Fibrinogen organization at the cell-material interface directs endothelial cell behavior

Fibrinogen (FG) adsorption on surfaces with controlled fraction of —OH groups was investigated with AFM and correlated to the initial interaction of primary endothelial cells (HUVEC). The —OH content was tailored making use of a family of copolymers consisting of ethyl acrylate (EA) and hydroxyl ethyl acrylate (HEA) in different ratios. The supramolecular distribution of FG changed from an organized network-like structure on the most hydrophobic surface (—OH ₀ ) to dispersed molecular aggregate one as the fraction of —OH groups increases, indicating a different conformation by the adsorbed protein. The best cellular interaction was observed on the most hydrophobic (—OH ₀ ) surface where FG assembled in a fibrin-like appearance in the absence of any thrombin. Likewise, focal adhesion formation and actin cytoskeleton development was poorer as the fraction of hydroxy groups on the surface was increased. The biological activity of the surface-induced FG network to provide 3D cues in a potential tissue engineered scaffold, making use of electrospun PEA fibers (—OH ₀ ), seeded with human umbilical vein endothelial cells was investigated. The FG assembled on the polymer fibers gave rise to a biologically active network able to direct cell orientation along the fibers (random or aligned), promote cytoskeleton organization and focal adhesion formation.