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Virijević K, Živanović MN, Nikolić D, Milivojević N, Pavić J, Morić I, Šenerović L, Dragačević L, Thurner PJ, Rufin M, Andriotis OG, Ljujić B, Miletić Kovačević M, Papić M, Filipović N. AI-Driven Optimization of PCL/PEG Electrospun Scaffolds for Enhanced In Vivo Wound Healing. ACS Appl Mater Interfaces 2024. [PMID: 38659385 DOI: 10.1021/acsami.4c03266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Here, an artificial intelligence (AI)-based approach was employed to optimize the production of electrospun scaffolds for in vivo wound healing applications. By combining polycaprolactone (PCL) and poly(ethylene glycol) (PEG) in various concentration ratios, dissolved in chloroform (CHCl3) and dimethylformamide (DMF), 125 different polymer combinations were created. From these polymer combinations, electrospun nanofiber meshes were produced and characterized structurally and mechanically via microscopic techniques, including chemical composition and fiber diameter determination. Subsequently, these data were used to train a neural network, creating an AI model to predict the optimal scaffold production solution. Guided by the predictions and experimental outcomes of the AI model, the most promising scaffold for further in vitro analyses was identified. Moreover, we enriched this selected polymer combination by incorporating antibiotics, aiming to develop electrospun nanofiber scaffolds tailored for in vivo wound healing applications. Our study underscores three noteworthy conclusions: (i) the application of AI is pivotal in the fields of material and biomedical sciences, (ii) our methodology provides an effective blueprint for the initial screening of biomedical materials, and (iii) electrospun PCL/PEG antibiotic-bearing scaffolds exhibit outstanding results in promoting neoangiogenesis and facilitating in vivo wound treatment.
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Affiliation(s)
- Katarina Virijević
- Institute for Information Technologies, University of Kragujevac, 34000Kragujevac ,Serbia
| | - Marko N Živanović
- Institute for Information Technologies, University of Kragujevac, 34000Kragujevac ,Serbia
| | - Dalibor Nikolić
- Institute for Information Technologies, University of Kragujevac, 34000Kragujevac ,Serbia
| | - Nevena Milivojević
- Institute for Information Technologies, University of Kragujevac, 34000Kragujevac ,Serbia
| | - Jelena Pavić
- Institute for Information Technologies, University of Kragujevac, 34000Kragujevac ,Serbia
| | - Ivana Morić
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, 11000Belgrade, Serbia
| | - Lidija Šenerović
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, 11000Belgrade, Serbia
| | - Luka Dragačević
- Institute of Virology, Vaccines and Sera "Torlak″, 11000Belgrade ,Serbia
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Wien, Austria
| | - Manuel Rufin
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Wien, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Wien, Austria
| | - Biljana Ljujić
- Department of Genetics, Faculty of Medical Sciences, University of Kragujevac, 34000Kragujevac, Serbia
| | - Marina Miletić Kovačević
- Department of Histology and Embryology, Faculty of Medical Sciences, University of Kragujevac, 34000Kragujevac, Serbia
| | - Miloš Papić
- Department of Dentistry, Faculty of Medical Sciences, University of Kragujevac, 34000Kragujevac, Serbia
| | - Nenad Filipović
- Faculty of Engineering, University of Kragujevac, 34000Kragujevac, Serbia
- BioIRC─Bioengineering Research and Development Center, 34000Kragujevac,Serbia
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2
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Reisinger AG, Bittner-Frank M, Thurner PJ, Pahr DH. The 2-layer elasto-visco-plastic rheological model for the material parameter identification of bone tissue extended by a damage law. J Mech Behav Biomed Mater 2024; 150:106259. [PMID: 38039773 DOI: 10.1016/j.jmbbm.2023.106259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 10/24/2023] [Accepted: 11/16/2023] [Indexed: 12/03/2023]
Abstract
The response of bone tissue to mechanical load is complex and includes plastic hardening, viscosity and damage. The quantification of these effects plays a mayor role in bone research and in biomechanical clinical trials as to better understand related diseases. In this study, the damage growth in individual wet human trabeculae subjected to cyclic overloading is quantified by inverse rheological modeling. Therefore, an already published rheological material model, that includes linear elasticity, plasticity and viscosity is extended by a damage law. The model is utilized in an optimization process to identify the corresponding material parameters and damage growth in single human trabeculae under tensile load. Results show that the damage model is leading to a better fit of the test data with an average root-mean-square-error (RMSE) of 2.52 MPa compared to the non-damage model with a RMSE of 3.03 MPa. Although this improvement is not significant, the damage model qualitatively better represents the data as it accounts for the visible stiffness reduction along the load history. It returns realistic stiffness values of 11.92 GPa for the instantaneous modulus and 5.73 GPa for the long term modulus of wet trabecular human bone. Further, the growth of damage in the tissue along the load history is substantial, with values above 0.8 close to failure. The relative loss of stiffness per cycle is in good agreement with comparable literature. Inverse rheological modeling proves to be a valuable tool for quantifying complex constitutive behavior from a single mechanical measurement. The evolution of damage in the tissue can be identified continuously over the load history and separated from other effects.
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Affiliation(s)
- Andreas G Reisinger
- Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Austria; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Austria.
| | - Martin Bittner-Frank
- Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Austria; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Austria
| | - Dieter H Pahr
- Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Austria; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Austria
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3
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Handelshauser M, Chiang YR, Marchetti-Deschmann M, Thurner PJ, Andriotis OG. Collagen fibril tensile response described by a nonlinear Maxwell model. J Mech Behav Biomed Mater 2023; 145:105991. [PMID: 37480709 DOI: 10.1016/j.jmbbm.2023.105991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 06/20/2023] [Accepted: 06/23/2023] [Indexed: 07/24/2023]
Abstract
Collagen fibrils are the basic structural building blocks that provide mechanical properties such as stiffness, toughness, and strength to tissues from the nano- to the macroscale. Collagen fibrils are highly hydrated and transient deformation mechanisms contribute to their mechanical behavior. One approach to describe and quantify the apparent viscoelastic behavior of collagen fibrils is to find rheological models and fit the resulting empirical equations to experimental data. In this study, we consider a nonlinear rheological Maxwell model for this purpose. The model was fitted to tensile stress-time data from experiments conducted in a previous study on hydrated and partially dehydrated individual collagen fibrils via AFM. The derivative tensile modulus, estimated from the empirical equation, increased for decreasing hydration of the collagen fibril. The viscosity is only marginally affected by hydration but shows a dependency with strain rate, suggesting thixotropic behavior for low strain rates.
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Affiliation(s)
- Martin Handelshauser
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria; Institute of Chemical Technologies and Analytics, TU Wien, 1060, Vienna, Austria
| | - You-Rong Chiang
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria
| | | | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria.
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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: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Tomasch J, Maleiner B, Heher P, Rufin M, Andriotis OG, Thurner PJ, Redl H, Fuchs C, Teuschl-Woller AH. Changes in Elastic Moduli of Fibrin Hydrogels Within the Myogenic Range Alter Behavior of Murine C2C12 and Human C25 Myoblasts Differently. Front Bioeng Biotechnol 2022; 10:836520. [PMID: 35669058 PMCID: PMC9164127 DOI: 10.3389/fbioe.2022.836520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 04/29/2022] [Indexed: 11/13/2022] Open
Abstract
Fibrin hydrogels have proven highly suitable scaffold materials for skeletal muscle tissue engineering in the past. Certain parameters of those types of scaffolds, however, greatly affect cellular mechanobiology and therefore the myogenic outcome. The aim of this study was to identify the influence of apparent elastic properties of fibrin scaffolds in 2D and 3D on myoblasts and evaluate if those effects differ between murine and human cells. Therefore, myoblasts were cultured on fibrin-coated multiwell plates (“2D”) or embedded in fibrin hydrogels (“3D”) with different elastic moduli. Firstly, we established an almost linear correlation between hydrogels’ fibrinogen concentrations and apparent elastic moduli in the range of 7.5 mg/ml to 30 mg/ml fibrinogen (corresponds to a range of 7.7–30.9 kPa). The effects of fibrin hydrogel elastic modulus on myoblast proliferation changed depending on culture type (2D vs 3D) with an inhibitory effect at higher fibrinogen concentrations in 3D gels and vice versa in 2D. The opposite effect was evident in differentiating myoblasts as shown by gene expression analysis of myogenesis marker genes and altered myotube morphology. Furthermore, culture in a 3D environment slowed down proliferation compared to 2D, with a significantly more pronounced effect on human myoblasts. Differentiation potential was also substantially impaired upon incorporation into 3D gels in human, but not in murine, myoblasts. With this study, we gained further insight in the influence of apparent elastic modulus and culture type on cellular behavior and myogenic outcome of skeletal muscle tissue engineering approaches. Furthermore, the results highlight the need to adapt parameters of 3D culture setups established for murine cells when applied to human cells.
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Affiliation(s)
- Janine Tomasch
- Department Life Science Engineering, University of Applied Sciences Technikum Wien, Vienna, Austria
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- *Correspondence: Andreas H. Teuschl-Woller,
| | - Babette Maleiner
- Department Life Science Engineering, University of Applied Sciences Technikum Wien, Vienna, Austria
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
| | - Philipp Heher
- Ludwig Randall Centre for Cell and Molecular Biophysics, King’s College London, Guy’s Campus, London, United Kingdom
| | - Manuel Rufin
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria
| | - Orestis G. Andriotis
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria
| | - Philipp J. Thurner
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria
| | - Heinz Redl
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Ludwig Boltzmann Institute for Traumatology, The Research Center in Cooperation with AUVA, Vienna, Austria
| | - Christiane Fuchs
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- Wellman Center for Photomedicine, MGH, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Andreas H. Teuschl-Woller
- Department Life Science Engineering, University of Applied Sciences Technikum Wien, Vienna, Austria
- The Austrian Cluster for Tissue Regeneration, Vienna, Austria
- *Correspondence: Andreas H. Teuschl-Woller,
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Nalbach M, Chalupa-Gantner F, Spoerl F, de Bar V, Baumgartner B, Andriotis OG, Ito S, Ovsianikov A, Schitter G, Thurner PJ. Instrument for tensile testing of individual collagen fibrils with facile sample coupling and uncoupling. Rev Sci Instrum 2022; 93:054103. [PMID: 35649813 DOI: 10.1063/5.0072123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 04/12/2022] [Indexed: 06/15/2023]
Abstract
Collagen is the major structural protein in human bodies constituting about 30% of the entire protein mass. Through a self-assembly process, triple helical collagen molecules assemble into high aspect-ratio fibers of tens to hundreds of nanometer diameter, known as collagen fibrils (CFs). In the last decade, several methods for tensile testing these CFs emerged. However, these methods are either overly time-consuming or offer low data acquisition bandwidth, rendering dynamic investigation of tensile properties impossible. Here, we describe a novel instrument for tensile testing of individual CFs. CFs are furnished with magnetic beads using a custom magnetic tweezer. Subsequently, CFs are lifted by magnetic force, allowing them to be picked-up by a microgripper structure, which is mounted on a cantilever-based interferometric force probe. A piezo-lever actuator is used to apply tensile displacements and to perform tensile tests of tethered CFs, after alignment. Once the mechanical tests are finished, CFs are removed from the microgripper by application of a magnetic field. Our novel instrument enables tensile tests with at least 25-fold increased throughput compared to tensile testing with an atomic force microscope while achieving force resolution (p-p) of 10 nN at a strain resolution better than 0.1%.
