title: Failure of mineralized collagen fibrils: modeling the role of collagen cross-linking.
abstract: Experimental evidence demonstrates that collagen cross-linking in bone tissue significantly influences its deformation and failure behavior yet difficulties exist in determining the independent biomechanical effects of collagen cross-linking using in vitro and in vivo experiments. The aim of this study is to use a nano-scale composite material model of mineral and collagen to determine the independent roles of enzymatic and non-enzymatic cross-linking on the mechanical behavior of a mineralized collagen fibril. Stress-strain curves were obtained under tensile loading conditions without any collagen cross-links, with only enzymatic cross-links (modeled by cross-linking the end terminal position of each collagen domain), or with only non-enzymatic cross-links (modeled by random placement of cross-links within the collagen-collagen interfaces). Our results show enzymatic collagen cross-links have minimal effect on the predicted stress-strain curve and produce a ductile material that fails through debonding of the mineral-collagen interface. Conversely, non-enzymatic cross-links significantly alter the predicted stress-strain response by inhibiting collagen sliding. This inhibition leads to greater load transfer to the mineral, which minimally affects the predicted stress, increases modulus and decreases post-yield strain and toughness. As a consequence the toughness of bone that has more non-enzymatically mediated collagen cross-links will be drastically reduced.
authors.affiliation: School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA. siegmund@purdue.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Siegmund
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Allen
authors.forename: David B
authors.initials: DB
authors.lastname: Burr
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic; D024022:Fibrillar Collagens / Q000737:chemistry*; D006801:Humans; D008954:Models, Biological; D013314:Stress, Mechanical
chemical_list: D024022:Fibrillar Collagens