Evaluation of cell behaviour related to physico-chemical properties of polymeric membranes to be used in bioartificial organs

In bioartificial organs using isolated cells, polymeric semipermeable membranes are used as immunoselective barriers as a means for cell oxygenation and also as substrata for adhesion of anchoragedependent cells. The capacity of the membrane to perform its functions and to provide a cytocompatible support for cell culture depends in particular on its surface properties. In this study we investigated the physico-chemical aspects of the interaction between the membrane and mammalian cells in order to provide guidelines to the selection of cytocompatible membranes. We evaluated the adhesion and metabolic behaviour of isolated liver cells cultured on various polymeric membranes such as those modifed by protein adsorption. The physico-chemical properties of the membranes were characterised by contact angle measurements. The different parameters such as acid (γ⁺), base (γ^-) and Lifshitz-van der Waals (γ^LW) of the surface free energy were calculated according to Good-van Ossâ's model. The adsorption of protein modified markedly both contact angle and components of membrane surface tension. In particular, base parameter of surface tension decreased drastically with increased water contact angle. For each investigated membrane we observed that cell adhesion increased with increasing base parameter of membrane surface tension. The absolute value of cell adhesion is higher in the presence of serum proteins adsorbed on the membrane surface, which change the wettability by increasing the base parameter of surface tension. Also, the metabolic functions improve on hydrophilic membranes. Liver cells synthesised urea with a rate that increased with increasing base parameter value of membrane surface tension. The metabolic activity is particularly expressed at high levels when cells were cultured on polycarbonate and cellulose acetate membranes.