The Experts below are selected from a list of 14025 Experts worldwide ranked by ideXlab platform

Angelo Karunaratne - One of the best experts on this subject based on the ideXlab platform.

  • mechanical response of cortical bone in compression and tension at the mineralized fibrillar level in steroid induced Osteoporosis
    Composites Part B-engineering, 2020
    Co-Authors: Li Xi, Wenwang Wu, Zhaoliang Qu, Angelo Karunaratne, Binbin Liao, Ying Li, Daining Fang
    Abstract:

    Abstract Nanocomposites like bone are used in vivo in a dynamic mechanical environment, and musculoskeletal fracture during traumatic events lead to pain and immobilisation, especially significant in elderly and patients with metabolic bone diseases. To mitigate against these occurrences, it is essential to understand the dynamic mechanical response of bone over short timescales, but the underlying matrix-level mechanisms are not well understood. Here, we studied the mechanical response of cortical bone at nano- and micro-scale in a mouse model with glucocorticoid induced Osteoporosis and their wild type littermates using real-time synchrotron small-angle X-ray diffraction (SAXD) combined with in situ compression testing and micro-tensile testing under controlled strain rates. Under compression, the tissue modulus, yield stress, effective fibril modulus and fibrillar reorientation rate in osteoporotic bone is significantly lower than that in healthy bone. Under tension, when going from low to high strain rates, the effective fibril modulus of healthy bone increase by a factor of 4.8, but this tendency is suppressed in osteoporotic bone. Also, bone microstructure in osteoporotic showed large fraction of cavities with disrupted mineralization. Our results demonstrate how the nano- and microscale deformation mechanisms of bone ultrastructure change in osteoporotic bone under compression and tension. Our results suggest that material level changes of bone matrix contributed to the reduced mechanical competence of bone in metabolic bone diseases such as Osteoporosis.

  • bone matrix development in steroid induced Osteoporosis is associated with a consistently reduced fibrillar stiffness linked to altered bone mineral quality
    Acta Biomaterialia, 2018
    Co-Authors: Angelo Karunaratne, P De Falco, Ettore Barbieri, Liz Bentley, Christopher T Esapa, Nicholas J Terrill, Steve D M Brown, Roger D Cox, G R Davis
    Abstract:

    Abstract Glucocorticoid-induced Osteoporosis (GIOP) is a major secondary form of Osteoporosis, with the fracture risk significantly elevated – at similar levels of bone mineral density – in patients taking glucocorticoids compared with non-users. The adverse bone structural changes at multiple hierarchical levels in GIOP, and their mechanistic consequences leading to reduced load-bearing capacity, are not clearly understood. Here we combine experimental X-ray nanoscale mechanical imaging with analytical modelling of the bone matrix mechanics to determine mechanisms causing bone material quality deterioration during development of GIOP. In situ synchrotron small-angle X-ray diffraction combined with tensile testing was used to measure nanoscale deformation mechanisms in a murine model of GIOP, due to a corticotrophin-releasing hormone promoter mutation, at multiple ages (8-, 12-, 24- and 36 weeks), complemented by quantitative micro-computed tomography and backscattered electron imaging to determine mineral concentrations. We develop a two-level hierarchical model of the bone matrix (mineralized fibril and lamella) to predict fibrillar mechanical response as a function of architectural parameters of the mineralized matrix. The fibrillar elastic modulus of GIOP-bone is lower than healthy bone throughout development, and nearly constant in time, in contrast to the progressively increasing stiffness in healthy bone. The lower mineral platelet aspect ratio value for GIOP compared to healthy bone in the multiscale model can explain the fibrillar deformation. Consistent with this result, independent measurement of mineral platelet lengths from wide-angle X-ray diffraction finds a shorter mineral platelet length in GIOP. Our results show how lowered mineralization combined with altered mineral nanostructure in GIOP leads to lowered mechanical competence. Significance Statement Increased fragility in musculoskeletal disorders like Osteoporosis are believed to arise due to alterations in bone structure at multiple length-scales from the organ down to the supramolecular-level, where collagen molecules and elongated mineral nanoparticles form stiff fibrils. However, the nature of these molecular-level alterations are not known. Here we used X-ray scattering to determine both how bone fibrils deform in secondary Osteoporosis, as well as how the fibril orientation and mineral nanoparticle structure changes. We found that osteoporotic fibrils become less stiff both because the mineral nanoparticles became shorter and less efficient at transferring load from collagen, and because the fibrils are more randomly oriented. These results will help in the design of new composite musculoskeletal implants for bone repair.

