| An optical approach has been developed for a continuous measurement of glucose in physiological environments. This approach utilizes a small length of dialysis hollow fiber as the sensing element. The hollow fiber contains a carbohydrate receptor, Concanavalin A (Con A), immobilized on its inner surface and a high molecular weight fluorescein labelled dextran as a competing ligand. A single optical fiber is inserted in one end of the hollow fiber and both ends of the hollow fiber are sealed. The dialysis fiber is freely permeable to glucose, yet is essentially impermeable to the dextran contained within its luminal space. Both glucose and dextran bind to Con A. Glucose in the medium diffuses into the sensing element and competes with dextran for binding to Con A. At equilibrium, the level of free fluorescence in the fiber lumen is measured optically via the optical fiber and is correlated to the concentration of glucose. Contrary to the present detection techniques where the measurement is based on the consumption rate of glucose in an enzymatic or electrochemical reaction, this approach works in equilibrium conditions. The sensor neither consumes the reactant nor produces any product. |
