Protein Adsorption, Cell Adhesion and Polymer Surfaces: Molecular Processes and Experimental Methods

Adsorption of extracellular matrix (ECM) proteins in competition with other substances is a key to explain the relationship between substratum surface hydrophobicity and mammalian cell adhesion: when polystyrene substrata were exposed simultaneously to ECM protein and a PEO-PPO-PEO polymer surfactant (Pluronic F68), either by pre-conditioning or through protein cell secretion, a weaker substratum hydrophobicity favoured adsorption of the protein and subsequent cell adhesion. This knowledge was used to achieve a selective adhesion of different types of mammalian cells on tracks (a few tens of mm wide) produced on polystyrene by photolithography and oxygen plasma treatment, conditioning the substratum with a solution of ECM protein and Pluronic F68. Examination of a broader range of substrata confirmed that inhibition of cell adhesion on hydrophobic substrata is due to adsorption of substances competing with extracellular matrix proteins. However it also showed that substratum surface properties more subtle than overall wettability are important. In situ observation of the nanoscale organisation of collagen adsorbed in the absence of competitor, using atomic force microscopy (AFM), showed that a smooth substratum surface allows collagen mobility and aggregation of molecular ends in the adsorbed phase. The organisation obtained after drying (smooth film, pattern) was examined by combining AFM, XPS and radiolabelling and found to be influenced by substratum roughness, substratum hydrophobicity and drying rate.