1
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Gouws XA, Mastnak A, Kreplak L, Rutenberg AD. Anisotropic swelling due to hydration constrains anisotropic elasticity in biomaterial fibers. J Mech Behav Biomed Mater 2024; 160:106749. [PMID: 39317097 DOI: 10.1016/j.jmbbm.2024.106749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Revised: 08/08/2024] [Accepted: 09/14/2024] [Indexed: 09/26/2024]
Abstract
Naturally occurring protein fibers often undergo anisotropic swelling when hydrated. Within a tendon, a hydrated collagen fibril's radius expands by 40% but its length only increases by 5%. The same effect, with a similar relative magnitude, is observed for single hair shafts. Fiber hydration is known to affect elastic properties. Here we show that anisotropic swelling constrains the anisotropic linear elastic properties of fibers. First we show, using data from disparate previously reported studies, that anisotropic swelling can be described as an approximately linear function of water content. Then, under the observation that the elastic energy of swelling can be minimized by the anisotropic shape, we relate swelling anisotropy to elastic anisotropy - assuming radial (transverse) symmetry within a cylindrical geometry. We find an upper bound for the commonly measured axial Poisson ratio νzx<1/2. This is significantly below recently estimated values for collagen fibrils extracted from tissue-level measurements, but is consistent with both single hair shaft and single collagen fibril mechanical and hydration studies. Using νzx, we can then constrain the product γ≡(1-νxy)Ez/Ex - where νxy is the seldom measured transverse Poisson ratio and Ez/Ex is the ratio of axial to radial Young's moduli.
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Affiliation(s)
- Xander A Gouws
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Ana Mastnak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Andrew D Rutenberg
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 4R2, Nova Scotia, Canada.
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2
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Vassaux M. Heterogeneous Structure and Dynamics of Water in a Hydrated Collagen Microfibril. Biomacromolecules 2024; 25:4809-4818. [PMID: 38975936 DOI: 10.1021/acs.biomac.4c00183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Collagen type I is well-known for its outstanding mechanical properties which it inherits from its hierarchical structure. Collagen type I fibrils may be viewed as a heterogeneous material made of protein, macromolecules (such as glycosaminoglycans and proteoglycans) and water. Water content modulates the properties of these fibrils. Yet, the properties of water and the fine interactions of water with the protein constituent of these heterofibrils have only received limited attention. Here, we propose to model collagen type I fibrils as a hydrated structure made of tropocollagen molecules assembled in a microfibril crystal. We perform large-scale all-atom molecular dynamics simulations of the hydration of collagen fibrils beyond the onset of disassembly. We found that the structural and dynamic properties of water vary strongly with the level of hydration of the microfibril. More importantly, we found that the properties vary spatially within the 67 nm D-spacing periodic structure. Alteration of the structural and dynamical properties of the collagen microfibril occur first in the gap region. Overall, we identify that the change in the role of water molecules from glue to lubricant between tropocollagen molecules arises around 100% hydration while the microfibril begins to disassemble beyond 130% water content. Our findings are supported by a decrease in hydrogen bonding, recovery of bulk water properties and amorphization of the tropocollagen molecules packing. Our simulations reveal the structure and dynamics of hydrated collagen fibrils with unprecedented spatial resolution from physiological conditions to disassembly. Beyond the process of self-assembly and the emergence of mechanical properties of collagen type I fibrils, our results may also provide new insights into mineralization of collagen fibrils.
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Affiliation(s)
- Maxime Vassaux
- Univ. Rennes, CNRS, IPR - UMR 6251, Rennes, 35000, France
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3
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Blaker CL, Ashton DM, Hartnell N, Little CB, Clarke EC. Tendon biomechanical properties are altered by storage duration but not freeze-thaw temperatures or cycles. J Orthop Res 2024; 42:1180-1189. [PMID: 38245841 DOI: 10.1002/jor.25783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/11/2023] [Accepted: 12/24/2023] [Indexed: 01/22/2024]
Abstract
Tendon allograft and xenograft processing often involves one or more steps of freezing and thawing. As failure strength is an important graft consideration, this study aimed to evaluate effects on failure properties when varying freeze-thaw conditions. Kangaroo tendons, a potential xenograft source, were used to evaluate changes in ultimate tensile strength (UTS), failure strain and elastic modulus after exposure to different freezer-storage temperatures (-20°C vs. -80°C), storage durations (1, 3, 6, 9, or 12 months), number of freeze-thaw cycles (1, 2, 3, 4, 5, or 10), or freeze-thaw temperature ranges (including freezing in liquid nitrogen to thawing at 37°C). Tendons stored for 6 or more months had significantly increased UTS and elastic modulus compared with 1 or 3 months of storage. This increase occurred irrespective of the freezing temperature (-20°C vs. -80°C) or the number of freeze-thaw cycles (1 vs. 10). In contrast, UTS, failure strain and the elastic modulus were no different between storage temperatures, number of freeze-thaw cycles and multiple freeze-thaw cycles across a range of freeze and thaw temperatures. Common freeze-thaw protocols did not negatively affect failure properties, providing flexibility for graft testing, storage, transportation and decellularisation procedures. However, the change in properties with the overall storage duration has implications for assessing the consistent performance of grafts stored for short versus extended periods of time (<6 months vs. >6 months), and the interpretation of data obtained from tissues of varying or unknown storage durations.
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Affiliation(s)
- Carina L Blaker
- Murray Maxwell Biomechanics Laboratory, Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney and the Northern Sydney Local Health District, Sydney, New South Wales, Australia
- Sydney Musculoskeletal Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Dylan M Ashton
- Murray Maxwell Biomechanics Laboratory, Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney and the Northern Sydney Local Health District, Sydney, New South Wales, Australia
- Sydney Musculoskeletal Health, The University of Sydney, Sydney, New South Wales, Australia
| | | | - Christopher B Little
- Sydney Musculoskeletal Health, The University of Sydney, Sydney, New South Wales, Australia
- Raymond Purves Bone and Joint Research Laboratories, Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney and the Northern Sydney Local Health District, Sydney, New South Wales, Australia
| | - Elizabeth C Clarke
- Murray Maxwell Biomechanics Laboratory, Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney and the Northern Sydney Local Health District, Sydney, New South Wales, Australia
- Sydney Musculoskeletal Health, The University of Sydney, Sydney, New South Wales, Australia
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4
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Bracher S, Voumard B, Simon M, Kochetkova T, Pretterklieber M, Zysset P. Bone collagen tensile properties of the aging human proximal femur. Bone Rep 2024; 21:101773. [PMID: 38778833 PMCID: PMC11109327 DOI: 10.1016/j.bonr.2024.101773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 04/11/2024] [Accepted: 05/10/2024] [Indexed: 05/25/2024] Open
Abstract
Despite the dominant role of bone mass in osteoporotic fractures, aging bone tissue properties must be thoroughly understood to improve osteoporosis management. In this context, collagen content and integrity are considered important factors, although limited research has been conducted on the tensile behavior of demineralized compact bone in relation to its porosity and elastic properties in the native mineralized state. Therefore, this study aims (i) at examining the age-dependency of mineralized bone and collagen micromechanical properties; (ii) to test whether, and if so to which extent, collagen properties contribute to mineralized bone mechanical properties. Two cylindrical cortical bone samples from fresh frozen human anatomic donor material were extracted from 80 proximal diaphyseal sections from a cohort of 24 female and 19 male donors (57 to 96 years at death). One sample per section was tested in uniaxial tension under hydrated conditions. First, the native sample was tested elastically (0.25 % strain), and after demineralization, up to failure. Morphology and composition of the second specimen was assessed using micro-computed tomography, Raman spectroscopy, and gravimetric methods. Simple and multiple linear regression were employed to relate morphological, compositional, and mechanical variables with age and sex. Macro-tensile properties revealed that only elastic modulus of native samples was age dependent whereas apparent elastic modulus was sex dependent (p < 0.01). Compositional and morphological analysis detected a weak but significant age and sex dependency of relative mineral weight (r = -0.24, p < 0.05) and collagen disorder ratio (I∼1670/I∼1640, r = 0.25, p < 0.05) and a strong sex dependency of bone volume fraction while generally showing consistent results in mineral content assessment. Young's modulus of demineralized bone was significantly related to tissue mineral density and Young's modulus of native bone. The results indicate that mechanical properties of the organic phase, that include collagen and non-collagenous proteins, are independent of donor age. The observed reduction in relative mineral weight and corresponding overall stiffer response of the collagen network may be caused by a reduced number of mineral-collagen connections and a lack of extrafibrillar and intrafibrillar mineralization that induces a loss of waviness and a collagen fiber pre-stretch.
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Affiliation(s)
- Stefan Bracher
- ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland
| | - Benjamin Voumard
- ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland
| | - Mathieu Simon
- ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland
| | - Tatiana Kochetkova
- ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland
| | - Michael Pretterklieber
- Division of Macroscopic and Clinical Anatomy, Gottfried Schatz Research Center, Medical University of Graz, Austria
- Division of Anatomy, Center for Anatomy and Cell Biology, Medical University of Vienna, Austria
| | - Philippe Zysset
- ARTORG Center for Biomedical Engineering Research, University of Bern, Switzerland
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5
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Jacobson AM, Zhao X, Sommer S, Sadik F, Warden SJ, Newman C, Siegmund T, Allen MR, Surowiec RK. A comprehensive set of ultrashort echo time magnetic resonance imaging biomarkers to assess cortical bone health: A feasibility study at clinical field strength. Bone 2024; 181:117031. [PMID: 38311304 PMCID: PMC10923147 DOI: 10.1016/j.bone.2024.117031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/10/2024]
Abstract
INTRODUCTION Conventional bone imaging methods primarily use X-ray techniques to assess bone mineral density (BMD), focusing exclusively on the mineral phase. This approach lacks information about the organic phase and bone water content, resulting in an incomplete evaluation of bone health. Recent research highlights the potential of ultrashort echo time magnetic resonance imaging (UTE MRI) to measure cortical porosity and estimate BMD based on signal intensity. UTE MRI also provides insights into bone water distribution and matrix organization, enabling a comprehensive bone assessment with a single imaging technique. Our study aimed to establish quantifiable UTE MRI-based biomarkers at clinical field strength to estimate BMD and microarchitecture while quantifying bound water content and matrix organization. METHODS Femoral bones from 11 cadaveric specimens (n = 4 males 67-92 yrs of age, n = 7 females 70-95 yrs of age) underwent dual-echo UTE MRI (3.0 T, 0.45 mm resolution) with different echo times and high resolution peripheral quantitative computed tomography (HR-pQCT) imaging (60.7 μm voxel size). Following registration, a 4.5 mm HR-pQCT region of interest was divided into four quadrants and used across the multi-modal images. Statistical analysis involved Pearson correlation between UTE MRI porosity index and a signal-intensity technique used to estimate BMD with corresponding HR-pQCT measures. UTE MRI was used to calculate T1 relaxation time and a novel bound water index (BWI), compared across subregions using repeated measures ANOVA. RESULTS The UTE MRI-derived porosity index and signal-intensity-based estimated BMD correlated with the HR-pQCT variables (porosity: r = 0.73, p = 0.006; BMD: r = 0.79, p = 0.002). However, these correlations varied in strength when we examined each of the four quadrants (subregions, r = 0.11-0.71). T1 relaxometry and the BWI exhibited variations across the four subregions, though these differences were not statistically significant. Notably, we observed a strong negative correlation between T1 relaxation time and the BWI (r = -0.87, p = 0.0006). CONCLUSION UTE MRI shows promise for being an innocuous method for estimating cortical porosity and BMD parameters while also giving insight into bone hydration and matrix organization. This method offers the potential to equip clinicians with a more comprehensive array of imaging biomarkers to assess bone health without the need for invasive or ionizing procedures.
