Physiological differences between spheroids of varying sizes at separate sampling times.

Oxygen concentration over time (Δ % O2) within the spheroids is reported as individual linewidth of the spheroids as a percentage of the fully oxygenated probe and media linewidth. The viable rim of the spheroid, where oxygen is not limited, is calculated based on the total oxygen measurable in the spheroid. The hypoxic zone, where oxygen is limited, is calculated based on the determination of the viable rim, the refinement of which allows for the quantification of the size of the senescent zone within the RTG-2 spheroid. Results are presented as the average of three individual experiments.