Miniaturized fiber-optic hybrid sensor for continuous glucose monitoring in subcutaneous tissue

A new optical fiber microsensor for continuous measurement of glucose in subcutaneous tissue is described. The hybrid sensor consists of two oxygen optodes wherein one optode contains immobilized glucose oxidase. The glucose signal which is a difference between pO2 of both optodes allows the compensation of oxygen fluctuations in intercellular fluid. Based on the results of investigations of the oxygen dependence on sensor response, the optimization by thickening the diffusion barrier of glucose sensitive optode is done. The loss of the sensing resolution for glucose is compensated by the increased sensitivity of the oxygen transducer at the low oxygen concentrations. The optimized sensor is free of oxygen fluctuations in the expected pO2 range between 53 and 95 hPa and the sensor output is linear in the physiological relevant glucose range up to 20 mM. The use of the reference oxygen sensor allows also the compensation of the slight temperature fluctuations.