Thermal changes in young and mature bone nanostructure probed with Ca 2p excitations

Abstract

Thermal dependence of mineralized bone structure is examined both experimentally by measuring the near edge X-ray absorption fine structure (NEXAFS) and theoretically by applying the 3DSL model to clarify relationship between the local electronic and atomic structure and hierarchical organization of skeleton. The high energy resolution NEXAFS spectra are acquired near the Ca 2p edges in native bone heated from RT up to 450C and hydroxyapatite (Ca10(PO4)6(OH)2, OH-Ap) to understand the interplay of short-, long-and super-range order parameters of bone matter. Our focus is on the thermal changes of spectral distribution of oscillator strength for Ca 2p 1 2, ⁄ 3 2 ⁄ → 3d transition in bone and OH-Ap. The investigations have confirmed the assignment of the OH-Ap-to-bone spectral changes to the predicted hierarchy effect on electronic and atomic structure of mineralized bone. At RT the OH-Ap-to-bone red shift 3d of the transition energy is found equal ≈ 0.2 eV and ≈ 0.1 eV for mature and young bone respectively. We stated that the shift behaves irregular and its magnitude varies from 0.1 eV up to 0.3 eV when the heating temperature grows. Two mechanisms associated with the thermal-induced dehydration of the inter-nanocrystallite spaces and with the subsequent atomic restructuring of the nanocrystallite interface in mineralized phase are revealed. We have detected that the OH-Ap-to-bone red shifts of the Ca 2p → 3d transition in young bone are smaller than those of in mature bone. The origin of the age differences is discussed.

Raman and XANES Spectroscopic Study of the Influence of Coordination Atomic and Molecular Environments in Biomimetic Composite Materials Integrated with Dental Tissue

“…Thus, for stoichiometric HAp (H S ), wide L 2 and L 3 absorption edge bands with high-intensity maxima in the 345-350 eV and 352-354 eV regions are observed in the calcium spectra. This fact correlates with known information about the dominance of the Ca II state and the influence of the OH environment on the experimental width of the L 2 and L 3 main absorption maxima [68,75]. In turn, for the reference nano-cHAp samples (H 1 , H 2 , H 3 ) synthesised using the chemical deposition method, a broadening of the L 2 and L 3 absorption bands is observed, but with pronounced satellites corresponding to the predominance of Ca II states.…”

Development of a Hybrid Biomimetic Enamel-Biocomposite Interface and a Study of Its Molecular Features Using Synchrotron Submicron ATR-FTIR Microspectroscopy and Multivariate Analysis Techniques

“…The results of work on the analysis of the surface layers of nanocrystalline biogenic and synthetic apatite [ 94 ] have already demonstrated differences in the local atomic and molecular environment of calcium atoms, which may affect the formation of the HAp–organic matrix bond [ 22 ]. As studies on the surface of biogenic apatite nanocrystals have shown, the environment of calcium atoms corresponds to the Ca-ON environment [ 94 , 95 ]. Therefore, in the S IV interface formation process under consideration, the repeated calcium alkali treatment process can contribute to the formation of conditions when the pretreated enamel surface after etching has bonds characteristic of the enamel apatite complex before treatment and contribute to the formation of bonds with amino acids in the composition of the booster used.…”

Crystalline and amorphous calcium carbonate as structural components of the Calappa granulata exoskeleton

“…On the other hand, the lattice modes that appear in the low-frequency part of the Raman spectrum can be safely used for the identification of the crystalline CaCO 3 polytypes, as they are mostly affected by the symmetry of the crystal (Nehrke et al, 2012). NEXAFS spectroscopy is also applied for the study of calcified tissues (Konashuk et al, 2018;Pavlychev et al, 2016;Petrova et al, 2017). It is element specific and probes the partial density of empty electronic states providing information on the local bonding configuration and symmetry (Stöhr, 2003).…”