Li Xi - One of the best experts on this subject based on the ideXlab platform.

  • mechanical response of cortical bone in compression and tension at the mineralized fibrillar level in steroid induced Osteoporosis
    Composites Part B-engineering, 2020
    Co-Authors: Li Xi, Wenwang Wu, Zhaoliang Qu, Angelo Karunaratne, Binbin Liao, Ying Li, Daining Fang
    Abstract:

    Abstract Nanocomposites like bone are used in vivo in a dynamic mechanical environment, and musculoskeletal fracture during traumatic events lead to pain and immobilisation, especially significant in elderly and patients with metabolic bone diseases. To mitigate against these occurrences, it is essential to understand the dynamic mechanical response of bone over short timescales, but the underlying matrix-level mechanisms are not well understood. Here, we studied the mechanical response of cortical bone at nano- and micro-scale in a mouse model with glucocorticoid induced Osteoporosis and their wild type littermates using real-time synchrotron small-angle X-ray diffraction (SAXD) combined with in situ compression testing and micro-tensile testing under controlled strain rates. Under compression, the tissue modulus, yield stress, effective fibril modulus and fibrillar reorientation rate in osteoporotic bone is significantly lower than that in healthy bone. Under tension, when going from low to high strain rates, the effective fibril modulus of healthy bone increase by a factor of 4.8, but this tendency is suppressed in osteoporotic bone. Also, bone microstructure in osteoporotic showed large fraction of cavities with disrupted mineralization. Our results demonstrate how the nano- and microscale deformation mechanisms of bone ultrastructure change in osteoporotic bone under compression and tension. Our results suggest that material level changes of bone matrix contributed to the reduced mechanical competence of bone in metabolic bone diseases such as Osteoporosis.

P De Falco - One of the best experts on this subject based on the ideXlab platform.

  • bone matrix development in steroid induced Osteoporosis is associated with a consistently reduced fibrillar stiffness linked to altered bone mineral quality
    Acta Biomaterialia, 2018
    Co-Authors: Angelo Karunaratne, P De Falco, Ettore Barbieri, Liz Bentley, Christopher T Esapa, Nicholas J Terrill, Steve D M Brown, Roger D Cox, G R Davis
    Abstract:

    Abstract Glucocorticoid-induced Osteoporosis (GIOP) is a major secondary form of Osteoporosis, with the fracture risk significantly elevated – at similar levels of bone mineral density – in patients taking glucocorticoids compared with non-users. The adverse bone structural changes at multiple hierarchical levels in GIOP, and their mechanistic consequences leading to reduced load-bearing capacity, are not clearly understood. Here we combine experimental X-ray nanoscale mechanical imaging with analytical modelling of the bone matrix mechanics to determine mechanisms causing bone material quality deterioration during development of GIOP. In situ synchrotron small-angle X-ray diffraction combined with tensile testing was used to measure nanoscale deformation mechanisms in a murine model of GIOP, due to a corticotrophin-releasing hormone promoter mutation, at multiple ages (8-, 12-, 24- and 36 weeks), complemented by quantitative micro-computed tomography and backscattered electron imaging to determine mineral concentrations. We develop a two-level hierarchical model of the bone matrix (mineralized fibril and lamella) to predict fibrillar mechanical response as a function of architectural parameters of the mineralized matrix. The fibrillar elastic modulus of GIOP-bone is lower than healthy bone throughout development, and nearly constant in time, in contrast to the progressively increasing stiffness in healthy bone. The lower mineral platelet aspect ratio value for GIOP compared to healthy bone in the multiscale model can explain the fibrillar deformation. Consistent with this result, independent measurement of mineral platelet lengths from wide-angle X-ray diffraction finds a shorter mineral platelet length in GIOP. Our results show how lowered mineralization combined with altered mineral nanostructure in GIOP leads to lowered mechanical competence. Significance Statement Increased fragility in musculoskeletal disorders like Osteoporosis are believed to arise due to alterations in bone structure at multiple length-scales from the organ down to the supramolecular-level, where collagen molecules and elongated mineral nanoparticles form stiff fibrils. However, the nature of these molecular-level alterations are not known. Here we used X-ray scattering to determine both how bone fibrils deform in secondary Osteoporosis, as well as how the fibril orientation and mineral nanoparticle structure changes. We found that osteoporotic fibrils become less stiff both because the mineral nanoparticles became shorter and less efficient at transferring load from collagen, and because the fibrils are more randomly oriented. These results will help in the design of new composite musculoskeletal implants for bone repair.

