PROJECT SUMMARY Type 1 diabetes (T1D) is an autoimmune disease in which the insulin-producing β-cells of the pancreas are destroyed. T1D affects 3 million children and adults in the US with healthcare costs exceeding $15 billion. Standard therapy with exogenous insulin is burdensome, associated with a significant danger of hypoglycemia, and only partially efficacious in preventing long-term complications. Transplantation of allogeneic islets from cadaveric donors in conjunction with chronic immunosuppression has been recently shown to be effective in restoring euglycemia in clinical trials. However, the long-term future of cell replacement therapy for T1D requires a reliable and replenishable β-cell source and elimination of the need for chronic immunosuppression. β-cells derived from human pluripotent stem cells (hPSC) represent a transformative, unlimited source of insulin- producing cells for the treatment of T1D. However, the resulting cell population is heterogeneous and the development of mature insulin-producing cells is inconsistent. Furthermore, significant barriers related to long- term engraftment and function without chronic immunosuppression prevent the application of these promising cells. The objective of this project is to engineer biomaterials that (i) promote maturation and function of human pluripotent stem cell (hPSC)-derived β-cells and (ii) protect them from rejection by the immune system without the need for chronic immunosuppression. It is hypothesized that synthetic hydrogels with optimal biophysical and biochemical characteristics will provide a material platform that directs hPSC-derived β-cell maturation, engraftment and function without chronic immunosuppression. Aim 1: Engineer synthetic hydrogel formulations that promote survival, maturation, and function of immature β-cells. Aim 2: Evaluate engineered hydrogels as delivery carriers for β-cell transplantation in diabetic, immunocompromised mice. Aim 3: Engineer immunomodulatory hydrogels to promote hPSC-derived β-cell immune-acceptance and function in diabetic, immunocompetent humanized mice without chronic immunosuppression. This highly innovative novel strategy is fundamentally different from ongoing work in the field in terms of (i) engineering materials that provide microenvironmental cues to promote maturation of β-cells and local immune acceptance to eliminate the need of chronic systemic immunosuppressive drugs, (ii) transplantation into a clinically-translatable extrahepatic site with high vascularization and engraftment potential, and (iii) evaluation in humanized mice to provide proof-of- efficacy as a prelude to clinical translation. This project will provide a significant foundation for translation of this promising human cell source and will establish innovative materials that promote survival, engraftment, and function of human stem cell-derived β-cells in immunocompetent diabetic hosts.