Influence of inflammatory cells and serum on the performance of implantable glucose sensors

The objective of this investigation was to evaluate the influence of polymo rphonuclear granulocytes on the performance of uncoated and cellulose aceta te/Nafion (R) coated amperometric glucose sensors in vitro. The response of these sensors was also investigated in serum. Uncoated and coated sensors showed lower sensitivities to glucose, with a significant drift in sensor o utput upon exposure to serum or leukocytes. Although the use of a coating r esulted in higher sensitivity, the progressive loss of output was not compl etely prevented. Stimulated granulocytes were shown to excrete components, probably catalase and myeloperoxidase, which consumed the hydrogen peroxide formed by the oxidation of glucose. In addition, adsorbed serum proteins f ormed a diffusional barrier for glucose. Furthermore, serum was found to co ntain low-molecular weight components that alone inhibited glucose oxidase activity. Based on preliminary electrochemical results, we postulate that r abbit serum contains oxidizing substrates that compete with molecular oxyge n for the acceptance of electrons from the oxidized enzyme. Consequently, f uture efforts should be aimed at elucidating the mechanisms involved in the interference of unknown serum components with electron transfer. In additi on, further investigations have to be performed to develop an outer membran e that minimizes protein adsorption as well as the actions of inflammatory cells. (C) 2000 John Wiley & Sons, Inc.