Biocompatibility studies on a glucose biosensor : investigation of the in-vivo sensitivity loss phenomenon

Abstract

Since the inception of the in-vivo electrochemical glucose biosensor, great expectations seemed to await insulin-dependent diabetics. However, even after decades of intense research, the sensor still suffers a major disadvantage: loss of sensitivity upon implantation in-vivo . If an implantable glucose biosensor is to be developed and used for reliable, long-term measurements of glucose, it will be important to address interactions between the sensor and tissue that may affect the sensor's performance as well as the tissue state. The sensor which has been developed in the Wilson group has been shown to be nontoxic, nonmutagenic, and noncarcinogenic to the tissue (1). However, the performance of the sensor in the tissue needs to be addressed. In this work, sensor performance is evaluated in relation to interactions of the sensor with endogenous biological molecules and cells.

Chapter 1 provides background information about diabetes, the glucose biosensor, and the biocompatibility issue. Proteins are known to adsorb on the surface of foreign objects implanted in-vivo (2) and are thought to affect the sensor's response (3,4). In chapter 2, a biocompatible polymer designed to prevent adsorption of protein was coated as an outer membrane on the sensor. The in-vivo response of the biocompatible membrane-coated sensor was compared to the in-vivo response of sensors that were not coated with the biocompatible membrane. In chapter 3, biomolecules extracted from previously implanted glucose biosensors were characterized and identified. The purpose of the work was to determine the kinds of molecules taken up by the glucose biosensor that may potentially effect the sensor's in-vivo response. In chapter 4, cellular interaction with the sensor was studied. We wanted to examine whether or not macrophages grow on the surface of the sensor or in the vicinity of the sensing area. In either case, the sensor's response may be affected by the presence of macrophages.