Development of an Array of Ion-Selective Microelectrodes Aimed for the Monitoring of Extracellular Ionic Activities

In this study, we present the development and the characterization of a generic platform for cell culture able to monitor extracellular ionic activities (K+, NH4+) for real-time monitoring of cell-based responses, such as necrosis, apoptosis, or differentiation. The platform for cell culture is equipped with an array of 16 silicon nitride micropipet-based ion-selective microelectrodes with a diameter of either 2 or 6 μm. This array is located at the bottom of a 200-μm-wide and 350-μm-deep microwell where the cells are cultured. The characterization of the ion-selective microelectrode arrays in different standard and physiological solutions is presented. Near-Nernstian slopes were obtained for potassium- (58.6 ± 0.8 mV/pK, n = 15) and ammonium-selective microelectrodes (59.4 ± 3.9 mV/pNH4, n = 13). The calibration curves were highly reproducible and showed an average drift of 4.4 ± 2.3 mV/h (n = 10. Long-term behavior and response after immersion in physiological solutions are also presented. The lifetime of the sensors was found to be extremely long with a high recovery rate