Fig. 1. Non-invasive monitoring of dissolved gases in routine human cell cultures using luminescence-based optical sensors.

(Top left inset) simplified schematic depicting a macroscopic view of the dO₂ (left) and dCO₂ (right) sensor spots affixed to the growth substrate (inside of the culture vessel). The fiber-optic probes transfer light at a specified wavelength from outside of the vessel to excite the sensor spots, which then emit a fluorescent signal. These signals are equated to concentration values for dO₂ and dCO₂. For each cell line assessed, levels of dO₂ and dCO₂ were non-invasively monitored in the culture medium of three identical flasks using luminescence-based optical sensor spots every 8 h. In parallel, three culture flasks were sacrificially sampled for pH measurements and live-cell counts, yielding a time course of pH, dO₂, dCO₂, and live cell counts. (Top right inset) timeline of sampling regime showing the timing of pH (blue dots), dO₂ (yellow) dots, dCO₂ (red dots), and live cell counts (green dots). n = 3 measurements (biological replicates) for each variable at each 8 h time-point.