E. Suraniti, S. Ben-Amor, P. Landry, M. Rigoulet, E. Fontaine, S. Bottari, A. Devin, N. Sojic, N. Mano, S. Arbault
Angew. Chem. Int. Ed. 2014, 126, 6773-6776.

Mitochondria consume oxygen at the respiratory chain and convert redox energy into ATP. As a side process, they produce reactive oxygen species (ROS), which physiological activities still need to be understood. However, current analytical methods do not allow monitoring quantitatively and unambiguously mitochondrial ROS. We have developed electrochemical biosensors based on peroxidase-redox polymer-modified electrodes, providing a selective detection of H2O2 with nanomolar sensitivity, a linear response over 5 concentration-decades and fast response-time. The release of H2O2 by mitochondria was then monitored under phosphorylating or inhibited respiration conditions. We report the detection of two concomitant regimes of H2O2 release: large fluxes (hundreds of nM) under complex III-inhibition, and bursts of a few nanomolars immediately following mitochondria activation. These unprecedented bursts of H2O2 are assigned to the role of mitochondria as the hub of redox signaling in cells.