Long-term stability of electroenzymatic glucose sensors implanted in mice. An update

Protection of the enzyme layer of glutaraldehyde vapor-stabilized glucose oxidase-based glucose sensors from attack by proteolytic enzymes and peritoneal macrophages can be accomplished by covering with a regenerated cellulose (viscose) membrane, as commonly used for laboratory dialysis. These implanted sensors are not externally polarized, but continuously consume oxygen and glucose and generate gluconic acid and hydrogen peroxide. On the average (sensors in 45 mice) the activity declines with time, almost vanishing by 600 days. However, the fact that some sensors retain nearly all of their activity for over 500 days indicates that glucose sensors can be made with a life span compatible with the requirements for an artificial pancreas (glucose sensor/insulin pump). Limited observation with similar implanted lactate sensors indicates their life span to be shorter.