Influence of substratum surface properties on the organization of adsorbedcollagen films: In situ characterization by atomic force microscopy

Atomic force microscopy (AFM) imaging and force-distance curves have been u sed to investigate, in situ, the nanoscale organization of collagen adsorbe d on polymer substrata covering a wide range of surface roughness and surfa ce hydrophobicity: bisphenol A polycarbonate (PC), poly(ethylene terephthal ate) (PET), and poly(vinylidene difluoride) (PVdF) used as such or treated by an oxygen plasma discharge (ox). After collagen adsorption, PC and PCox showed patterned structures under water, the size of which was influenced b y substratum surface oxidation. These structures are attributed to aggregat ed ends of collagen molecules. Extended rupture lengths were observed in th e force-distance curves, suggesting that bundles of collagen molecules adhe re to the AFM probe and are progressively torn out upon probe retraction. I n contrast, on PET, PETox, PVdF, and PVdFox, adsorbed collagen formed a smo oth, homogeneous film devoid of any topographic feature, and no extended ru pture lengths were observed. After drying, holes in the collagen film were observed on PET and PVdF and not on PETox and PVdFox. The influence of subs tratum roughness and physicochemical properties is discussed, considering t he mobility of collagen molecules at the interface.