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Affiliation(s)
- Mathis Nalbach
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
| | | | - Felix Spoerl
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
| | - Victor de Bar
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
| | - Benedikt Baumgartner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
| | - Shingo Ito
- Automation and Control Institute, TU Wien, Gußhausstraße 27-29/E376, 1040 Vienna, Austria
| | - Aleksandr Ovsianikov
- Institute of Materials Science and Technology, TU Wie, Getreidemarkt 9/E308, 1060 Vienna, Austria
| | - Georg Schitter
- Automation and Control Institute, TU Wien, Gußhausstraße 27-29/E376, 1040 Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7/Objekt 8, 1060 Vienna, Austria
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7
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Brereton CJ, Yao L, Davies ER, Zhou Y, Vukmirovic M, Bell JA, Wang S, Ridley RA, Dean LSN, Andriotis OG, Conforti F, Brewitz L, Mohammed S, Wallis T, Tavassoli A, Ewing RM, Alzetani A, Marshall BG, Fletcher SV, Thurner PJ, Fabre A, Kaminski N, Richeldi L, Bhaskar A, Schofield CJ, Loxham M, Davies DE, Wang Y, Jones MG. Pseudohypoxic HIF pathway activation dysregulates collagen structure-function in human lung fibrosis. eLife 2022; 11:e69348. [PMID: 35188460 PMCID: PMC8860444 DOI: 10.7554/elife.69348] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 01/04/2022] [Indexed: 12/13/2022] Open
Abstract
Extracellular matrix (ECM) stiffening with downstream activation of mechanosensitive pathways is strongly implicated in fibrosis. We previously reported that altered collagen nanoarchitecture is a key determinant of pathogenetic ECM structure-function in human fibrosis (Jones et al., 2018). Here, through human tissue, bioinformatic and ex vivo studies we provide evidence that hypoxia-inducible factor (HIF) pathway activation is a critical pathway for this process regardless of the oxygen status (pseudohypoxia). Whilst TGFβ increased the rate of fibrillar collagen synthesis, HIF pathway activation was required to dysregulate post-translational modification of fibrillar collagen, promoting pyridinoline cross-linking, altering collagen nanostructure, and increasing tissue stiffness. In vitro, knockdown of Factor Inhibiting HIF (FIH), which modulates HIF activity, or oxidative stress caused pseudohypoxic HIF activation in the normal fibroblasts. By contrast, endogenous FIH activity was reduced in fibroblasts from patients with lung fibrosis in association with significantly increased normoxic HIF pathway activation. In human lung fibrosis tissue, HIF-mediated signalling was increased at sites of active fibrogenesis whilst subpopulations of human lung fibrosis mesenchymal cells had increases in both HIF and oxidative stress scores. Our data demonstrate that oxidative stress can drive pseudohypoxic HIF pathway activation which is a critical regulator of pathogenetic collagen structure-function in fibrosis.
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Affiliation(s)
- Christopher J Brereton
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Liudi Yao
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Elizabeth R Davies
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Yilu Zhou
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Milica Vukmirovic
- Section of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Yale University School of MedicineNew HavenUnited States
- Leslie Dan Faculty of Pharmacy, University of TorontoTorontoCanada
| | - Joseph A Bell
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Siyuan Wang
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Robert A Ridley
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Lareb SN Dean
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU WienViennaAustria
| | - Franco Conforti
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Lennart Brewitz
- Department of Chemistry and the Ineos Oxford Institute for Antimicrobial Research, Chemistry Research LaboratoryOxfordUnited Kingdom
| | - Soran Mohammed
- School of Chemistry, University of SouthamptonSouthamptonUnited Kingdom
| | - Timothy Wallis
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Ali Tavassoli
- School of Chemistry, University of SouthamptonSouthamptonUnited Kingdom
| | - Rob M Ewing
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Aiman Alzetani
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Benjamin G Marshall
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Sophie V Fletcher
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- University Hospital SouthamptonSouthamptonUnited Kingdom
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU WienViennaAustria
| | - Aurelie Fabre
- Department of Histopathology, St. Vincent's University Hospital & UCD School of Medicine, University College DublinDublinIreland
| | - Naftali Kaminski
- Section of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Yale University School of MedicineNew HavenUnited States
| | - Luca Richeldi
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Unità Operativa Complessa di Pneumologia, Università Cattolica del Sacro Cuore, Fondazione Policlinico A. Gemelli IRCCSRomeItaly
| | - Atul Bhaskar
- Faculty of Engineering and Physical Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Christopher J Schofield
- Department of Chemistry and the Ineos Oxford Institute for Antimicrobial Research, Chemistry Research LaboratoryOxfordUnited Kingdom
| | - Matthew Loxham
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Donna E Davies
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Yihua Wang
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Biological Sciences, Faculty of Environmental and Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
| | - Mark G Jones
- Clinical and Experimental Sciences, Faculty of Medicine, University of SouthamptonSouthamptonUnited Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital SouthamptonSouthamptonUnited Kingdom
- Institute for Life Sciences, University of SouthamptonSouthamptonUnited Kingdom
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Steindl J, Ehrmann K, Gorsche C, Huang C, Koch T, Steinbauer P, Rohatschek A, Andriotis OG, Thurner PJ, Prado‐Roller A, Stampfl J, Liska R. Maleimide‐styrene‐butadiene
terpolymers: acrylonitrile‐butadiene‐styrene
inspired
photopolymers for additive manufacturing. POLYM INT 2022. [DOI: 10.1002/pi.6351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Johannes Steindl
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
| | - Katharina Ehrmann
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
| | - Christian Gorsche
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
| | - Ching‐Chung Huang
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
| | - Thomas Koch
- Institute of Materials Science and Technology Technische Universität Wien Vienna Austria
| | - Patrick Steinbauer
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
- Christian Doppler Laboratory for Advanced Polymers for Biomaterials and 3D Printing Technische Universität Wien Vienna Austria
| | - Andreas Rohatschek
- Institute of Lightweight Design and Structural Biomechanics Technische Universität Wien Vienna Austria
- Austrian Cluster for Tissue Regeneration Vienna Austria
- Biointerface Doctorate School, TU Wien Vienna Austria
| | - Orestis G. Andriotis
- Institute of Lightweight Design and Structural Biomechanics Technische Universität Wien Vienna Austria
- Austrian Cluster for Tissue Regeneration Vienna Austria
| | - Philipp J. Thurner
- Institute of Lightweight Design and Structural Biomechanics Technische Universität Wien Vienna Austria
- Austrian Cluster for Tissue Regeneration Vienna Austria
- Biointerface Doctorate School, TU Wien Vienna Austria
| | - Alexander Prado‐Roller
- Department of Inorganic Chemistry – Functional Materials, Faculty of Chemistry University of Vienna Vienna Austria
| | - Jürgen Stampfl
- Institute of Materials Science and Technology Technische Universität Wien Vienna Austria
- Austrian Cluster for Tissue Regeneration Vienna Austria
| | - Robert Liska
- Institute for Applied Synthetic Chemistry Technische Universität Wien Vienna Austria
- Austrian Cluster for Tissue Regeneration Vienna Austria
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9
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Golman M, Abraham AC, Kurtaliaj I, Marshall BP, Hu YJ, Schwartz AG, Guo XE, Birman V, Thurner PJ, Genin GM, Thomopoulos S. Toughening mechanisms for the attachment of architectured materials: The mechanics of the tendon enthesis. Sci Adv 2021; 7:eabi5584. [PMID: 34826240 PMCID: PMC8626067 DOI: 10.1126/sciadv.abi5584] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 10/06/2021] [Indexed: 05/09/2023]
Abstract
Architectured materials offer tailored mechanical properties but are limited in engineering applications due to challenges in maintaining toughness across their attachments. The enthesis connects tendon and bone, two vastly different architectured materials, and exhibits toughness across a wide range of loadings. Understanding the mechanisms by which this is achieved could inform the development of engineered attachments. Integrating experiments, simulations, and previously unexplored imaging that enabled simultaneous observation of mineralized and unmineralized tissues, we identified putative mechanisms of enthesis toughening in a mouse model and then manipulated these mechanisms via in vivo control of mineralization and architecture. Imaging uncovered a fibrous architecture within the enthesis that controls trade-offs between strength and toughness. In vivo models of pathology revealed architectural adaptations that optimize these trade-offs through cross-scale mechanisms including nanoscale protein denaturation, milliscale load-sharing, and macroscale energy absorption. Results suggest strategies for optimizing architecture for tough bimaterial attachments in medicine and engineering.
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Affiliation(s)
- Mikhail Golman
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Adam C. Abraham
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
| | - Iden Kurtaliaj
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Brittany P. Marshall
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Yizhong Jenny Hu
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Andrea G. Schwartz
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University, St. Louis, MO 63130, USA
| | - X. Edward Guo
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Victor Birman
- Missouri University of Science and Technology, Rolla, MO 65409, USA
| | - Philipp J. Thurner
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - Guy M. Genin
- NSF Science and Technology Center for Engineering Mechanobiology, Washington University, St. Louis, MO 63130, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
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10
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Nedelkovski V, Andriotis OG, Wieland K, Gasser C, Steiger-Thirsfeld A, Bernardi J, Lendl B, Pretterklieber ML, Thurner PJ. Microbeam bending of hydrated human cortical bone lamellae from the central region of the body of femur shows viscoelastic behaviour. J Mech Behav Biomed Mater 2021; 125:104815. [PMID: 34678618 DOI: 10.1016/j.jmbbm.2021.104815] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 04/30/2021] [Accepted: 09/03/2021] [Indexed: 12/27/2022]
Abstract
Bone is a biological tissue with unique mechanical properties, owing to a complex hierarchical structure ranging from the nanoscale up to the macroscale. To better understand bone mechanics, investigation of mechanical properties of all structural elements at every hierarchical level and how they interact is necessary. Testing of bone structures at the lower microscale, e.g. bone lamellae, has been least performed and remains a challenge. Focused ion beam (FIB) milling is an attractive technique for machining microscopic samples from bone material and performing mechanical testing at the microscale using atomic force microscopy (AFM) and nanoindentation setups. So far, reported studies at this length scale have been performed on bone samples of animal origin, mostly in a dehydrated state, except for one study. Here we present an AFM-based microbeam bending method for performing bending measurements in both dehydrated and rehydrated conditions at the microscale. Single lamella bone microbeams of four human donors, aged 65-94 yrs, were machined via FIB and tested both in air and fully submerged in Hank's Balanced Salt Solution (HBSS) to investigate the effect of (de)hydration and to a certain extent, of age, on bone mechanics. Bending moduli were found to reduce up to 5 times after 2 h of rehydration and no trend of change in bending moduli with respect to age could be observed. Mechanical behavior changed from almost purely elastic to viscoelastic upon rehydration and a trend of lower dissipated energy in samples from older donors could be observed in the rehydrated state. These results confirm directly the importance of water for the mechanical properties of bone tissue at the microscale. Moreover, the trend of lowered capability of energy dissipation in older donors may contribute to a decrease of fracture toughness and thus an increase in bone fragility with age.
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Affiliation(s)
- Vedran Nedelkovski
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria
| | - Karin Wieland
- Institute of Chemical Technologies and Analytics, TU Wien, 1060, Vienna, Austria
| | - Christoph Gasser
- Institute of Chemical Technologies and Analytics, TU Wien, 1060, Vienna, Austria
| | | | - Johannes Bernardi
- University Service Center for Transmission Electron Microscopy, TU Wien, 1040, Vienna, Austria
| | - Bernhard Lendl
- Institute of Chemical Technologies and Analytics, TU Wien, 1060, Vienna, Austria
| | - Michael L Pretterklieber
- Center for Anatomy and Cell Biology, Division of Anatomy, Medical University of Vienna, 1090, Vienna, Austria; Division of Macroscopic and Clinical Anatomy, Medical University Graz, 8010, Graz, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria.
