I22-Small angle scattering & Diffraction
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Minghui
Sun
,
Zheng
Dong
,
Liyuan
Wu
,
Haodong
Yao
,
Wenchao
Niu
,
Deting
Xu
,
Ping
Chen
,
Himadri S.
Gupta
,
Yi
Zhang
,
Yuhui
Dong
,
Chunying
Chen
,
Lina
Zhao
Open Access
Abstract: Structural disclosure of biological materials can help our understanding of design disciplines in nature and inspire research for artificial materials. Synchrotron microfocus X-ray diffraction is one of the main techniques for characterizing hierarchically structured biological materials, especially the 3D orientation distribution of their interpenetrating nanofiber networks. However, extraction of 3D fiber orientation from X-ray patterns is still carried out by iterative parametric fitting, with disadvantages of time consumption and demand for expertise and initial parameter estimates. When faced with high-throughput experiments, existing analysis methods cannot meet the real time analysis challenges. In this work, using the assumption that the X-ray illuminated volume is dominated by two groups of nanofibers in a gradient biological composite, a machine-learning based method is proposed for fast and automatic fiber orientation metrics prediction from synchrotron X-ray micro-focused diffraction data. The simulated data were corrupted in the training procedure to guarantee the prediction ability of the trained machine-learning algorithm in real-world experimental data predictions. Label transformation was used to resolve the jump discontinuity problem when predicting angle parameters. The proposed method shows promise for application in the automatic data-processing pipeline for fast analysis of the vast data generated from multiscale diffraction-based tomography characterization of textured biomaterials.
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May 2023
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[25602]
Open Access
Abstract: The bone-cartilage unit (BCU) is a universal feature in diarthrodial joints, which is mechanically-graded and subjected to shear and compressive strains. Changes in the BCU have been linked to osteoarthritis (OA) progression. Here we report existence of a physiological internal strain gradient (pre-strain) across the BCU at the ultrastructural scale of the extracellular matrix (ECM) constituents, specifically the collagen fibril. We use X-ray scattering that probes changes in the axial periodicity of fibril-level D-stagger of tropocollagen molecules in the matrix fibrils, as a measure of microscopic pre-strain. We find that mineralized collagen nanofibrils in the calcified plate are in tensile pre-strain relative to the underlying trabecular bone. This behaviour contrasts with the previously accepted notion that fibrillar pre-strain (or D-stagger) in collagenous tissues always reduces with mineralization, via reduced hydration and associated swelling pressure. Within the calcified part of the BCU, a finer-scale gradient in pre-strain (0.6% increase over ~50μm) is observed. The increased fibrillar pre-strain is linked to prior research reporting large tissue-level residual strains under compression. The findings may have biomechanical adaptative significance: higher in-built molecular level resilience/damage resistance to physiological compression, and disruption of the molecular-level pre-strains during remodelling of the bone-cartilage interface may be potential factors in osteoarthritis-based degeneration.
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Sep 2022
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[18524]
Open Access
Abstract: Fibrotic scarring is prevalent in a range of collagenous tissue disorders. Understanding the role of matrix biophysics in contributing to fibrotic progression is important to develop therapies, as well as to elucidate biological mechanisms. Here, we demonstrate how microfocus small-angle X-ray scattering (SAXS), with in situ mechanics and correlative imaging, can provide quantitative and position-resolved information on the fibrotic matrix nanostructure and its mechanical properties. We use as an example the case of keloid scarring in skin. SAXS mapping reveals heterogeneous gradients in collagen fibrillar concentration, fibril pre-strain (variations in D-period) and a new interfibrillar component likely linked to proteoglycans, indicating evidence of a complex 3D structure at the nanoscale. Furthermore, we demonstrate a proof-of-principle for a diffraction-contrast correlative imaging technique, incorporating, for the first time, DIC and SAXS, and providing an initial estimate for measuring spatially resolved fibrillar-level strain and reorientation in such heterogeneous tissues. By application of the method, we quantify (at the microscale) fibrillar reorientations, increases in fibrillar D-period variance, and increases in mean D-period under macroscopic tissue strains of ~20%. Our results open the opportunity of using synchrotron X-ray nanomechanical imaging as a quantitative tool to probe structure–function relations in keloid and other fibrotic disorders in situ.
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Mar 2022
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[11806]
Abstract: Mutable connective tissues of the sea cucumbers’ dermis can assume three different mechanical states (soft, standard and stiff) according to the chemical changes in the water.
