EVALUATION OF AN IMMUNOISOLATION MEMBRANE FORMED BY INCORPORATING A POLYVINYL-ALCOHOL HYDROGEL WITHIN A MICROPOROUS FILTER SUPPORT

An immunoisolation membrane formed by incorporating a high water conte nt polyvinyl alcohol (PVA) hydrogel into a microporous polyether sulfo ne (PES) filter has been investigated in this study. The PVA hydrogel is formed in situ within the filter pores via glutaraldehyde (GA) cros slinking under acidic conditions. The tortuous nature of the microporo us filter pores securely anchors the embedded hydrogel to provide exce llent structural integrity. The high void fraction of the PES filter s upport (>80%) and high water content of the PVA hydrogel (>85% water b y weight) allow excellent solute transport rates, while an appropriate level of glutaraldehyde crosslinking supplies the required molecular size selectivity. In vitro permeability measurements made with solutes covering a wide range of molecular sizes demonstrate high transport r ates for small nutrient molecules with rapidly diminishing permeabilit ies above a molecular weight of approximately 1,000 Dalton. Implantati on experiments show that the membrane properties are not deleteriously affected by prolonged in vivo exposure or common sterilization techni ques. Thus, this hybrid hydrogel/filter membrane system offers a promi sing approach to the immunoisolation of implanted cells. (C) 1997 Else vier Science Inc.