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11
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Frank M, Grabos A, Reisinger AG, Burr DB, Pahr DH, Allen MR, Thurner PJ. Effects of anti-resorptive treatment on the material properties of individual canine trabeculae in cyclic tensile tests. Bone 2021; 150:115995. [PMID: 33940224 DOI: 10.1016/j.bone.2021.115995] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 04/25/2021] [Accepted: 04/28/2021] [Indexed: 01/22/2023]
Abstract
Osteoporosis is defined as a decrease of bone mass and strength, as well as an increase in fracture risk. It is conventionally treated with antiresorptive drugs, such as bisphosphonates (BPs) and selective estrogen receptor modulators (SERMs). Although both drug types successfully decrease the risk of bone fractures, their effect on bone mass and strength is different. For instance, BP treatment causes an increase of bone mass, stiffness and strength of whole bones, whereas SERM treatment causes only small (4%) increases of bone mass, but increased bone toughness. Such improved mechanical behavior of whole bones can be potentially related to the bone mass, bone structure or material changes. While bone mass and architecture have already been investigated previously, little is known about the mechanical behavior at the tissue/material level, especially of trabecular bone. As such, the goal of the work presented here was to fill this gap by performing cyclic tensile tests in a wet, close to physiologic environment of individual trabeculae retrieved from the vertebrae of beagle dogs treated with alendronate (a BP), raloxifene (a SERM) or without treatments. Identification of material properties was performed with a previously developed rheological model and of mechanical properties via fitting of envelope curves. Additionally, tissue mineral density (TMD) and microdamage formation were analyzed. Alendronate treatment resulted in a higher trabecular tissue stiffness and strength, associated with higher levels of TMD. In contrast, raloxifene treatment caused a higher trabecular toughness, pre-dominantly in the post-yield region. Microdamage formation during testing was not affected by either anti-resorptive treatment regimens. These findings highlight that the improved mechanical behavior of whole bones after anti-resorptive treatment is at least partly caused by improved material properties, with different mechanisms for alendronate and raloxifene. This study further shows the power of performing a mechanical characterization of trabecular bone at the level of individual trabeculae for better understanding of clinically relevant mechanical behavior of bone.
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Affiliation(s)
- Martin Frank
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7, 1060 Vienna, Austria.
| | - Andreas Grabos
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7, 1060 Vienna, Austria; Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, 340 West 10th Street Fairbanks Hall, Suite 6200, Indianapolis, USA
| | - Andreas G Reisinger
- Department of Anatomy and Biomechanics, Division Biomechanics, Karl Landsteiner University of Health Sciences, Dr.-Karl-Dorrek-Straße 30, 3500 Krems an der Donau, Austria.
| | - David B Burr
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, 340 West 10th Street Fairbanks Hall, Suite 6200, Indianapolis, USA.
| | - Dieter H Pahr
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7, 1060 Vienna, Austria; Department of Anatomy and Biomechanics, Division Biomechanics, Karl Landsteiner University of Health Sciences, Dr.-Karl-Dorrek-Straße 30, 3500 Krems an der Donau, Austria.
| | - Matthew R Allen
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, 340 West 10th Street Fairbanks Hall, Suite 6200, Indianapolis, USA.
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7, 1060 Vienna, Austria.
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12
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Frank M, Reisinger AG, Pahr DH, Thurner PJ. Effects of Osteoporosis on Bone Morphometry and Material Properties of Individual Human Trabeculae in the Femoral Head. JBMR Plus 2021; 5:e10503. [PMID: 34189388 PMCID: PMC8216141 DOI: 10.1002/jbm4.10503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 03/30/2021] [Accepted: 04/10/2021] [Indexed: 12/02/2022] Open
Abstract
Osteoporosis is the most common bone disease and is conventionally classified as a decrease of total bone mass. Current diagnosis of osteoporosis is based on clinical risk factors and dual energy X‐ray absorptiometry (DEXA) scans, but changes in bone quantity (bone mass) and quality (trabecular structure, material properties, and tissue composition) are not distinguished. Yet, osteoporosis is known to cause a deterioration of the trabecular network, which might be related to changes at the tissue scale—the material properties. The goal of the current study was to use a previously established test method to perform a thorough characterization of the material properties of individual human trabeculae from femoral heads in cyclic tensile tests in a close to physiologic, wet environment. A previously developed rheological model was used to extract elastic, viscous, and plastic aspects of material behavior. Bone morphometry and tissue mineralization were determined with a density calibrated micro‐computed tomography (μCT) set‐up. Osteoporotic trabeculae neither showed a significantly changed material or mechanical behavior nor changes in tissue mineralization, compared with age‐matched healthy controls. However, donors with osteopenia indicated significantly reduced apparent yield strain and elastic work with respect to osteoporosis, suggesting possible initial differences at disease onset. Bone morphometry indicated a lower bone volume to total volume for osteoporotic donors, caused by a smaller trabecular number and a larger trabecular separation. A correlation of age with tissue properties and bone morphometry revealed a similar behavior as in osteoporotic bone. In the range studied, age does affect morphometry but not material properties, except for moderately increased tissue strength in healthy donors and moderately increased hardening exponent in osteoporotic donors. Taken together, the distinct changes of trabecular bone quality in the femoral head caused by osteoporosis and aging could not be linked to suspected relevant changes in material properties or tissue mineralization. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Martin Frank
- Institute of Lightweight Design and Structural Biomechanics TU Wien Gumpendorfer Straße 7 Vienna 1060 Austria
| | - Andreas G Reisinger
- Department of Anatomy and Biomechanics, Division Biomechanics Karl Landsteiner University of Health Sciences Dr. Karl-Dorrek-Straße 30 Krems 3500 Austria
| | - Dieter H Pahr
- Institute of Lightweight Design and Structural Biomechanics TU Wien Gumpendorfer Straße 7 Vienna 1060 Austria.,Department of Anatomy and Biomechanics, Division Biomechanics Karl Landsteiner University of Health Sciences Dr. Karl-Dorrek-Straße 30 Krems 3500 Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics TU Wien Gumpendorfer Straße 7 Vienna 1060 Austria
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13
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Bailey S, Sroga GE, Hoac B, Katsamenis OL, Wang Z, Bouropoulos N, McKee MD, Sørensen ES, Thurner PJ, Vashishth D. The role of extracellular matrix phosphorylation on energy dissipation in bone. eLife 2020; 9:58184. [PMID: 33295868 PMCID: PMC7746230 DOI: 10.7554/elife.58184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 12/07/2020] [Indexed: 01/22/2023] Open
Abstract
Protein phosphorylation, critical for cellular regulatory mechanisms, is implicated in various diseases. However, it remains unknown whether heterogeneity in phosphorylation of key structural proteins alters tissue integrity and organ function. Here, osteopontin phosphorylation level declined in hypo- and hyper- phosphatemia mouse models exhibiting skeletal deformities. Phosphorylation increased cohesion between osteopontin polymers, and adhesion of osteopontin to hydroxyapatite, enhancing energy dissipation. Fracture toughness, a measure of bone’s mechanical competence, increased with ex-vivo phosphorylation of wildtype mouse bones and declined with ex-vivo dephosphorylation. In osteopontin-deficient mice, global matrix phosphorylation level was not associated with toughness. Our findings suggest that phosphorylated osteopontin promotes fracture toughness in a dose-dependent manner through increased interfacial bond formation. In the absence of osteopontin, phosphorylation increases electrostatic repulsion, and likely protein alignment and interfilament distance leading to decreased fracture resistance. These mechanisms may be of importance in other connective tissues, and the key to unraveling cell–matrix interactions in diseases.
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Affiliation(s)
- Stacyann Bailey
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
| | - Grazyna E Sroga
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
| | - Betty Hoac
- Faculty of Dentistry, McGill University, Montreal, Canada
| | - Orestis L Katsamenis
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, United Kingdom
| | - Zehai Wang
- Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, United States
| | | | - Marc D McKee
- Faculty of Dentistry, McGill University, Montreal, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, Canada
| | - Esben S Sørensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - Deepak Vashishth
- Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, United States
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14
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Reisinger AG, Frank M, Thurner PJ, Pahr DH. A two-layer elasto-visco-plastic rheological model for the material parameter identification of bone tissue. Biomech Model Mechanobiol 2020; 19:2149-2162. [PMID: 32377934 PMCID: PMC7603462 DOI: 10.1007/s10237-020-01329-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 04/13/2020] [Indexed: 11/29/2022]
Abstract
The ability to measure bone tissue material properties plays a major role in diagnosis of diseases and material modeling. Bone's response to loading is complex and shows a viscous contribution to stiffness, yield and failure. It is also ductile and damaging and exhibits plastic hardening until failure. When performing mechanical tests on bone tissue, these constitutive effects are difficult to quantify, as only their combination is visible in resulting stress-strain data. In this study, a methodology for the identification of stiffness, damping, yield stress and hardening coefficients of bone from a single cyclic tensile test is proposed. The method is based on a two-layer elasto-visco-plastic rheological model that is capable of reproducing the specimens' pre- and postyield response. The model's structure enables for capturing the viscously induced increase in stiffness, yield, and ultimate stress and for a direct computation of the loss tangent. Material parameters are obtained in an inverse approach by optimizing the model response to fit the experimental data. The proposed approach is demonstrated by identifying material properties of individual bone trabeculae that were tested under wet conditions. The mechanical tests were conducted according to an already published methodology for tensile experiments on single trabeculae. As a result, long-term and instantaneous Young's moduli were obtained, which were on average 3.64 GPa and 5.61 GPa, respectively. The found yield stress of 16.89 MPa was lower than previous studies suggest, while the loss tangent of 0.04 is in good agreement. In general, the two-layer model was able to reproduce the cyclic mechanical test data of single trabeculae with an root-mean-square error of 2.91 ± 1.77 MPa. The results show that inverse rheological modeling can be of great advantage when multiple constitutive contributions shall be quantified based on a single mechanical measurement.
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Affiliation(s)
- Andreas G Reisinger
- Division Biomechanics, Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Krems an der Donau, Austria.
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria.
| | - Martin Frank
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - Dieter H Pahr
- Division Biomechanics, Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Krems an der Donau, Austria
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
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15
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Frank M, Fischer JT, Thurner PJ. Microdamage formation in individual bovine trabeculae during fatigue testing. J Biomech 2020; 115:110131. [PMID: 33257009 DOI: 10.1016/j.jbiomech.2020.110131] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 10/26/2020] [Accepted: 11/09/2020] [Indexed: 11/17/2022]
Abstract
Ageing, disease and osteoporosis treatment have been linked to accumulation of microdamage, which is caused by repetitive loading and may eventually causes fatigue failure of bones. Post-hoc investigations for in vivo loading and in vitro experiments have been developed to better understand microdamage formation. In this context, previous studies were not able to discriminate the effects caused by structural changes of the trabecular network from differences of tissue/material properties on microdamage formation. In the present study a fatigue test protocol was established to induce microdamage at a defined tensile stress state of individual trabeculae. Further, a thorough analysis of microdamage analysis was presented for 2D and 3D confocal images, enabling a comparison between the tissue and the meso-scale. Eight individual trabeculae were tested for 1500 cycles, six for 2100 cycles and seven for 3000 cycles (close to failure). Microdamage increased slowly from 1500 to 2100 cycles and showed a rapid increase at 3000 cycles. Diffuse damage was mainly present, although also linear microcracks were visible at 2100 and 3000 cycles. Average microcrack length was 93 µm and diffuse damage density was 4.4% for samples tested for 3000 cycles, comparable to previous studies on trabecular bone cores. Only one to three large microdamage sites were observed in the central region, connected to the trabecular surface with small straight cracks. The presented procedure is a first step to better understand how microdamage formation is influenced by material properties in aged and diseased bone, independently of deteriorated trabecular microarchitecture.
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Affiliation(s)
- Martin Frank
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Str. 7, BE02, 1060 Vienna, Austria.
| | - Julia-Theresa Fischer
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Str. 7, BE02, 1060 Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Str. 7, BE02, 1060 Vienna, Austria.
