Determination of glucose in blood based on the intrinsic fluorescence of glucose oxidase

A method for the determination of glucose based on the alteration of the intrinsic fluorescence of glucose oxidase during the enzymatic reaction is proposed. Addition of glucose to a solution containing the enzyme does not immediately alter the fluorescence, which remains virtually constant over a given interval, after which it increases sharply and eventually levels off. The origin of the signal can be ascribed to the different fluorescence properties of the oxidized and reduced forms of the enzyme. Based on such differences, a mathematical model relating the concentrations of glucose, glucose oxidase, and oxygen in solution with the time at which the fluorescence change occurs was developed. The experimental results were consistent with the model's predictions. The proposed method allows the determination of glucose over the range 5 x 10(-4)-2 x 10(-2) M, with a precision of 2.1% as relative standard deviation. The method was used to determine the analyte in blood with good accuracy and precision.