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Affiliation(s)
- Andrea M Jacobson
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA; Dept. of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - Xuandong Zhao
- Dept. of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - Stefan Sommer
- Swiss Center for Musculoskeletal Imaging (SCMI), Balgrist Campus, Zurich, Switzerland; Advanced Clinical Imaging Technology (ACIT), Siemens Healthineers International AG, Zurich, Switzerland.
| | - Farhan Sadik
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
| | - Stuart J Warden
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University Indianapolis, Indianapolis, IN, USA.
| | - Christopher Newman
- Dept. of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - Thomas Siegmund
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
| | - Matthew R Allen
- Dept. of Anatomy, Physiology, and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - Rachel K Surowiec
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA; Dept. of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA.
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6
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Deymier AC, Deymier PA. Open-system force-elongation relationship of collagen in chemo-mechanical equilibrium with water. J Mech Behav Biomed Mater 2024; 152:106464. [PMID: 38367533 DOI: 10.1016/j.jmbbm.2024.106464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 02/07/2024] [Accepted: 02/13/2024] [Indexed: 02/19/2024]
Abstract
A significant deformation mechanism of collagen at low loads is molecular uncoiling and rearrangement. Although the effect of hydration and cross-linking has been investigated at larger loads when collagen undergoes molecular sliding, their effects on collagen molecular reorganization remain unclear. Here we develop two thermodynamic models that use the notion of open-system elasticity to elucidate the effect of swelling due to water uptake during deformation of collagen networks under low and high cross-linking conditions. With low crosslinking, entropic contributions dominate resulting in rejection of solvent from the polymer network leading to reduced collagen stiffness with increased loads. Contrarily, high cross-linking inhibits initial coiling and structural kinking and the mechanical behavior is dominated by elastic energy. In this configuration, the solvent content depends on the sign of the applied load resulting in a non-linear open-system stress-strain relationship. The models provide insight on the parameters that impact the stress-strain relationships of hydrated collagen and can inform the way collagenous matrices are treated both in medical and laboratory settings.
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Affiliation(s)
- A C Deymier
- Department of Biomedical Engineering, UConn Health, Farmington, CT, USA.
| | - P A Deymier
- Department of Materials Science and Engineering, University of Arizona, Tucson, AZ, 85721, USA
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7
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Magerle R, Zech P, Dehnert M, Bendixen A, Otto A. Rate-independent hysteretic energy dissipation in collagen fibrils. SOFT MATTER 2024; 20:2831-2839. [PMID: 38456340 DOI: 10.1039/d3sm01625k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2024]
Abstract
Nanoindentation cycles measured with an atomic force microscope on hydrated collagen fibrils exhibit a rate-independent hysteresis with return point memory. This previously unknown energy dissipation mechanism describes in unified form elastoplastic indentation, capillary adhesion, and surface leveling at indentation velocities smaller than 1 μm s-1, where viscous friction is negligible. A generic hysteresis model, based on force-distance data measured during one large approach-retract cycle, predicts the force (output) and the dissipated energy for arbitrary indentation trajectories (input). While both quantities are rate independent, they do depend nonlinearly on indentation history and on indentation amplitude.
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Affiliation(s)
- Robert Magerle
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09107 Chemnitz, Germany.
| | - Paul Zech
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09107 Chemnitz, Germany.
| | - Martin Dehnert
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09107 Chemnitz, Germany.
| | - Alexandra Bendixen
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09107 Chemnitz, Germany.
| | - Andreas Otto
- Fakultät für Naturwissenschaften, Technische Universität Chemnitz, 09107 Chemnitz, Germany.
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8
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Díaz-de-la-Loza MDC, Stramer BM. The extracellular matrix in tissue morphogenesis: No longer a backseat driver. Cells Dev 2024; 177:203883. [PMID: 37935283 DOI: 10.1016/j.cdev.2023.203883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/31/2023] [Accepted: 11/03/2023] [Indexed: 11/09/2023]
Abstract
The forces driving tissue morphogenesis are thought to originate from cellular activities. While it is appreciated that extracellular matrix (ECM) may also be involved, ECM function is assumed to be simply instructive in modulating the cellular behaviors that drive changes to tissue shape. However, there is increasing evidence that the ECM may not be the passive player portrayed in developmental biology textbooks. In this review we highlight examples of embryonic ECM dynamics that suggest cell-independent activity, along with developmental processes during which localized ECM alterations and ECM-autonomous forces are directing changes to tissue shape. Additionally, we discuss experimental approaches to unveil active ECM roles during tissue morphogenesis. We propose that it may be time to rethink our general definition of morphogenesis as a cellular-driven phenomenon and incorporate an underappreciated, and surprisingly dynamic ECM.
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Affiliation(s)
| | - Brian M Stramer
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK.
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9
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Kohler R, Creecy A, Williams DR, Allen MR, Wallace JM. Effects of novel raloxifene analogs alone or in combination with mechanical loading in the Col1a2 G610c/+ murine model of osteogenesis imperfecta. Bone 2024; 179:116970. [PMID: 37977416 PMCID: PMC10843597 DOI: 10.1016/j.bone.2023.116970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/10/2023] [Accepted: 11/14/2023] [Indexed: 11/19/2023]
Abstract
Osteogenesis imperfecta (OI) is a hereditary bone disease in which gene mutations affect collagen formation, leading to a weak, brittle bone phenotype that can cause severe skeletal deformity and increased fracture risk. OI interventions typically repurpose osteoporosis medications to increase bone mass, but this approach does not address compromised tissue-level material properties. Raloxifene (RAL) is a mild anti-resorptive used to treat osteoporosis that has also been shown to increase bone strength by a-cellularly increasing bone bound water content, but RAL cannot be administered to children due to its hormonal activity. The goal of this study was to test a RAL analog with no estrogen receptor (ER) signaling but maintained ability to reduce fracture risk. The best performing analog from a previous analog characterization project, named RAL-ADM, was tested in an in vivo study. Female wildtype (WT) and Col1a2G610C/+ (G610C) mice were randomly assigned to treated or untreated groups, for a total of 4 groups (n = 15). Starting at 10 weeks of age, all mice underwent compressive tibial loading 3×/week to induce an anabolic bone formation response in conjunction with RAL-ADM treatment (0.5 mg/kg; 5×/week) for 6 weeks. Tibiae were scanned via microcomputed tomography then tested to failure in four-point bending. RAL-ADM had reduced ER affinity, and increased post-yield properties, but did not improve bone strength in OI animals, suggesting some properties can be improved by RAL analogs but further development is needed to create an analog with decidedly positive impacts to OI bone.
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Affiliation(s)
- Rachel Kohler
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States
| | - Amy Creecy
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States
| | - David R Williams
- Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Matthew R Allen
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Joseph M Wallace
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States.
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10
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Klahr B, Lanzendorf JZ, Thiesen JLM, Pinto OT, Müller LG, Carniel TA, Fancello EA. On the contribution of solid and fluid behavior to the modeling of the time-dependent mechanics of tendons under semi-confined compression. J Mech Behav Biomed Mater 2023; 148:106220. [PMID: 37944227 DOI: 10.1016/j.jmbbm.2023.106220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 10/10/2023] [Accepted: 10/31/2023] [Indexed: 11/12/2023]
Abstract
The present work aims to investigate whether it is possible to identify and quantify the contributions of the interstitial fluid and the solid skeleton to the overall time-dependent behavior of tendons based on a single mechanical test. For this purpose, the capabilities of three different time-dependent models (a viscoelastic, a poroelastic and a poroviscoelastic) were investigated in the modeling of the experimental behavior obtained from semi-confined compression with stress relaxation tests transverse to collagen fibers. The main achieved result points out that the poroviscoelastic model was the only one capable to characterize both the experimental responses of the force and volume changes of the tissue samples. Moreover, further analysis of this model shows that while the kinematics of the sample are mainly governed by the fluid flow (pore pressure contribution of the model), the behavior intrinsically associated with the viscoelastic solid skeleton makes a significant contribution to the experimental force response. This study reinforces the importance of taking both the experimental kinematics and kinetics of tendon tissues into account during the constitutive characterization procedure.
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Affiliation(s)
- Bruno Klahr
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Jonas Zin Lanzendorf
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - José Luís Medeiros Thiesen
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Otávio Teixeira Pinto
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Liz Girardi Müller
- Graduate Program in Environmental Sciences, Community University of Chapecó Region, Chapecó, Santa Catarina, Brazil
| | - Thiago André Carniel
- Graduate Program in Health Sciences, Community University of Chapecó Region, Chapecó, Santa Catarina, Brazil; Polytechnic School, Community University of Chapecó Region, Chapecó, Santa Catarina, Brazil.
| | - Eduardo Alberto Fancello
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil; University Hospital, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
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11
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DiCecco LA, Gao R, Gray JL, Kelly DF, Sone ED, Grandfield K. Liquid Transmission Electron Microscopy for Probing Collagen Biomineralization. NANO LETTERS 2023; 23:9760-9768. [PMID: 37669509 DOI: 10.1021/acs.nanolett.3c02344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Collagen biomineralization is fundamental to hard tissue assembly. While studied extensively, collagen mineralization processes are not fully understood, with the majority of theories derived from electron microscopy (EM) under static, dehydrated, or frozen conditions, unlike the liquid phase environment where mineralization occurs. Herein, novel liquid transmission EM (TEM) strategies are presented, in which collagen mineralization was explored in liquid for the first time via TEM. Custom thin-film enclosures were employed to visualize the mineralization of reconstituted collagen fibrils in a calcium phosphate and polyaspartic acid solution to promote intrafibrillar mineralization. TEM highlighted that at early time points precursor mineral particles attached to collagen and progressed to crystalline mineral platelets aligned with fibrils at later time points. This aligns with observations from other techniques and validates the liquid TEM approach. This work provides a new liquid imaging approach for exploring collagen biomineralization, advancing toward understanding disease pathogenesis and remineralization strategies for hard tissues.
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Affiliation(s)
- Liza-Anastasia DiCecco
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802-4400, United States
| | - Ruixin Gao
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON M5S 3G9, Canada
| | - Jennifer L Gray
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Deborah F Kelly
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802-4400, United States
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center for Structural Oncology, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Eli D Sone
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON M5S 3G9, Canada
- Department of Materials Science and Engineering, University of Toronto, Toronto, ON M5S 3E4, Canada
- Faculty of Dentistry, University of Toronto, Toronto, ON M5G 1X3, Canada
| | - Kathryn Grandfield
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada
- School of Biomedical Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada
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12
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Qian W, Gamsjaeger S, Paschalis EP, Graeff-Armas LA, Bare SP, Turner JA, Lappe JM, Recker RR, Akhter MP. Bone intrinsic material and compositional properties in postmenopausal women diagnosed with long-term Type-1 diabetes. Bone 2023; 174:116832. [PMID: 37385427 PMCID: PMC11302406 DOI: 10.1016/j.bone.2023.116832] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 06/12/2023] [Accepted: 06/21/2023] [Indexed: 07/01/2023]
Abstract
The incidence of diabetes mellitus and the associated complications are growing worldwide, affecting the patients' quality of life and exerting a considerable burden on health systems. Yet, the increase in fracture risk in type 1 diabetes (T1D) patients is not fully captured by bone mineral density (BMD), leading to the hypothesis that alterations in bone quality are responsible for the increased risk. Material/compositional properties are important aspects of bone quality, yet information on human bone material/compositional properties in T1D is rather sparse. The purpose of the present study is to measure both the intrinsic material behaviour by nanoindentation, and material compositional properties by Raman spectroscopy as a function of tissue age and microanatomical location (cement lines) in bone tissue from iliac crest biopsies from postmenopausal women diagnosed with long-term T1D (N = 8), and appropriate sex-, age-, BMD- and clinically-matched controls (postmenopausal women; N = 5). The results suggest elevation of advanced glycation endproducts (AGE) content in the T1D and show significant differences in mineral maturity / crystallinity (MMC) and glycosaminoglycan (GAG) content between the T1D and control groups. Furthermore, both hardness and modulus by nanoindentation are greater in T1D. These data suggest a significant deterioration of material strength properties (toughness) and compositional properties in T1D compared with controls.
