Platinized Aligned Carbon Nanotube-Sheathed Carbon Fiber Microelectrodes for In Vivo Amperometric Monitoring of Oxygen

The abnormal level of O-2 could disturb various neurochemical processes and even induce neural injury and brain dysfunction. In order to assess critical roles of O-2 in the neurochemical processes, it is essential to perform in vivo monitoring of the dynamic changes of O-2. In this study, we develop a new electrochemical method for selectively monitoring O-2 in vivo, using platinized vertically aligned carbon nanotube (VACNT)-sheathed carbon fibers (Pt/VACNT-CFs) as the electrodes. The VACNT-sheathed CFs (VACNT-CFs) are produced via the pyrolysis of iron phthalocyanine (FePc) on the surface of CFs, followed by electrochemical deposition of platinum nanoparticles to form Pt/VACNT-CFs. The resulting Pt/VACNT-CF microelectrodes exhibit fast overall kinetics for the O-2 reduction via a four-electron reduction process without the formation of toxic H2O2 intermediate. Consequently, effective and selective electrochemical methods are developed for the measurements of O2 in rat brain with the Pt/VACNT-CF microelectrodes, even in the presence of some species at their physiological levels, such as ascorbic acid, dopamine, uric acid, 5-hydroxytryptamine, and of the O-2 fluctuation in rat brain in the early stage of global cerebral ischemia/reperfusion, mild hyperoxia, and hypoxia induced by exposing the animal, for a short time, to O-2 and N-2 respectively, and hindfeet pinch. The use of VACNT-CF as the support for Pt effectively improves the stability of Pt, as compared with the bare CF support, while the FePc pyrolysis ensures the VACNT-CFs to be reproducibly produced. Thus, this study offers a novel and reliable strategy for preparing new microelectrodes for in vivo monitoring of O-2 in various physiological processes with a high sensitivity and selectivity.