Islets transplanted into a 14 day preconditioned nanofiber pocket restore normoglycemia in preliminary transplants. (A) Minimally invasive injection of islets into the pocket can be ultrasound-assisted (yellow arrow: 28G needle). (B) Preconditioning scheme introduces islets 2 weeks after the nanofiber encapsulation device. (C) Syngeneic islets transplanted without nanofibers were placed under the kidney capsule or freely floating in the intraperitoneal cavity resulting in blood glucose reduction (blue line, n = 5, mean ± SEM). Islets were transplanted inside a FTY720 PHBV/PCL salt-leached nanofiber pocket at the time of implantation without correction of blood glucose (black line, n = 5, mean ± SEM). (D) Islets introduced to a FTY720 PHBV/PCL salt-leached nanofiber preconditioned pocket reach normoglycemia (n = 2, mean ± SEM). Glucose increase beyond day 24 is attributed to the islet containing implant being removed, indicating glucose control was derived from transplanted cells.