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Affiliation(s)
- Wen Qian
- University of Nebraska, Lincoln, NE, USA
| | | | | | | | - Sue P Bare
- Osteoporosis Research Center, Creighton University, Omaha, NE, USA
| | | | - Joan M Lappe
- Osteoporosis Research Center, Creighton University, Omaha, NE, USA
| | - Robert R Recker
- Osteoporosis Research Center, Creighton University, Omaha, NE, USA
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13
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Tits A, Blouin S, Rummler M, Kaux JF, Drion P, van Lenthe GH, Weinkamer R, Hartmann MA, Ruffoni D. Structural and functional heterogeneity of mineralized fibrocartilage at the Achilles tendon-bone insertion. Acta Biomater 2023; 166:409-418. [PMID: 37088163 DOI: 10.1016/j.actbio.2023.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/30/2023] [Accepted: 04/13/2023] [Indexed: 04/25/2023]
Abstract
A demanding task of the musculoskeletal system is the attachment of tendon to bone at entheses. This region often presents a thin layer of fibrocartilage (FC), mineralized close to the bone and unmineralized close to the tendon. Mineralized FC deserves increased attention, owing to its crucial anchoring task and involvement in enthesis pathologies. Here, we analyzed mineralized FC and subchondral bone at the Achilles tendon-bone insertion of rats. This location features enthesis FC anchoring tendon to bone and sustaining tensile loads, and periosteal FC facilitating bone-tendon sliding with accompanying compressive and shear forces. Using a correlative multimodal investigation, we evaluated potential specificities in mineral content, fiber organization and mechanical properties of enthesis and periosteal FC. Both tissues had a lower degree of mineralization than subchondral bone, yet used the available mineral very efficiently: for the same local mineral content, they had higher stiffness and hardness than bone. We found that enthesis FC was characterized by highly aligned mineralized collagen fibers even far away from the attachment region, whereas periosteal FC had a rich variety of fiber arrangements. Except for an initial steep spatial gradient between unmineralized and mineralized FC, local mechanical properties were surprisingly uniform inside enthesis FC while a modulation in stiffness, independent from mineral content, was observed in periosteal FC. We interpreted these different structure-property relationships as a demonstration of the high versatility of FC, providing high strength at the insertion (to resist tensile loading) and a gradual compliance at the periosteal surface (to resist contact stresses). STATEMENT OF SIGNIFICANCE: Mineralized fibrocartilage (FC) at entheses facilitates the integration of tendon in bone, two strongly dissimilar tissues. We focus on the structure-function relationships of two types of mineralized FC, enthesis and periosteal, which have clearly distinct mechanical demands. By investigating them with multiple high-resolution methods in a correlative manner, we demonstrate differences in fiber architecture and mechanical properties between the two tissues, indicative of their mechanical roles. Our results are relevant both from a medical viewpoint, targeting a clinically relevant location, as well as from a material science perspective, identifying FC as high-performance versatile composite.
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Affiliation(s)
- Alexandra Tits
- Mechanics of Biological and Bioinspired Materials Laboratory, Department of Aerospace and Mechanical Engineering, University of Liège, Liège, Belgium.
| | - Stéphane Blouin
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, 1st Medical Department Hanusch Hospital, Vienna, Austria
| | - Maximilian Rummler
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
| | - Jean-François Kaux
- Department of Physical Medicine and Sports Traumatology, University of Liège and University Hospital of Liège, Liège, Belgium
| | - Pierre Drion
- Experimental Surgery unit, GIGA & Credec, University of Liège, Liège, Belgium
| | | | - Richard Weinkamer
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
| | - Markus A Hartmann
- Ludwig Boltzmann Institute of Osteology at Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling, 1st Medical Department Hanusch Hospital, Vienna, Austria
| | - Davide Ruffoni
- Mechanics of Biological and Bioinspired Materials Laboratory, Department of Aerospace and Mechanical Engineering, University of Liège, Liège, Belgium.
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14
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Caruso I, Yin K, Divakar P, Wegst UGK. Tensile properties of freeze-cast collagen scaffolds: How processing conditions affect structure and performance in the dry and fully hydrated states. J Mech Behav Biomed Mater 2023; 144:105897. [PMID: 37343356 PMCID: PMC10771887 DOI: 10.1016/j.jmbbm.2023.105897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 05/02/2023] [Accepted: 05/04/2023] [Indexed: 06/23/2023]
Abstract
Tensile properties of directionally freeze-cast biopolymer scaffolds are rarely reported, even though they are of interest from a fundamental science perspective and critical in applications such as scaffolds for the regeneration of nerves or when used as ureteral stents. The focus of this study is on collagen scaffolds freeze-cast with two different applied cooling rates (10 °C/min and 1 °C/min) in two freezing directions (longitudinal and radial). Reported are the results of a systematic structural characterization of dry scaffolds by scanning electron microscopy and the mechanical characterization in tension of both dry and fully hydrated scaffolds. Systematic structure-property-processing correlations are obtained for a comparison of the tensile performance of longitudinally and radially freeze-cast collagen scaffolds with their performance in compression. Collated, the correlations, obtained both in tension in this study and in compression for collagen and chitosan in two earlier reports, not only enable the custom-design of freeze-cast biopolymer scaffolds for biomedical applications but also provide new insights into similarities and differences of scaffold and cell-wall structure formation during the directional solidification of "smooth" and "fibrillar" biopolymers.
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Affiliation(s)
- Isabella Caruso
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA; Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kaiyang Yin
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA; Department of Physics, Northeastern University, Boston, MA, USA; Department of Microsystems Engineering and Cluster of Excellence livMatS@FIT, University of Freiburg, Freiburg, Germany
| | - Prajan Divakar
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
| | - Ulrike G K Wegst
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA; Department of Physics, Northeastern University, Boston, MA, USA.
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15
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Chretien A, Mabilleau G, Lebacq J, Docquier PL, Behets C. Beneficial Effects of Zoledronic Acid on Tendons of the Osteogenesis Imperfecta Mouse (Oim). Pharmaceuticals (Basel) 2023; 16:832. [PMID: 37375779 DOI: 10.3390/ph16060832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 05/19/2023] [Accepted: 05/24/2023] [Indexed: 06/29/2023] Open
Abstract
Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue characterized by spontaneous fractures, bone deformities, impaired growth and posture, as well as extra-skeletal manifestations. Recent studies have underlined an impairment of the osteotendinous complex in mice models of OI. The first objective of the present work was to further investigate the properties of tendons in the osteogenesis imperfecta mouse (oim), a model characterized by a mutation in the COL1A2 gene. The second objective was to identify the possible beneficial effects of zoledronic acid on tendons. Oim received a single intravenous injection of zoledronic acid (ZA group) at 5 weeks and were euthanized at 14 weeks. Their tendons were compared with those of untreated oim (oim group) and control mice (WT group) by histology, mechanical tests, western blotting and Raman spectroscopy. The ulnar epiphysis had a significantly lower relative bone surface (BV/TV) in oim than WT mice. The tendon of the triceps brachii was also significantly less birefringent and displayed numerous chondrocytes aligned along the fibers. ZA mice showed an increase in BV/TV of the ulnar epiphysis and in tendon birefringence. The tendon of the flexor digitorum longus was significantly less viscous in oim than WT mice; in ZA-treated mice, there was an improvement of viscoelastic properties, especially in the toe region of stress-strain curve, which corresponds to collagen crimp. The tendons of both oim and ZA groups did not show any significant change in the expression of decorin or tenomodulin. Finally, Raman spectroscopy highlighted differences in material properties between ZA and WT tendons. There was also a significant increase in the rate of hydroxyproline in the tendons of ZA mice compared with oim ones. This study highlighted changes in matrix organization and an alteration of mechanical properties in oim tendons; zoledronic acid treatment had beneficial effects on these parameters. In the future, it will be interesting to better understand the underlying mechanisms which are possibly linked to a greater solicitation of the musculoskeletal system.
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Affiliation(s)
- Antoine Chretien
- Pole of Morphology, Institute of Experimental and Clinical Research, Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Guillaume Mabilleau
- Univ Angers, Nantes Université, Oniris, Inserm, UMR_S 1229-RMeS, REGOS, SFR ICAT, F-49000 Angers, France
- Centre Hospitalier Universitaire d'Angers, Department of Cell and Tissue Pathology, Bone Pathology Unit, F-49000 Angers, France
| | - Jean Lebacq
- Institute of NeuroScience (IoNS), Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Pierre-Louis Docquier
- Neuromusculoskeletal Lab, Institute of Experimental and Clinical Research, Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Catherine Behets
- Pole of Morphology, Institute of Experimental and Clinical Research, Université Catholique de Louvain, 1200 Brussels, Belgium
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16
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Al-Qudsy L, Hu YW, Xu H, Yang PF. Mineralized Collagen Fibrils: An Essential Component in Determining the Mechanical Behavior of Cortical Bone. ACS Biomater Sci Eng 2023; 9:2203-2219. [PMID: 37075172 DOI: 10.1021/acsbiomaterials.2c01377] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
Bone comprises mechanically different materials in a specific hierarchical structure. Mineralized collagen fibrils (MCFs), represented by tropocollagen molecules and hydroxyapatite nanocrystals, are the fundamental unit of bone. The mechanical characterization of MCFs provides the unique adaptive mechanical competence to bone to withstand mechanical load. The structural and mechanical role of MCFs is critical in the deformation mechanisms of bone and the marvelous strength and toughness possessed by bone. However, the role of MCFs in the mechanical behavior of bone across multiple length scales is not fully understood. In the present study, we shed light upon the latest progress regarding bone deformation at multiple hierarchical levels and emphasize the role of MCFs during bone deformation. We propose the concept of hierarchical deformation of bone to describe the interconnected deformation process across multiple length scales of bone under mechanical loading. Furthermore, how the deterioration of bone caused by aging and diseases impairs the hierarchical deformation process of the cortical bone is discussed. The present work expects to provide insights on the characterization of MCFs in the mechanical properties of bone and lays the framework for the understanding of the multiscale deformation mechanics of bone.
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Affiliation(s)
- Luban Al-Qudsy
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an 710072, China
- Department of Medical Instrumentation Engineering Techniques, Electrical Engineering Technical College, Middle Technical University, 8998+QHJ Baghdad, Iraq
| | - Yi-Wei Hu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an 710072, China
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an 710072, China
| | - Peng-Fei Yang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an 710072, China
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17
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Rennekamp B, Karfusehr C, Kurth M, Ünal A, Monego D, Riedmiller K, Gryn'ova G, Hudson DM, Gräter F. Collagen breaks at weak sacrificial bonds taming its mechanoradicals. Nat Commun 2023; 14:2075. [PMID: 37045839 PMCID: PMC10097693 DOI: 10.1038/s41467-023-37726-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 03/29/2023] [Indexed: 04/14/2023] Open
Abstract
Collagen is a force-bearing, hierarchical structural protein important to all connective tissue. In tendon collagen, high load even below macroscopic failure level creates mechanoradicals by homolytic bond scission, similar to polymers. The location and type of initial rupture sites critically decide on both the mechanical and chemical impact of these micro-ruptures on the tissue, but are yet to be explored. We here use scale-bridging simulations supported by gel electrophoresis and mass spectrometry to determine breakage points in collagen. We find collagen crosslinks, as opposed to the backbone, to harbor the weakest bonds, with one particular bond in trivalent crosslinks as the most dominant rupture site. We identify this bond as sacrificial, rupturing prior to other bonds while maintaining the material's integrity. Also, collagen's weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing.
