Methods for Oxygen Determination in an NMR Bioreactor as a Surrogate Marker for Metabolomic Studies in Living Cell...

Nuclear magnetic resonance (NMR) approaches have been described as a powerful method for measuring oxygen in tissue cultures and body fluids by using relaxation time dependencies of substances on pO₂. The present NMR study describes methods to longitudinally monitor global, in situ intracellular, and spatially resolved oxygen tension in culture media and 3D cell cultures using relaxation times of water without the need to use external sensors. ¹H NMR measurements of water using a modified inversion recovery pulse scheme were employed for global, i.e., intra- and extracellular oxygen estimation in an NMR-bioreactor. The combination of ¹H relaxation time T₁ and diffusion measurements of water was employed for in situ cellular oxygen content determination. Spatially selective water relaxation time estimations were used for spatially resolved oxygen quantification along the NMR tube length. The inclusion in a study protocol of the presented techniques for oxygen quantification, as a surrogate marker of oxidative phosphorylation (OXPHOS), provides the possibility to measure mitochondrial respiration and metabolic changes simultaneously.