Platinized aligned carbon nanotube-sheathed carbon fiber microelectrodes for in vivo amperometric monitoring of oxygen.

The abnormal level of O2 could disturb various neurochemical processes and even induce neural injury and brain dysfunction. In order to assess critical roles of O2 in the neurochemical processes, it is essential to perform in vivo monitoring of the dynamic changes of O2. In this study, we develop a new electrochemical method for selectively monitoring O2 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 O2 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 O2 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 O2 and N2, 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 O2 in various physiological processes with a high sensitivity and selectivity.