Non-invasive glucose monitoring is desired to reduce the pain of blood sampling, which is an important step toward improved control of blood glucose for diabetics. Poor control results in debilitating complications, but the bother associated with testing typically leads to low patient compliance with recommended monitoring frequencies. The concept of implantable fluorescent sensors that can be monitored transdermally would be an attractive solution to the problem, but many obstacles to practical use have been identified. This work aims to use polyelectrolyte microcapsules to overcome drawbacks of previously proposed systems. Methods for fabricating these structures have been developed over the past few years, with precision control over mechanical and chemical properties, thus, "tuning" of the structures to fit different applications may be possible. Recent work has produced fundamental knowledge on the properties of these nanostructured capsules, yet there has been little reported by way of practical application. Since biomedical applications have not been pursued, no work has been done to assess the biocompatibility of the materials used. An interdisciplinary research team will evaluate the potential for polyelectrolyte microcapsules to function as carriers for fluorescence sensing chemistry using an integrative approach to sensor design that considers material, chemical, optical, and biological properties. The work will clarify basic questions regarding the process of encapsulation, then use these data to engineer sensor properties that will possess clinically relevant response characteristics. The stability of the structures will be assessed over time in increasingly physiological conditions, and methods to overcome problems with fouling and enzyme degradation will be identified to allow progress to continue. Finally, the biocompatibility of the materials used will be studied from molecule to device level, in vitro and in vivo, to determine baseline host response and risk factors for device failure.