Surface study of polycarbonate membranes used as a substratum for animal cell culture

The aim of this work is to investigate the relationships between the chemical composition of a polymer surface and its physico‐chemical properties. The study of track‐etched membranes was undertaken in order to understand and control better the attachment of epithelial cells for reconstituting a highly differentiated cell tissue. The bis‐phenol A polycarbonate membrane surface properties have been modified by various procedures: sulphochromic acid, nitration, oxygen and ammonia radio frequency (rf) glow discharge, corona discharge. The surface chemical composition was determined by x‐ray photoelectron spectroscopy and the surface free energy was computed from the contact angle of various liquids. The presence of sulphur and nitrogen‐containing groups bound to the surface has been demonstrated after application of the corresponding wet surface treatments. All surface treatments lead to an increase of the oxygen surface concentration, the highest value being obtained after nitration. As a result, the polar contribution to the surface free energy also is increased; this seems to be correlated with the surface concentration of oxygen bearing a high electron density. The cell adhesion and growth on the membranes is improved by the surface treatments applied, in particular by oxygen rf glow discharge. However, steam sterilization tends to remove the effects of earlier surface modification; this seems to be more pronounced when the sample is in direct contact with liquid water.