An Amperometric Biosensor Based on Glucose Oxidase Immobilized in a Sol-Gel Polyvinyl Alcohol/Silica Hybrid Composite Film on a Prussian Blue Modified Electrode

An amperometric glucose biosensor was fabricated by entrapment of glucose oxidase in a composite matrix of silica sol-gel and polyvinyl alcohol physically layered on top of a Prussian blue-modified Pt electrode. This biosensor functions through the detection of hydrogen peroxide produced by the glucose oxidase-catalyzed oxidation of glucose at -0.05 V. The biosensor exhibited high selectivity, and a sensitivity of 3.41 mu A/mM, due to a combination of electroreduction of H2O2 at the surface of the modified Pt electrode at low potential and a sympathetic microenvironment for enzyme immobilization provided by the silica sol-gel. The biosensor had a linear response to glucose over the range 5.0 x 10(-5) to 2.5 x 10(-3) M, with a response time of less than 8 sec. The detection limit of the biosensor is 4.0 mu M, based on a signal-to-noise ratio of 3. The biosensor exhibits satisfactory long-term stability; 85% of its original activity was retained after 30 days of storage in phosphate buffer (pH 6.9; 0.1 M) at 4 degrees C.