Reagentless amperometric glucose biosensor based on the immobilization of glucose oxidase on a ferrocene@NaY zeolite composite

Ferrocene (Fc) was encapsulated in the cavities of a NaY zeolite by vapor diffusion via sublimation at below 100 A degrees C. The resulting Fc@NaY zeolite composite was investigated by power X-ray diffraction, diffuse reflectance UV-vis and FT-IR spectroscopy, and by cyclic voltammetry. The results indicated that Fc was encapsulated into the zeolite whose microporous structure had remained intact. The Fc in the silica matrix had retained its electroactivity and did not leach out. A glucose biosensor was obtained by immobilization of the modified zeolite and glucose oxidase on a carbon paste electrode. It displays a linear response to glucose (from 0.8 mu M to 4.0 mM), a detection limit of 0.2 mu M, and a response time of 4 s. The good performance of the biosensor is ascribed to the biocompatibility of the zeolite and presence of Fc which facilitates the electron transfer from the enzyme to the surface of the electrode.