Fibronectin at Polymer Surfaces with Graduated Characteristics

Abstract

Globular proteins adsorbed onto artificialmaterials often exhibit different functional characteristics due to an altered availability formolecular interactions. This effect is caused by the patterns of substrate-protein interactions and is attributable to conformational changes as well as to the orientation and/or the anchorage of the surface-confined proteins. To highlight this interrelation we report a detailed experimental investigation of the adsorption and displacement of fibronectin, a key protein of the extracellular matrix that enables cell adhesion, at a set of polymer thin films with various hydrophilicity, charge density and swelling characteristics. The patterns of protein displacement were analysed quantitatively for several substrates and adsorbed protein amounts, referring to a model recently suggested by Huetz et al. (Langmuir 11:3145–3152, 1995). The patterns of protein displacement were related to the substrate characteristics and the conditions applied during the formation of the protein layer (i. e. the solution concentration). These findings were compared with the reorganisation of adsorbed fibronectin on the compared polymer substrates by endothelial cells in culture. The results demonstrate that a certain binding strength of fibronectin is required to support the cell-driven formation of fibronectin fibrils, which, in turn, is an important prerequisite for the differentiation of the cells.