Encapsulated islet transplantation

Islet transplantation may provide a prospective treatment for type 1 diabetes. To enable islet transplantation and restore autonomous glucose monitoring and insulin secretion, islets or β cells can be encapsulated in immuno-protective, polymeric micro- or macroscale coatings that allow the selective exchange of nutrients and small proteins while preventing the infiltration of immune mediators that cause immunorecognition. However, several challenges remain to be addressed before islet-encapsulation technologies can be used in human patients. In this Review, we highlight different islet-encapsulation designs, examining how these can be optimized to improve material biocompatibility, oxygen supply and revascularization at transplant sites and to reduce excessive fibrotic responses. We also discuss how islet-encapsulation approaches can be combined with immunotherapy and gene editing, highlighting regulatory hurdles that will need to be addressed to enable translation to the clinic.