Fluorescence-based optical glucose sensing

Abstract

Previous studies have indicated that optical means of blood glucose detection are feasible and provide a minimally invasive alternative to current commercially available modalities. Fluorescence spectroscopy has shown promise in many examples of optical diagnostics and offers the advantage of specificity to particular analytes. Discussed in this thesis are the most recent experimental results of a fluorescence-based glucose sensor in vivo with external monitoring equipment. Polymer spheres containing a competitive binding glucose assay featuring two fluorophores that interact in a resonance energy transfer are implanted under the skin of an animal model, the hairless rat, and preliminary testing on the longevity, feasibility, and responsiveness of the sensor is reported. Fluorophore excitation and signal acquisition occurs via a custom fiber bundle probe that can be placed in direct contact with the subject's skin, delivering argon ion laser light to the sensor through a central fiber and receiving emissions through surrounding fibers. Spectral analysis is performed using a spectrometer and charge-coupled device (CCD) camera connected to a computer. Also included in this thesis is a discussion of modifications made to the Monte Carlo photon propagation modeling software to accommodate spectral input in the form of a Gaussian distributed source (e.g. laser) or an arbitrary user-defined spectrum (e.g. HgXe arc lamp). The new code offers the user the ability to input source information as well as tissue property responses to changes in photon wavelength.