Fig. 5: Oxygen gradient stimulation with spatiotemporal detection.

a Eleven positions within the oxygen gradient were selected as regions of interest for calcium, ATP, and insulin responses. b Fura ratios for oxygen concentrations were recorded at 1-min intervals for 46 time points. The Fura ratios remained relatively low until above 10%, where they increased with increasing oxygen. The observed transient oscillations suggested nuances to calcium signaling, which led to subsequent Fourier analysis. Note that this 1-min sampling was significantly slower than the 15 s acquisition that we achieved for the fixed location, single oxygen imaging in the previous figure. Thus, these results could potentially underestimate actual calcium oscillations. c Insulin secretion was quantified via a built-in sensor. A jump occurred at oxygen levels of approximately 8–12% (*p = 0.057). d Mitochondrial ATP was quantified via fluorescence labeling, showing modest increases until the same 8–12% oxygen range, where the response dipped before rising again near 20%. These results suggested that Beta TC6 cells did mount ATP responses to glucose. These responses exhibited a transition between 8–12% oxygen that may be related to changes in metabolites