Type 1 diabetes (T1D) is an autoimmune disease that affects 1.25 million Americans. Although there have been many technological advancements that improve the care and maintenance of the disease, there is currently still no cure. Transplanting islets of Langerhans has shown potential to maintain normoglycemia in patients, and to prolong the effects of this cell therapy, tissue engineering devices have been used to protect the cells from the host’s immune response. However, the mass transport of oxygen and nutrients in these devices for islet survival and insulin secretion has been limited due to the long distances between cells and the host’s vasculature system and slow diffusion rates. Pre- vascularization of the scaffold is a process in which the scaffold is implanted and allowed to vascularize before the cells are transplanted. This may improve success of the implant by providing a closer source of metabolic transport for the cells.
In the first chapter, we demonstrated a technique to optically measure oxygen concentrations non-invasively in subcutaneously implanted PDMS-based tissue scaffolds over eight weeks. Tracking oxygen diffusion rates at the site of implantation over time may provide insight into the vascularization process and the optimal time for pre- vascularization. To further increase reliability of the oxygen measurements, in the second chapter, an optical oxygen sensor is developed that uses the phase shift between the sinusoidally modulated excitation and emission signals. Fewer sampling points are needed to accurately characterize a wave function than an exponential function, which yields more robust and reliable measurements.