Modeling and measuring visco-elastic properties: From collagen molecules to collagen fibrils |
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| Institution: | 1. Biomechanics Group, Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy;2. Department of Civil Engineering, University of Minnesota, 142 Civil Engineering Building, 500 Pillsbury Drive S.E., Minneapolis, MN 55455-0116, USA;1. Department of Orthopedic Surgery, VU University Medical Center, Amsterdam, The Netherlands;2. MOVE Research Institute, VU University, Amsterdam, The Netherlands;3. Biomaterials Innovation Research Center, Division of Biomedical Engineering, Department of Medicine, Brigham and Women''s Hospital, Harvard Medical School, Boston, MA, USA;4. Harvard-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA;5. Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA;6. Department of Bioindustrial Technologies, College of Animal Bioscience and Technology, Konkuk University, Hwayang-dong, Gwangjin-gu, Seoul, Republic of Korea;7. Department of Physics, King Abdulaziz University, Jeddah, Saudi Arabia;1. Department of Biomedical Engineering, Tulane University, New Orleans, USA;2. Department of Applied and Computational Mathematics and Statistics, University of NotreDame, Notre Dame, USA;1. Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK;2. Institute for Lightweight Design and Structural Biomechanics, Faculty of Engineering and the Environment, Vienna University of Technology, Gusshausstrasse 27-29, Vienna 1040, Austria;3. The Brooke Laboratories, Division of Infection, Inflammation and Immunity, Faculty of Medicine, University of Southampton, SO16 6YD, Southampton, UK;4. National Centre of Advanced Tribology at Southampton, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK |
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| Abstract: | Collagen is the main structural protein in vertebrate biology, determining the mechanical behavior of connective tissues such as tendon, bone and skin. Although extensive efforts in the study of the origin of collagen exceptional mechanical properties, a deep knowledge of the relationship between molecular structure and mechanical properties remains elusive, hindered by the complex hierarchical structure of collagen-based tissues. Understanding the viscoelastic behavior of collagenous tissues requires knowledge of the properties at each structural level. Whole tissues have been studied extensively, but less is known about the mechanical behavior at the submicron, fibrillar and molecular level. Hence, we investigate the viscoelastic properties at the molecular level by using an atomistic modeling approach, performing in silico creep tests of a collagen-like peptide. The results are compared with creep and relaxation tests at the level of isolated collagen fibrils performed previously using a micro-electro-mechanical systems platform. Individual collagen molecules present a non-linear viscoelastic behavior, with a Young's modulus increasing from 6 to 16 GPa (for strains up to 20%), a viscosity of 3.84±0.38 Pa s, and a relaxation time in the range of 0.24–0.64 ns. At the fibrils level, stress–strain–time data indicate that isolated fibrils exhibit viscoelastic behavior that could be fitted using the Maxwell–Weichert model. The fibrils showed an elastic modulus of 123±46 MPa. The time-dependent behavior was well fit using the two-time-constant Maxwell–Weichert model with a fast time response of 7±2 s and a slow time response of 102±5 s. |
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| Keywords: | Collagen Visco-elastic properties Atomistic simulations Micro-electro-mechanical systems Biomechanics |
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