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16
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Steinbauer P, Rohatschek A, Andriotis O, Bouropoulos N, Liska R, Thurner PJ, Baudis S. Single-Molecule Force Spectroscopy Reveals Adhesion-by-Demand in Statherin at the Protein-Hydroxyapatite Interface. Langmuir 2020; 36:13292-13300. [PMID: 33118809 PMCID: PMC7660943 DOI: 10.1021/acs.langmuir.0c02325] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 10/09/2020] [Indexed: 06/11/2023]
Abstract
Achieving strong adhesion in wet environments remains a technological challenge in biomedical applications demanding biocompatibility. Attention for adhesive motifs meeting such demands has largely been focused on marine organisms. However, bioadhesion to inorganic surfaces is also present in the human body, in the hard tissues of teeth and bones, and is mediated through serines (S). The specific amino acid sequence DpSpSEEKC has been previously suggested to be responsible for the strong binding abilities of the protein statherin to hydroxyapatite, where pS denotes phosphorylated serine. Notably, similar sequences are present in the non-collagenous bone protein osteopontin (OPN) and the mussel foot protein 5 (Mefp5). OPN has previously been shown to promote fracture toughness and physiological damage formation. Here, we investigated the adhesion strength of the motif D(pS)(pS)EEKC on substrates of hydroxyapatite, TiO2, and mica using atomic force microscopy (AFM) single-molecule force spectroscopy (SMFS). Specifically, we investigated the dependence of adhesion force on phosphorylation of serines by comparing findings with the unphosphorylated variant DSSEEKC. Our results show that high adhesion forces of over 1 nN on hydroxyapatite and on TiO2 are only present for the phosphorylated variant D(pS)(pS)EEKC. This warrants further exploitation of this motif or similar residues in technological applications. Further, the dependence of adhesion force on phosphorylation suggests that biological systems potentially employ an adhesion-by-demand mechanism via expression of enzymes that up- or down-regulate phosphorylation, to increase or decrease adhesion forces, respectively.
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Affiliation(s)
- Patrick Steinbauer
- Christian
Doppler Laboratory for Advanced Polymers for Biomaterials and 3D Printing, TU Wien, Vienna 1060, Austria
- Institute
of Applied Synthetic Chemistry, Division of Macromolecular Chemistry, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
| | - Andreas Rohatschek
- Institute
of Lightweight Design and Structural Biomechanics, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
- Biointerface
Doctorate School, TU Wien, Vienna 1060, Austria
| | - Orestis Andriotis
- Institute
of Lightweight Design and Structural Biomechanics, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
| | - Nikolaos Bouropoulos
- Department
of Materials Science, University of Patras, Rio Patras GR-26504, Greece
- Foundation
for Research and Technology Hellas, Institute of Chemical Engineering
and High Temperature Chemical Processes, FORTH/ICE-HT, Patras 26504, Greece
| | - Robert Liska
- Institute
of Applied Synthetic Chemistry, Division of Macromolecular Chemistry, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
- Biointerface
Doctorate School, TU Wien, Vienna 1060, Austria
| | - Philipp J. Thurner
- Institute
of Lightweight Design and Structural Biomechanics, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
- Biointerface
Doctorate School, TU Wien, Vienna 1060, Austria
| | - Stefan Baudis
- Christian
Doppler Laboratory for Advanced Polymers for Biomaterials and 3D Printing, TU Wien, Vienna 1060, Austria
- Institute
of Applied Synthetic Chemistry, Division of Macromolecular Chemistry, TU Wien, Vienna 1060, Austria
- Austrian
Cluster for Tissue Regeneration, Vienna 1200, Austria
- Biointerface
Doctorate School, TU Wien, Vienna 1060, Austria
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17
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Dobos A, Van Hoorick J, Steiger W, Gruber P, Markovic M, Andriotis OG, Rohatschek A, Dubruel P, Thurner PJ, Van Vlierberghe S, Baudis S, Ovsianikov A. Thiol-Gelatin-Norbornene Bioink for Laser-Based High-Definition Bioprinting. Adv Healthc Mater 2020; 9:e1900752. [PMID: 31347290 DOI: 10.1002/adhm.201900752] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Indexed: 11/06/2022]
Abstract
Two-photon polymerization (2PP) is a lithography-based 3D printing method allowing the fabrication of 3D structures with sub-micrometer resolution. This work focuses on the characterization of gelatin-norbornene (Gel-NB) bioinks which enables the embedding of cells via 2PP. The high reactivity of the thiol-ene system allows 2PP processing of cell-containing materials at remarkably high scanning speeds (1000 mm s-1 ) placing this technology in the domain of bioprinting. Atomic force microscopy results demonstrate that the indentation moduli of the produced hydrogel constructs can be adjusted in the 0.2-0.7 kPa range by controlling the 2PP processing parameters. Using this approach gradient 3D constructs are produced and the morphology of the embedded cells is observed in the course of 3 weeks. Furthermore, it is possible to tune the enzymatic degradation of the crosslinked bioink by varying the applied laser power. The 3D printed Gel-NB hydrogel constructs show exceptional biocompatibility, supported cell adhesion, and migration. Furthermore, cells maintain their proliferation capacity demonstrated by Ki-67 immunostaining. Moreover, the results demonstrate that direct embedding of cells provides uniform distribution and high cell loading independently of the pore size of the scaffold. The investigated photosensitive bioink enables high-definition bioprinting of well-defined constructs for long-term cell culture studies.
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Affiliation(s)
- Agnes Dobos
- TU Wien3D Printing and Biofabrication GroupInstitute of Materials Science and Technology Getreidemarkt 9 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration
| | - Jasper Van Hoorick
- Polymer Chemistry and Biomaterials GroupCentre of Macromolecular ChemistryGhent University Krijgslaan 281, S4 9000 Ghent Belgium
- Brussels PhotonicsDepartment of Applied Physics and PhotonicsFlanders Make and Vrije Universiteit Brussel Pleinlaan 2 1000 Brussels Belgium
| | - Wolfgang Steiger
- TU Wien3D Printing and Biofabrication GroupInstitute of Materials Science and Technology Getreidemarkt 9 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration
| | - Peter Gruber
- TU Wien3D Printing and Biofabrication GroupInstitute of Materials Science and Technology Getreidemarkt 9 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration
| | - Marica Markovic
- TU Wien3D Printing and Biofabrication GroupInstitute of Materials Science and Technology Getreidemarkt 9 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration
| | - Orestis G. Andriotis
- Austrian Cluster for Tissue Regeneration
- TU Wien, Institute of Lightweight Design and Structural Biomechanics Getreidemarkt 9 1060 Vienna Austria
| | - Andreas Rohatschek
- Austrian Cluster for Tissue Regeneration
- TU Wien, Institute of Lightweight Design and Structural Biomechanics Getreidemarkt 9 1060 Vienna Austria
| | - Peter Dubruel
- Polymer Chemistry and Biomaterials GroupCentre of Macromolecular ChemistryGhent University Krijgslaan 281, S4 9000 Ghent Belgium
| | - Philipp J. Thurner
- Austrian Cluster for Tissue Regeneration
- TU Wien, Institute of Lightweight Design and Structural Biomechanics Getreidemarkt 9 1060 Vienna Austria
| | - Sandra Van Vlierberghe
- Polymer Chemistry and Biomaterials GroupCentre of Macromolecular ChemistryGhent University Krijgslaan 281, S4 9000 Ghent Belgium
- Brussels PhotonicsDepartment of Applied Physics and PhotonicsFlanders Make and Vrije Universiteit Brussel Pleinlaan 2 1000 Brussels Belgium
| | - Stefan Baudis
- TU WienInstitute of Applied Synthetic Chemistry Getreidemarkt 9 1060 Vienna Austria
| | - Aleksandr Ovsianikov
- TU Wien3D Printing and Biofabrication GroupInstitute of Materials Science and Technology Getreidemarkt 9 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration
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18
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Nedelkovski V, Hahn R, Mayrhofer PH, Steiger-Thirsfeld A, Bernardi J, Thurner PJ. Influence of experimental constraints on micromechanical assessment of micromachined hard-tissue samples. J Mech Behav Biomed Mater 2020; 106:103741. [PMID: 32250952 DOI: 10.1016/j.jmbbm.2020.103741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 02/14/2020] [Accepted: 03/10/2020] [Indexed: 11/26/2022]
Abstract
Continuing technological advancement of mechanical characterization at the microscale has enabled the isolation of micron-sized specimens and their direct mechanical characterization. Such techniques, initially developed for engineering materials and MEMS, can also be applied on hard biological materials. Bone is a material with a complex hierarchical structure ranging from the macro- all the way down to the nanoscale. To fully understand bone tissue mechanics, knowledge of the mechanics of all structural elements i.e. at every length scale is necessary. Particularly, the mechanical properties of microstructural elements, such as bone lamellae are still largely unknown. In the last decade, testing protocols have been devised to close this gap including bending and compression of micrometer-sized bone specimens. However, the precision and accuracy of results obtained have not been discussed. In this study, we aim to do exactly this: we validate microbeam bending by testing silicon microbeams with known mechanical constants, and evaluate the precision and sources of errors in both microbeam bending and micropillar compression by means of finite element (FE) modeling. Bending of Si-microbeams reproduced the expected value for the bending modulus within 17% accuracy, although the effect of geometrical uncertainties was estimated to result in relative errors of up to 50%. The deformation of constraining bulk material had a smaller influence, with relative errors of 11%, for microbeam bending and 25% for micropillar compression. For the latter this error could be sufficiently eliminated by the Sneddon correction. The tapering of micropillars had a negligible effect on overall apparent stiffness, but induced inhomogeneous stress state within micropillars may lead to superposed structural deformation mechanisms and be responsible for failure patterns observed in past studies.
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Affiliation(s)
- Vedran Nedelkovski
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria
| | - Rainer Hahn
- Institute of Materials Science and Technology, TU Wien, 1060, Vienna, Austria
| | - Paul H Mayrhofer
- Institute of Materials Science and Technology, TU Wien, 1060, Vienna, Austria
| | | | - Johannes Bernardi
- University Service Center for Transmission Electron Microscopy, TU Wien, 1040, Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060, Vienna, Austria.
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19
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Andriotis OG, Elsayad K, Smart DE, Nalbach M, Davies DE, Thurner PJ. Hydration and nanomechanical changes in collagen fibrils bearing advanced glycation end-products. Biomed Opt Express 2019; 10:1841-1855. [PMID: 31086707 PMCID: PMC6484996 DOI: 10.1364/boe.10.001841] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/20/2019] [Accepted: 02/20/2019] [Indexed: 05/07/2023]
Abstract
Accumulation of advanced glycation end-products (AGEs) in biological tissues occurs as a consequence of normal ageing and pathology. Most biological tissues are composed of considerable amounts of collagen, with collagen fibrils being the most abundant form. Collagen fibrils are the smallest discernible structural elements of load-bearing tissues and as such, they are of high biomechanical importance. The low turnover of collagen cause AGEs to accumulate within the collagen fibrils with normal ageing as well as in pathologies. We hypothesized that collagen fibrils bearing AGEs have altered hydration and mechanical properties. To this end, we employed atomic force and Brillouin light scattering microscopy to measure the extent of hydration as well as the transverse elastic properties of collagen fibrils treated with ribose. We find that hydration is different in collagen fibrils bearing AGEs and this is directly related to their mechanical properties. Collagen fibrils treated with ribose showed increased hydration levels and decreased transverse stiffness compared to controlled samples. Our results show that BLS and AFM yield complementary evidence on the effect of hydration on the nanomechanical properties of collagen fibrils.
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Affiliation(s)
- Orestis G. Andriotis
- Insitute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
| | - Kareem Elsayad
- Advanced Microscopy Section, Vienna Biocenter Core Facilities GmbH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - David E. Smart
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Mathis Nalbach
- Insitute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
| | - Donna E. Davies
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Philipp J. Thurner
- Insitute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
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20
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Lunzer M, Shi L, Andriotis OG, Gruber P, Markovic M, Thurner PJ, Ossipov D, Liska R, Ovsianikov A. A Modular Approach to Sensitized Two-Photon Patterning of Photodegradable Hydrogels. Angew Chem Int Ed Engl 2018; 57:15122-15127. [PMID: 30191643 PMCID: PMC6391948 DOI: 10.1002/anie.201808908] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Indexed: 11/09/2022]
Abstract
Photodegradable hydrogels have emerged as useful platforms for research on cell function, tissue engineering, and cell delivery as their physical and chemical properties can be dynamically controlled by the use of light. The photo-induced degradation of such hydrogel systems is commonly based on the integration of photolabile o-nitrobenzyl derivatives to the hydrogel backbone, because such linkers can be cleaved by means of one- and two-photon absorption. Herein we describe a cytocompatible click-based hydrogel containing o-nitrobenzyl ester linkages between a hyaluronic acid backbone, which is photodegradable in the presence of cells. It is demonstrated for the first time that by using a cyclic benzylidene ketone-based small molecule as photosensitizer the efficiency of the two-photon degradation process can be improved significantly. Biocompatibility of both the improved two-photon micropatterning process as well as the hydrogel itself is confirmed by cell culture studies.
