Excellent spatial and temporal resolution and physico-chemical properties of ultramicroélectrodes (UME) induce high detection sensitivity, thus being particularly well adapted to the study of biological mechanisms of secretion from a single cell. In the " semi-artificial synapse " configuration, the short distance between the transmitting cell and the UME causes appropriate local concentration to be electrochemically detected. UME allows the detection of minute amount of electroactive molecules in real time. This analytical technique was used, completed or adapted to study two major biological phenomena: vesicular exocytosis and cellular oxidative stress. Amperometric investigations of exocytosis, a key mechanism involved in cell communication, allow quantitative monitoring of the kinetics of intravesicular species release into extracellular medium. An UME, placed in the external environment, does not provide any information about vesicles status before fusion. In order to complement this information, we have developed, through microfabrication techniques, a device constituted by conductive and transparent ITO electrodes for combinated detection by amperometry and optical microscopy (TIRFM) for the study of BON BC21 cells secretion. Amperometry at four different constant potentials, used in the laboratory for the detection of ROS/RNS released by macrophages, immune cells, requires a large number of experiments to overcome the cell variability and differences in UME sensitivity. To significantly reduce the experimental duration, we have developed a device constituted by four measuring chambers, each containing a set of three electrodes. These four chambers will allow real time and simultaneous monitoring of changes in production of H2O2, ONOO-, NO* and NO2- by a single cell.
