Amphiphilic membranes with controlled mesh dimensions for insulin delivery

A series of amphiphilic networks (membranes), consisting of hydrophilic pol y(N,N-dimethylacrylamide) (PDMAAM) main chains crosslinked by hydrophobic t elechelic polyisobutylene di- and trimethacrylates (MA-PIB-MA or circle div ide (PEB-MA)(3)) have been synthesized and used for the preparation of thin -walled tubules suitable for the immunoisolation of porcine islets. The mol ecular weight cut-off (MWCO) ranges, insulin and glucose diffusion coeffici ents and permeabilities of various membranes have been determined. The mole cular weight of the PDMAAM moiety between two hydrophobic crosslinking poin ts M-c,M-hydrophilic) controls permeability, which in turn can be controlle d by synthesis conditions. The strengths and elongations of water-swollen m embranes crosslinked with circle divide (PIB-MA)(3) are superior by a facto r of about two to those prepared with MA-PIB-MA. Based on the values from t hese experiments, a well-defined membrane prepared with circle divide (PEB- MA)(3) was selected and used to encapsulate porcine islet cells. Gratifying ly, the encapsulated islet cells remain functional and viable, and cells wi thin the tubule release insulin upon glucose challenge. These in vitro expe riments are sufficiently promising to encourage us to continue our studies to develop a bioartificial pancreas.