Microencapsulation of pancreatic islets in a water insoluble polyacrylate

Rat pancreatic islets were encapsulated in a water insoluble polyacrylate (Eudragit RL), a model polymer, by coaxial extrusion and interfacial precipitation. Despite exposure to organic solvents and nonsolvents (diethyl phthalate, corn oil, and mineral oil) and to shear, the islets survived encapsulation. They continued to secrete insulin into the tissue culture medium and responded to glucose in both static glucose challenges and perifusion assays as well and as long as control islets which were not encapsulated, but were maintained in tissue culture alongside the encapsulated islets. Unfortunately, there was a great deal of variability in the performance of all islets studied, making unequivocal conclusions difficult. Some encapsulated islets survived more than 140 days in vitro and histologically appeared healthy. However, there appeared to be a general deterioration in insulin secretion capacity following prolonged culture in all islets, with corresponding changes (e.g., central necrosis) visible by microscopy. Although Eudragit RL is not practical as an encapsulation polymer, this study was useful in demonstrating that islets may be encapsulated in materials other than alginate-polylysine, and ultimately in materials that may have a more optimum blend of the desired properties: biocompatibility, permselectivity, and mechanical durability.