Electrochemical Microsensor for In Vivo Measurements of Oxygen Based on Nafion and Methylviologen Modified Carbon Fiber Microelectrode

An electrochemical microsensor based on carbon fiber microelectrode (CFME) chemically modified with the perfluorinated cation-exchange polymer, Nafion and methylviologen (MV) and its application for in vivo voltammetric measurements of oxygen (O2) are described. The microsensor shows a high catalytic activity for the reduction of O2 with a good reproducibility, high sensitivity and selectivity and significant ability against electrode fouling. The current is linear with the concentration of O2in a range from 9.0×10–6to 2.0×10–4 mol/L with a calculated detection limit, at a signal-to-noise ratio of 3 to 1, of 5.0×10–6 mol/L and correlation coefficient of 0.9985. The relative standard deviation for 2.0×10–4 mol/L O2 is 1.7% (n = 2). Some compounds common to biological fluids such as glucose, ascorbic acid, uric acid, catecholamine, glutamate, glutathione, Mg2+, Ca2+, Na+, K+and Cl–are tested in vitro and show no interferences with the voltammetric responses to O2. In vivo performance of the O2 microsensors is demonstrated by measurements of local changes in O2 in the brain of anesthetized rat before and during transient ischemia.