Competitive adsorption of proteins: key of the relationship between substratum surface properties and adhesion of epithelial cells.

The adhesion of Hep G2 cells was investigated using different substrata (commercial substrata, polystyrene modified by oxygen or ammonia plasma discharge), the surface properties of which were characterized (surface chemical composition, water contact angle, zeta potential). Some substrata were pre-conditioned with solutions of extracellular matrix (ECM) protein (collagen, laminin, fibronectin), solutions of albumin or polylysin, fetal calf serum or culture medium. The culture medium contained the surfactant Pluronic F68; cycloheximide was added in certain tests to inhibit protein synthesis. Cells spread within 1.5 h provided ECM proteins were present at the surface. Adsorption of ECM proteins was subject to competition with adsorption of Pluronic F68. When the substratum was exposed simultaneously to ECM protein and Pluronic F68, either by pre-conditioning or through protein cell secretion, a weaker substratum hydrophobicity favored adsorption of the proteins and subsequent cell adhesion. On the other hand, when ECM proteins were pre-adsorbed, they were not displaced by Pluronic F68 and cell adhesion was not influenced by substratum hydrophobicity. When ECM proteins were present, no difference was observed between substrata of similar hydrophobicity carrying positive or negative charges, respectively. In absence of ECM proteins, the presence of cationic sites at the substratum surface (NH3 plasma treatment, adsorption of polylysine) allowed cell attachment but no spreading within 1.5 h.