Daining Fang - One of the best experts on this subject based on the ideXlab platform.

  • mechanical response of cortical bone in compression and tension at the mineralized fibrillar level in steroid induced Osteoporosis
    Composites Part B-engineering, 2020
    Co-Authors: Li Xi, Wenwang Wu, Zhaoliang Qu, Angelo Karunaratne, Binbin Liao, Ying Li, Daining Fang
    Abstract:

    Abstract Nanocomposites like bone are used in vivo in a dynamic mechanical environment, and musculoskeletal fracture during traumatic events lead to pain and immobilisation, especially significant in elderly and patients with metabolic bone diseases. To mitigate against these occurrences, it is essential to understand the dynamic mechanical response of bone over short timescales, but the underlying matrix-level mechanisms are not well understood. Here, we studied the mechanical response of cortical bone at nano- and micro-scale in a mouse model with glucocorticoid induced Osteoporosis and their wild type littermates using real-time synchrotron small-angle X-ray diffraction (SAXD) combined with in situ compression testing and micro-tensile testing under controlled strain rates. Under compression, the tissue modulus, yield stress, effective fibril modulus and fibrillar reorientation rate in osteoporotic bone is significantly lower than that in healthy bone. Under tension, when going from low to high strain rates, the effective fibril modulus of healthy bone increase by a factor of 4.8, but this tendency is suppressed in osteoporotic bone. Also, bone microstructure in osteoporotic showed large fraction of cavities with disrupted mineralization. Our results demonstrate how the nano- and microscale deformation mechanisms of bone ultrastructure change in osteoporotic bone under compression and tension. Our results suggest that material level changes of bone matrix contributed to the reduced mechanical competence of bone in metabolic bone diseases such as Osteoporosis.

Wenwang Wu - One of the best experts on this subject based on the ideXlab platform.

  • mechanical response of cortical bone in compression and tension at the mineralized fibrillar level in steroid induced Osteoporosis
    Composites Part B-engineering, 2020
    Co-Authors: Li Xi, Wenwang Wu, Zhaoliang Qu, Angelo Karunaratne, Binbin Liao, Ying Li, Daining Fang
    Abstract:

    Abstract Nanocomposites like bone are used in vivo in a dynamic mechanical environment, and musculoskeletal fracture during traumatic events lead to pain and immobilisation, especially significant in elderly and patients with metabolic bone diseases. To mitigate against these occurrences, it is essential to understand the dynamic mechanical response of bone over short timescales, but the underlying matrix-level mechanisms are not well understood. Here, we studied the mechanical response of cortical bone at nano- and micro-scale in a mouse model with glucocorticoid induced Osteoporosis and their wild type littermates using real-time synchrotron small-angle X-ray diffraction (SAXD) combined with in situ compression testing and micro-tensile testing under controlled strain rates. Under compression, the tissue modulus, yield stress, effective fibril modulus and fibrillar reorientation rate in osteoporotic bone is significantly lower than that in healthy bone. Under tension, when going from low to high strain rates, the effective fibril modulus of healthy bone increase by a factor of 4.8, but this tendency is suppressed in osteoporotic bone. Also, bone microstructure in osteoporotic showed large fraction of cavities with disrupted mineralization. Our results demonstrate how the nano- and microscale deformation mechanisms of bone ultrastructure change in osteoporotic bone under compression and tension. Our results suggest that material level changes of bone matrix contributed to the reduced mechanical competence of bone in metabolic bone diseases such as Osteoporosis.