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 μA/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 5.0×10⁻⁵ to 2.5×10⁻³ M, with a response time of less than 8 sec. The detection limit of the biosensor is 4.0 μM, 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 °C.
Advanced Science Letters Vol. 3, Issue 4, p. 476-481