scholarly journals Fibrillar-Level Strain Gradients Across the Calcified Bone-Cartilage Interface

2021 ◽  
Author(s):  
Waqas Badar ◽  
Husna Ali ◽  
Olivia N Brooker ◽  
E. Newham ◽  
Tim Snow ◽  
...  
Keyword(s):  
Molecular Level ◽  
Swelling Pressure ◽  
Tissue Level ◽  
Research Reporting ◽  
The Matrix ◽  
Calcified Tissue ◽  
Osteoarthritis Progression ◽  
Residual Strains ◽  
Adaptative Significance ◽  
Collagenous Tissues

AbstractThe bone-cartilage interface (BCI) and underlying calcified plate is a universal feature in diarthrodial joints. The BCI is an important mechanically-graded interface subjected to shear and compressive strains, and changes at the BCI have been linked to osteoarthritis progression. Here we report the existence of a physiological internal strain gradient (pre-strain) across the BCI at the ultrastructural scale of the extracellular matrix 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 BCI are in tension 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 due to reduced hydration and associated swelling pressure. Within the calcified tissue, a finer-scale gradient in pre-strain over ~50μm is likely linked to the tidemark. The increased fibrillar pre-strain at the BCI 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 the disruption of the molecular-level pre-strains during remodelling of the BCI may be a potential factor in osteoarthritis-based degeneration.

Morphology of High-Performance Rigid-Rod Polymer Fibers and Molecular Composites

1989 ◽  
Vol 47 ◽  
pp. 338-339
Author(s):  
W.W. Adams ◽  
S. J. Krause
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Liquid Crystalline ◽  
Molecular Level ◽  
Synergistic Effects ◽  
Tensile Modulus ◽  
Commercial Development ◽  
The Matrix ◽  
Molecular Composites ◽  
Rigid Rod

Rigid-rod polymers such as PBO, poly(paraphenylene benzobisoxazole), Figure 1a, are now in commercial development for use as high-performance fibers and for reinforcement at the molecular level in molecular composites. Spinning of liquid crystalline polyphosphoric acid solutions of PBO, followed by washing, drying, and tension heat treatment produces fibers which have the following properties: density of 1.59 g/cm3; tensile strength of 820 kpsi; tensile modulus of 52 Mpsi; compressive strength of 50 kpsi; they are electrically insulating; they do not absorb moisture; and they are insensitive to radiation, including ultraviolet. Since the chain modulus of PBO is estimated to be 730 GPa, the high stiffness also affords the opportunity to reinforce a flexible coil polymer at the molecular level, in analogy to a chopped fiber reinforced composite. The objectives of the molecular composite concept are to eliminate the thermal expansion coefficient mismatch between the fiber and the matrix, as occurs in conventional composites, to eliminate the interface between the fiber and the matrix, and, hopefully, to obtain synergistic effects from the exceptional stiffness of the rigid-rod molecule. These expectations have been confirmed in the case of blending rigid-rod PBZT, poly(paraphenylene benzobisthiazole), Figure 1b, with stiff-chain ABPBI, poly 2,5(6) benzimidazole, Fig. 1c A film with 30% PBZT/70% ABPBI had tensile strength 190 kpsi and tensile modulus of 13 Mpsi when solution spun from a 3% methane sulfonic acid solution into a film. The modulus, as predicted by rule of mixtures, for a film with this composition and with planar isotropic orientation, should be 16 Mpsi. The experimental value is 80% of the theoretical value indicating that the concept of a molecular composite is valid.

Residual Stress Measurements in Continuous Fiber Titanium Matrix Composites

1992 ◽  
Vol 36 ◽  
pp. 481-488 ◽  
Author(s):  
M. R. James ◽  
M. A. Bourke ◽  
J. A. Goldstone ◽  
A. C. Lawson
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Thin Sheet ◽  
Matrix Composites ◽  
X Ray ◽  
Residual Stress State ◽  
Longitudinal Residual Stress ◽  
The Matrix ◽  
Reinforcement Fiber ◽  
Residual Strains

AbstractMetal matrix composites develop residual strains after consolidation due to the thermal expansion mismatch between the reinforcement fiber and the matrix. X-ray and neutron diffraction measured values for the longitudinal residual stress in the matrix of three titanium MMCs are reported. For thick composites (> 6 plies) the surface stress measured by x-ray diffraction matches that determined by neutron diffraction and therefore represents the stress in the bulk region consisting of the fibers and matrix. For thin sheet composites, the surface values are lower than in the interior and increase as the outer rows of fibers are approached. While a rationale for this behavior has yet to be developed, accounting for composite thickness is important when using x-ray measured values to validate analytic and finite element calculations of the residual stress state.

