The Study Of The Implantable Glucose Biosensor Based On The Spiral-type Pt-Ir Electrode

Currently,diabetic patients mainly use the second generation of portable meter to monitor their blood glucose.Patients with type II diabetes are required need to test the glucose level at least twice a day while patients with type I diabetes have to detect four times a day to judge the trend of fluctuations in blood glucose.Although this method is relatively easier and cheaper,it is unable to predict the blood glucose fluctuation trend and regularity,especially unpredictiable death caused by hypoglycemia(low glucose level).Commercially available sensors mainly utilizing a needle type electrode,such design has two advantages:1)produce minimumly trauma after inplantation;2)minimize the formation of fibrous capsule around the electrode.However,the disadvantages of such design is that the GOD could only be deposited around the surface of needle,casing a short life time for the sensor(less than a week).In this paper,a novel electrochemical sensor was fabricated by utilizing a spiral platinum-iridium alloy electrode,which could enhance the loading of glucose oxidase and also increase the active area of the working electrode.The morphology of polyurethane(PU)semi-permeable membrane was observed by scanning electron microscope(SEM),and the performance of the sensor were investigated by cyclic voltammetry and chronoamperometry upon the influence of the thickness and content of PU as well as the enzyme concentration.The result shows that the sensitivity of the as-prepared spiral sensor is 20-30 nA/mM,which could be linearly detected the physiological glucose concentration between 2 mM and 30 mM.The sensors also exhibit good repeatability,stability and selectivity.Based on the optimized Expoxy-PU membrane,the biocompitiable composite hydrogels wered coated as the outer membrane,which is expected to reduce protein deposition and fibrous capsule.The performance of sensors,such as sensitivity,linear range and selectivity,are throughly studied in this chapter.Finally,the performance between our spiral electrod and GS100 glucose sensor(WPI,USA)were thoroughly evaluated,and the results show thatour spiral electrode could be an ideal candidate of long-term implantable sensor for continuous glucose monitoring in the future.