Analysis of key parameters of glucose sensors

The response of enzyme electrode glucose sensors implanted in tissues to physiologic blood glucose oscillations is simulated. Models describe both oxygen-based and peroxide-based glucose sensors in spatially homogeneous medium simulating some mass transfer properties of tissue. Pass-through ratios and delays are reported as a function of frequency for the oxygen-based sensor, and the effects on continuous blood glucose monitoring are illustrated using data from the literature. Certain peroxide-based sensor designs may produce common signals for different glucose concentrations, a characteristic not found in oxygen-based sensors. The dynamic response depends on the frequency of glucose oscillation and is sensitive to sensor type, enzyme activity, and diffusional resistance (1).; In order to minimize the effects of enzyme inactivation and measurement error, a sensor model in cylindrical coordinates is proposed and tested in silico over time periods up to 300 days. The results show that this design does minimize enzyme inactivation effects and measurement errors far better than the 1-D design. Such a sensor (or an array of these sensors) may allow for real-time continuous tissue glucose monitoring.; The design lessons learned from this project are: (1) Peroxide-mediated inactivation of glucose oxidase makes peroxide-based glucose sensors impractical for long-term use. (2) Glucose-mediated inactivation of glucose oxidase makes any 1-D sensor design difficult; glucose oxidase activity in 1-D sensor designs can be preserved somewhat by the addition of excess catalase. (3) The stoichiometric imbalance between glucose and oxygen availability in tissues suggests that a 1-D sensor will necessarily have poor sensitivity over the range of interest of glucose concentrations as long as the potentiostatic glucose-modulated oxygen sensor principle is employed. (4) The best long-term potentiostatic glucose-modulated oxygen sensor implementation is a 2-D/3-D design that limits glucose entry via an aperture in a thin upper layer of silicone rubber. This design allows for the most active area of enzymatic activity to shift over time while preserving most of the ability of the sensor to detect glucose.