scholarly journals Preparation and Evaluation of Intravaginal Ring Containing Drospirenone

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Ying Zhang ◽  
Chun-Xiao Li ◽  
Mei-Ying Ning ◽  
Xue-Yan Duan ◽  
Ying Liu
Keyword(s):  
Light Exposure ◽  
In Vitro Release ◽  
Tissue Level ◽  
Strong Light ◽  
Reservoir System ◽  
The Matrix ◽  
Reservoir Type ◽  
Preparation And Evaluation ◽  
Effective Contraceptive

In the present study, we investigated the feasibility of the vaginal administration of drospirenone silicone IVR. The in vitro release characteristics of matrix-type and reservoir-type IVR were compared under sink conditions in 21 days. At the same time, API excipients compatibility and preformulation study was performed by HPLC, IR, and DSC methods. Biocompatibility of reservoir system was evaluated by tolerability on tissue level in rats. It was found that, under strong light exposure, high temperature, and high humidity conditions, drospirenone and excipients had no significant interactions. The daily release of reservoir-type IVR was about 0.5 mg/d sustaining 21 days, which significantly decreased the burst effect compared with the matrix system. When drospirenone was modified by the PVPk30 in the reservoir system formulation, the daily release rate increased to 1.0 mg/d sustaining 21 days. The cumulative release of reservoir-type IVR was fitted to zero release equation. In addition, biocompatibility of drospirenone IVR system in this dosage is safe. It is feasibility feasibile to further developed for safe, convenient, and effective contraceptive drug delivery with reduced dosing interval.

Collagen organization in articular cartilage, determined by X-ray diffraction, and its relationship to tissue function

1981 ◽  
Vol 212 (1188) ◽  
pp. 299-304 ◽  
Keyword(s):  
Surface Layer ◽  
Deep Layer ◽  
Articular Surface ◽  
Swelling Pressure ◽  
Bimodal Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Collagen Organization ◽  
Patellar Cartilage ◽  
Calcified Tissue

X-ray diffraction has been used to measure the preferred orientation of the collagen fibrils, and their angular distribution within the tissue, as a function of depth from the articular surface in patellar cartilage. Measurements have been made at four different sites chosen to represent differing surface curvatures and régimes of wear. The orientation of fibrils in the surface layer allows it to oppose the swelling pressure exerted by the gel of hydrated glycosaminoglycans within the cartilage. An intermediate layer (where a bimodal distribution of fibrils is sometimes resolved) allows the orientation of the fibrils to change, with increasing depth, until they are roughly perpendicular to the articular surface. In this deep layer the fibrils can tie into the underlying calcified tissue so as to firmly anchor the cartilage. In the plane of the surface the fibrils tend to be aligned in the direction of stress caused by motion.

scholarly journals A novel fibre-ensemble level constitutive model for exogenous cross-linked collagenous tissues

2016 ◽  
Vol 6 (1) ◽  
pp. 20150090 ◽  
Author(s):  
Michael S. Sacks ◽  
Will Zhang ◽  
Silvia Wognum
Keyword(s):  
Constitutive Model ◽  
Soft Tissues ◽  
Fibrous Tissue ◽  
Collagen Fibre ◽  
Tissue Response ◽  
Loading Path ◽  
Cross Linking ◽  
The Matrix ◽  
The Cross ◽  
Collagenous Tissues

Exogenous cross-linking of soft collagenous tissues is a common method for biomaterial development and medical therapies. To enable improved applications through computational methods, physically realistic constitutive models are required. Yet, despite decades of research, development and clinical use, no such model exists. In this study, we develop the first rigorous full structural model (i.e. explicitly incorporating various features of the collagen fibre architecture) for exogenously cross-linked soft tissues. This was made possible, in-part, with the use of native to cross-linked matched experimental datasets and an extension to the collagenous structural constitutive model so that the uncross-linked collagen fibre responses could be mapped to the cross-linked configuration. This allowed us to separate the effects of cross-linking from kinematic changes induced in the cross-linking process, which in turn allowed the non-fibrous tissue matrix component and the interaction effects to be identified. It was determined that the matrix could be modelled as an isotropic material using a modified Yeoh model. The most novel findings of this study were that: (i) the effective collagen fibre modulus was unaffected by cross-linking and (ii) fibre-ensemble interactions played a large role in stress development, often dominating the total tissue response (depending on the stress component and loading path considered). An important utility of the present model is its ability to separate the effects of exogenous cross-linking on the fibres from changes due to the matrix. Applications of this approach include the utilization in the design of novel chemical treatments to produce specific mechanical responses and the study of fatigue damage in bioprosthetic heart valve biomaterials.

