Atomic Force Microscopy surface nanocharacterization of UV-irradiated collagen thin films

Collagen, the most abundant protein in mammals, is a basic component of the extracellular matrix and due to its unique properties it is widely used as biomaterial, scaffold and culture substrate for cell and tissue regeneration studies. Due to human skin chronic exposure to sun light and since UV rays are used as sterilizing and cross-linking methods the clarification of the UV light-collagen interactions are very crucial. Moreover, since the majority of the biological reactions occur on surfaces or interfaces the influence of UV light on the surface of collagen-based materials attracts the scientific interest, especially in the biomaterials science. Surface-nanoscale characterization could be performed with Atomic Force Microscopy (AFM), which is a powerful tool and offers quantitative and qualitative information. Its ability of high resolution imaging and non-destructive characterization makes it very attractive for biological samples investigation. The aim of this paper was to determine the surface properties and alterations of collagen thin films after UV-irradiations using AFM techniques. Furthermore, it was aimed to investigate the possible different influence on the surface when the collagen solution or the thin films were irradiated. In this paper topographic AFM images were acquired from thin films, formed from both irradiated and non-irradiated collagen solutions, with spin coating procedure. The results demonstrated that the UV irradiation have different results when it is applied in the collagen solution or in the film after the spin coating methodology. For short irradiation times (<;120 min) UV caused only rather small changes in the morphology of the studied films although fluorescence and absorption studies confirmed collagen photodegradation. The surface roughness and topography altered after 3 and 7 hours, respectively, while the fibrous structure was completely destroyed after 15 hours. Surface roughness of the films depends on whether the solution was irradiated or the film and on the time irradiation. The fully clarification of the role of the UV light on collagen thin films will enable the proper design and control of collagen based nanobiomaterials with appropriate and improved surface properties.