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Affiliation(s)
- Benedikt Rennekamp
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany
- Max Planck School Matter to Life, Jahnstrasse 29, 69120, Heidelberg, Germany
| | - Christoph Karfusehr
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
- Max Planck School Matter to Life, Jahnstrasse 29, 69120, Heidelberg, Germany
- Physics Department and ZNN, Technical University Munich, Coulombwall 4a, 85748, Garching, Germany
| | - Markus Kurth
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany
| | - Aysecan Ünal
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany
- Max Planck School Matter to Life, Jahnstrasse 29, 69120, Heidelberg, Germany
| | - Debora Monego
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
| | - Kai Riedmiller
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
| | - Ganna Gryn'ova
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany
- Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany
| | - David M Hudson
- Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Frauke Gräter
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118, Heidelberg, Germany.
- Interdisciplinary Center for Scientific Computing, Heidelberg University, INF 205, 69120, Heidelberg, Germany.
- Max Planck School Matter to Life, Jahnstrasse 29, 69120, Heidelberg, Germany.
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18
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Carniel TA, Eckert JP, Atuatti EB, Klahr B, Thiesen JLM, Mentges J, Pinto OT, Müller LG, Fancello EA. Is the fluid volume fraction equal to the water content in tendons? Insights on biphasic modeling. J Mech Behav Biomed Mater 2023; 140:105703. [PMID: 36764169 DOI: 10.1016/j.jmbbm.2023.105703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 01/12/2023] [Accepted: 02/01/2023] [Indexed: 02/09/2023]
Abstract
The mass density of highly hydrated soft tissues is generally assumed to be very close to that of the water, resulting that the fluid mass fraction (water content) being equal to the fluid volume fraction. Within this context, the present study aims to investigate whether such an assumption actually holds for tendon tissues and to what extent it may affect the constitutive characterizations based on biphasic (poroelastic) models. Once the water content was assessed by a classical drying assay, the fluid volume fraction was obtained based on an image segmentation approach. The main achieved results point out that the fluid volume fraction is ∼20% higher than the water content in the studied tendons (flexor digitorum profundus bovine tendons). Based on this, it is shown that the use of the water content instead of the fluid volume fraction may considerably bias the results drawn by biphasic modeling of tendons. Accordingly, a proper measurement of the fluid volume fraction is then required.
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Affiliation(s)
- Thiago André Carniel
- Polytechnic School, Community University of Chapecó Region, Chapecó, SC, Brazil.
| | - João Paulo Eckert
- Polytechnic School, Community University of Chapecó Region, Chapecó, SC, Brazil
| | | | - Bruno Klahr
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil
| | | | - Julia Mentges
- Polytechnic School, Community University of Chapecó Region, Chapecó, SC, Brazil
| | - Otávio Teixeira Pinto
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil
| | - Liz Girardi Müller
- Graduate Program in Environmental Sciences, Community University of Chapecó Region, Chapecó, SC, Brazil
| | - Eduardo Alberto Fancello
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil; University Hospital, Federal University of Santa Catarina, Florianópolis, SC, Brazil
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19
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Merryweather DJ, Weston N, Roe J, Parmenter C, Lewis MP, Roach P. Exploring the microstructure of hydrated collagen hydrogels under scanning electron microscopy. J Microsc 2023; 290:40-52. [PMID: 36718074 DOI: 10.1111/jmi.13174] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 01/05/2023] [Accepted: 01/25/2023] [Indexed: 02/01/2023]
Abstract
Collagen hydrogels are a rapidly expanding platform in bioengineering and soft materials engineering for novel applications focused on medical therapeutics, medical devices and biosensors. Observations linking microstructure to material properties and function enables rational design strategies to control this space. Visualisation of the microscale organisation of these soft hydrated materials presents unique technical challenges due to the relationship between hydration and the molecular organisation of a collagen gel. Scanning electron microscopy is a robust tool widely employed to visualise and explore materials on the microscale. However, investigation of collagen gel microstructure is difficult without imparting structural changes during preparation and/or observation. Electrons are poorly propagated within liquid-phase materials, limiting the ability of electron microscopy to interrogate hydrated gels. Sample preparation techniques to remove water induce artefactual changes in material microstructure particularly in complex materials such as collagen, highlighting a critical need to develop robust material handling protocols for the imaging of collagen hydrogels. Here a collagen hydrogel is fabricated, and the gel state explored under high-vacuum (10-6 Pa) and low-vacuum (80-120 Pa) conditions, and in an environmental SEM chamber. Visualisation of collagen fibres is found to be dependent on the degree of sample hydration, with higher imaging chamber pressures and humidity resulting in decreased feature fidelity. Reduction of imaging chamber pressure is used to induce evaporation of gel water content, revealing collagen fibres of significantly larger diameter than observed in samples dehydrated prior to imaging. Rapid freezing and cryogenic handling of the gel material is found to retain a porous 3D structure following sublimation of the gel water content. Comparative analysis of collagen hydrogel materials demonstrates the care needed when preparing hydrogel samples for electron microscopy.
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Affiliation(s)
- Daniel J Merryweather
- Department of Chemistry, School of Science, Loughborough University, Leicestershire, UK
| | - Nicola Weston
- Nanoscale and Microscale Research Centre, University of Nottingham, Nottingham, UK
| | - Jordan Roe
- Department of Chemistry, School of Science, Loughborough University, Leicestershire, UK.,Department of Materials, Loughborough University, Leicestershire, UK
| | | | - Mark P Lewis
- National Centre for Sport and Exercise Medicine (NCSEM), School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, UK
| | - Paul Roach
- Department of Chemistry, School of Science, Loughborough University, Leicestershire, UK
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20
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Doyle ME, Dalgarno K, Masoero E, Ferreira AM. Advances in biomimetic collagen mineralisation and future approaches to bone tissue engineering. Biopolymers 2023; 114:e23527. [PMID: 36444710 PMCID: PMC10078151 DOI: 10.1002/bip.23527] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 11/10/2022] [Accepted: 11/11/2022] [Indexed: 11/30/2022]
Abstract
With an ageing world population and ~20% of adults in Europe being affected by bone diseases, there is an urgent need to develop advanced regenerative approaches and biomaterials capable to facilitate tissue regeneration while providing an adequate microenvironment for cells to thrive. As the main components of bone are collagen and apatite mineral, scientists in the tissue engineering field have attempted in combining these materials by using different biomimetic approaches to favour bone repair. Still, an ideal bone analogue capable of mimicking the distinct properties (i.e., mechanical properties, degradation rate, porosity, etc.) of cancellous bone is to be developed. This review seeks to sum up the current understanding of bone tissue mineralisation and structure while providing a critical outlook on the existing biomimetic strategies of mineralising collagen for bone tissue engineering applications, highlighting where gaps in knowledge exist.
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Affiliation(s)
| | - Kenny Dalgarno
- School of EngineeringNewcastle UniversityNewcastle upon TyneUK
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21
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Silva Barreto I, Pierantoni M, Hammerman M, Törnquist E, Le Cann S, Diaz A, Engqvist J, Liebi M, Eliasson P, Isaksson H. Nanoscale characterization of collagen structural responses to in situ loading in rat Achilles tendons. Matrix Biol 2023; 115:32-47. [PMID: 36435426 DOI: 10.1016/j.matbio.2022.11.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/29/2022] [Accepted: 11/21/2022] [Indexed: 11/24/2022]
Abstract
The specific viscoelastic mechanical properties of Achilles tendons are highly dependent on the structural characteristics of collagen at and between all hierarchical levels. Research has been conducted on the deformation mechanisms of positional tendons and single fibrils, but knowledge about the coupling between the whole tendon and nanoscale deformation mechanisms of more commonly injured energy-storing tendons, such as Achilles tendons, remains sparse. By exploiting the highly periodic arrangement of tendons at the nanoscale, in situ loading of rat Achilles tendons during small-angle X-ray scattering acquisition was used to investigate the collagen structural response during load to rupture, cyclic loading and stress relaxation. The fibril strain was substantially lower than the applied tissue strain. The fibrils strained linearly in the elastic region of the tissue, but also exhibited viscoelastic properties, such as an increased stretchability and recovery during cyclic loading and fibril strain relaxation during tissue stress relaxation. We demonstrate that the changes in the width of the collagen reflections could be attributed to strain heterogeneity and not changes in size of the coherently diffracting domains. Fibril strain heterogeneity increased with applied loads and after the toe region, fibrils also became increasingly disordered. Additionally, a thorough evaluation of radiation damage was performed. In conclusion, this study clearly displays the simultaneous structural response and adaption of the collagen fibrils to the applied tissue loads and provide novel information about the transition of loads between length scales in the Achilles tendon.
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Affiliation(s)
| | - Maria Pierantoni
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Malin Hammerman
- Department of Biomedical Engineering, Lund University, Lund, Sweden; Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Elin Törnquist
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Sophie Le Cann
- CNRS, Univ Paris Est Creteil, Univ Gustave Eiffel, UMR 8208, MSME, Créteil F-94010, France
| | - Ana Diaz
- Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Jonas Engqvist
- Division of Solid Mechanics, Lund University, Lund, Sweden
| | - Marianne Liebi
- Paul Scherrer Institut, Villigen PSI, Switzerland; Department of Physics, Chalmers University, Gothenburg, Sweden; Center of X-ray Analytics, Empa, Swiss Federal Laboratories for Materials Science and Technology, St.Gallen, Switzerland
| | - Pernilla Eliasson
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden; Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden.
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22
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Hu Y, Buehler MJ. End-to-End Protein Normal Mode Frequency Predictions Using Language and Graph Models and Application to Sonification. ACS NANO 2022; 16:20656-20670. [PMID: 36416536 DOI: 10.1021/acsnano.2c07681] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The prediction of mechanical and dynamical properties of proteins is an important frontier, especially given the greater availability of proteins structures. Here we report a series of models that provide end-to-end predictions of nanodynamical properties of proteins, focused on high-throughput normal mode predictions directly from the amino acid sequence. Using neural network models within the family of Natural Language Processing and graph-based methods, we offer atomistically based mechanistic predictions of key protein mechanical features. The models include an end-to-end long short-term memory (LSTM) model, an end-to-end transformer model, a graph-based transformer model, and an equivariant graph neural network. All four models show exceptional performance, with the graph-based transformer architecture offering the best results but at the cost of requiring a graph structure as input. Conversely, the LSTM and transformer models offer end-to-end sequence-to-property prediction capabilities, providing efficient avenues for protein engineering, analysis, and design. We compare our results against published data based on a Principal Neighborhood Aggregation graph neural network, revealing that the transformer model offers better performance while also being able to predict a large set of the first 64 normal mode frequencies, simultaneously. The use of the end-to-end transformer model may facilitate other downstream applications through the use of transfer learning, and it offers a comprehensive prediction of dynamical properties without any structural knowledge, directly from the amino acid sequence. We demonstrate a potential application in scientific sonification, where the normal mode frequencies are transposed to generate audible signals for a detailed analysis of subtle changes of protein sequences.
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Affiliation(s)
- Yiwen Hu
- Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States
| | - Markus J Buehler
- Laboratory for Atomistic and Molecular Mechanics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States
- Center for Computational Science and Engineering, Schwarzman College of Computing, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, United States
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23
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Zhang W, Bertinetti L, Yavuzsoy EC, Gao C, Schneck E, Fratzl P. Submicron-Sized In Situ Osmotic Pressure Sensors for In Vitro Applications in Biology. Adv Healthc Mater 2022; 12:e2202373. [PMID: 36541931 DOI: 10.1002/adhm.202202373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/06/2022] [Indexed: 12/24/2022]
Abstract
Physical forces are important cues in determining the development and the normal function of biological tissues. While forces generated by molecular motors have been widely studied, forces resulting from osmotic gradients have been less considered in this context. A possible reason is the lack of direct in situ measurement methods that can be applied to cell and organ culture systems. Herein, novel kinds of resonance energy transfer (FRET)-based liposomal sensors are developed, so that their sensing range and sensitivity can be adjusted to satisfy physiological osmotic conditions. Several types of sensors are prepared, either based on polyethylene glycol- (PEG)ylated liposomes with steric stabilization and stealth property or on crosslinked liposomes capable of enduring relatively harsh environments for liposomes (e.g., in the presence of biosurfactants). The sensors are demonstrated to be effective in the measurement of osmotic pressures in pre-osteoblastic in vitro cell culture systems by means of FRET microscopy. This development paves the way toward the in situ sensing of osmotic pressures in biological culture systems.