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Affiliation(s)
- Markus Lunzer
- Institute of Materials Science and TechnologyTU WienGetreidemarkt 9/3081060ViennaAustria
- Institute of Applied Synthetic ChemistryTU WienGetreidemarkt 9/163-MC1060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Liyang Shi
- Department of Chemistry-Ångström LaboratoryUppsala UniversityLägerhyddsvägen 1751 21UppsalaSweden
| | - Orestis G. Andriotis
- Institute of Lightweight Design and Structural BiomechanicsTU WienGetreidemarkt 9/3171060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Peter Gruber
- Institute of Materials Science and TechnologyTU WienGetreidemarkt 9/3081060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Marica Markovic
- Institute of Materials Science and TechnologyTU WienGetreidemarkt 9/3081060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Philipp J. Thurner
- Institute of Lightweight Design and Structural BiomechanicsTU WienGetreidemarkt 9/3171060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Dmitri Ossipov
- Department of Chemistry-Ångström LaboratoryUppsala UniversityLägerhyddsvägen 1751 21UppsalaSweden
- Department of Biosciences and NutritionKarolinska InstitutetNovum, 141 83 HuddingeStockholmSweden
| | - Robert Liska
- Institute of Applied Synthetic ChemistryTU WienGetreidemarkt 9/163-MC1060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
| | - Aleksandr Ovsianikov
- Institute of Materials Science and TechnologyTU WienGetreidemarkt 9/3081060ViennaAustria
- Austrian Cluster for Tissue RegenerationAustria
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21
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Lunzer M, Shi L, Andriotis OG, Gruber P, Markovic M, Thurner PJ, Ossipov D, Liska R, Ovsianikov A. A Modular Approach to Sensitized Two‐Photon Patterning of Photodegradable Hydrogels. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201808908] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Markus Lunzer
- Institute of Materials Science and TechnologyTU Wien Getreidemarkt 9/308 1060 Vienna Austria
- Institute of Applied Synthetic ChemistryTU Wien Getreidemarkt 9/163-MC 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Liyang Shi
- Department of Chemistry-Ångström LaboratoryUppsala University Lägerhyddsvägen 1 751 21 Uppsala Sweden
| | - Orestis G. Andriotis
- Institute of Lightweight Design and Structural BiomechanicsTU Wien Getreidemarkt 9/317 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Peter Gruber
- Institute of Materials Science and TechnologyTU Wien Getreidemarkt 9/308 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Marica Markovic
- Institute of Materials Science and TechnologyTU Wien Getreidemarkt 9/308 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Philipp J. Thurner
- Institute of Lightweight Design and Structural BiomechanicsTU Wien Getreidemarkt 9/317 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Dmitri Ossipov
- Department of Chemistry-Ångström LaboratoryUppsala University Lägerhyddsvägen 1 751 21 Uppsala Sweden
- Department of Biosciences and NutritionKarolinska Institutet Novum, 141 83 Huddinge Stockholm Sweden
| | - Robert Liska
- Institute of Applied Synthetic ChemistryTU Wien Getreidemarkt 9/163-MC 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
| | - Aleksandr Ovsianikov
- Institute of Materials Science and TechnologyTU Wien Getreidemarkt 9/308 1060 Vienna Austria
- Austrian Cluster for Tissue Regeneration Austria
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22
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Mesquida P, Kohl D, Andriotis OG, Thurner PJ, Duer M, Bansode S, Schitter G. Evaluation of surface charge shift of collagen fibrils exposed to glutaraldehyde. Sci Rep 2018; 8:10126. [PMID: 29973604 PMCID: PMC6031691 DOI: 10.1038/s41598-018-28293-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 05/24/2018] [Indexed: 11/18/2022] Open
Abstract
Collagen fibrils are a major component of the extracellular matrix. They form nanometer-scale “cables” acting as a scaffold for cells in animal tissues and are widely used in tissue-engineering. Besides controlling their structure and mechanical properties, it is crucial to have information of their surface charge, as this affects how cells attach to the scaffold. Here, we employed Kelvin-probe Force Microscopy to determine the electrostatic surface potential at the single-fibril level and investigated how glutaraldehyde, a well-established protein cross-linking agent, shifts the surface charge to more negative values without disrupting the fibrils themselves. This shift can be interpreted as the result of the reaction between the carbonyl groups of glutaraldehyde and the amine groups of collagen. It reduces the overall density of positively charged amine groups on the collagen fibril surface and, ultimately, results in the observed negative shift of the surface potential measured. Reactions between carbonyl-containing compounds and proteins are considered the first step in glycation, the non-enzymatic reaction between sugars and proteins. It is conceivable that similar charge shifts happen in vivo caused by sugars, which could have serious implications on age-related diseases such as diabetes and which has been hypothesised for many years.
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Affiliation(s)
- Patrick Mesquida
- Automation and Control Institute (ACIN), TU Wien, Gusshausstrasse 27-29, A-1040, Vienna, Austria. .,Department of Physics, King's College London, Strand, London, WC2R 2LS, United Kingdom.
| | - Dominik Kohl
- Automation and Control Institute (ACIN), TU Wien, Gusshausstrasse 27-29, A-1040, Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, A-1060, Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, A-1060, Vienna, Austria
| | - Melinda Duer
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
| | - Sneha Bansode
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
| | - Georg Schitter
- Automation and Control Institute (ACIN), TU Wien, Gusshausstrasse 27-29, A-1040, Vienna, Austria
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23
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Jones MG, Andriotis OG, Roberts JJ, Lunn K, Tear VJ, Cao L, Ask K, Smart DE, Bonfanti A, Johnson P, Alzetani A, Conforti F, Doherty R, Lai CY, Johnson B, Bourdakos KN, Fletcher SV, Marshall BG, Jogai S, Brereton CJ, Chee SJ, Ottensmeier CH, Sime P, Gauldie J, Kolb M, Mahajan S, Fabre A, Bhaskar A, Jarolimek W, Richeldi L, O'Reilly KM, Monk PD, Thurner PJ, Davies DE. Nanoscale dysregulation of collagen structure-function disrupts mechano-homeostasis and mediates pulmonary fibrosis. eLife 2018; 7:36354. [PMID: 29966587 PMCID: PMC6029847 DOI: 10.7554/elife.36354] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 06/06/2018] [Indexed: 12/21/2022] Open
Abstract
Matrix stiffening with downstream activation of mechanosensitive pathways is strongly implicated in progressive fibrosis; however, pathologic changes in extracellular matrix (ECM) that initiate mechano-homeostasis dysregulation are not defined in human disease. By integrated multiscale biomechanical and biological analyses of idiopathic pulmonary fibrosis lung tissue, we identify that increased tissue stiffness is a function of dysregulated post-translational collagen cross-linking rather than any collagen concentration increase whilst at the nanometre-scale collagen fibrils are structurally and functionally abnormal with increased stiffness, reduced swelling ratio, and reduced diameter. In ex vivo and animal models of lung fibrosis, dual inhibition of lysyl oxidase-like (LOXL) 2 and LOXL3 was sufficient to normalise collagen fibrillogenesis, reduce tissue stiffness, and improve lung function in vivo. Thus, in human fibrosis, altered collagen architecture is a key determinant of abnormal ECM structure-function, and inhibition of pyridinoline cross-linking can maintain mechano-homeostasis to limit the self-sustaining effects of ECM on progressive fibrosis. Idiopathic pulmonary fibrosis (IPF) is a devastating disease of the lung, which scars the tissue and gradually destroys the organ, ultimately leading to death. It is still unclear what exactly causes this scarring, but it is thought that increasing amounts of proteins in the space surrounding the cells of the lungs, the extracellular matrix, could play a role. These proteins, including collagen, normally form a ‘scaffold’ to stabilize cells, but if they accumulate uncontrollably, they can render tissues rigid. It has been assumed that these changes are a consequence of the disease. However, recent evidence suggests that the increased stiffness itself could stimulate cells to produce even more extracellular matrix, driving the progression of the disease. A better understanding of what exactly causes the tissue to become gradually stiffer may identify new ways to block the progression of IPF. Now, Jones et al. compared measurements of the tissue stiffness and the collagen structure taken from samples of patients with IPF. The results showed that the collagen fibres were faulty and had an abnormal shape. This suggests that these problems, rather than an increased amount of collagen, alter the flexibility of the lung tissue. Jones et al. also found that a specific family of proteins, which helps to connect the collagen fibres, was increased in the tissue of patients with IPF. When these proteins were blocked with a newly developed drug, the collagen structure returned to normal and the stiffness of the tissue decreased. As a consequence, the lung capacity improved. This suggests that treatment approaches that help to maintain a normal collagen structure, may in future prevent the stiffening of the lung tissue and so limit feed-forward mechanisms that drive progressive IPF. Moreover, it indicates that measurements of the structure of collagen rather than the its total concentration could serve as a more suitable indicator for the disease.
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Affiliation(s)
- Mark G Jones
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Orestis G Andriotis
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt, Austria
| | | | - Kerry Lunn
- Synairgen Research Ltd, Southampton, United Kingdom
| | | | - Lucy Cao
- Pharmaxis Ltd, Frenchs Forest, Australia
| | - Kjetil Ask
- Department of Medicine, Firestone Institute for Respiratory Health, McMaster University and The Research Institute of St. Joe's Hamilton, Hamilton, Canada
| | - David E Smart
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Alessandra Bonfanti
- Aeronautics, Astronautics and Computational Engineering, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom
| | - Peter Johnson
- Department of Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, United Kingdom.,Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Aiman Alzetani
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,University Hospital Southampton, Southampton, United Kingdom
| | - Franco Conforti
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Regan Doherty
- Biomedical Imaging Unit, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Chester Y Lai
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Benjamin Johnson
- CRUK and NIHR Experimental Cancer Medicine Centre, Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Konstantinos N Bourdakos
- Department of Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, United Kingdom.,Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Sophie V Fletcher
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,University Hospital Southampton, Southampton, United Kingdom
| | - Ben G Marshall
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,University Hospital Southampton, Southampton, United Kingdom
| | - Sanjay Jogai
- University Hospital Southampton, Southampton, United Kingdom
| | - Christopher J Brereton
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Serena J Chee
- University Hospital Southampton, Southampton, United Kingdom.,CRUK and NIHR Experimental Cancer Medicine Centre, Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Christian H Ottensmeier
- CRUK and NIHR Experimental Cancer Medicine Centre, Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Patricia Sime
- Division of Pulmonary and Critical Care Medicine, University of Rochester School of Medicine and Dentistry, Rochester, United States
| | - Jack Gauldie
- Department of Medicine, Firestone Institute for Respiratory Health, McMaster University and The Research Institute of St. Joe's Hamilton, Hamilton, Canada
| | - Martin Kolb
- Department of Medicine, Firestone Institute for Respiratory Health, McMaster University and The Research Institute of St. Joe's Hamilton, Hamilton, Canada
| | - Sumeet Mahajan
- Department of Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, United Kingdom.,Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Aurelie Fabre
- Department of Histopathology, St. Vincent's University Hospital & UCD School of Medicine, University College Dublin, Dublin, Ireland
| | - Atul Bhaskar
- Aeronautics, Astronautics and Computational Engineering, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom
| | | | - Luca Richeldi
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy
| | - Katherine Ma O'Reilly
- Mater Misericordiae University Hospital, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | | | - Philipp J Thurner
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt, Austria
| | - Donna E Davies
- NIHR Southampton Biomedical Research Centre, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
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24
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Tusan CG, Man YH, Zarkoob H, Johnston DA, Andriotis OG, Thurner PJ, Yang S, Sander EA, Gentleman E, Sengers BG, Evans ND. Collective Cell Behavior in Mechanosensing of Substrate Thickness. Biophys J 2018; 114:2743-2755. [PMID: 29874622 PMCID: PMC6027966 DOI: 10.1016/j.bpj.2018.03.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 03/02/2018] [Accepted: 03/20/2018] [Indexed: 11/06/2022] Open
Abstract
Extracellular matrix stiffness has a profound effect on the behavior of many cell types. Adherent cells apply contractile forces to the material on which they adhere and sense the resistance of the material to deformation-its stiffness. This is dependent on both the elastic modulus and the thickness of the material, with the corollary that single cells are able to sense underlying stiff materials through soft hydrogel materials at low (<10 μm) thicknesses. Here, we hypothesized that cohesive colonies of cells exert more force and create more hydrogel deformation than single cells, therefore enabling them to mechanosense more deeply into underlying materials than single cells. To test this, we modulated the thickness of soft (1 kPa) elastic extracellular-matrix-functionalized polyacrylamide hydrogels adhered to glass substrates and allowed colonies of MG63 cells to form on their surfaces. Cell morphology and deformations of fluorescent fiducial-marker-labeled hydrogels were quantified by time-lapse fluorescence microscopy imaging. Single-cell spreading increased with respect to decreasing hydrogel thickness, with data fitting to an exponential model with half-maximal response at a thickness of 3.2 μm. By quantifying cell area within colonies of defined area, we similarly found that colony-cell spreading increased with decreasing hydrogel thickness but with a greater half-maximal response at 54 μm. Depth-sensing was dependent on Rho-associated protein kinase-mediated cellular contractility. Surface hydrogel deformations were significantly greater on thick hydrogels compared to thin hydrogels. In addition, deformations extended greater distances from the periphery of colonies on thick hydrogels compared to thin hydrogels. Our data suggest that by acting collectively, cells mechanosense rigid materials beneath elastic hydrogels at greater depths than individual cells. This raises the possibility that the collective action of cells in colonies or sheets may allow cells to sense structures of differing material properties at comparatively large distances.
