USE OF CHARGED MEMBRANES TO CONTROL INTERFERENCE BY BODY CHEMICALS INA GLUCOSE BIOSENSOR

The prerequisite for the continuous in vivo monitoring of glucose conc entration is the development of an implantable glucose sensor with lon g-term stability. A new enzyme electrode concept featuring fluid-state glucose oxidase modified carbon Powder along with a cross-linked gluc ose oxidase enzyme layer has been developed. The glucose sensor incorp orating this enzyme electrode has been tested in vitro at 37 degrees C . It has a lifetime of three months after which it can be recharged wi th fresh enzyme. The next step in the characterization of this sensor is its in vitro behaviour in the presence of interfering substances co mmonly encountered in human blood. Here we report such a study of the sensor. The glucose diffusion membranes used were polycarbonate membra nes. We used standard polycarbonate membranes (membranes treated with polyvinylpyrrolidone or PVP), PVP-free polycarbonate membranes, and st andard polycarbonate membranes coated with positively and negatively c harged hydrogel layers. The sensors showed a response to glucose conce ntrations <300 mg dL(-1) both in pure phosphate buffer and in the pres ence of interferences. The influence of ascorbic acid, bilirubin, crea tinine, L-cystine, glycine, uric acid and urea on the amperometric sig nal of the sensor was investigated. The polycarbonate membrane coated with the negatively charged hydrogel layer provided good protection fo r the enzyme electrode, especially in the presence of ascorbic acid an d uric acid.