Fig. 4

SPRM uncovers high-resolution sub-cellular oscillations in pancreatic beta-cells. (a) SPRM image highlighting two ROIs: I and II corresponding to a cell and the extracellular background, respectively. The image is segmented into multiple channels (pixels) of 1 μm² labelled (i,j). (b) A stack of channels demonstrating ultra-high-density recording of normalized intensity oscillations with a resolution of 1 μm², shown in b(i). Exemplar traces are presented in b(ii) and b(iii) for the background and cell channels, respectively. (c) Pearson’s cross-correlation between the ultra-high-density channels, mapped in c(i) with the corresponding histogram depicted in c(ii). In b(i) and c(i), the cells are located between channels 4000 and 6000. (d) The map illustrates the outcome of Pearson’s cross-correlation, comparing a signal extracted by averaging an exemplar individual cell (with ROI I used as an example) to the local high-density sub-cellular signals (i.e., channels). This analysis highlights both the spatial and temporal heterogeneity present in the resulting signals.