Collagen films adsorbed on native and oxidized poly(ethylene terephtalate): morphology after drying

The collagen layer formed by adsorption of collagen on native (PETn) and surface oxidized poly(ethylene terephtalate) (PETox) was studied by X-ray photoelectron spectroscopy and atomic force microscopy (AFM). On PETox, for adsorption times up to a few hours, the collagen molecules form a network, the nodes of which seem to be responsible for a dot-like morphology. On PETn, at very short adsorption times and consequently low surface coverages, the adsorbed molecules are displaced by the AFM tip. This effect reveals lower interactions between the collagen and the surface after drying compared to PETox. At higher coverages, the surface morphology is similar to that obtained for PETox. After an adsorption time of 24 h, an aggregation of collagen molecules is observed for both substrates. The results are discussed with regard to the interactions between collagen and the substrate in water, the events occurring during the drying process and the mobility of collagen molecules in the dry state.