Fiber-optic glucose biosensor based on glucose oxidase immobilised in a silica gel matrix

A monolithic silica gel matrix with entrapped glucose oxidase was constructed as a bioactive element in an optical biosensor for glucose determination. Physicochemical and biochemical characterizations of the catalytic matrix were performed, and the intrinsic fluorescence of immobilised glucose oxidase (GOD) was investigated in the UV and visible range by performing steady state and time course measurements. In all cases, the silica gel matrix proved to be a suitable support for optical biosensing owing to its superior optical properties (e.g., high transmittance and reliable fluorescence and GOD absorption spectra after immobilisation). From steady state measurements, calibration curves were obtained as a function of glucose concentration. When time course measurements were performed, the silica gel support displayed a larger linear calibration range and higher sensitivity than other immobilisation systems. In addition, a glucose optical biosensor was developed and characterised using as catalytic element GOD immobilised on a gel disk bound to a bundle of optical fibres.