Spatial resolution of exocytosis across a single cell by a microwell-based individually addressable thin film ultra-microelectrode array

We report the fabrication and characterization of micro well-based individually addressable ultra-microelectrode arrays (MEAs) and their application to spatially and temporally resolved detection of neurotransmitter release across a single pheochromocytoma (PC 12) cell. The MEAs consist of sixteen 4-μm-width square microelectrodes, or twenty-five 3-μm-width square microelectrodes, or thirty-six 2-jim-width square microelectrodes. Each MEA is tightly defined in a 30×30 μm square area, which is further encased inside a 40×40 μm SU-8 microwell. We demonstrate the excellent stability and reproducibility of these microelectrodes by using cyclic voltammetry and we have performed recording of spatially resolution of single cell exocytosis with multiple ultra-microelectrodes in 2-μm resolution.