A fiberoptic cholesterol biosensor with an oxygen optrode as the transducer.

A biosensor for the continuous optical determination of cholesterol is presented. Cholesterol oxidase is immobilized covalently on a nylon membrane and the consumption of oxygen is measured by following, via fiberoptic bundles, the changes in fluorescence of an oxygen-sensitive dye whose fluorescence is dynamically quenched by molecular oxygen. The dye is dissolved in a very thin silicone membrane placed beneath the enzyme layer. During interaction of the enzyme with cholesterol, oxygen is consumed, which is indicated by the fluorescent dye. At pH 7.25, the analytical range of the sensor is 0.2 to 3 mM and the time to reach a full steady state in a flowing solution ranges from 7 to 12 min.