scholarly journals Microstructure-based numerical simulation of the mechanical behaviour of ocular tissue

2019 ◽  
Vol 16 (154) ◽  
pp. 20180685 ◽  
Author(s):  
Dong Zhou ◽  
Ahmed Abass ◽  
Ashkan Eliasy ◽  
Harald P. Studer ◽  
Alexander Movchan ◽  
...  
Keyword(s):  
Collagen Fibril ◽  
Material Model ◽  
Ocular Tissues ◽  
X Ray ◽  
Material Parameters ◽  
Fine Mesh ◽  
Constitutive Material Model ◽  
X Ray Scattering ◽  
Age Related ◽  
Ray Scattering

This paper aims to present a novel full-eye biomechanical material model that incorporates the characteristics of ocular tissues at microstructural level, and use the model to analyse the age-related stiffening in tissue behaviour. The collagen content in ocular tissues, as obtained using X-ray scattering measurements, was represented by sets of Zernike polynomials that covered both the cornea and sclera, then used to reconstruct maps of collagen fibril magnitude and orientation on the three-dimensional geometry of the eye globe. Fine-mesh finite-element (FE) models with eye-specific geometry were built and supported by a user-defined material model (UMAT), which considered the regional variation of fibril density and orientation. The models were then used in an iterative inverse modelling study to derive the material parameters that represent the experimental behaviour of ocular tissues from donors aged between 50 and 90 years obtained in earlier ex vivo studies. Sensitivity analysis showed that reducing the number of directions that represented the anisotropy of collagen fibril orientation at each X-ray scattering measurement point from 180 to 16 would have limited and insignificant effect on the FE solution (0.08%). Inverse analysis resulted in material parameters that provided a close match with experimental intraocular pressure–deformation behaviour with a root mean square of error between 3.6% and 4.3%. The results also demonstrated a steady increase in mechanical stiffness in all ocular regions with age. A constitutive material model based on distributions of collagen fibril density and orientation has been developed to enable the accurate representation of the biomechanical behaviour of ocular tissues. The model offers a high level of control of stiffness and anisotropy across ocular globe, and therefore has the potential for use in planning surgical and medical procedures.

scholarly journals Pilot study on the effects of preservatives on corneal collagen parameters measured by small angle X-ray scattering analysis

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Susyn Joan Kelly ◽  
Lizette duPlessis ◽  
John Soley ◽  
Frazer Noble ◽  
Hannah Carolyn Wells ◽  
...  
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Diameter Distribution ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Triton X ◽  
Fibril Diameter ◽  
Corneal Collagen ◽  
Ray Scattering

Abstract Objective Small angle X-ray scattering (SAXS) analysis is a sensitive way of determining the ultrastructure of collagen in tissues. Little is known about how parameters measured by SAXS are affected by preservatives commonly used to prevent autolysis. We determined the effects of formalin, glutaraldehyde, Triton X and saline on measurements of fibril diameter, fibril diameter distribution, and D-spacing of corneal collagen using SAXS analysis. Results Compared to sections of sheep and cats’ corneas stored frozen as controls, those preserved in 5% glutaraldehyde and 10% formalin had significantly larger mean collagen fibril diameters, increased fibril diameter distribution and decreased D-spacing. Sections of corneas preserved in Triton X had significantly increased collagen fibril diameters and decreased fibril diameter distribution. Those preserved in 0.9% saline had significantly increased mean collagen fibril diameters and decreased diameter distributions. Subjectively, the corneas preserved in 5% glutaraldehyde and 10% formalin maintained their transparency but those in Triton X and 0.9% saline became opaque. Subjective morphological assessment of transmission electron microscope images of corneas supported the SAXS data. Workers using SAXS analysis to characterize collagen should be alerted to changes that can be introduced by common preservatives in which their samples may have been stored.

Collagen Fibril Orientation in Ovine and Bovine Leather Affects Strength: A Small Angle X-ray Scattering (SAXS) Study

2011 ◽  
Vol 59 (18) ◽  
pp. 9972-9979 ◽  
Author(s):  
Melissa M. Basil-Jones ◽  
Richard L. Edmonds ◽  
Sue M. Cooper ◽  
Richard G. Haverkamp
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Collagen Fibril Alignment and Deformation during Tensile Strain of Leather: A Small-Angle X-ray Scattering Study

2012 ◽  
Vol 60 (5) ◽  
pp. 1201-1208 ◽  
Author(s):  
Melissa M. Basil-Jones ◽  
Richard L. Edmonds ◽  
Gillian E. Norris ◽  
Richard G. Haverkamp
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Tensile Strain ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Ray Scattering

scholarly journals Effects of Preservatives on Corneal Collagen Parameters Measured by Small Angle X-Ray Scattering Analysis

2020 ◽  
Author(s):  
Susyn Kelly ◽  
Lizette duPlessis ◽  
John Soley ◽  
Frazer Noble ◽  
Hannah Carolyn Wells ◽  
...  
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Diameter Distribution ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Triton X ◽  
Fibril Diameter ◽  
Corneal Collagen ◽  
Ray Scattering

Abstract Objective: Small angle X-ray scattering (SAXS) analysis is a sensitive method for determining the ultrastructure of collagen in various tissues. Little is known about how parameters measured by SAXS are affected by preservatives, commonly used to prevent autolysis and strengthen sample tissues. We determined the effects of formalin, glutaraldehyde, Triton X and saline on measurements of fibril diameter, fibril diameter distribution, and D-spacing of corneal collagen using SAXS analysis. Results: Compared to control sheep and cats’ corneas, frozen at -80 °C, those preserved in 5% glutaraldehyde and 10% formalin had significantly larger mean collagen fibril diameters, increased fibril diameter distribution and decreased D-spacing. Corneas preserved in Triton X had significantly increased collagen fibril diameters and decreased fibril diameter distribution. Corneas preserved in 0.9% saline had significantly increased mean collagen fibril diameters and decreased diameter distributions. Subjectively, the corneas preserved in 5% glutaraldehyde and 10% formalin maintained their transparency but those in Triton X and 0.9% saline became opaque. Subjective morphological assessment of transmission electron microscope images of corneas supported the SAXS data. Workers using SAXS analysis to characterize collagen should be alerted to changes that can be introduced by common preservatives in which their samples may have been stored.

