved fluorescence and phosphorescence lifetime imaging methods. We will investigate the influence of different aerated and hypoxic micro-environmental conditions by using phosphorescent sensors which are both oxygen and hydrogen ion sensitive. As phosphorescent sensors novel synthesized complexes based on Ir(III), where iridium is in oxidation state III, will be used. Simultaneously, cell metabolism will be monitored by the autofluorescence intensity and fluorescence lifetime of metabolic coenzymes as nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). The German research group has extensive knowledge and experience with luminescence lifetime techniques (FLIM/PLIM) to study energy metabolism and associated changes in intracellular and extracellular pH as well as cellular oxygenation. On the other hand, the research group in Russia has extensive expertise in the design, synthesis and applications of novel phosphorescent transition metal complexes. In this framework, the German research group will perform in-vitro experiments and assays with human keratinocytes HaCaT and oral squamous carcinoma cell lines SCC under different oxygen levels. Metabolic modifications and possible alterations in pH will be investigated using FLIM of NADH and FAD and PLIM of novel phosphorescent iridium sensor probes. Visits of the participants are planned on both sites. Two-photon excited FLIM/PLIM imaging with time correlated single photon counting (TCSPC) will be used in the study. Our efforts will generate new tools for investigating functional phosphorescence lifetime imaging with novel iridium complexes. The result will be knowledge on the correlation between energy metabolism, oxygen tension, and intracellular pH levels. The timespan of the collaborative project is expected to be 3 years. A possible project extension might encompass novel oxygen and pH sensing in complex cellular systems as organoids and resected biopsies with advanced improvements for clinical diagnostic applications.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research, until 3/2022
• Cooperation Partner: Ilya Kritchenkov, until 3/2022