title: Investigation of the three-dimensional orientation of mineralized collagen fibrils in human lamellar bone using synchrotron X-ray phase nano-tomography.
abstract: We investigate the three-dimensional (3-D) organization of mineralized collagen fibrils in human cortical bone based on synchrotron X-ray phase nano-tomography images. In lamellar bone the collagen fibrils are assumed to have a plywood-like arrangement, but due to experimental limitations the 3-D fibril structure has only been deduced from section surfaces so far and the findings have been controversial. Breakthroughs in synchrotron tomographic imaging have given access to direct 3-D information on the bone structure at the nanoscale level. Using an autocorrelation-based orientation measure we confirm that the fibrils are unidirectional in quasi-planes of sub-lamellae and find two specific dominant patterns, oscillating and twisted plywoods coexisting in a single osteon. Both patterns exhibit smooth orientation changes between adjacent quasi-planes. Moreover, we find that the periodic changes in collagen fibril orientation are independent of fluctuations in local mass density. These data improve our understanding of the lamellar arrangement in bone and allow more detailed investigations of structure-function relationships at this scale, providing templates for bio-inspired materials. The presented methodology can be applied to non-destructive 3-D characterization of the sub-micron scale structure of other natural and artificial mineralized biomaterials.
authors.affiliation: Julius Wolff Institute and Berlin-Brandenburg School for Regenerative Therapies, Charité Universitätsmedizin, Berlin, Germany. peter.varga@charite.de
authors.forename: Peter
authors.initials: P
authors.lastname: Varga
authors.forename: Alexandra
authors.initials: A
authors.lastname: Pacureanu
authors.forename: Max
authors.initials: M
authors.lastname: Langer
authors.forename: Heikki
authors.initials: H
authors.lastname: Suhonen
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hesse
authors.forename: Quentin
authors.initials: Q
authors.lastname: Grimal
authors.forename: Peter
authors.initials: P
authors.lastname: Cloetens
authors.forename: Kay
authors.initials: K
authors.lastname: Raum
authors.forename: Françoise
authors.initials: F
authors.lastname: Peyrin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005269:Femur / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000648:ultrastructure*; D024022:Fibrillar Collagens / Q000648:ultrastructure*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D066298:In Vitro Techniques; D008903:Minerals / Q000032:analysis*; D011487:Protein Conformation; D017356:Synchrotrons; D014056:Tomography, X-Ray / Q000379:methods*
chemical_list: D024022:Fibrillar Collagens; D008903:Minerals
keywords: Lamellar bone; Mineralized collagen fibril; Osteon; Plywood arrangement; X-ray phase nano-tomography