Liver assist devices have been developed in the last few decades to support patients with liver failure on the road to either recovery or transplantation. The efficiency of hollow fiber based bioartificial livers depends greatly on the choice of membrane in terms of permeability, cut off and biocompatibility. The aim of this study was thus to investigate the impact of different fiber types (micro filtration, plasma fractionation, ultra filtration) and of mass transfer on the functions of cells cultivated in the outer cartridge. After assessing the membrane's hydraulic resistance and porosity, mass transfer studies were first performed with a marker - vitamin B12 - and completed by a mathematical model in order to determine the preponderant transfer effect for each type of module (diffusion vs convection). GA human hepatoblastoma cells were then studied during 72 h of culture, with regard to their colonization in the bioreactor cell compartment, viability and metabolic activities (glucose consumption, ammonia, lactate and alpha-fetoprotein synthesis). Mass transfers were significantly influenced by both the type of hollow fiber and the operating conditions. Finally, certain criteria were discussed for the final choice of membrane for liver supply application. (C) 2009 Elsevier B.V. All rights reserved.