Collagen Fibril Orientation in Tissue Specimens from Atherosclerotic Plaque Explored Using Small Angle X-Ray Scattering

2021 ◽  
Author(s):  
Herbert Silva ◽  
Christopher Tassone ◽  
Elsie Gyang Ross ◽  
Jason T Lee ◽  
Wei Zhou ◽  
...  
Keyword(s):  
Atherosclerotic Plaque ◽  
Small Angle ◽  
Collagen Fibril ◽  
Soft Tissues ◽  
Plaque Rupture ◽  
Fibrous Tissue ◽  
Building Blocks ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Abstract Atherosclerotic plaques can gradually develop in certain arteries. Disruption of fibrous tissue in plaques can result in plaque rupture and thromboembolism, leading to heart attacks and strokes. Collagen fibrils are important tissue building blocks and tissue strength depends on how fibrils are oriented. Fibril orientation in plaque tissue may potentially influence vulnerability to disruption. While X-ray scattering has previously been used to characterize fibril orientations in soft tissues and bones, it has never been used for characterization of human atherosclerotic plaque tissue. This study served to explore fibril orientation in specimens from human plaques using small angle X-ray scattering. Plaque tissue was extracted from human femoral and carotid arteries, and each tissue specimen contained a region of calcified material. 3D collagen fibril orientation was determined along scan lines that started away from and then extended towards a given calcification. At locations several millimeters or more from a calcification, fibrils were found to be oriented predominantly in the circumferential direction of the plaque tissue. However, in a number of cases, the dominant fibril direction changed markedly near a calcification, from circumferential to longitudinal. Further study is needed to elucidate how these fibril patterns may change plaque tissue behavior.

scholarly journals Small-angle X-ray scattering of nanoporous materials

2020 ◽  
Vol 5 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Samuel S. Welborn ◽  
Eric Detsi
Keyword(s):  
Small Angle ◽  
Nanoporous Materials ◽  
General Process ◽  
X Ray ◽  
Material Parameters ◽  
X Ray Scattering ◽  
Ray Scattering

Schematic of the general process of small-angle X-ray scattering acquisition, fitting, and modeling to determine material parameters of nanoporous materials.

Small-angle X-ray scattering study of intramuscular fish bone: collagen fibril superstructure determined from equidistant meridional reflections

2008 ◽  
Vol 41 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Christian Burger ◽  
Hong-wen Zhou ◽  
Igors Sicŝ ◽  
Benjamin S. Hsiao ◽  
Benjamin Chu ◽  
...  
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Axial Direction ◽  
Fish Bone ◽  
Preferred Orientation ◽  
Bone Collagen ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ray Scattering

New insights into the bone collagen fibril superstructure have been obtained by novel small-angle X-ray scattering analysis. The analysis was carried out on the small-angle equidistant meridional reflections resulting from the periodic structure of collagen fibrils in their axial direction. Conventional two-dimensional analysis is difficult because of the large discrepancy of longitudinal and lateral length scales for individual fibrils, as well as their preferred orientation. The new approach represents an unapproximated analysis of the equidistant meridional reflections, which takes the exact separation of preferred orientation and fibril size effects into account. The analytical results (e.g.axial period, fibril diameteretc.) agree well with the parameters obtained from transmission electron microscopy.

scholarly journals Effects of Preservatives on Corneal Collagen Parameters Measured by Small Angle X-ray Scattering Analysis

2020 ◽  
Author(s):  
Susyn Kelly ◽  
Lizette duPlessis ◽  
John Soley ◽  
Frazer Noble ◽  
Hannah Catherine Wells ◽  
...  
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Diameter Distribution ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Triton X ◽  
Fibril Diameter ◽  
Corneal Collagen ◽  
Ray Scattering

Abstract Background: Collagen is a prominent structural protein in biological tissue, and little is known about the effect of preservatives, commonly used to preserve and study tissue, on collagen structures. Method: The study determined the effects of commonly used tissue preservatives on measurements of fibril diameter, fibril diameter distribution, and D-spacing of corneal collagen made using small angle X-ray scattering (SAXS) analysis. Results: Compared to control sheep and cats’ corneas that were preserved frozen at -80 °C, those preserved in 5% glutaraldehyde and 10% formalin had significantly larger mean collagen fibril diameters, increased fibril diameter distribution and decreased D-spacing. Corneas preserved in Triton X had significantly increased mean collagen fibril diameters and orientation indexes with decreased fibril diameter distribution. Corneas preserved in 0.9% saline had significantly increased mean collagen fibril diameters and decreased diameter distributions. Subjectively, the corneas preserved in 5% glutaraldehyde and 10% formalin maintained their transparency but those in Triton X and 0.9% saline became opaque. Subjective morphological assessment of transmission electron microscope images of corneas supported the SAXS data. Conclusions: Workers using SAXS analysis to characterize collagen should be alerted to changes that can be introduced by common preservatives in which their samples may have been stored.

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