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Affiliation(s)
- Camelia G Tusan
- Centre for Human Development, Stem Cells and Regeneration, Human Development and Health, Institute of Developmental Sciences, University of Southampton, Southampton, United Kingdom
| | - Yu-Hin Man
- Centre for Human Development, Stem Cells and Regeneration, Human Development and Health, Institute of Developmental Sciences, University of Southampton, Southampton, United Kingdom; Mechanical Engineering, University of Southampton, Southampton, United Kingdom
| | - Hoda Zarkoob
- Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, Iowa
| | - David A Johnston
- Biomedical Imaging Unit, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, Technische Universität Wien, Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, Technische Universität Wien, Vienna, Austria
| | - Shoufeng Yang
- Mechanical Engineering, University of Southampton, Southampton, United Kingdom; Department of Mechanical Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Edward A Sander
- Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, Iowa
| | - Eileen Gentleman
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
| | - Bram G Sengers
- Mechanical Engineering, University of Southampton, Southampton, United Kingdom
| | - Nicholas D Evans
- Centre for Human Development, Stem Cells and Regeneration, Human Development and Health, Institute of Developmental Sciences, University of Southampton, Southampton, United Kingdom; Mechanical Engineering, University of Southampton, Southampton, United Kingdom.
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25
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Núñez JA, Goring A, Javaheri B, Razi H, Gomez-Nicola D, Pitsillides AA, Thurner PJ, Gomez-Nicola D, Schneider P, Clarkin CE, Clarkin CE. Regional diversity in the murine cortical vascular network is revealed by synchrotron X-ray tomography and is amplified with age. Eur Cell Mater 2018; 35:281-299. [PMID: 29790567 DOI: 10.22203/ecm.v035a20] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cortical bone is permeated by a system of pores, occupied by the blood supply and osteocytes. With ageing, bone mass reduction and disruption of the microstructure are associated with reduced vascular supply. Insight into the regulation of the blood supply to the bone could enhance the understanding of bone strength determinants and fracture healing. Using synchrotron radiation-based computed tomography, the distribution of vascular canals and osteocyte lacunae was assessed in murine cortical bone and the influence of age on these parameters was investigated. The tibiofibular junction from 15-week- and 10-month-old female C57BL/6J mice were imaged post-mortem. Vascular canals and three-dimensional spatial relationships between osteocyte lacunae and bone surfaces were computed for both age groups. At 15 weeks, the posterior region of the tibiofibular junction had a higher vascular canal volume density than the anterior, lateral and medial regions. Intracortical vascular networks in anterior and posterior regions were also different, with connectedness in the posterior higher than the anterior at 15 weeks. By 10 months, cortices were thinner, with cortical area fraction and vascular density reduced, but only in the posterior cortex. This provided the first evidence of age-related effects on murine bone porosity due to the location of the intracortical vasculature. Targeting the vasculature to modulate bone porosity could provide an effective way to treat degenerative bone diseases, such as osteoporosis.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - C E Clarkin
- Department of Biological Sciences, University of Southampton, SO17 1BJ, Southampton,
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26
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Kain L, Andriotis OG, Gruber P, Frank M, Markovic M, Grech D, Nedelkovski V, Stolz M, Ovsianikov A, Thurner PJ. Calibration of colloidal probes with atomic force microscopy for micromechanical assessment. J Mech Behav Biomed Mater 2018; 85:225-236. [PMID: 29933150 DOI: 10.1016/j.jmbbm.2018.05.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 05/08/2018] [Accepted: 05/16/2018] [Indexed: 10/24/2022]
Abstract
Mechanical assessment of biological materials and tissue-engineered scaffolds is increasingly focusing at lower length scale levels. Amongst other techniques, atomic force microscopy (AFM) has gained popularity as an instrument to interrogate material properties, such as the indentation modulus, at the microscale via cantilever-based indentation tests equipped with colloidal probes. Current analysis approaches of the indentation modulus from such tests require the size and shape of the colloidal probe as well as the spring constant of the cantilever. To make this technique reproducible, there still exist the challenge of proper calibration and validation of such mechanical assessment. Here, we present a method to (a) fabricate and characterize cantilevers with colloidal probes and (b) provide a guide for estimating the spring constant and the sphere diameter that should be used for a given sample to achieve the highest possible measurement sensitivity. We validated our method by testing agarose samples with indentation moduli ranging over three orders of magnitude via AFM and compared these results with bulk compression tests. Our results show that quantitative measurements of indentation modulus is achieved over three orders of magnitude ranging from 1 kPa to 1000 kPa via AFM cantilever-based microindentation experiments. Therefore, our approach could be used for quantitative micromechanical measurements without the need to perform further validation via bulk compression experiments.
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Affiliation(s)
- Lukas Kain
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria
| | - Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria.
| | - Peter Gruber
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Martin Frank
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Marica Markovic
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - David Grech
- Nano Research Group, Department of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK
| | - Vedran Nedelkovski
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Martin Stolz
- National Centre for Advanced Tribology at Southampton, Faculty of Engineering and the Environment, University of Southampton, UK
| | - Aleksandr Ovsianikov
- Institute of Materials Science and Technology, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, 1060 Vienna, Austria; Austrian Cluster for Tissue Regeneration, 1200 Vienna, Austria
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Abstract
Tissue hydration is well known to influence tissue mechanics and can be tuned via osmotic pressure. Collagen fibrils are nature's nanoscale building blocks to achieve biomechanical function in a broad range of biological tissues and across many species. Intrafibrillar covalent cross-links have long been thought to play a pivotal role in collagen fibril elasticity, but predominantly at large, far from physiological, strains. Performing nanotensile experiments of collagen fibrils at varying hydration levels by adjusting osmotic pressure in situ during atomic force microscopy experiments, we show the power the intrafibrillar noncovalent interactions have for defining collagen fibril tensile elasticity at low fibril strains. Nanomechanical tensile tests reveal that osmotic pressure increases collagen fibril stiffness up to 24-fold in transverse (nanoindentation) and up to 6-fold in the longitudinal direction (tension), compared to physiological saline in a reversible fashion. We attribute the stiffening to the density and strength of weak intermolecular forces tuned by hydration and hence collagen packing density. This reversible mechanism may be employed by cells to alter their mechanical microenvironment in a reversible manner. The mechanism could also be translated to tissue engineering approaches for customizing scaffold mechanics in spatially resolved fashion, and it may help explain local mechanical changes during development of diseases and inflammation.
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Affiliation(s)
- Orestis G Andriotis
- Institute of Lightweight Design and Structural Biomechanics , Vienna University of Technology , Getreidemarkt 9 , 1060 Vienna , Austria
| | - Sylvia Desissaire
- Institute of Lightweight Design and Structural Biomechanics , Vienna University of Technology , Getreidemarkt 9 , 1060 Vienna , Austria
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics , Vienna University of Technology , Getreidemarkt 9 , 1060 Vienna , Austria
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28
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Spiesz EM, Thorpe CT, Thurner PJ, Screen HRC. Structure and collagen crimp patterns of functionally distinct equine tendons, revealed by quantitative polarised light microscopy (qPLM). Acta Biomater 2018; 70:281-292. [PMID: 29409868 PMCID: PMC5894809 DOI: 10.1016/j.actbio.2018.01.034] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 01/19/2018] [Accepted: 01/24/2018] [Indexed: 01/15/2023]
Abstract
Structure-function relationships in tendons are directly influenced by the arrangement of collagen fibres. However, the details of such arrangements in functionally distinct tendons remain obscure. This study demonstrates the use of quantitative polarised light microscopy (qPLM) to identify structural differences in two major tendon compartments at the mesoscale: fascicles and interfascicular matrix (IFM). It contrasts functionally distinct positional and energy storing tendons, and considers changes with age. Of particular note, the technique facilitates the analysis of crimp parameters, in which cutting direction artefact can be accounted for and eliminated, enabling the first detailed analysis of crimp parameters across functionally distinct tendons. IFM shows lower birefringence (0.0013 ± 0.0001 [−]), as compared to fascicles (0.0044 ± 0.0005 [−]), indicating that the volume fraction of fibres must be substantially lower in the IFM. Interestingly, no evidence of distinct fibre directional dispersions between equine energy storing superficial digital flexor tendons (SDFTs) and positional common digital extensor tendons (CDETs) were noted, suggesting either more subtle structural differences between tendon types or changes focused in the non-collagenous components. By contrast, collagen crimp characteristics are strongly tendon type specific, indicating crimp specialisation is crucial in the respective mechanical function. SDFTs showed much finer crimp (21.1 ± 5.5 µm) than positional CDETs (135.4 ± 20.1 µm). Further, tendon crimp was finer in injured tendon, as compared to its healthy equivalents. Crimp angle differed strongly between tendon types as well, with average of 6.5 ± 1.4° in SDFTs and 13.1 ± 2.0° in CDETs, highlighting a substantially tighter crimp in the SDFT, likely contributing to its effective recoil capacity. Statement of Significance This is the first study to quantify birefringence in fascicles and interfascicular matrix of functionally distinct energy storing and positional tendons. It adopts a novel method – quantitative polarised light microscopy (qPLM) to measure collagen crimp angle, avoiding artefacts related to the direction of histological sectioning, and provides the first direct comparison of crimp characteristics of functionally distinct tendons of various ages. A comparison of matched picrosirius red stained and unstained tendons sections identified non-homogenous staining effects, and leads us to recommend that only unstained sections are analysed in the quantitative manner. qPLM is successfully used to assess birefringence in soft tissue sections, offering a promising tool for investigating the structural arrangements of fibres in (soft) tissues and other composite materials.
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Affiliation(s)
- Ewa M Spiesz
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom; Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
| | - Chavaunne T Thorpe
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom; Comparative Biomedical Sciences, Royal Veterinary College, Royal College Street, London NW1 0TU, United Kingdom.
| | - Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, A-1060 Vienna, Austria.
| | - Hazel R C Screen
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, United Kingdom.
