Design of an optical probe and signal processing for an implantable fluorescence-based glucose sensor

A painless monitoring procedure which diabetics can use in a blood glucose control protocol is an elusive goal. While completely noninvasive measurements are the technique of choice, minimally invasive procedures using implanted sensor chemistry offer significant advantages in specificity. Therefore, a project towards the development of implantable fluorescence sensors has been undertaken.; The overall goal of this research was to evaluate the potential for transdermal glucose sensing using light intensity measurements. The first goal was to model, design, construct, and test an optical system for measuring fluorescent emission from implanted sensors. The second goal was to develop appropriate data analysis algorithms to convert the multivariate optical measurements into predictions of glucose concentration.; A fiber-optic probe was built and interfaced with a custom-designed spectrometer for collection of in vivo data. Comparisons with commercial fluorometers show the superiority of the constructed device when tested with the specific dyes used in this project. Data collected with sensor solutions similar to what is envisioned for the implantable system showed a nonlinear response of fluorescence with glucose concentration. Reasonable prediction results were obtained over the clinically important region using polynomial regression with peak intensity ratios. The determinations meet the requirements for clinical use and show promise for further improvement in the future.; While the use of actual sensor spheres for implantation was not possible due to the slow reverse response and the difficulty in manufacturing spheres small enough for injection, in vivo experiments were conducted using "simulated" sensors that had constant fluorescence characteristics. The constructed optical system works well for the collection of signals from implanted fluorescent particles, but difficulty in achieving repeatable injection depths and color ratios confounded attempts to make true quantitative measurements. It is expected that the developed probe and data processing methods will be used with glucose-responsive hydrogel beads once the reversibility and manufacturing issues are addressed.