Implantable Glucose Sensors: Comparison between in Vitro and in Vivo Kinetics

This study was aimed at validating the in vitro estimated response characteristics of implanted glucose oxidase/H2O2electrodes with respect to their in vivo function. Mono-exponential non-linear regression analysis of sensor current vs. time curves in response to square alterations in glucose concentration gave response times T95of between 1 and 5 min. Non-primed glucose infusions were applied to dogs with these electrodes implanted subcutaneously. The simultaneously monitored in vivo data were subjected to non-linear regression analysis. The time constants T of increases or decreases after starting or ending the glucose load were (mean ± SEM) 53 ± 10 and 26 ± 4 min (significant difference, p < 0.05) in sensor current, 28 ± 8 and 15 ± 2 min (NS) in whole blood, and 26 ± 5 and 18 ± 2 min (NS) in plasma. The in vivo kinetic patterns of sensors were not related to their in vitro response times. Non-linear regression analysis of in vitro responses of glucose sensors under clearly defined conditions is recommended as a basis for further studies. The physiological delay in the subcutaneous glucose system needs more attention in this field of research.