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Affiliation(s)
- Wenbo Zhang
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany
| | - Luca Bertinetti
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany.,B CUBE Center for Molecular Bioengineering, Technische Universität Dresden, 01307, Dresden, Germany
| | - Efe Cuma Yavuzsoy
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany
| | - Changyou Gao
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Emanuel Schneck
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany.,Department of Physics, Technische Universität Darmstadt, 64289, Darmstadt, Germany
| | - Peter Fratzl
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany
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Sauer K, Zizak I, Forien JB, Rack A, Scoppola E, Zaslansky P. Primary radiation damage in bone evolves via collagen destruction by photoelectrons and secondary emission self-absorption. Nat Commun 2022; 13:7829. [PMID: 36539409 PMCID: PMC9768145 DOI: 10.1038/s41467-022-34247-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 10/18/2022] [Indexed: 12/24/2022] Open
Abstract
X-rays are invaluable for imaging and sterilization of bones, yet the resulting ionization and primary radiation damage mechanisms are poorly understood. Here we monitor in-situ collagen backbone degradation in dry bones using second-harmonic-generation and X-ray diffraction. Collagen breaks down by cascades of photon-electron excitations, enhanced by the presence of mineral nanoparticles. We observe protein disintegration with increasing exposure, detected as residual strain relaxation in pre-stressed apatite nanocrystals. Damage rapidly grows from the onset of irradiation, suggesting that there is no minimal 'safe' dose that bone collagen can sustain. Ionization of calcium and phosphorous in the nanocrystals yields fluorescence and high energy electrons giving rise to structural damage that spreads beyond regions directly illuminated by the incident radiation. Our findings highlight photoelectrons as major agents of damage to bone collagen with implications to all situations where bones are irradiated by hard X-rays and in particular for small-beam mineralized collagen fiber investigations.
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Affiliation(s)
- Katrein Sauer
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, Department for Operative, Preventive and Pediatric Dentistry, Aßmannshauser Straße 4-6, 14197 Berlin, Germany
| | - Ivo Zizak
- grid.424048.e0000 0001 1090 3682Helmholtz-Zentrum Berlin, Department for Structure and Dynamics of Energy Materials (SE-ASD), Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Jean-Baptiste Forien
- grid.250008.f0000 0001 2160 9702Lawrence Livermore National Laboratory, Materials Science Division, 7000 East Ave, Livermore, CA 94550 USA
| | - Alexander Rack
- grid.5398.70000 0004 0641 6373ESRF - The European Synchrotron, Structure of Materials Group - ID19, CS 40220, F-38043, Grenoble, Cedex 9 France
| | - Ernesto Scoppola
- grid.461615.10000 0000 8925 2562Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Am Mühlenberg 1, 14476 Potsdam, Brandenburg Germany
| | - Paul Zaslansky
- grid.6363.00000 0001 2218 4662Charité – Universitätsmedizin Berlin, Department for Operative, Preventive and Pediatric Dentistry, Aßmannshauser Straße 4-6, 14197 Berlin, Germany
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25
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Andriotis OG, Nalbach M, Thurner PJ. Mechanics of isolated individual collagen fibrils. Acta Biomater 2022; 163:35-49. [PMID: 36509398 DOI: 10.1016/j.actbio.2022.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 11/15/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022]
Abstract
Collagen fibrils are the fundamental structural elements in vertebrate animals and compose a framework that provides mechanical support to load-bearing tissues. Understanding how these fibrils initially form and mechanically function has been the focus of a myriad of detailed investigations over the last few decades. From these studies a great amount of knowledge has been acquired as well as a number of new questions to consider. In this review, we examine the current state of our knowledge of the mechanical properties of extant fibrils. We emphasize on the mechanical response and related deformation of collagen fibrils upon tension, which is the predominant load imposed in most collagen-rich tissues. We also illuminate the gaps in knowledge originating from the intriguing results that the field is still trying to interpret. STATEMENT OF SIGNIFICANCE: : Collagen is the result of millions of years of biological evolution and is a unique family of proteins, the majority of which provide mechanical support to biological tissues. Cells produce collagen molecules that self-assemble into larger structures, known as collagen fibrils. As simple as they appear under an optical microscope, collagen fibrils display a complex ultrastructural architecture tuned to the external forces that are imposed upon them. Even more complex is the way collagen fibrils deform under loading, and the nature of the mechanisms that drive their formation in the first place. Here, we present a cogent synthesis of the state-of-knowledge of collagen fibril mechanics. We focus on the information we have from in vitro experiments on individual, isolated from tissues, collagen fibrils and the knowledge available from in silico tests.
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Affiliation(s)
- Orestis G Andriotis
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria
| | - Mathis Nalbach
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria
| | - Philipp J Thurner
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria.
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26
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Erlich A, Étienne J, Fouchard J, Wyatt T. How dynamic prestress governs the shape of living systems, from the subcellular to tissue scale. Interface Focus 2022; 12:20220038. [PMID: 36330322 PMCID: PMC9560792 DOI: 10.1098/rsfs.2022.0038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 09/08/2022] [Indexed: 10/16/2023] Open
Abstract
Cells and tissues change shape both to carry out their function and during pathology. In most cases, these deformations are driven from within the systems themselves. This is permitted by a range of molecular actors, such as active crosslinkers and ion pumps, whose activity is biologically controlled in space and time. The resulting stresses are propagated within complex and dynamical architectures like networks or cell aggregates. From a mechanical point of view, these effects can be seen as the generation of prestress or prestrain, resulting from either a contractile or growth activity. In this review, we present this concept of prestress and the theoretical tools available to conceptualize the statics and dynamics of living systems. We then describe a range of phenomena where prestress controls shape changes in biopolymer networks (especially the actomyosin cytoskeleton and fibrous tissues) and cellularized tissues. Despite the diversity of scale and organization, we demonstrate that these phenomena stem from a limited number of spatial distributions of prestress, which can be categorized as heterogeneous, anisotropic or differential. We suggest that in addition to growth and contraction, a third type of prestress-topological prestress-can result from active processes altering the microstructure of tissue.
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Affiliation(s)
| | - Jocelyn Étienne
- Université Grenoble Alpes, CNRS, LIPHY, 38000 Grenoble, France
| | - Jonathan Fouchard
- Laboratoire de Biologie du Développement, Institut de Biologie Paris Seine (IBPS), Sorbonne Université, CNRS (UMR 7622), INSERM (URL 1156), 7 quai Saint Bernard, 75005 Paris, France
| | - Tom Wyatt
- Wellcome Trust–Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, UK
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27
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Yin NH, Parker AW, Matousek P, Birch HL. Chemical Markers of Human Tendon Health Identified Using Raman Spectroscopy: Potential for In Vivo Assessment. Int J Mol Sci 2022; 23:ijms232314854. [PMID: 36499181 PMCID: PMC9737356 DOI: 10.3390/ijms232314854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 11/15/2022] [Accepted: 11/22/2022] [Indexed: 12/04/2022] Open
Abstract
The purpose of this study is to determine whether age-related changes to tendon matrix molecules can be detected using Raman spectroscopy. Raman spectra were collected from human Achilles (n = 8) and tibialis anterior (n = 8) tendon tissue excised from young (17 ± 3 years) and old (72 ± 7 years) age groups. Normalised Raman spectra underwent principal component analysis (PCA), to objectively identify differences between age groups and tendon types. Certain Raman band intensities were correlated with levels of advanced glycation end-product (AGE) collagen crosslinks, quantified using conventional destructive biochemistry techniques. Achilles and tibialis anterior tendons in the old age group demonstrated significantly higher overall Raman intensities and fluorescence levels compared to young tendons. PCA was able to distinguish young and old age groups and different tendon types. Raman intensities differed significantly for several bands, including those previously associated with AGE crosslinks, where a significant positive correlation with biochemical measures was demonstrated. Differences in Raman spectra between old and young tendon tissue and correlation with AGE crosslinks provides the basis for quantifying age-related chemical modifications to tendon matrix molecules in intact tissue. Our results suggest that Raman spectroscopy may provide a powerful tool to assess tendon health and vitality in the future.
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Affiliation(s)
- Nai-Hao Yin
- Department of Orthopaedics and Musculoskeletal Science, University College London, UCL Stanmore Campus, RNOH, Brockley Hill, London HA7 4LP, UK
| | - Anthony W. Parker
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, UKRI, Harwell Campus, Didcot OX11 0QX, UK
| | - Pavel Matousek
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, UKRI, Harwell Campus, Didcot OX11 0QX, UK
| | - Helen L. Birch
- Department of Orthopaedics and Musculoskeletal Science, University College London, UCL Stanmore Campus, RNOH, Brockley Hill, London HA7 4LP, UK
- Correspondence: ; Tel.: +44-(0)208-016-8577
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28
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Badar W, Ali H, Brooker ON, Newham E, Snow T, Terrill NJ, Tozzi G, Fratzl P, Knight MM, Gupta HS. Collagen pre-strain discontinuity at the bone—Cartilage interface. PLoS One 2022; 17:e0273832. [PMID: 36108273 PMCID: PMC9477506 DOI: 10.1371/journal.pone.0273832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/17/2022] [Indexed: 11/18/2022] Open
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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Affiliation(s)
- Waqas Badar
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
| | - Husna Ali
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
| | - Olivia N. Brooker
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
| | - Elis Newham
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
| | - Tim Snow
- Harwell Science and Innovation Campus, Diamond Light Source, Harwell, Didcot, United Kingdom
| | - Nicholas J. Terrill
- Harwell Science and Innovation Campus, Diamond Light Source, Harwell, Didcot, United Kingdom
| | - Gianluca Tozzi
- School of Engineering, University of Greenwich, Chatham Maritime ME4 4TB, UK
| | - Peter Fratzl
- Department of Biomaterials, Max-Planck-Institute of Colloids and Interfaces, Potsdam Wissenschaftspark, Golm, Germany
| | - Martin M. Knight
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
| | - Himadri S. Gupta
- Institute of Bioengineering and School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom
- * E-mail:
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29
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Zhang Y, Zhang W, Snow T, Ju Y, Liu Y, Smith AJ, Prabakar S. Minimising Chemical Crosslinking for Stabilising Collagen in Acellular Bovine Pericardium: Mechanistic Insights via Structural Characterisations. Acta Biomater 2022; 152:113-123. [DOI: 10.1016/j.actbio.2022.08.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/10/2022] [Accepted: 08/24/2022] [Indexed: 11/01/2022]
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30
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The sacrotuberous ligament is preloaded in situ. J Mech Behav Biomed Mater 2022; 134:105368. [DOI: 10.1016/j.jmbbm.2022.105368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/06/2022] [Accepted: 07/09/2022] [Indexed: 11/19/2022]
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31
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Influence of moisture content of frozen and embalmed human cadavers for identification of dentinal microcracks using micro-computed tomography. J Mech Behav Biomed Mater 2022; 133:105310. [PMID: 35696968 DOI: 10.1016/j.jmbbm.2022.105310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/31/2022] [Accepted: 06/02/2022] [Indexed: 10/18/2022]
Abstract
The aim of this study was to investigate the influence of moisture content in frozen and embalmed human cadavers on the detection of dentinal microcracks using micro-computed tomography (micro-CT). The group of embalmed specimens included three mandibular and two maxillary segments each containing one tooth. The group of frozen cadavers consisted of two frozen mandibular bone-blocks with two teeth and one mandibular segment containing one tooth. The final number of teeth for each preservation method was n = 5. All specimens were scanned with eight different moisture conditions: 48 h wet, 2 h dry, 48 h wet, 24 h dry, 48 h wet, 1 wk dry, 48 h wet, 1 wk dry. Micro-CT images were screened for the presence of dentinal microcracks. Statistical analysis was performed by nonparametric analysis of variance (α = 5%). Only few microcracks were observed in wet and in 2 h dried bone-blocks with no significant differences (p = 0.63 and p = 0.23, respectively). There was a significant and steady increase of microcracks within the groups of dried specimens as follows: 2 h dry < 24 h dry < first wk dry < second wk dry (all p < 0.008). Preservation method had no significant influence on the visibility of microcracks (p = 0.98). Identification of dentinal microcracks on micro-CT images is influenced by moisture content of cadaveric bone-blocks irrespective of the preservation method.