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29
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Jenkins T, Katsamenis OL, Andriotis OG, Coutts LV, Carter B, Dunlop DG, Oreffo ROC, Cooper C, Harvey NC, Thurner PJ, The OStEO Group. The inferomedial femoral neck is compromised by age but not disease: Fracture toughness and the multifactorial mechanisms comprising reference point microindentation. J Mech Behav Biomed Mater 2017; 75:399-412. [PMID: 28803114 PMCID: PMC5619645 DOI: 10.1016/j.jmbbm.2017.06.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 06/26/2017] [Accepted: 06/28/2017] [Indexed: 12/19/2022]
Abstract
The influence of ageing on the fracture mechanics of cortical bone tissue is well documented, though little is known about if and how related material properties are further affected in two of the most prominent musculoskeletal diseases, osteoporosis and osteoarthritis (OA). The femoral neck, in close proximity to the most pertinent osteoporotic fracture site and near the hip joint affected by osteoarthritis, is a site of particular interest for investigation. We have recently shown that Reference Point micro-Indentation (RPI) detects differences between cortical bone from the femoral neck of healthy, osteoporotic fractured and osteoarthritic hip replacement patients. RPI is a new technique with potential for in vivo bone quality assessment. However, interpretation of RPI results is limited because the specific changes in bone properties with pathology are not well understood and, further, because it is not conclusive what properties are being assessed by RPI. Here, we investigate whether the differences previously detected between healthy and diseased cortical bone from the femoral neck might reflect changes in fracture toughness. Together with this, we investigate which additional properties are reflected in RPI measures. RPI (using the Biodent device) and fracture toughness tests were conducted on samples from the inferomedial neck of bone resected from donors with: OA (41 samples from 15 donors), osteoporosis (48 samples from 14 donors) and non age-matched cadaveric controls (37 samples from 10 donoros) with no history of bone disease. Further, a subset of indented samples were imaged using micro-computed tomography (3 osteoporotic and 4 control samples each from different donors) as well as fluorescence microscopy in combination with serial sectioning after basic fuchsin staining (7 osteoporotic and 5 control samples from 5 osteoporotic and 5 control donors). In this study, the bulk indentation and fracture resistance properties of the inferomedial femoral neck in osteoporotic fracture, severe OA and control bone were comparable (p > 0.05 for fracture properties and <10% difference for indentation) but fracture toughness reduced with advancing age (7.0% per decade, r = -0.36, p = 0.029). Further, RPI properties (in particular, the indentation distance increase, IDI) showed partial correlation with fracture toughness (r = -0.40, p = 0.023) or derived elastic modulus (r = -0.40, p = 0.023). Multimodal indent imaging revealed evidence of toughening mechanisms (i.e. crack deflection, bridging and microcracking), elastoplastic response (in terms of the non-conical imprint shape and presence of pile-up) and correlation of RPI with damage extent (up to r = 0.79, p = 0.034) and indent size (up to r = 0.82, p < 0.001). Therefore, crack resistance, deformation resistance and, additionally, micro-structure (porosity: r = 0.93, p = 0.002 as well as pore proximity: r = -0.55, p = 0.027 for correlation with IDI) are all contributory to RPI. Consequently, it becomes clear that RPI measures represent a multitude of properties, various aspects of bone quality, but are not necessarily strongly correlated to a single mechanical property. In addition, osteoporosis or osteoarthritis do not seem to further influence fracture toughness of the inferomedial femoral neck beyond natural ageing. Since bone is highly heterogeneous, whether this finding can be extended to the whole femoral neck or whether it also holds true for other femoral neck quadrants or other material properties remains to be shown.
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Affiliation(s)
- T Jenkins
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK; Gait Laboratory, Queen Mary's Hospital, St George's University Hospitals NHS Foundation Trust, London, UK
| | - O L Katsamenis
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK; µ-VIS X-ray Imaging Centre, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK
| | - O G Andriotis
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria
| | - L V Coutts
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - B Carter
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - D G Dunlop
- University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - R O C Oreffo
- Bone and Joint Research Group, Centre for Human Development, Stem Cells and Regeneration, Institute for Development Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - C Cooper
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK; NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford, UK; NIHR Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - N C Harvey
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK; NIHR Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - P J Thurner
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Vienna, Austria.
| | - The OStEO Group
- University Hospital Southampton NHS Foundation Trust, Southampton, UK; MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK; NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford, UK; Portsmouth Hospitals NHS Trust, Portsmouth, UK; University College London, London, UK
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30
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Nobakhti S, Katsamenis OL, Zaarour N, Limbert G, Thurner PJ. Elastic modulus varies along the bovine femur. J Mech Behav Biomed Mater 2017; 71:279-285. [DOI: 10.1016/j.jmbbm.2017.03.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 03/05/2017] [Accepted: 03/25/2017] [Indexed: 11/26/2022]
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31
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Coutts LV, Jenkins T, Oreffo ROC, Dunlop DG, Cooper C, Harvey NC, Thurner PJ. Local Variation in Femoral Neck Cortical Bone: In Vitro Measured Bone Mineral Density, Geometry and Mechanical Properties. J Clin Densitom 2017; 20:205-215. [PMID: 26710681 DOI: 10.1016/j.jocd.2015.10.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 10/12/2015] [Accepted: 10/21/2015] [Indexed: 01/08/2023]
Abstract
Age- and disease (osteoporotic fractured and osteoarthritic tissue)-related changes in the distribution of cortical bone were examined, using a multimodality approach, including measurement of local density, geometry and mechanical properties, where changes in these properties can give rise to instability and increasing probability of fracture. In contrast to the majority of previously reported research, this study also focuses on the characteristic non-circular femoral neck cross-sectional geometry and variation in bone mineral density (BMD) around the femoral neck. Twenty-two osteoarthritic and 7 osteoporotic femoral neck slices, collected from elective and trauma-related arthroplasty, and 16 cadaveric donor tissue controls were tested mechanically using Reference Point Indentation (BioDent™, Active Life Technologies®, Santa Barbara, CA) and then scanned with in vitro-based radiography intended to replicate the dual-energy X-ray absorptiometry technique. All parameters were measured regionally around the circumference of the femoral neck, allowing examination of spatial variability within the cortical bone. Fractured tissue was less resistant to indentation in the thinner superolateral segment compared to other segments and other groups. BMD around the fractured femoral necks appeared more consistent than that of nonfractured tissue, where BMD was reduced in the superolateral segment for the other groups. Cortical bone was thin in the superolateral segment for all groups except for the osteoarthritic group, and was thicker in the inferomedial segment for both osteoarthritic and fractured groups, resulting in the largest variation in buckling ratio (ratio of cortical bone diameter to cortical bone thickness) around the femoral neck for the fractured group. With age, healthy controls appeared to have lower inferomedial cortical thickness, whereas no significant differences in Reference Point Indentation measurements and density were observed. The study has highlighted several (both quality- and quantity-related) parameters that may be used to improve prediction of fracture risk.
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Affiliation(s)
- Louise V Coutts
- Faculty of Engineering and Environment and Faculty of Medicine, University of Southampton, Southampton, UK.
| | - Thomas Jenkins
- Faculty of Engineering and Environment and Faculty of Medicine, University of Southampton, Southampton, UK
| | - Richard O C Oreffo
- Faculty of Engineering and Environment and Faculty of Medicine, University of Southampton, Southampton, UK
| | - Doug G Dunlop
- Southampton University Hospitals NHS Trust, Southampton, UK
| | - Cyrus Cooper
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK
| | - Nicholas C Harvey
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK
| | - Philipp J Thurner
- Faculty of Engineering and Environment and Faculty of Medicine, University of Southampton, Southampton, UK; Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria
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32
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Andriotis OG, Chang SW, Vanleene M, Howarth PH, Davies DE, Shefelbine SJ, Buehler MJ, Thurner PJ. Structure-mechanics relationships of collagen fibrils in the osteogenesis imperfecta mouse model. J R Soc Interface 2016; 12:20150701. [PMID: 26468064 PMCID: PMC4614505 DOI: 10.1098/rsif.2015.0701] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The collagen molecule, which is the building block of collagen fibrils, is a triple helix of two α1(I) chains and one α2(I) chain. However, in the severe mouse model of osteogenesis imperfecta (OIM), deletion of the COL1A2 gene results in the substitution of the α2(I) chain by one α1(I) chain. As this substitution severely impairs the structure and mechanics of collagen-rich tissues at the tissue and organ level, the main aim of this study was to investigate how the structure and mechanics are altered in OIM collagen fibrils. Comparing results from atomic force microscopy imaging and cantilever-based nanoindentation on collagen fibrils from OIM and wild-type (WT) animals, we found a 33% lower indentation modulus in OIM when air-dried (bound water present) and an almost fivefold higher indentation modulus in OIM collagen fibrils when fully hydrated (bound and unbound water present) in phosphate-buffered saline solution (PBS) compared with WT collagen fibrils. These mechanical changes were accompanied by an impaired swelling upon hydration within PBS. Our experimental and atomistic simulation results show how the structure and mechanics are altered at the individual collagen fibril level as a result of collagen gene mutation in OIM. We envisage that the combination of experimental and modelling approaches could allow mechanical phenotyping at the collagen fibril level of virtually any alteration of collagen structure or chemistry.
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Affiliation(s)
- O G Andriotis
- Institute for Lightweight Design and Structural Biomechanics, Vienna University of Technology, Getreidemarkt 9, Vienna 1060, Austria Bioengineering Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK
| | - S W Chang
- Department of Civil Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - M Vanleene
- Department of Bioengineering, Imperial College London, London, UK
| | - P H Howarth
- The Brooke Laboratories, Division of Infection, Inflammation and Immunity, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - D E Davies
- The Brooke Laboratories, Division of Infection, Inflammation and Immunity, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - S J Shefelbine
- Department of Bioengineering, Imperial College London, London, UK Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA
| | - M J Buehler
- Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA Center for Computational Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - P J Thurner
- Institute for Lightweight Design and Structural Biomechanics, Vienna University of Technology, Getreidemarkt 9, Vienna 1060, Austria Bioengineering Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK
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33
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Niehaus WL, Howlin RP, Johnston DA, Bull DJ, Jones GL, Calton E, Mavrogordato MN, Clarke SC, Thurner PJ, Faust SN, Stoodley P. Development of X-ray micro-focus computed tomography to image and quantify biofilms in central venous catheter models in vitro. Microbiology (Reading) 2016; 162:1629-1640. [PMID: 27384949 DOI: 10.1099/mic.0.000334] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bacterial infections of central venous catheters (CVCs) cause much morbidity and mortality, and are usually diagnosed by concordant culture of blood and catheter tip. However, studies suggest that culture often fails to detect biofilm bacteria. This study optimizes X-ray micro-focus computed tomography (X-ray µCT) for the quantification and determination of distribution and heterogeneity of biofilms in in vitro CVC model systems.Bacterial culture and scanning electron microscopy (SEM) were used to detect Staphylococcus epidermidis ATCC 35984 biofilms grown on catheters in vitro in both flow and static biofilm models. Alongside this, X-ray µCT techniques were developed in order to detect biofilms inside CVCs. Various contrast agent stains were evaluated using energy-dispersive X-ray spectroscopy (EDS) to further optimize these methods. Catheter material and biofilm were segmented using a semi-automated matlab script and quantified using the Avizo Fire software package. X-ray µCT was capable of distinguishing between the degree of biofilm formation across different segments of a CVC flow model. EDS screening of single- and dual-compound contrast stains identified 10 nm gold and silver nitrate as the optimum contrast agent for X-ray µCT. This optimized method was then demonstrated to be capable of quantifying biofilms in an in vitro static biofilm formation model, with a strong correlation between biofilm detection via SEM and culture. X-ray µCT has good potential as a direct, non-invasive, non-destructive technology to image biofilms in CVCs, as well as other in vivo medical components in which biofilms accumulate in concealed areas.
