FIG. 7.

H₂O₂ production and degradation by MCs: validation of single-cell measurements using the ElProScan with cell population measurements by ESR and an AUR assay. (A, B) Chronoamperometric (CA) measurements of single MCs (n = 5–11) with a 10 μm Pt-UME versus Ag/AgCl. (C) Control in cell-free PBS-I (n = 4). (D, E) Cell population measurements with ESR (n = 3). (F) Control in cell-free PBS-I (n = 3). (G, H) Cell population measurements with the fluorescence-based AUR assay (n = 3). (I) Control in cell-free PBS-I (n = 11). For each approach in (A–I), one representative experiment is shown; results for ESR and AUR are expressed in arbitrary/fluorescence units (AU and FU, respectively). While CA measurements were conducted continuously (1 Hz sampling rate), in ESR- and AUR experiments, H₂O₂ was determined at selected time points for a pool of 25,000 cells each. Protocol for all experiments: 1 μM of the phorbol ester TPA (or its solvent DMSO, 0.2%) was applied 30 min after the initial equilibration phase. Thirty to 40 min later, either H₂O₂ (10 μM) or A. dest. was added. The same protocol was followed for cell-free control experiments shown in C, F, I, with TPA being replaced by DMSO. (A, D, G) TPA-stimulated cells with (red) and without (black) further treatment with H₂O₂. (B, E, H) Unstimulated cells challenged with H₂O₂ (red) or A. dest. (black). (C, F, I) Cell-free control experiments with DMSO and H₂O₂ (red) or A. dest. (black). AUR control experiments were terminated by addition of catalase (100 U/mL; arrow) to test the assay for selectivity to H₂O₂. AUR, Amplex^® UltraRed.