Gamma Irradiation of Poly(lactide‐co‐glycolide) Scaffolds Reduces the Mechanical Stability and Function of Islet Grafts in Diabetic Nonhuman Primates

Clinical islet transplantation has long been investigated as a potential cure for type 1 diabetes (T1D), yet standard intrahepatic delivery leaves islets prone to an instant blood-mediated inflammatory response. Herein, we investigated the design of microporous poly(D,l-lactide-co-glycolide) (PLG) scaffolds for extrahepatic islet transplantation in mouse and nonhuman primate (NHP) models. Acellular scaffolds elicited only a mild inflammatory response following implantation into the omentum. On scaffold islet transplantation had extensive insulin staining at 4 weeks yet modest insulin requirement reductions in diabetic NHP recipients. Scaffolds were sterilized by irradiation and exhibited fragility during seeding and implantation, motivating an increase in the manufacturing ratio of PLG:NaCl from 1:30 to 1.25:30 w/w. These scaffolds exhibited no differences in porosity or interior geometry between sterilization conditions, and transplants in mice restored normoglycemia. We piloted a modified scaffold study in a fourth NHP, and although scaffold integrity was improved, the transplant outcome was similar. We subsequently tested intermediate PLG:NaCl ratios in mice, finding that a 1.15:30 ratio achieved a balance of mechanical stability and islet compatibility. Overall, these studies identify that scaffold porosity can be adjusted to account for the impact of sterilization on transplantation.