title: Mechanical properties of native and cross-linked type I collagen fibrils.
abstract: Micromechanical bending experiments using atomic force microscopy were performed to study the mechanical properties of native and carbodiimide-cross-linked single collagen fibrils. Fibrils obtained from a suspension of insoluble collagen type I isolated from bovine Achilles tendon were deposited on a glass substrate containing microchannels. Force-displacement curves recorded at multiple positions along the collagen fibril were used to assess the bending modulus. By fitting the slope of the force-displacement curves recorded at ambient conditions to a model describing the bending of a rod, bending moduli ranging from 1.0 GPa to 3.9 GPa were determined. From a model for anisotropic materials, the shear modulus of the fibril is calculated to be 33 +/- 2 MPa at ambient conditions. When fibrils are immersed in phosphate-buffered saline, their bending and shear modulus decrease to 0.07-0.17 GPa and 2.9 +/- 0.3 MPa, respectively. The two orders of magnitude lower shear modulus compared with the Young's modulus confirms the mechanical anisotropy of the collagen single fibrils. Cross-linking the collagen fibrils with a water-soluble carbodiimide did not significantly affect the bending modulus. The shear modulus of these fibrils, however, changed to 74 +/- 7 MPa at ambient conditions and to 3.4 +/- 0.2 MPa in phosphate-buffered saline.
authors.affiliation: Polymer Chemistry and Biomaterials, Faculty of Science and Technology and Institute for Biomedical Technology, University of Twente, Enschede, The Netherlands.
authors.forename: Lanti
authors.initials: L
authors.lastname: Yang
authors.forename: Kees O
authors.initials: KO
authors.lastname: van der Werf
authors.forename: Carel F C
authors.initials: CF
authors.lastname: Fitié
authors.forename: Martin L
authors.initials: ML
authors.lastname: Bennink
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Dijkstra
authors.forename: Jan
authors.initials: J
authors.lastname: Feijen
mesh_terms: D000818:Animals; D016880:Anisotropy; D001703:Biophysics / Q000379:methods*; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D024042:Collagen Type I / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004867:Equipment Design; D005109:Extracellular Matrix / Q000378:metabolism; D024022:Fibrillar Collagens / Q000737:chemistry; D018625:Microscopy, Atomic Force; D015233:Models, Statistical; D011312:Pressure; D013314:Stress, Mechanical; D013696:Temperature
chemical_list: D024042:Collagen Type I; D003432:Cross-Linking Reagents; D024022:Fibrillar Collagens; D003094:Collagen