Comparison of Disk and Nanotip Electrodes for Measurement of Single-Cell Amperometry during Exocytotic Release

We compare single-cell amperometric measurements of exocytosis from pheochromocytoma (PC12) cells between two types of electrodes, carbon fiber disk microelectrodes and nanotip conical-shape carbon fiber microelectrodes. During the exocytotic process, individual exocytotic release events, measured as current spikes at the electrode, offer quantitative and dynamic information about the chemical release from cells. Using two electrodes gives rise to an unequal distance between the fusion pore and the electrode as well as fusion pore size, which leads to different average spike shapes. Nanotip electrodes show a slightly higher and narrower spike than disk electrodes when measuring exocytosis. The estimated pore-electrode distance and fusion pore size for disk electrodes are 239 and 11.5 nm, while for nanotip electrodes, these are 215 and 18.2 nm, respectively. The data show that nanotip electrodes, despite showing slightly different dynamics for release, are quantitative in measuring the number of molecules released and can be used for quantitative comparison between exocytosis and vesicular content in intracellular vesicle impact electrochemical cytometry.