There is broad consensus that variable cross-linking of the extracellular matrix is responsible for such changes. This paper uses Small-angle X-ray Scattering (SAXS) measurements, a micromechanical viscoelastic model, and a molecular extended reptation theory to look for other causes beyond cross-linking.
We conclude that in potassium-ions enriched seawater, the interfibrillar matrix stiffens due to increased cross-linking, but this must also imply macromolecular chain scission change in molecular weight and increased friction between the chains.
In softening water solution (calcium-ions deprived seawater), the interfibrillar matrix softens because of decreased cross-linking, and simultaneously macromolecules chain recombine and friction between the chains decreases.
These findings allow us to conclude that the zero-shear viscosity increases more than five times during stiffening and reduces to 3% of its standard value during softening.
Also, we find that the fibril strains measured through SAXS seem to suggest that, in reference conditions, the interfibrillar matrix (artificial sea water) behaves similarly to a covalently cross-linked gel; instead, during softening and stiffening, it appears that the matrix shows stress relaxation akin to an ionic cross-linked gel.
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Feb 2022
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Open Access
Abstract: Biomechanical changes to the collagen fibrillar architecture in articular cartilage are believed to play a crucial role in enabling normal joint function. However, experimentally there is little quantitative knowledge about the structural response of the Type II collagen fibrils in cartilage to cyclic loading in situ, and the mechanisms that drive the ability of cartilage to withstand long-term repetitive loading. Here we utilize synchrotron small-angle X-ray scattering (SAXS) combined with in-situ cyclic loading of bovine articular cartilage explants to measure the fibrillar response in deep zone articular cartilage, in terms of orientation, fibrillar strain and inter-fibrillar variability in healthy cartilage and cartilage degraded by exposure to the pro-inflammatory cytokine IL-1β. We demonstrate that under repeated cyclic loading the fibrils reversibly change the width of the fibrillar orientation distribution whilst maintaining a largely consistent average direction of orientation. Specifically, the effect on the fibrillar network is a 3-dimensional conical orientation broadening around the normal to the joint surface, inferred by 3D reconstruction of X-ray scattering peak intensity distributions from the 2D pattern. Further, at the intrafibrillar level, this effect is coupled with reversible reduction in fibrillar pre-strain under compression, alongside increase in the variability of fibrillar pre-strain. In IL-1β degraded cartilage, the collagen rearrangement under cyclic loading is disrupted and associated with reduced tissue stiffness. These finding have implications as to how changes in local collagen nanomechanics might drive disease progression or vice versa in conditions such as osteoarthritis and provides a pathway to a mechanistic understanding of such diseases.
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Sep 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[9893, 11806, 12483]
Abstract: Metabolic bone diseases have an impact on the multi-scale structure of bone and its mechanical properties. This study aims to conduct quantitative analysis of the link between specific material-level changes and mechanical alterations of bone tissue. We combine several scanning probe methods with an analytical multiscale model to investigate these links in a mouse model (𝐶𝑟h−120∕+) with endogenous steroid production. Experimental results from our prior study are used, which showed significant changes in spatial maps of nano-scale orientation, mineralization, and microporosity in 𝐶𝑟h−120∕+ mice bone. An analytical composite/continuum mechanical model is incorporated with these experimental parameters to predict the progressive reduction in elastic moduli. The largest fractional reduction in elastic modulus is found to arise from incorporation of microscale porosity, followed by the reduced nanoscale degree of orientation. Our work provides both insights into the altered structure-performance relations and a systematic analytical framework for linking scanning micro- and nanoprobe experimental data on hierarchical structural materials to macroscopic biomechanical outcomes.
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Jun 2021
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I22-Small angle scattering & Diffraction
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Paolino
De Falco
,
Richard
Weinkamer
,
Wolfgang
Wagermaier
,
Chenghao
Li
,
Tim
Snow
,
Nicholas J.
Terrill
,
Himadri
Gupta
,
Pawan
Goyal
,
Martin
Stoll
,
Peter
Benner
,
Peter
Fratzl
Diamond Proposal Number(s):
[18524]
Open Access
Abstract: Small-angle X-ray scattering (SAXS) is an effective characterization technique for multi-phase nanocomposites. The structural complexity and heterogeneity of biological materials require the development of new techniques for the 3D characterization of their hierarchical structures. Emerging SAXS tomographic methods allow reconstruction of the 3D scattering pattern in each voxel but are costly in terms of synchrotron measurement time and computer time. To address this problem, an approach has been developed based on the reconstruction of SAXS invariants to allow for fast 3D characterization of nanostructured inhomogeneous materials. SAXS invariants are scalars replacing the 3D scattering patterns in each voxel, thus simplifying the 6D reconstruction problem to several 3D ones. Standard procedures for tomographic reconstruction can be directly adapted for this problem. The procedure is demonstrated by determining the distribution of the nanometric bone mineral particle thickness (T parameter) throughout a macroscopic 3D volume of bovine cortical bone. The T parameter maps display spatial patterns of particle thickness in fibrolamellar bone units. Spatial correlation between the mineral nanostructure and microscopic features reveals that the mineral particles are particularly thin in the vicinity of vascular channels.