The Importance of Interactions at the Molecular Level: A Spectroscopic Study of a New Composite Sorber Material

2017 ◽  
Vol 71 (10) ◽  
pp. 2278-2285 ◽  
Author(s):  
Valentina Crocellà ◽  
Elena Groppo ◽  
Alessandro Dani ◽  
Alberto Castellero ◽  
Silvia Bordiga ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Raman Spectroscopy ◽  
Composite Material ◽  
Composite System ◽  
Molecular Level ◽  
Water Molecules ◽  
Magnesium Perchlorate ◽  
The Matrix ◽  
Ft Ir ◽  
Ir And Raman

The functional properties of a new composite material having water vapor getter properties have been investigated by a large arsenal of characterization techniques. The composite system is originated by combining two constituents having very different chemical natures, a magnesium perchlorate (Mg(ClO4)2) salt and a polymeric acrylic matrix. In particular, Fourier transform infrared (FT-IR) and Raman spectroscopy have been fundamental to understand the type of interactions between the salt and the matrix in different hydration conditions. It was found that in the anhydrous composite system the dispersed Mg(ClO4)2 salt retains its molecular structure, because Mg2+ cations are still surrounded by their [ClO4]– counter-anions; at the same time, the salt and the polymeric matrix chemically interact each other at the molecular level. These interactions gradually vanish in the presence of water, and disappear in the fully hydrated composite system, where the Mg2+ cations are completely solvated by the water molecules.

Cartilage: Multiscale Structure and Biomechanical Properties

MRS Advances ◽  
2016 ◽  
Vol 1 (8) ◽  
pp. 509-519
Author(s):  
Ferenc Horkay ◽  
Peter J. Basser ◽  
Anne-Marie Hecht ◽  
Erik Geissler
Keyword(s):  
Hyaluronic Acid ◽  
Small Angle ◽  
Swelling Pressure ◽  
Biomechanical Properties ◽  
Tissue Level ◽  
Biological Functions ◽  
Osmotic Swelling ◽  
X Ray ◽  
X Ray Scattering ◽  
Compressive Resistance

ABSTRACTCartilage is a load bearing tissue that has multiple biological functions. The major proteoglycan in cartilage is the bottlebrush shaped aggrecan whose complexes with hyaluronic acid provide the compressive resistance of cartilage. The negatively charged aggrecan-hyaluronic acid complexes generate an osmotic swelling pressure within the tissue, which is balanced by the collagen network. To better understand the function of cartilage at the tissue level, we study aggrecan assemblies using an array of microscopic and macroscopic techniques. The organization of aggrecan assemblies at the supramolecular level is probed by light scattering, small-angle neutron scattering and small-angle X-ray scattering. Osmotic and rheological measurements are used to investigate the macroscopic physical properties.

scholarly journals Exploiting Molecular Basis of Age and Gender Differences in Outcomes of SARS-CoV-2 Infections.

2021 ◽  
Author(s):  
Daniele Mercatelli ◽  
Elisabetta Pedace ◽  
Federico Manuel Giorgi ◽  
Pietro Hiram Guzzi
Keyword(s):  
Molecular Mechanisms ◽  
Molecular Level ◽  
Tissue Level ◽  
Adverse Outcomes ◽  
Aging Effects ◽  
Age And Gender ◽  
Gender And Age ◽  
Age And Gender Differences ◽  
And Gender ◽  
Public Datasets

Motivation: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (coronavirus disease, 2019; COVID-19) is associated with adverse outcomes in patients. It has been observed that lethality seems to be related to the age of patients. Moreover, it has been demonstrated that ageing causes some modifications at a molecular level. Objective: The study aims to shed out light on a possible link between the increased COVID-19 lethality and the molecular changes that occur in elderly people. Methods: We considered public datasets on ageing-related genes and their expression at tissue level. We selected interactors that are known to be related to ageing process. Then, we performed a networkbased analysis to identify interactors significantly related to both SARS-CoV-2 and ageing. Finally, we investigated changes on the expression level of coding genes at tissue, gender and age level. Results We observed a significant intersection between some SARS-CoV-2 interactors and ageing-related genes suggesting that those genes are particularly affected by COVID-19 infection. Our analysis evidenced that virus infection particularly affects ageing molecular mechanisms centred around proteins EEF2, NPM1, HMGA1, HMGA2, APEX1, CHEK1, PRKDC, and GPX4. We found that HMGA1, and NPM1 have a different expression in lung of males, while HMGA1, APEX1, CHEK1, EEF2, and NPM1 present changes in expression in males due to aging effects. Conclusion Our study generated a mechanistic framework to explaining the correlation between COVID-19 incidence in elderly patients and molecular mechanisms of ageing. This will provide testable hypotheses for future investigation and pharmacological solutions tailored on specific age ranges.

