Spatiotemporal mapping of oxygen in a microbially-impacted packed bed using 19F Nuclear magnetic resonance oximetry

F-19 magnetic resonance has been used in the medical field for quantifying oxygenation in blood, tissues, and tumors. The F-19 NMR oximetry technique exploits the affinity of molecular oxygen for liquid fluorocarbon phases, and the resulting linear dependence of F-19 spin-lattice relaxation rate R-1 on local oxygen concentration. Bacterial biofilms, aggregates of bacteria encased in a self-secreted matrix of extracellular polymers, are important in environmental, industrial, and clinical settings and oxygen gradients represent a critical determinant of biofilm function. However, measurement of oxygen distribution in biofilms and biofouled porous media is difficult. Here the ability of F-19 NMR oximetry to accurately track oxygen profile development in microbial impacted packed bed systems without impacting oxygen transport is demonstrated. Time-stable and inert fluorocarbon containing particles are designed which act as oxygen reporters in porous media systems. Particles are generated by emulsifying and entrapping perfluorooctylbromide (PFOB) into alginate gel, resulting in oxygen-sensing alginate beads that are then used as the solid matrix of the packed bed. F-19 oxygenation maps, when combined with H-1 velocity maps, allow for insight into the interplay between fluid dynamics and oxygen transport phenomena in these complex biofouled systems. Spatial maps of oxygen consumption rate constants are calculated. The growth characteristics of two bacteria, a non-biofilm forming Escherichia coli and Staphylococcus epidermidis, a strong biofilm-former, are used to demonstrate the novel data provided by the method. (C) 2018 Elsevier Inc. All rights reserved.