Bioartificial organ containing cells encapsulated in a permselective

Abstract

A bioartificial organ for implanting to provide a therapeutic effect is prepared containing a core of living cells encapsulated in a foam-like membrane having three regions: a dense, fine-pored, permselective inner region, a middle region that lacks macrovoids and a fine-pored outer region. The membrane has a molecular weight cutoff that permits passage to nutrients to the cells but not passage of the cells. Preferably, the membrane is made of polyether sulfone, pores range in size between 0.02 .mu.m and 2.0 .mu.m and have polyhedrally symmetric boundaries and are arranged asymmetrically from one surface to the other. The membrane has an asymmetry factor AF relative to the maximum pore diameter of 0.01 to 2.0 and a ratio of the maximum mean free path length to the diameter of the largest pore of greater than 3. The membrane can be hydrophobic or hydrophilic. The bioartificial organ is formed by coextrusion or by stepwise assembly by forming the cell core and then applying the membrane. A polyether sulfone membrane is prepared from a solution containing by weight 12 to 35% polyether sulfone and 15 to 65% .epsilon.-caprolactam, and optionally 0 to 85% latent solvent, 0 to 15% thickner, to 5% non-solvent and 0 to 1% auxiliaries. Cells encapsulated can be cells that produce a neurotransmitter such as dopamine or a biologically active factor such as CNTF, NGF, GDNF, endorphins, catecholamines or enkephalins.