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32
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Surowiec RK, Allen MR, Wallace JM. Bone hydration: How we can evaluate it, what can it tell us, and is it an effective therapeutic target? Bone Rep 2022; 16:101161. [PMID: 35005101 PMCID: PMC8718737 DOI: 10.1016/j.bonr.2021.101161] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/10/2021] [Accepted: 12/11/2021] [Indexed: 12/22/2022] Open
Abstract
Water constitutes roughly a quarter of the cortical bone by volume yet can greatly influence mechanical properties and tissue quality. There is a growing appreciation for how water can dynamically change due to age, disease, and treatment. A key emerging area related to bone mechanical and tissue properties lies in differentiating the role of water in its four different compartments, including free/pore water, water loosely bound at the collagen/mineral interfaces, water tightly bound within collagen triple helices, and structural water within the mineral. This review summarizes our current knowledge of bone water across the four functional compartments and discusses how alterations in each compartment relate to mechanical changes. It provides an overview on the advent of- and improvements to- imaging and spectroscopic techniques able to probe nano-and molecular scales of bone water. These technical advances have led to an emerging understanding of how bone water changes in various conditions, of which aging, chronic kidney disease, diabetes, osteoporosis, and osteogenesis imperfecta are reviewed. Finally, it summarizes work focused on therapeutically targeting water to improve mechanical properties.
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Affiliation(s)
- Rachel K. Surowiec
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States
| | - Matthew R. Allen
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States
- Roudebush Veterans Administration Medical Center, Indianapolis, IN, United States
| | - Joseph M. Wallace
- Department of Biomedical Engineering, Indiana University Purdue University of Indianapolis, Indianapolis, IN, United States
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33
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Wang H, Liu Z, Lao J, Zhang S, Abzalimov R, Wang T, Chen X. High Energy and Power Density Peptidoglycan Muscles through Super-Viscous Nanoconfined Water. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2104697. [PMID: 35285168 PMCID: PMC9130901 DOI: 10.1002/advs.202104697] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/23/2021] [Indexed: 06/14/2023]
Abstract
Water-responsive (WR) materials that reversibly deform in response to humidity changes show great potential for developing muscle-like actuators for miniature and biomimetic robotics. Here, it is presented that Bacillus (B.) subtilis' peptidoglycan (PG) exhibits WR actuation energy and power densities reaching 72.6 MJ m-3 and 9.1 MW m-3 , respectively, orders of magnitude higher than those of frequently used actuators, such as piezoelectric actuators and dielectric elastomers. PG can deform as much as 27.2% within 110 ms, and its actuation pressure reaches ≈354.6 MPa. Surprisingly, PG exhibits an energy conversion efficiency of ≈66.8%, which can be attributed to its super-viscous nanoconfined water that efficiently translates the movement of water molecules to PG's mechanical deformation. Using PG, WR composites that can be integrated into a range of engineering structures are developed, including a robotic gripper and linear actuators, which illustrate the possibilities of using PG as building blocks for high-efficiency WR actuators.
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Affiliation(s)
- Haozhen Wang
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
- PhD Program in PhysicsThe Graduate Center of the City University of New York365 5th Ave.New YorkNY10016USA
| | - Zhi‐Lun Liu
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
- Department of Chemical EngineeringThe City College of New York275 Convent Ave.New YorkNY10031USA
| | - Jianpei Lao
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
- Department of Chemical EngineeringThe City College of New York275 Convent Ave.New YorkNY10031USA
| | - Sheng Zhang
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
| | - Rinat Abzalimov
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
| | - Tong Wang
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
| | - Xi Chen
- Advanced Science Research Center (ASRC)The City University of New York85 St. Nicholas TerraceNew YorkNY10031USA
- PhD Program in PhysicsThe Graduate Center of the City University of New York365 5th Ave.New YorkNY10016USA
- Department of Chemical EngineeringThe City College of New York275 Convent Ave.New YorkNY10031USA
- PhD Program in ChemistryThe Graduate Center of the City University of New York365 5th Ave.New YorkNY10016USA
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34
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Deng Z, Jia Z, Li L. Biomineralized Materials as Model Systems for Structural Composites: Intracrystalline Structural Features and Their Strengthening and Toughening Mechanisms. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2103524. [PMID: 35315243 PMCID: PMC9108615 DOI: 10.1002/advs.202103524] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/09/2022] [Indexed: 05/02/2023]
Abstract
Biomineralized composites, which are usually composed of microscopic mineral building blocks organized in 3D intercrystalline organic matrices, have evolved unique structural designs to fulfill mechanical and other biological functionalities. While it has been well recognized that the intricate architectural designs of biomineralized composites contribute to their remarkable mechanical performance, the structural features within and corresponding mechanical properties of individual mineral building blocks are often less appreciated in the context of bio-inspired structural composites. The mineral building blocks in biomineralized composites exhibit a variety of salient intracrystalline structural features, such as, organic inclusions, inorganic impurities (or trace elements), crystalline features (e.g., amorphous phases, single crystals, splitting crystals, polycrystals, and nanograins), residual stress/strain, and twinning, which significantly modify the mechanical properties of biogenic minerals. In this review, recent progress in elucidating the intracrystalline structural features of three most common biomineral systems (calcite, aragonite, and hydroxyapatite) and their corresponding mechanical significance are discussed. Future research directions and corresponding challenges are proposed and discussed, such as the advanced structural characterizations and formation mechanisms of intracrystalline structures in biominerals, amorphous biominerals, and bio-inspired synthesis.
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Affiliation(s)
- Zhifei Deng
- Department of Mechanical EngineeringVirginia Polytechnic Institute of Technology and State UniversityBlacksburgVA24060USA
| | - Zian Jia
- Department of Mechanical EngineeringVirginia Polytechnic Institute of Technology and State UniversityBlacksburgVA24060USA
| | - Ling Li
- Department of Mechanical EngineeringVirginia Polytechnic Institute of Technology and State UniversityBlacksburgVA24060USA
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35
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Rehydration of the Tendon Fascicle Bundles Using Simulated Body Fluid Ensures Stable Mechanical Properties of the Samples. MATERIALS 2022; 15:ma15093033. [PMID: 35591368 PMCID: PMC9104251 DOI: 10.3390/ma15093033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/31/2022] [Accepted: 04/11/2022] [Indexed: 11/24/2022]
Abstract
In this work, we investigate the influence of dehydration and subsequent rehydration of tendon fascicle bundles on their structural and mechanical properties by using distilled water, 0.9% NaCl, 10% NaCl, SBF, and double concentrated SBF (SBFx2). The properties of tendon fascicle bundles were investigated by means of uniaxial tests with relaxation periods and hysteresis for samples with various interfascicular matrix content, dissected from the anterior and posterior areas of bovine tendon. Uniaxial tests with relaxation periods and analysis of sample geometry and weight showed that dehydration alters the modulus of elasticity dependent on the interfascicular matrix content and influences the viscoelastic properties of tendon fascicle bundles. Tensile and relaxation tests revealed that changes resulting from excessive sample drying can be reversed by rehydration in an SBF bath solution for elastic strain range above the toe region. Rehydration in SBF solution led to minor differences in mechanical properties when compared to control samples. Moreover, anterior samples with greater interfascicular matrix content, despite their lower stiffness, are less sensitive to sample drying. The obtained results allow us to limit the discrepancies in the measurement of mechanical properties of wet biological samples and can be useful to researchers investigating soft tissue mechanics and the stability of transplant materials.
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36
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Bose S, Li S, Mele E, Silberschmidt VV. Exploring the Mechanical Properties and Performance of Type-I Collagen at Various Length Scales: A Progress Report. MATERIALS 2022; 15:ma15082753. [PMID: 35454443 PMCID: PMC9025246 DOI: 10.3390/ma15082753] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/04/2022] [Accepted: 04/06/2022] [Indexed: 12/30/2022]
Abstract
Collagen is the basic protein of animal tissues and has a complex hierarchical structure. It plays a crucial role in maintaining the mechanical and structural stability of biological tissues. Over the years, it has become a material of interest in the biomedical industries thanks to its excellent biocompatibility and biodegradability and low antigenicity. Despite its significance, the mechanical properties and performance of pure collagen have been never reviewed. In this work, the emphasis is on the mechanics of collagen at different hierarchical levels and its long-term mechanical performance. In addition, the effect of hydration, important for various applications, was considered throughout the study because of its dramatic influence on the mechanics of collagen. Furthermore, the discrepancies in reports of the mechanical properties of collagenous tissues (basically composed of 20-30% collagen fibres) and those of pure collagen are discussed.
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Affiliation(s)
- Shirsha Bose
- Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, Leicestershire, UK; (S.B.); (S.L.)
| | - Simin Li
- Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, Leicestershire, UK; (S.B.); (S.L.)
| | - Elisa Mele
- Department of Materials, Loughborough University, Loughborough LE11 3TU, Leicestershire, UK
- Correspondence: (E.M.); (V.V.S.)
| | - Vadim V. Silberschmidt
- Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU, Leicestershire, UK; (S.B.); (S.L.)
- Laboratory of Mechanics of Biocompatible Materials and Devices, Perm National Research Polytechnic University, 614990 Perm, Russia
- Correspondence: (E.M.); (V.V.S.)
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37
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Ping H, Wagermaier W, Horbelt N, Scoppola E, Li C, Werner P, Fu Z, Fratzl P. Mineralization generates megapascal contractile stresses in collagen fibrils. Science 2022; 376:188-192. [PMID: 35389802 DOI: 10.1126/science.abm2664] [Citation(s) in RCA: 52] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During bone formation, collagen fibrils mineralize with carbonated hydroxyapatite, leading to a hybrid material with excellent properties. Other minerals are also known to nucleate within collagen in vitro. For a series of strontium- and calcium-based minerals, we observed that their precipitation leads to a contraction of collagen fibrils, reaching stresses as large as several megapascals. The magnitude of the stress depends on the type and amount of mineral. Using in-operando synchrotron x-ray scattering, we analyzed the kinetics of mineral deposition. Whereas no contraction occurs when the mineral deposits outside fibrils only, intrafibrillar mineralization generates fibril contraction. This chemomechanical effect occurs with collagen fully immersed in water and generates a mineral-collagen composite with tensile fibers, reminiscent of the principle of reinforced concrete.
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Affiliation(s)
- Hang Ping
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road No. 122, Wuhan 430070, China.,Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Wolfgang Wagermaier
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Nils Horbelt
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Ernesto Scoppola
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Chenghao Li
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Peter Werner
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Zhengyi Fu
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road No. 122, Wuhan 430070, China
| | - Peter Fratzl
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
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Abstract
Bone is an outstanding, well-designed composite. It is constituted by a multi-level structure wherein its properties and behavior are dependent on its composition and structural organization at different length scales. The combination of unique mechanical properties with adaptive and self-healing abilities makes bone an innovative model for the future design of synthetic biomimetic composites with improved performance in bone repair and regeneration. However, the relation between structure and properties in bone is very complex. In this review article, we intend to describe the hierarchical organization of bone on progressively greater scales and present the basic concepts that are fundamental to understanding the arrangement-based mechanical properties at each length scale and their influence on bone’s overall structural behavior. The need for a better understanding of bone’s intricate composite structure is also highlighted.
