A reagentless hydrogen peroxide biosensor based on the coimmobilization of thionine and horseradish peroxidase by their cross-linking with glutaraldehyde on glassy carbon electrode

A novel reagentless H2O2 sensor, based on the coimmobilization of horseradish peroxidase (HRP) and the redox dye thionine by their cross-linking with glutaraldehyde on the surface of a glassy carbon electrode, was fabricated. This resulting modified electrode exhibited good electrochemical activity in aqueous solution, and the electron transfer rate constant between the derivative thionine and glassy carbon electrode was about 0.097 s(-1) (calculated from Laviron method). The apparent surface coverage of thionine was about 8.54 x 10(-12) mol cm(-2). It was found that thionine could mediate the electron transfer of HRP with the electrode substrate. Performance and characteristics of the biosensor were evaluated with respect to response time, detection limit, applied potential, pH, and temperature. The results indicate that this biosensor is of high sensitivity to hydrogen peroxide with a low detection limit down to 1.0 x 10(-7) molL(-1). Moreover, dopamine, ascorbic acid, and uric acid did not interfere with the determination of H2O2. Meanwhile, this enzyme electrode also showed good stability and reproducibility for long-term use.