title: The effects of UV irradiation on collagen D-band revealed by atomic force microscopy.
abstract: The objective of this paper was to investigate the influence of UV irradiation on collagen D-band periodicity by using the AFM imaging and nanoindentation methods. It is well known than UV irradiation is one of the main factors inducing destabilization of collagen molecules. Due to the human's skin chronic exposure to sun light, the research concerning the influence of UV radiation on collagen is of great interest. The impact of UV irradiation on collagen can be studied in nanoscale using Atomic Force Microscopy (AFM). AFM is a powerful tool as far as surface characterization is concerned, due to its ability to relate high resolution imaging with mechanical properties. Hence, high resolution images of individual collagen fibrils and load-displacement curves on the overlapping and gap regions, under various time intervals of UV exposure, were obtained. The results demonstrated that the UV rays affect the height level differences between the overlapping and gap regions. Under various time intervals of UV exposure, the height difference between overlaps and gaps reduced from ~3.7 nm to ~0.8 nm and the fibril diameters showed an average of 8-10% reduction. In addition, the irradiation influenced the mechanical properties of collagen fibrils. The Young's modulus values were reduced per 66% (overlaps) and 61% (gaps) compared to their initial values. The observed alterations on the structural and the mechanical properties of collagen fibrils are probably a consequence of the polypeptide chain scission due to the impact of the UV irradiation.
authors.affiliation: Biomedical Optics & Applied Biophysics Lab, Division of Electromagnetics, Electrooptics & Electronic Materials, School of Electrical and Computer Engineering, National Technical University of Athens, Iroon Polytechniou, Athens, Greece; Interuniversity Postgraduate Programme on Biomedical Engineering, Faculty of Medicine of the University of Patras, School of Electrical and Computer Engineering and the School of Mechanical Engineering of the National Technical University of Athens, Athens, Greece.
authors.forename: Stylianos V
authors.initials: SV
authors.lastname: Kontomaris
authors.forename: Dido
authors.initials: D
authors.lastname: Yova
authors.forename: Andreas
authors.initials: A
authors.lastname: Stylianou
authors.forename: Giorgos
authors.initials: G
authors.lastname: Balogiannis
mesh_terms: D000125:Achilles Tendon / Q000528:radiation effects*; D000818:Animals; D002417:Cattle; D003094:Collagen / Q000528:radiation effects*; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D003094:Collagen
keywords: AFM; UV irradiation; Young's modulus; collagen; nanoindentation