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Zhang Y, Hollis D, Ross R, Snow T, Terrill NJ, Lu Y, Wang W, Connelly J, Tozzi G, Gupta HS. Investigating the Fibrillar Ultrastructure and Mechanics in Keloid Scars Using In Situ Synchrotron X-ray Nanomechanical Imaging. MATERIALS 2022; 15:ma15051836. [PMID: 35269067 PMCID: PMC8911729 DOI: 10.3390/ma15051836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/24/2021] [Accepted: 01/21/2022] [Indexed: 12/10/2022]
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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Affiliation(s)
- Yuezhou Zhang
- Institute of Bioengineering and School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK; (Y.Z.); (W.W.)
| | - Dave Hollis
- LaVision UK, 2 Minton Place, Victoria Road, Bicester OX26 6QB, UK;
| | - Rosie Ross
- Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK; (R.R.); (J.C.)
| | - Tim Snow
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK; (T.S.); (N.J.T.)
| | - Nick J. Terrill
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK; (T.S.); (N.J.T.)
| | - Yongjie Lu
- Centre for Biomarkers and Biotherapeutics, Barts Cancer Institute, Queen Mary University of London, John Vane Science Centre, Charterhouse Square, London EC1M 5PZ, UK;
| | - Wen Wang
- Institute of Bioengineering and School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK; (Y.Z.); (W.W.)
| | - John Connelly
- Centre for Cell Biology and Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK; (R.R.); (J.C.)
| | - Gianluca Tozzi
- School of Engineering, London South Bank University, London SE1 0AA, UK;
| | - Himadri S. Gupta
- Institute of Bioengineering and School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK; (Y.Z.); (W.W.)
- Correspondence:
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Dwivedi KK, Lakhani P, Kumar S, Kumar N. Effect of collagen fibre orientation on the Poisson's ratio and stress relaxation of skin: an ex vivo and in vivo study. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211301. [PMID: 35345435 PMCID: PMC8941416 DOI: 10.1098/rsos.211301] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
During surgical treatment skin undergoes extensive deformation, hence it must be able to withstand large mechanical stresses without damage. Therefore, understanding the mechanical properties of skin becomes important. A detailed investigation on the relationship between the three-dimensional deformation response of skin and its microstructure is conducted in the current study. This study also discloses the underlying science of skin viscoelasticity. Deformation response of skin is captured using digital image correlation, whereas micro-CT, scanning electron microscopy and atomic force microscopy are used for microstructure analysis. Skin shows a large lateral contraction and expansion (auxeticity) when stretched parallel and perpendicular to the skin tension lines, respectively. Large lateral contraction is a result of fluid exudation from the tissue, while large rotation of the stiff collagen fibres in the loading direction explains the skin auxeticity. During stress relaxation, lateral contraction and fluid effluxion from skin reveal that tissue volume loss is the intrinsic science of skin viscoelasticity. Furthermore, the results obtained from in vivo study on human skin show the relevance of the ex vivo study to physiological conditions and stretching of the skin during its treatments.
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Affiliation(s)
- Krashn Kumar Dwivedi
- Department of Biomedical Engineering, Indian Institute of Technology, Ropar, India
| | - Piyush Lakhani
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
| | - Sachin Kumar
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
| | - Navin Kumar
- Department of Biomedical Engineering, Indian Institute of Technology, Ropar, India
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
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41
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Siriporananon C, Senawongse P, Sattabanasuk V, Srimaneekarn N, Sano H, Saikaew P. Effects of dentin surface preparations on bonding of self-etching adhesives under simulated pulpal pressure. Restor Dent Endod 2022; 47:e4. [PMID: 35284320 PMCID: PMC8891469 DOI: 10.5395/rde.2022.47.e4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/17/2021] [Accepted: 07/24/2021] [Indexed: 11/29/2022] Open
Abstract
Objectives This study evaluated the effects of different smear layer preparations on the dentin permeability and microtensile bond strength (µTBS) of 2 self-etching adhesives (Clearfil SE Bond [CSE] and Clearfil Tri-S Bond Universal [CTS]) under dynamic pulpal pressure. Materials and Methods Human third molars were cut into crown segments. The dentin surfaces were prepared using 4 armamentaria: 600-grit SiC paper, coarse diamond burs, superfine diamond burs, and carbide burs. The pulp chamber of each crown segment was connected to a dynamic intra-pulpal pressure simulation apparatus, and the permeability test was done under a pressure of 15 cmH2O. The relative permeability (%P) was evaluated on the smear layer-covered and bonded dentin surfaces. The teeth were bonded to either of the adhesives under pulpal pressure simulation, and cut into sticks after 24 hours water storage for the µTBS test. The resin-dentin interface and nanoleakage observations were performed using a scanning electron microscope. Statistical comparisons were done using analysis of variance and post hoc tests. Results Only the method of surface preparation had a significant effect on permeability (p < 0.05). The smear layers created by the carbide and superfine diamond burs yielded the lowest permeability. CSE demonstrated a higher µTBS, with these values in the superfine diamond and carbide bur groups being the highest. Microscopic evaluation of the resin-dentin interface revealed nanoleakage in the coarse diamond bur and SiC paper groups for both adhesives. Conclusions Superfine diamond and carbide burs can be recommended for dentin preparation with the use of 2-step CSE.
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Affiliation(s)
- Chantima Siriporananon
- Department of Operative Dentistry and Endodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
| | - Pisol Senawongse
- Department of Operative Dentistry and Endodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
| | - Vanthana Sattabanasuk
- Department of Operative Dentistry and Endodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
| | | | - Hidehiko Sano
- Department of Restorative Dentistry, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Pipop Saikaew
- Department of Operative Dentistry and Endodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
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Riedl P, Schricker M, Pompe T. Stiffness Variation of 3D Collagen Networks by Surface Functionalization of Network Fibrils with Sulfonated Polymers. Gels 2021; 7:266. [PMID: 34940326 PMCID: PMC8702206 DOI: 10.3390/gels7040266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/03/2021] [Accepted: 12/11/2021] [Indexed: 11/16/2022] Open
Abstract
Fibrillar collagen is the most prominent protein in the mammalian extracellular matrix. Therefore, it is also widely used for cell culture research and clinical therapy as a biomimetic 3D scaffold. Charged biopolymers, such as sulfated glycosaminoglycans, occur in vivo in close contact with collagen fibrils, affecting many functional properties such as mechanics and binding of growth factors. For in vitro application, the functions of sulfated biopolymer decorations of fibrillar collagen materials are hardly understood. Herein, we report new results on the stiffness dependence of 3D collagen I networks by surface functionalization of the network fibrils with synthetic sulfonated polymers, namely, poly(styrene sulfonate) (PSS) and poly(vinyl sulfonate) (PVS). A non-monotonic stiffness dependence on the amount of adsorbed polymer was found for both polymers. The stiffness dependence correlated to a transition from mono- to multilayer adsorption of sulfonated polymers on the fibrils, which was most prominent for PVS. PVS mono- and multilayers caused a network stiffness change by a factor of 0.3 and 2, respectively. A charge-dependent weakening of intrafibrillar salt bridges by the adsorbed sulfonated polymers leading to fibrillar softening is discussed as the mechanism for the stiffness decrease in the monolayer regime. In contrast, multilayer adsorption can be assumed to induce interfibrillar bridging and an increase in network stiffness. Our in vitro results have a strong implication on in vivo characteristics of fibrillar collagen I, as sulfated glycosaminoglycans frequently attach to collagen fibrils in various tissues, calling for an up to now overlooked impact on matrix and tendon mechanics.
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Affiliation(s)
| | | | - Tilo Pompe
- Institute of Biochemistry, Faculty of Life Sciences, Leipzig University, 04103 Leipzig, Germany; (P.R.); (M.S.)
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43
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Reversible changes in the 3D collagen fibril architecture during cyclic loading of healthy and degraded cartilage. Acta Biomater 2021; 136:314-326. [PMID: 34563724 PMCID: PMC8631461 DOI: 10.1016/j.actbio.2021.09.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 08/19/2021] [Accepted: 09/20/2021] [Indexed: 01/09/2023]
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. Statement of significance Structural deterioration in biomechanically loaded musculoskeletal organs, e.g., joint osteoarthritis and back pain, are linked to breakdown and changes in their collagen-rich cartilaginous tissue matrix. A critical component enabling cartilage biomechanics is the ultrastructural collagen fibrillar network in cartilage. However, experimental probes of the dynamic structural response of cartilage collagen to biomechanical loads are limited. Here, we use X-ray scattering during cyclic loading (as during walking) on joint tissue to show that cartilage fibrils resist loading by a reversible, three-dimensional orientation broadening and disordering mechanism at the molecular level, and that inflammation reduces this functionality. Our results will help understand how changes to small-scale tissue mechanisms are linked to ageing and osteoarthritic progression, and development of biomaterials for joint replacements.
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Shen J, Tong Q. Prestressing Strategy for Strengthening Biocomposites: A Numerical Study. ACS Biomater Sci Eng 2021; 7:5014-5021. [PMID: 34597016 DOI: 10.1021/acsbiomaterials.1c00988] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Natural materials developed in complex architectures that comprise hard and soft phases often display extraordinary mechanical properties, such as the combination of high strength and toughness. Besides the structural arrangements, residual stress is ubiquitous in those materials. Although evidence shows its significant role in the functionalities and properties of the composites, good or bad, residual stress is not fully understood and utilized. In this study, we show through extensive numerical simulations the role of the prestress in strengthening typical brick-and-mortar biocomposites. We investigate the influence of the prestressing modes, as well as the geometrical and material parameters. The results promise a deep understanding of the relation between the prestress and the material strength and may inspire a new dimension of material design.
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Affiliation(s)
- Jiahao Shen
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China
| | - Qi Tong
- Department of Aeronautics and Astronautics, Fudan University, Shanghai 200433, China
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45
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Morin C, Hellmich C, Nejim Z, Avril S. Fiber Rearrangement and Matrix Compression in Soft Tissues: Multiscale Hypoelasticity and Application to Tendon. Front Bioeng Biotechnol 2021; 9:725047. [PMID: 34712652 PMCID: PMC8546211 DOI: 10.3389/fbioe.2021.725047] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 09/06/2021] [Indexed: 11/13/2022] Open
Abstract
It is widely accepted that the nonlinear macroscopic mechanical behavior of soft tissue is governed by fiber straightening and re-orientation. Here, we provide a quantitative assessment of this phenomenon, by means of a continuum micromechanics approach. Given the negligibly small bending stiffness of crimped fibers, the latter are represented through a number of hypoelastic straight fiber phases with different orientations, being embedded into a hypoelastic matrix phase. The corresponding representative volume element (RVE) hosting these phases is subjected to “macroscopic” strain rates, which are downscaled to fiber and matrix strain rates on the one hand, and to fiber spins on the other hand. This gives quantitative access to the fiber decrimping (or straightening) phenomenon under non-affine conditions, i.e. in the case where the fiber orientations cannot be simply linked to the macroscopic strain state. In the case of tendinous tissue, such an RVE relates to the fascicle material with 50 μm characteristic length, made up of crimped collagen bundles and a gel-type matrix in-between. The fascicles themselves act as parallel fibers in a similar matrix at the scale of a tissue-related RVE with 500 μm characteristic length. As evidenced by a sensitivity analysis and confirmed by various mechanical tests, it is the initial crimping angle which drives both the degree of straightening and the shape of the macroscopic stress-strain curve, while the final linear portion of this curve depends almost exclusively on the collagen bundle elasticity. Our model also reveals the mechanical cooperation of the tissue’s key microstructural components: while the fibers carry tensile forces, the matrices undergo hydrostatic pressure.
