Fiber-optic flow-through sensor for online monitoring of glucose

A new microdialysis-based glucose-sensing system with an integrated fiber-optic hybrid sensor is presented. Design and dimensions of the cell are adapted for its coupling with commercially available microdialysis techniques, thereby providing a new system for continuous glucose monitoring. The glucose level is detected via oxygen consumption which occurs as a consequence of enzymatic reaction between immobilized glucose oxidase and glucose. The use of gas-permeable Tygon tubing ensures complete and constant air-saturation of the measuring fluid in the cell. Nevertheless, a reference oxygen optode is used to detect and to compensate response changes caused by events like bacterial growth, temperature fluctuations, or failure of the peristaltic pump. In contrast to widely used electrochemical sensors, the response of the microdialysis-based fiber-optic glucose sensor is highly selective, making this sensor approach particularly advantageous for continuous glucose monitoring of patients in intensive care units. The effects of flow rate, pH, temperature, and common interferences on the sensor response are presented and discussed in detail. The sensor is evaluated in vitro using a 3-day continuous test in glucose-spiked plasma. The ability to measure glucose in humans is demonstrated by coupling the flow-through cell and commercially available microdialysis catheter CMA60. A 24-h monitoring test using this setup is successfully applied to a healthy volunteer.