A hydrogen peroxide biosensor based on Al2O3 sol-gel immobilizing horseradish peroxidase and thionine

Horseradish peroxidase was selected as a model enzyme to fabricate a novel biosensor based on the co-immobilization of thionine. The interaction between enzyme and sol-gel was further studied by ultraviolet-visible spectrum, which showed that sol-gel did not affect the bioactivity of the enzyme. The optimum conditions were pH 7.0, 25 degreesC, the applied potential was -0.22 V. The biosensor had a fast response with a linear calibration range of 1.76 x 10(-3) similar to 5.5 x 10(-2) mol/L, a detection limit of 1.1 x 10(-4) mol/L. Both sensitivity and selectivity of the biosensor were ideal. The biosensor remained 80% of its activity after using three weeks.