In vivo rechargeable glucose biosensors

The development stages and evaluation of an implantable, rechargeable, glucose sensor for continuous in vivo monitoring of glucose concentration are overviewed. The present approach makes it possible to extend the sensor's lifetime by in situ sensor refilling replacing spent immobilized enzyme with fresh enzyme. In the rechargeable biosensor the enzyme, glucose oxidase, is immobilized on dispersed carbon powder which is then held in a liquid suspension. The construction of the biosensor is such that the spent immobilized enzyme can be removed from the sensor body and fresh enzyme suspension is simultaneously injected via septa, without sensor disassembly or surgical access. The rechargeable sensor body is resistant to all of the standard procedures for sterilization including autoclaving. The sensor can be refilled with fresh enzyme material after sterilization. Rechargeable sensors based on both hydrogen peroxide and oxygen measuring principles have been under development. This biosensor, with a miniature potentiostat and signal transmitter is integrated into a small independently functioning device suitable for canine or other large animal implantation. Evaluation of the sensors and their recharging protocols in vitro and in vivo are discussed.