The surface stability of polymers with adsorbed fibronectin.

Linear low-density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS), and polyethylene-co-ethacrylic acid (PE-EAA, 17.5% acid content) films were treated with an aqueous solution of fibronectin. Advancing contact angles of water (straight theta(a)) were used to monitor the change in the surface wettability of these films. With the exception of PE-EAA, all of the samples showed an increase in their wettability by water, indicating that the protein had adsorbed to the polymer surface. The stability of these protein-modified films against a buffered aqueous solution and against air under ambient conditions was monitored over time. The surface wettability of these protein-modified polymers, with the exception of PS, remained unchanged after heating against the buffer solution. In air, however, straight theta(a) increased over a period of 2 months. In addition, the effect of organic solvent extraction on the surface stability of these protein-modified films was investigated. Unmodified samples of LLDPE, PS, and PP were subjected to soxhlet extraction to remove impurities and low-molecular-weight oligomers prior to film preparation and subsequent treatment with fibronectin. These samples were left in air under ambient conditions for 2 months. There was no difference in the magnitude of the change in straight theta(a) for the protein-modified, extracted LLDPE film compared to the protein-modified, nonextracted polymer film. A slight decrease in the rate of thermal reconstruction was observed for the protein-modified extracted PS film compared to the protein-modified nonextracted sample, and a slight increase in the rate of thermal reconstruction was observed for the protein-modified extracted PP film compared to the protein-modified nonextracted sample.