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Affiliation(s)
- Claire Morin
- Mines Saint-Etienne, Univ. Lyon, Univ. Jean Monnet, INSERM, U1059 Sainbiose, Centre CIS, Saint-Etienne, France
| | - Christian Hellmich
- Institute for Mechanics of Materials and Structures, TU Wien - Vienna University of Technology, Vienna, Austria
| | - Zeineb Nejim
- Mines Saint-Etienne, Univ. Lyon, Univ. Jean Monnet, INSERM, U1059 Sainbiose, Centre CIS, Saint-Etienne, France
| | - Stéphane Avril
- Mines Saint-Etienne, Univ. Lyon, Univ. Jean Monnet, INSERM, U1059 Sainbiose, Centre CIS, Saint-Etienne, France.,Institute for Mechanics of Materials and Structures, TU Wien - Vienna University of Technology, Vienna, Austria
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46
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Mlyniec A, Dabrowska S, Heljak M, Weglarz WP, Wojcik K, Ekiert-Radecka M, Obuchowicz R, Swieszkowski W. The dispersion of viscoelastic properties of fascicle bundles within the tendon results from the presence of interfascicular matrix and flow of body fluids. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2021; 130:112435. [PMID: 34702520 DOI: 10.1016/j.msec.2021.112435] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 01/12/2023]
Abstract
In this work, we investigate differences in the mechanical and structural properties of tendon fascicle bundles dissected from different areas of bovine tendons. The properties of tendon fascicle bundles were investigated by means of uniaxial tests with relaxation periods and hysteresis, dynamic mechanical analysis (DMA), as well as magnetic resonance imaging (MRI). Uniaxial tests with relaxation periods revealed greater elastic modulus, hysteresis, as well as stress drop during the relaxation of samples dissected from the posterior side of the tendon. However, the normalized stress relaxation curves did not show a statistically significant difference in the stress drop between specimens cut from different zones or between different strain levels. Using dynamic mechanical analysis, we found that fascicle bundles dissected from the anterior side of the tendon had lower storage and loss moduli, which could result from altered fluid flow within the interfascicular matrix (IFM). The lower water content, diffusivity, and higher fractional anisotropy of the posterior part of the tendon, as observed using MRI, indicates a different structure of the IFM, which controls the flow of fluids within the tendon. Our results show that the viscoelastic response to dynamic loading is correlated with fluid flow within the IFM, which was confirmed during analysis of the MRI results. In contrast to this, the long-term relaxation of tendon fascicle bundles is controlled by viscoplasticity of the IFM and depends on the spatial distribution of the matrix within the tendon. Comparison of results from tensile tests, DMA, and MRI gives new insight into tendon mechanics and the role of the IFM. These findings may be useful in improving the diagnosis of tendon injury and effectiveness of medical treatments for tendinopathies.
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Affiliation(s)
- Andrzej Mlyniec
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland.
| | - Sylwia Dabrowska
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Marcin Heljak
- Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw, Poland
| | | | - Kaja Wojcik
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Martyna Ekiert-Radecka
- AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Krakow, Poland
| | - Rafal Obuchowicz
- Jagiellonian University Collegium Medicum, Department of Radiology, Krakow, Poland
| | - Wojciech Swieszkowski
- Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw, Poland
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47
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Fosca M, Basoli V, Della Bella E, Russo F, Vadala G, Alini M, Rau JV, Verrier S. Raman spectroscopy in skeletal tissue disorders and tissue engineering: present and prospective. TISSUE ENGINEERING PART B-REVIEWS 2021; 28:949-965. [PMID: 34579558 DOI: 10.1089/ten.teb.2021.0139] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Musculoskeletal disorders are the most common reason of chronic pain and disability representing worldwide an enormous socio-economic burden. In this review, new biomedical application fields for Raman spectroscopy (RS) technique related to skeletal tissues are discussed showing that it can provide a comprehensive profile of tissue composition in situ, in a rapid, label-free, and non-destructive manner. RS can be used as a tool to study tissue alterations associated to aging, pathologies, and disease treatments. The main advantage with respect to currently applied methods in clinics is its ability to provide specific information on molecular composition, which goes beyond other diagnostic tools. Being compatible with water, RS can be performed without pre-treatment on unfixed, hydrated tissue samples, without any labelling and chemical fixation used in histochemical methods. This review provides first the description of basic principles of RS as a biotechnology tool and introduces into the field of currently available RS based techniques, developed to enhance Raman signal. The main spectral processing statistical tools, fingerprint identification and available databases are mentioned. The recent literature has been analysed for such applications of RS as tendon and ligaments, cartilage, bone, and tissue engineered constructs for regenerative medicine. Several cases of proof-of-concept preclinical studies have been described. Finally, advantages, limitations, future perspectives, and challenges for translation of RS into clinical practice have been also discussed.
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Affiliation(s)
- Marco Fosca
- Istituto di Struttura della Materia Consiglio Nazionale delle Ricerche, 204549, Roma, Lazio, Italy;
| | - Valentina Basoli
- AO Research Institute Davos, 161930, Regenerative Orthopaedics, Davos, Graubünden, Switzerland;
| | - Elena Della Bella
- AO Research Institute Davos, 161930, Regenerative Orthopaedics, Davos, Graubünden, Switzerland;
| | - Fabrizio Russo
- Campus Bio-Medico University Hospital, 220431, Roma, Lazio, Italy;
| | - Gianluca Vadala
- Campus Bio-Medico University Hospital, 220431, Roma, Lazio, Italy;
| | - Mauro Alini
- AO Research Institute Davos, 161930, Regenerative Orthopaedics, Davos, Graubünden, Switzerland;
| | - Julietta V Rau
- Istituto di Struttura della Materia Consiglio Nazionale delle Ricerche, 204549, Roma, Lazio, Italy.,I M Sechenov First Moscow State Medical University, 68477, Moskva, Moskva, Russian Federation;
| | - Sophie Verrier
- AO Research Institute Davos, 161930, Regenerative Orthopaedics, Davos, Graubünden, Switzerland;
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Cutini M, Ugliengo P. Infrared harmonic features of collagen models at B3LYP-D3: From amide bands to the THz region. J Chem Phys 2021; 155:075102. [PMID: 34418922 DOI: 10.1063/5.0056422] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper, we have studied the vibrational spectral features for the collagen triple helix using a dispersion corrected hybrid density functional theory (DFT-D) approach. The protein is simulated by an infinite extended polymer both in the gas phase and in a water micro-solvated environment. We have adopted proline-rich collagen models in line with the high content of proline in natural collagens. Our scaled harmonic vibrational spectra are in very good agreement with the experiments and allow for the peak assignment of the collagen amide I and III bands, supporting or questioning the experimental interpretation by means of vibrational normal modes analysis. Furthermore, we demonstrated that IR spectroscopy in the THz region can detect the small variations inherent to the triple helix helicity (10/3 over 7/2), thus elucidating the packing state of the collagen. So far, identifying the collagen helicity is only possible by means of crystal x-ray diffraction.
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Affiliation(s)
- Michele Cutini
- Department of Chemistry and NIS (Nanostructured Interfaces and Surfaces) Center, University of Torino, Via P. Giuria 7, 10125 Turin, Italy
| | - Piero Ugliengo
- Department of Chemistry and NIS (Nanostructured Interfaces and Surfaces) Center, University of Torino, Via P. Giuria 7, 10125 Turin, Italy
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49
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Obarska-Kosinska A, Rennekamp B, Ünal A, Gräter F. ColBuilder: A server to build collagen fibril models. Biophys J 2021; 120:3544-3549. [PMID: 34265261 DOI: 10.1016/j.bpj.2021.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/21/2021] [Accepted: 07/07/2021] [Indexed: 11/17/2022] Open
Abstract
Type I collagen is the main structural component of many tissues in the human body. It provides excellent mechanical properties to connective tissue and acts as a protein interaction hub. There is thus a wide interest in understanding the properties and diverse functions of type I collagen at the molecular level. A precondition is an atomistic collagen I structure as it occurs in native tissue. To this end, we built full-atom models of cross-linked collagen fibrils by integrating the low-resolution structure of collagen fibril available from x-ray fiber diffraction with high-resolution structures of short collagen-like peptides from x-ray crystallography and mass spectrometry data. We created a Web resource of collagen models for 20 different species with a large variety of cross-link types and localization within the fibril to facilitate structure-based analyses and simulations of type I collagen in health and disease. To easily enable simulations, we provide parameters of the modeled cross-links for an Amber force field. The repository of collagen models is available at https://colbuilder.h-its.org.
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Affiliation(s)
- Agnieszka Obarska-Kosinska
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany; Hamburg Unit c/o DESY, European Molecular Biology Laboratory, Hamburg, Germany
| | - Benedikt Rennekamp
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany; Max Planck School Matter-to-Life (MtL), Heidelberg, Germany; Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
| | - Aysecan Ünal
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany; Max Planck School Matter-to-Life (MtL), Heidelberg, Germany
| | - Frauke Gräter
- Heidelberg Institute for Theoretical Studies, Heidelberg, Germany; Max Planck School Matter-to-Life (MtL), Heidelberg, Germany; Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany.
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50
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Meador WD, Zhou J, Malinowski M, Jazwiec T, Calve S, Timek TA, Rausch MK. The effects of a simple optical clearing protocol on the mechanics of collagenous soft tissue. J Biomech 2021; 122:110413. [PMID: 33905970 DOI: 10.1016/j.jbiomech.2021.110413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 03/12/2021] [Accepted: 03/20/2021] [Indexed: 11/18/2022]
Abstract
Optical clearing of biological tissues improves imaging depth for light transmission imaging modalities such as two-photon microscopy. In studies that investigate the interplay between microstructure and tissue-level mechanics, mechanical testing of cleared tissue may be useful. However, the effects of optical clearing on soft tissue mechanics have not been investigated. Thus, we set out to quantify the effects of a simple and effective optical clearing protocol on the mechanics of soft collagenous tissues using ovine mitral valve anterior leaflets as a model system. First, we demonstrate the effectiveness of an isotonic glycerol-DMSO optical clearing protocol in two-photon microscopy. Second, we evaluate the mechanical effects of optical clearing on leaflets under equibiaxial tension in a dependent study design. Lastly, we quantify the shrinkage strain while traction-free and the contractile forces while constrained during clearing. We found the optical clearing protocol to improve two-photon imaging depth from ~100 μm to ~500-800 μm, enabling full-thickness visualization of second-harmonic generation, autofluorescent, and fluorophore-tagged structures. Under equibiaxial tension, cleared tissues exhibited reduced circumferential (p < 0.001) and radial (p = 0.009) transition stretches (i.e. stretch where collagen is recruited), and reduced radial stiffness (p = 0.031). Finally, during clearing we observed ~10-15% circumferential and radial compressive strains, and when constrained, ~2mN of circumferential and radial traction forces. In summary, we suggest the use of this optical clearing agent with mechanical testing be done with care, as it appears to alter the tissue's stress-free configuration and stiffness, likely due to tissue dehydration.
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Affiliation(s)
- William D Meador
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, United States
| | - Jennifer Zhou
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, United States
| | - Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, United States; Department of Cardiac Surgery, Medical University of Silesia, School of Medicine in Katowice, Katowice, Poland
| | - Tomasz Jazwiec
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, United States; Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Sarah Calve
- Department of Mechanical Engineering, University of Colorado - Boulder, Boulder, CO, United States
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, United States
| | - Manuel K Rausch
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, United States; Department of Aerospace Engineering & Engineering Mechanics, University of Texas at Austin, Austin, TX, United States; Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX, United States.
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