Profiling H2O2 from single COS-7 cells by means of scanning electrochemical microscopy

We report quantitative determination of extracellular H2O2 released from single COS-7 cells with high spatial resolution, using scanning electrochemical microscopy (SECM). Our strategy of depth scan imaging in vertical x-z plane was conveniently utilized to a single cell for obtaining probe approach curves (PACs) to any positions on the membrane of a live cell by simply drawing a vertical line on one depth SECM image. This SECM mode provides an efficient way to record a batch of PACs, and visualize cell topography simultaneously. The H2O2 concentration at the membrane surface in the center of an intact COS-7 cell was deconvoluted from apparent O2, and determined to be 0.020 mM by overlapping the experimental PAC with the simulated one having a known H2O2 release value. The H2O2 profile determined in this way gives insight into physiological activity of single live cells. In addition, intracellular H2O2 profile was demonstrated using confocal microscopy by labelling the cells with a luminomphore, 2′,7′-dichlorodihydrofluorescein diacetate. The two methodologies have illustrated complementary experimental results of H2O2 detection, indicating that H2O2 generation is centered at endoplasmic reticula. [Display omitted] •Extracellular H2O2 of single COS-7 cells was spatially determined using SECM.•Depth scan imaging was used for PACs above any position of the cell.•The H2O2 concentration above single and confluent cells were deconvoluted from O2.•Intracellular H2O2 profile was shown using confocal microscopy.•Insight into physiology and pathology of any single live cells is anticipated.