Investigation of Intracellular Reactions Using Ultramicroelectrodes

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1. Ultramicro Pt disk electrodes with tip radii less than 5mum were fabricated via the processes ; electrochemical etching of Pt wire, sealing the Pt fine wire with a soft glass, and polishing the tip. The electrochemical characteristics of the resultant microelectrodes was investigated and found that constant potential amperometry and differential amperometry for oxygen reduction using the microelectrodes afford the oxygen concentration in the local region.2. Intracellular oxygen concentration in a protoplast from Bryopsis plumosa was determined by constant current amperometry. The intracellular oxygen reduction current increased upon light irradiation, indicating that the real-time tracing of the intracellular oxygen is possible by the present method. From the detailcd analyzes of diferential amperometric measurements using the microelectrode located near the cell, the oxygen influx or efflux was determined at a single cell level.3. The permeability of Ru (NH3) 63+ and Fe (CN) 63- through an ion channel in a planar lipid membrane was evaluated by amperometric measurements using microelectrode located near the membrane. The membrane permselectivity of the viable protoplast was also carried out by amperometry.4. Micro NO sensor and micro O_2 sensor were fabricated by immobilizing respectively Ni porphyrin and superoxide dismutase/catalase onto microelectrodes. We implanted these microsensors into rat brain and measured in vivo concentrations of NO and O_2