In vitro and in vivo performance of porcine islets encapsulated in interfacially photopolymerized poly(ethylene glycol) diacrylate membranes

The usefulness of interfacial photopolymerization of poly(ethylene glycol) (PEG) diacrylate at a variety of concentrations and molecular weights to fo rm hydrogel membranes for encapsulating porcine islets of Langerhans was in vestigated. The results from this study show in vitro and in vivo function of PEG-encapsulated porcine islets and the ability of PEG membranes to prev ent immune rejection in a discordant xenograft model. Encapsulated islets d emonstrated an average viability of 85% during the first week after encapsu lation, slightly but significantly lower than unencapsulated controls. Enca psulated porcine islets were shown to be glucose responsive using static gl ucose stimulation and perifusion assays. Higher rates of insulin release we re observed for porcine islets encapsulated in lower concentrations of PEG diacrylate (10-13%), not significantly reduced relative to unencapsulated c ontrols, than were observed in islets encapsulated in higher concentrations (25%) of PEG diacrylate. Perifusion results showed biphasic insulin releas e from encapsulated islets in response to glucose stimulation. Streptozotoc in-induced diabetic athymic mice maintained normoglycemia for up to 110 day s after the implantation of 5,000-8,000 encapsulated porcine islet equivale nts into the peritoneal cavity. Normoglycemia was also confirmed in these a nimals using glucose tolerance tests. PEG diacrylate-encapsulated porcine i slets were shown to be viable and contain insulin after 30 days in the peri toneal cavity of Sprague-Dawley rats, a discordant xenograft model. From th ese studies, we conclude that PEG diacrylate encapsulation of porcine islet s by interfacial photopolymerization shows promise for use as a method of x enoprotection toward a bioartifical endocrine pancreas.