title: Full-Field Calcium K-Edge X-ray Absorption Near-Edge Structure Spectroscopy on Cortical Bone at the Micron-Scale: Polarization Effects Reveal Mineral Orientation.
abstract: Here, we show results on X-ray absorption near edge structure spectroscopy in both transmission and X-ray fluorescence full-field mode (FF-XANES) at the calcium K-edge on human bone tissue in healthy and diseased conditions and for different tissue maturation stages. We observe that the dominating spectral differences originating from different tissue regions, which are well pronounced in the white line and postedge structures are associated with polarization effects. These polarization effects dominate the spectral variance and must be well understood and modeled before analyzing the very subtle spectral variations related to the bone tissue variations itself. However, these modulations in the fine structure of the spectra can potentially be of high interest to quantify orientations of the apatite crystals in highly structured tissue matrices such as bone. Due to the extremely short wavelengths of X-rays, FF-XANES overcomes the limited spatial resolution of other optical and spectroscopic techniques exploiting visible light. Since the field of view in FF-XANES is rather large the acquisition times for analyzing the same region are short compared to, for example, X-ray diffraction techniques. Our results on the angular absorption dependence were verified by both site-matched polarized Raman spectroscopy, which has been shown to be sensitive to the orientation of bone building blocks and by mathematical simulations of the angular absorbance dependence. As an outlook we further demonstrate the polarization based assessment of calcium-containing crystal orientation and specification of calcium in a beta-tricalcium phosphate (β-Ca3(PO4)2 scaffold implanted into ovine bone. Regarding the use of XANES to assess chemical properties of Ca in human bone tissue our data suggest that neither the anatomical site (tibia vs jaw) nor pathology (healthy vs necrotic jaw bone tissue) affected the averaged spectral shape of the XANES spectra.
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hesse
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Murielle
authors.initials: M
authors.lastname: Salome
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Hiram
authors.initials: H
authors.lastname: Castillo-Michel
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.|Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8220, Laboratoire D'Archéologie Moléculaire et Structurale (LAMS), Paris, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Cotte
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.|LPS UMR8502 - Université Paris , Sud-91405 Orsay, cedex - France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Fayard
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Sahle
authors.affiliation: European Synchrotron Radiation Facility , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Wout
authors.initials: W
authors.lastname: De Nolf
authors.affiliation: Charité-Universitätsmedizin Berlin , Berlin, Germany.|Czech Technical University in Prague , Faculty of Nuclear Science and Physical Engineering, 166 36 Prague 6, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Hradilova
authors.affiliation: MIT , Department of Civil and Environmental Engineering, 77 Massachusetts Avenue, 02139 Cambridge, Massachussetts, United States.
authors.forename: Admir
authors.initials: A
authors.lastname: Masic
authors.affiliation: Technical University of Berlin , Institute for Optics and Atomic Physics, 10623 Berlin, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Kanngießer
authors.affiliation: RMS Foundation , CH-2544 Bettlach, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Bohner
authors.affiliation: AO Research Institute Davos , 7270 Davos, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Varga
authors.affiliation: Charité-Universitätsmedizin Berlin , Berlin, Germany.
authors.forename: Kay
authors.initials: K
authors.lastname: Raum
authors.affiliation: Charité-Universitätsmedizin Berlin , Berlin, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schrof
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry; D003198:Computer Simulation; D000071538:Cortical Bone / Q000737:chemistry*; D005453:Fluorescence; D006801:Humans; D008903:Minerals / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D056928:X-Ray Absorption Spectroscopy; D014965:X-Rays
chemical_list: D002130:Calcium Phosphates; D008903:Minerals; C485817:beta-tricalcium phosphate; D002118:Calcium