Ultramicro‐H2O2 Electrode for Fabrication of the in Vivo Biosensor

Recent studies have demonstrated that the in vivo electrochemical sensor is a powerful tool for clinical and neurochemical monitoring. Such a sensor is required to be very small in size, highly reliable, and simple to operate. Carbon fiber has been considered to be one of the useful materials for ultramicroelectrodes. Selectivity of the carbon fiber electrode is strongly dependent on the potential range of the electroactive species. For example, this electrode can respond to several compounds such as dopamine, its derivatives, and ascorbic acid, which oxidize approximately at similar potential. Therefore, some modifications are required to improve the selectivity of the carbon fiber electrode. Biosensors are analytical devices that combine a molecular recognition element of biological origin with a physicochemical transducer. Biosensors possess excellent selectivity because a catalyzed reaction in a biological system requires specific substrates. The detection of hydrogen peroxide has become an established approach to the construction of biosensors based on electrodes containing immobilized oxidases. Reactions catalyzed by oxidases produce hydrogen peroxide, which can be detected with several electrodes. Aoki et al. reported that the carbon fiber electrode could be applied in determining concentrations of hydrogen peroxide higher than 0.1 mM. However, more sensitive detection of hydrogen peroxide was not successful because of the difficulty in background correction.' Our previous results indicate that rigid control of the preelectrolysis (activation) provides excellent sensitivity and reproducibility. In this study, electrochemical operations for preelectrolysis and measuring have been examined in order to determine hydrogen peroxide sensitivity. Reduction of inhibitions based on ascorbic acid and albumin protein is also discussed. Moreover, this carbon fiber electrode is applied to the biosensor configuration for glucose detection.