scholarly journals Experimental Pharmacology of Glucosamine Sulfate

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Riccardo Chiusaroli ◽  
Tiziana Piepoli ◽  
Tiziano Zanelli ◽  
Paola Ballanti ◽  
Marco Lanza ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Clinical Studies ◽  
Tissue Level ◽  
Glucosamine Sulfate ◽  
Relevant Model ◽  
Osteoarthritic Cartilage ◽  
Experimental Pharmacology ◽  
The Matrix ◽  
Cartilage Breakdown

Several clinical studies demonstrated that glucosamine sulfate (GS) is effective in controlling osteoarthritis (OA), showing a structure-modifying action. However, little is known about the molecular mechanism(s) by which GS exerts such action and about the effects of GS at a tissue level on osteoarthritic cartilage and other joint structures. Here we provide mechanistic evidence suggesting that in vitro GS attenuates NF-κB activation at concentrations in the range of those observed after GS administration to volunteers and patients, thus strengthening previous findings. Furthermore, we describe the effects of GS at a tissue level on the progression of the disease in a relevant model of spontaneous OA, the STR/ort mouse. In this model, the administration of GS at human corresponding doses was associated with a significant decrease of OA scores. Histomorphometry showed that the lesion surface was also significantly decreased, while the number of viable chondrocytes within the matrix was significantly increased. GS improved the course of OA in the STR/Ort mouse, by delaying cartilage breakdown as assessed histologically and histomorphometrically.

Assessment of Three Possible Criteria for Remodelling of Collagen Gels and Collagenous Tissues

2010 ◽  
Author(s):  
Martin Kroon
Keyword(s):  
Deformation Gradient ◽  
Collagen Gel ◽  
Collagen Matrix ◽  
Experimental Results ◽  
Cauchy Stress ◽  
Collagen Gels ◽  
Collagen Fibres ◽  
The Matrix ◽  
Collagenous Tissues ◽  
External Loads

Collagenous tissues are living structures, in which new material may be added and the structural organisation may change over time. The maintenance of the collagen matrix is accomplished by fibre-producing cells, such as fibroblasts. During maintenance, the extracellular matrix (ECM) influences the development, shape, migration, proliferation, survival, and function of the cells. The mobility of the fibroblasts and their ability to contract the ECM are important properties for a proper maintenance of the ECM [1,2]. The purpose of the present paper is to shed some more light on the interaction between the ECM and the fibre-producing cells. The fibroblasts remodel the collagen gel by reorienting the individual collagen fibres. This reorientation of fibres is described by an evolution law, which depends on a continuum mechanics entity. Three possible choices are assessed: reorientation towards increasing Cauchy stress, increasing elastic stretch, and increasing current stiffness of the material. The model is compared with experimental results, and the three different criteria are evaluated in terms of the predicted distribution of collagen fibres after remodeling and resulting stress-strain relations. Experimental results from tissue equivalents in the form of collagen gels are used when assessing the three criteria [3]. We consider a network of collagen fibres, where the fibres are embedded in a matrix fluid. The collagen fabric and the surrounding fluid are assumed to be the only load-carrying constituents in the material. Embedded in and attached to the collagen fabric is also a population of fibroblasts. The collagen fabric is composed of collagen fibres, which in turn are bundles of collagen fibrils. The deformation of a line element in the matrix is described by the deformation gradient F(X) = ∂x/∂X, which is decomposed according to F = FelFlfFr, see Fig. 1. The fibroblasts’ remodelling of the collagen fabric results in a new matrix configuration Ωr. This deformation of the matrix is described by Fr. The configuration Ωr does not necessarily fulfill equilibrium, and the deformation gradient Flf takes the matrix to the state Ωlf, that fulfils global equilibrium with no external loads applied. Finally, if external loads are applied to the material, the configuration Ωel is attained, and this deformation is described by the deformation gradient Fel.

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