Application of Prussian blue based composite film with functionalized organic polymer to construction of enzymatic glucose biosensor

We describe and characterize an amperometric biosensor utilizing the electrocatalytic reduction of hydrogen peroxide at a glassy carbon electrode modified with a novel composite film of Prussian Blue and polypyrrole derivative, polymerized 4(pyrrole-1-yl) benzoic acid, overcoated with the covalently bound glucose oxidase enzyme. The addition of a functionalized organic component to Prussian Blue permits permanent attachment of an enzyme, exhibits an overall stabilizing effect, and it seems to support fast propagation of charge within the Prussian Blue based composite film. Preliminary diagnostic experiments have been done using cyclic voltammetry, chronocoulometry and rotating disk volatmmetry. The rate of hydrogen peroxide reduction at the composite film in the potassium containing phosphate buffer (pH 6) is expected to be very fast because the overall process is controlled by diffusion of hydrogen peroxide in solution. The fact that the reduction of enzymatically produced hydrogen peroxide proceeds at a fairly negative potential, 0 V (vs. SCE) (pH 6), makes the system largely free of common interferences (e.g., ascorbic acid or uric acid). The proposed biosensor permitted reproducible and reliable determinations of glucose in real (i.e., in pharmaceutical and food) samples also under the flow-injection analysis conditions. The detection limit and sensitivity have been found to be on the level of 1 x 10(-5) mol dm(-3) and 0.7 muA/1 mmol dm(-3) (2.5 muA/cm(2)/1 mmol dm(-3)), respectively.