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Affiliation(s)
- Wilmari L Niehaus
- National Centre for Advanced Tribology at Southampton (nCATS), Faculty of Engineering and the Environment (FEE), University of Southampton, UK.,Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Southampton NIHR Biomedical Research Centre and NIHR Respiratory Biomedical Research Unit, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Faculty of Medicine, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Robert P Howlin
- Southampton NIHR Biomedical Research Centre and NIHR Respiratory Biomedical Research Unit, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Centre for Biological Sciences, Faculty of Natural and Environmental Sciences and Institute for Life Sciences, University of Southampton, Southampton, UK
| | - David A Johnston
- Faculty of Medicine, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Biomedical Imaging Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Daniel J Bull
- Engineering Materials Research Group, FEE, University of Southampton, UK
| | - Gareth L Jones
- Centre for Hybrid Biodevices, Electronics and Computer Science, University of Southampton, UK
| | - Elizabeth Calton
- Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | | | - Stuart C Clarke
- Faculty of Medicine, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Southampton NIHR Biomedical Research Centre and NIHR Respiratory Biomedical Research Unit, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Philipp J Thurner
- Bioengineering Science Research Group, FEE, University of Southampton, UK.,Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria
| | - Saul N Faust
- Faculty of Medicine, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Southampton NIHR Biomedical Research Centre and NIHR Respiratory Biomedical Research Unit, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Southampton NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Paul Stoodley
- National Centre for Advanced Tribology at Southampton (nCATS), Faculty of Engineering and the Environment (FEE), University of Southampton, UK.,Center for Microbial Interface Biology (CMIB), Departments of Microbial Infection and Immunity, and Orthopaedics, The Ohio State University, Columbus, OH, USA
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34
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Thurner PJ. Commentary on: Mechanical properties of cortical bone and their relationships with age, gender, composition and microindentation properties in the elderly. Bone 2016; 87:159-60. [PMID: 27091226 DOI: 10.1016/j.bone.2016.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 04/08/2016] [Accepted: 04/09/2016] [Indexed: 10/21/2022]
Affiliation(s)
- Philipp J Thurner
- Institute of Lightweight Design and Structural Biomechanics, TU Wien, Vienna, Austria; Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK.
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35
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Katsamenis OL, Jenkins T, Thurner PJ. Toughness and damage susceptibility in human cortical bone is proportional to mechanical inhomogeneity at the osteonal-level. Bone 2015; 76:158-68. [PMID: 25863123 DOI: 10.1016/j.bone.2015.03.020] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 03/18/2015] [Accepted: 03/27/2015] [Indexed: 01/16/2023]
Abstract
Limitations associated with current clinical fracture risk assessment tools highlight the need for increased understanding of the fracture mechanisms of the bone and, ideally, a means of assessing this in vivo. Being a multi-layered hierarchical structure, the overall properties of the bone are dictated by its structural and compositional properties over multiple length scales. In this study, we investigate the osteonal-, micro- and tissue-level mechanical behaviour of cortical bone tissue samples from young and elderly donors through atomic force microscope (AFM) cantilever-based nanoindentation, reference point microindentation (RPI) and fracture toughness experiments respectively. We demonstrate that bone's fracture toughness and crack growth resistance at the tissue-level are significantly correlated to damage susceptibility at the micro-level, and mechanical inhomogeneity between lamellae and interlamellar areas at the osteonal-level. In more detail, reduced nanoelasticity inhomogeneity of lamellar/interlamellar layers within the osteons correlated to increased indentation depth at the micro-level and an overall reduction in crack-growth toughness and fracture toughness of the tissue. Our data also suggest that deterioration of bone's mechanical properties is expressed concurrently at these three levels, and that mechanical inhomogeneity between the principal structural units of the cortical tissue holds a key role on bone's toughness behaviour. We hypothesise that the reduction in nanoelasticity inhomogeneity is--at least to some extent--responsible for the inability of the microstructure to effectively adapt to the applied load, e.g. by redistributing strains, in a non-catastrophic manner preventing damage formation and propagation. Our hypothesis is further supported by synchrotron radiation micro-computed tomography (SRμCT) data, which show that failure of tougher bone specimens is governed by increased deflection of the crack path and broadly spread damage around the crack-tip. In contrast, shorter and more direct crack paths as well as less-distributed damage were evidenced during failure of the weaker specimens. Overall, this multi-scale study highlights the importance of elasticity inhomogeneity within the osteon to the damage susceptibility and consequently to the fracture resistance of the tissue.
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Affiliation(s)
- Orestis L Katsamenis
- μVIS X-ray Imaging Centre, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK; Bioengineering Sciences Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK.
| | - Thomas Jenkins
- Bioengineering Sciences Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK
| | - Philipp J Thurner
- Bioengineering Sciences Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ Southampton, UK; Institute for Lightweight Design and Structural Biomechanics, Vienna University of Technology, 1040 Vienna, Austria.
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36
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Rmaile A, Carugo D, Capretto L, Wharton JA, Thurner PJ, Aspiras M, Ward M, De Jager M, Stoodley P. An experimental and computational study of the hydrodynamics of high-velocity water microdrops for interproximal tooth cleaning. J Mech Behav Biomed Mater 2015; 46:148-57. [PMID: 25792412 DOI: 10.1016/j.jmbbm.2015.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 01/28/2015] [Accepted: 02/01/2015] [Indexed: 10/24/2022]
Abstract
The flow field and local hydrodynamics of high-velocity water microdrops impacting the interproximal (IP) space of typodont teeth were studied experimentally and computationally. Fourteen-day old Streptococcus mutans biofilms in the IP space were treated by a prototype AirFloss delivering 115 µL of water at a maximum exit-velocity of 60 ms(-1) in a 33-ms burst. Using high-speed imaging, footage was generated showing the details of the burst, and demonstrating the removal mechanism of the biofilms. Footage was also generated to characterize the viscoelastic behavior of the biofilms when impacted by an air-only burst, which was compared to the water burst. Image analysis demonstrated the importance of fluid forces on the removal pattern of interdental biofilms. X-ray micro-Computed Tomography (µ-CT) was used to obtain 3D images of the typodont and the IP spaces. Computational Fluid Dynamics (CFD) simulations were performed to study the effect of changing the nozzle position and design on the hydrodynamics within the IP space. Results confirmed our previous data regarding the wall shear stress generated by high-velocity water drops which dictated the efficacy of biofilm detachment. Finally, we showed how CFD models could be used to optimize water drop or burst design towards a more effective biofilm removal performance.
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Affiliation(s)
- A Rmaile
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK.
| | - D Carugo
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - L Capretto
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - J A Wharton
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - P J Thurner
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - M Aspiras
- Philips Oral Healthcare Inc. (POH), Bothell, WA, USA
| | - M Ward
- Philips Oral Healthcare Inc. (POH), Bothell, WA, USA
| | - M De Jager
- Philips Research, Oral Healthcare Research, Eindhoven, The Netherlands
| | - P Stoodley
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK; Center for Microbial Interface Biology, Departments of Microbial Infection and Immunity, and Orthopaedics, The Ohio State University, Columbus, OH, USA
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Jenkins T, Coutts LV, Dunlop DG, Oreffo ROC, Cooper C, Harvey NC, Thurner PJ. Variability in reference point microindentation and recommendations for testing cortical bone: maximum load, sample orientation, mode of use, sample preparation and measurement spacing. J Mech Behav Biomed Mater 2015; 42:311-24. [PMID: 25455607 DOI: 10.1016/j.jmbbm.2014.09.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/19/2014] [Accepted: 09/27/2014] [Indexed: 10/24/2022]
Abstract
Reference Point Indentation (RPI) is a novel microindentation tool that has emerging clinical potential for the assessment of fracture risk as well as use as a laboratory tool for straight-forward mechanical characterisation of bone. Despite increasing use of the tool, little research is available to advise the set-up of testing protocols or optimisation of testing parameters. Here we consider five such parameters: maximum load, sample orientation, mode of use, sample preparation and measurement spacing, to investigate how they affect the Indentation Distance Increase (IDI), the most published measurement parameter associated with the RPI device. The RPI tool was applied to bovine bone; indenting in the proximal midshaft of five femora and human bone; indenting five femoral heads and five femoral neck samples. Based on the findings of these studies we recommend the following as the best practice. (1) Repeat measurements should be utilised to reduce the coefficient of variation (e.g. 8-15 repeats to achieve a 5-10% error, however the 3-5 measurements used here gives a 15-20% error). (2) IDI is dependent on maximum load (r=0.45 on the periosteal surface and r=0.94 on the machined surface, p<0.05), mode of use (i.e. comparing the device held freehand compared to fixed in its stand, p=0.04) and surface preparation (p=0.004) so these should be kept consistent throughout testing. Though sample orientation appears to have minimal influence on IDI (p>0.05), care should also be taken in combining measurements from different orientations. (3) The coefficient of variation is higher (p=0.04) when holding the device freehand, so it should ideally be kept supported in its stand. (4) Removing the periosteum (p=0.04) and machining the surface of the bone (p=0.08) reduces the coefficient of variation, so should be performed where practical. (5) There is a hyperbolic relationship between thickness and IDI (p<0.001) with a sample thickness 10 fold greater than the maximum indentation depth recommended, to ensure a representative measurement. (6) Measurement spacing does not appear to influence the IDI (p>0.05), so it can be as low as 500 µm. By following these recommendations, RPI users can minimise the potential confounding effects associated with the variables investigated here and reduce the coefficient of variation, hence achieving more consistent testing. This optimisation of the technique enhances both the clinical and laboratory potential of the tool.
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Affiliation(s)
- T Jenkins
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - L V Coutts
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - D G Dunlop
- University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - R O C Oreffo
- Bone and Joint Research Group, Centre for Human Development, Stem Cells and Regeneration, Institute for Development Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - C Cooper
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK; NIHR Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford, UK; NIHR Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, UK
| | - N C Harvey
- MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK; NIHR Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, UK
| | - P J Thurner
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK; Institute for Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gußhausstraße 27-29, 1040 Vienna, Austria.
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Karavasili C, Katsamenis OL, Bouropoulos N, Nazar H, Thurner PJ, van der Merwe SM, Fatouros DG. Preparation and characterization of bioadhesive microparticles comprised of low degree of quaternization trimethylated chitosan for nasal administration: effect of concentration and molecular weight. Langmuir 2014; 30:12337-12344. [PMID: 25247739 DOI: 10.1021/la5030636] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Toward the development of microparticulate carriers for nasal administration, N-trimethylchitosan chloride (TMC) of low molecular weight (LMW) and high molecular weight (HMW) and low degree of quaternization (16% and 27%, respectively) was co-formulated into microparticles comprising of dipalmatoylphosphatidylcholine (DPPC) and poly(lactic-co-glycolic) acid (PLGA) via the spray-drying technique. The chitosan derivatives were characterized by means of nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transfrom infrared (FTIR) spectroscopy. The size and morphology of the produced microparticles were assessed by scanning electron microscopy (SEM), whereas their mucoadhesive properties were investigated by means of atomic force microscopy-force spectroscopy (AFM-FS). The results showed that microparticles exhibit mucoadhesion when TMC is present on their surface above a threshold of TMC (>0.3% w/w).
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Affiliation(s)
- Christina Karavasili
- Laboratory of Pharmaceutical Technology, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki , GR-54124 Thessaloniki, Greece
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Abstract
Strength is the most widely reported parameter with regards to bone failure. However, bone contains pre-existing damage and stress concentration sites, perhaps making measures of fracture toughness more indicative of the resistance of the tissue to withstand fracture. Several toughening mechanisms have been identified in bone, prominently, at the microscale. More recently, nanoscale toughness mechanisms, such as sacrificial-bonds and hidden-length or dilatational band formation, mediated by noncollagenous proteins, have been reported. Absence of specific noncollagenous proteins results in lowered fracture toughness in animal models. Further, roles of several other, putative influencing, factors such as closely bound water, collagen cross-linking and citrate bonds in bone mineral have also been proposed. Yet, it is still not clear if and which mechanisms are hallmarks of osteoporosis disease and how they influence fracture risk. Further insights on the workings of such influencing factors are of high importance for developing complementary diagnostics and therapeutics strategies.
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Affiliation(s)
- