Polyurethane-silicone macrocapsules: possible role in the immunoisolation of islets of Langerhans

One of the possibilities to overcome the immunologicaì problems related to islets transplantation is the immunoisolation of the grafts. This goal can be achieved by incapsulation of the purified islets of Langerhans (lL) In semipermeable biocompatible macrocapsules. We studied the permeabitity to glucose, insulin, albumin, immunoglobulines and blood white cells of macrocapsules prepared using as biomatenial a blend of polyurethanes and silicone. The macrocapsules were obtained by plugging segments of tubes prepared by a spraying and phase inversion technique that produced a microporous structure, with a thin skin on the inside of the tube. In addition, preliminary results are reported on the response of macroencapsulated pig lL to glucose stimulation, Glucose and insulin diffusion from the macrocapsules to the incubation medium reached the plateau after 10 anld 30 minutes respectively. Albumin, immunoglobulines and blood white cells remained inside the macrocapsules. Macroencapsulated pig lL secreted ,1.5 uu/is/min and 2.2 uu/is/mtn in the presence of .50 and 400mg/dl glucose concentrations respectively. These results suggest the possibiìity of using polyunethane-silicone macrocapsules for allo- and xeno-transplantations of islet of Langerhans.