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Apr 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[9893]
Abstract: Determining multiscale, concurrent strain and deformation mechanisms in hierarchical biological materials is a crucial engineering goal, to understand structural optimization strategies in Nature. However, experimentally characterizing complex strain and displacement fields within a 3D hierarchical composite, in a multiscale full-field manner, is challenging. Here, we determined the in-situ strains at the macro-, meso- and molecular-levels in stomatopod cuticle simultaneously, by exploiting the anisotropy of the 3D fibre diffraction coupled with sample rotation. The results demonstrate the method, using the mineralized 3D α-chitin fibre networks as strain sensors, can capture sub-micron deformation of a single lamella (mesoscale), can extract strain information of multiple constituents concurrently, and shows that α-chitin fibre networks deform elastically while the surrounding matrix deforms plastically before systematic failure under compression. Further, the results demonstrate a molecular-level pre-strain gradient in chitin fibres, resulting from different mineralization degrees in the exo- and endo cuticle.
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Oct 2020
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I22-Small angle scattering & Diffraction
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Abstract: Glucocorticoid (or steroid) induced osteoporosis (GIOP) is the leading form of secondary osteoporosis, affecting up to 50% of patients receiving chronic glucocorticoid therapy. Bone quantity (bone mass) changes in GIOP patients alone are inadequate to explain the increased fracture risk, and bone material changes (bone quality) at multiple levels have been implicated in the reduced mechanics. Quantitative analysis of specific material-level changes is limited. Here, we combined multiscale experimental techniques (scanning small/wide-angle X-ray scattering/diffraction, backscattered electron imaging, and X-ray radiography) to investigate these changes in a mouse model (Crh−120/+) with chronic endogenous steroid production. Nanoscale degree of orientation, the size distribution of mineral nanocrystals in the bone matrix, the spatial map of mineralisation on the femoral cortex, and the microporosity showed significant changes between GIOP and the control, especially in the endosteal cortex. Our work can provide insight into the altered structure-property relationship leading to lowered mechanical properties in GIOP.
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Sep 2020
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I22-Small angle scattering & Diffraction
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L.
Xi
,
P.
De Falco
,
E.
Barbieri
,
A.
Karunaratne
,
L.
Bentley
,
C. T.
Esapa
,
G. R.
Davis
,
N. J.
Terrill
,
R. D.
Cox
,
N. M.
Pugno
,
R. V.
Thakker
,
R.
Weinkamer
,
W. W.
Wu
,
D. N.
Fang
,
H. S.
Gupta
Diamond Proposal Number(s):
[9893, 11806, 12483]
Abstract: As bone is used in a dynamic mechanical environment, understanding the structural origins of its time-dependent mechanical behaviour – and the alterations in metabolic bone disease – is of interest. However, at the scale of the mineralized fibrillar matrix (nanometre-level), the nature of the strain-rate dependent mechanics is incompletely understood. Here, we investigate the fibrillar- and mineral-deformation behaviour in a murine model of Cushing’s syndrome, used to understand steroid induced osteoporosis, using synchrotron small- and wide-angle scattering/diffraction combined with in situ tensile testing at three strain rates ranging from 10-4 to 10-1 s-1. We find that the effective fibril- and mineral-modulus and fibrillar-reorientation show no significant increase with strain-rate in osteoporotic bone, but increase significantly in normal (wild-type) bone. By applying a fibril-lamellar two-level structural model of bone matrix deformation to fit the results, we obtain indications that altered collagen-mineral interactions at the nanoscale – along with altered fibrillar orientation distributions – may be the underlying reason for this altered strain-rate sensitivity. Our results suggest that an altered strain-rate sensitivity of the bone matrix in osteoporosis may be one of the contributing factors to reduced mechanical competence in such metabolic bone disorders, and that increasing this sensitivity may improve biomechanical performance.
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Nov 2019
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