Progress toward implantable fluorescence-based sensors for monitoring glucose levels in interstitial fluid
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A painless monitoring procedure for diabetics has proven to be an elusive goal. While completely noninvasive measurements are the desired technique, minimally invasive procedures using implanted fluorescence sensor chemistry offer significant advantages in specificity over current noninvasive approaches. The goal was to evaluate the potential for transdermal glucose sensing using intensity measurements from implanted microspheres. A fiber-optic probe and spectrometer were custom-built for collection of in vivo data. Comparisons with commercial fluorometers show the constructed device is adequate for this project. Data collected with sensor solutions showed a nonlinear response of fluorescence with glucose concentration. Reasonable prediction results were obtained over the clinically important region with polynomial regression using peak intensity ratios. The determinations meet the requirements for clinical use and show promise for further improvement in the future. While the details for manufacturing the actual sensor spheres for implantation are being considered, in vivo experiments have been conducted using `simulated' sensors. The constructed 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 manufacturing issues are addressed.