Design and in vitro studies of a needle-type glucose sensor for subcutaneous monitoring

International audienceA new miniaturized glucose oxidase based needle-type glu¬ cose mlcrosensor has been developed for subcutaneous glu¬ cose monitoring. The sensor Is equivalent In shape and size to a 26-gauge needle (0.45-mm o.d.) and can be Implanted with ease without any Incision. The novel configuration greatly facilitates the deposition of enzyme and polymer films so that sensors with characteristics suitable for In vivo use (upper limit of linear range > 15 mM, response time 60%). The sensor response is largely Independent of ox¬ ygen tension In the normal physiological range. It also ex¬ hibits good selectivity against common interferences except for the exogenous drug acetaminophen

Progress toward the Development of an Implantable Sensor for Glucose

International audienceThe development of an electrochemically based implant¬ able sensor for glucose is described. The sensor is needle-shaped, about the size of a 28-gauge needle. It is flexible and must be implanted subcutaneously by using a 21-gauge catheter, which is then removed. When com¬ bined with a monitoring unit, this device, based on the glucose oxidase-catalyzed oxidation of glucose, reliably monitors glucose concentrations for as long as 10 days in rats. Various design considerations, including the deci¬ sion to monitor the hydrogen peroxide produced in the enzymatic reaction, are discussed. Glucose constitutes the most important future target analyte for continuous monitoring, but the basic methodology developed for glucose could be applied to several other analytes such as lactate or ascorbate. The success in implementation of such a device depends on a reaction of the tissue surrounding the implant so as not to interfere with the proper functioning of the sensor. Histochemical evidence indicates that the tissue response leads to enhanced sensor performance. Additional Keyphrases: enzyme electrode • glucose oxidase • electrochemistry • subcutaneous sensor Determination of concentrations of glucose in blood has long been recognized as an important clinical diag¬ nostic test for diabetes. Thirty years ago, Clark and Lyons (1) suggested coupling an enzymatic reaction to electrochemical monitoring in what was subsequently called an enzyme electrode. This device made possible the largely selective detection of glucose in both serum and whole blood, and commercially available clinical analyzers from Yellow Springs Instruments and Beck-man Instruments, among others, have been available for some time. A significant breakthrough occurred in the early 1980s, when self-monitoring of blood glucose became possible through the development of dry chem¬ ical strips for use with a single drop of blood. The resulting reaction (again, typically involving the glu¬ cose oxidase-catalyzed oxidation of glucose) could be followed by monitoring the formation of product spec-trophotometrically or electrochemically. More recently, the possibility of monitoring glucose by noninvasiv