Caged pancreatic islet for IDDM.

The goals of this research are to improve the functionality (insulin secretion rate and pattern) and to expand the life-span of immunoprotected pancreatic islets. The low functionality (less than 15% of the insulin release rate of native islets in pancreas) required a large number of islets within the implant, which causes complications in surgery and discomfort for patients. The limited life-span of the islets in a biohybrid artificial pancreas (BAP) may require frequent cell reseeding and cause further supply problems in islet transplantation. Improved islet functionality and prolonged life-span will minimize the volume of the BAP by reducing the number of islets needed for diabetic patients to achieve normoglycaemia and reduce problems associated with islet supply. It is hypothesized in this research that 1) by mimicking facilitated oxygen transport in avascular tissues, the immunoprotected islets release a higher amount of insulin, recover their intrinsic biphasic release pattern, and prolong their life-span, and 2) insulinotropic agents further promote insulin secretion from islets. Based on these hypotheses, a new BAP system will be designed which contains the water-soluble polymeric conjugates of oxygen carriers (or oxygen binding vehicles) and islet stimulants of sulfonylurea compounds and glucagon-like insulinotropic peptide-1 with entrapped islets in the BAP. The research examines their effects on islet viability, the amount of insulin secretion, the insulin release profile, and the life-span of immunoprotected pancreatic islets. Especially, the combined synergy effects of both hypotheses will be emphasized. The successful results in improving functionality and life-span of islets entrapped in an immunoprotected membrane can be applied in the delivery of microencapsulated therapeutic cells and to the miniaturization of a BAP. In addition, the approaches proposed in this research will provide a potential solution to the shortage problem of human cell or tissue sources.