PREPARATION AND CHARACTERIZATION OF PERMSELECTIVE, BIOCOMPATIBLE MEMBRANES FOR THE MACROENCAPSULATION OF PANCREATIC-ISLETS

Polymeric membranes were prepared by mixing poly(vinyl alcohol) (PVA) and poly(acrilic acid) (PAA) solutions (10/90 weight ratio), freeze-dr ying and crosslinking under vacuum. The membranes were then coated wit h alginic acid sodium salt, and gelation was accomplished by calcium c hloride. The resulting membrane structure was essentially trabecular, with pore size ranging from 50 to 100 mum. Glucose and insulin diffusi ons reached a plateau at 2 and 32 min, respectively. Immunoglobulins a nd red blood cells did not cross the membranes. Gel-permeation HPLC sh owed that the membrane wall was impermeable to compounds with a molecu lar weight higher than 100 000 D. Biocompatibility of the membranes wa s demonstrated by showing minimal fibrotic reaction at 3 weeks after i ntraperitoneal implantation into mice. Porcine islets were placed into the membranes and cultured at 37-degrees-C for 7 days, at which time the incapsulated islets were shown to release insulin in response to g lucose. These results support the use of PVA/PAA membranes for bioarti ficial pancreas studies.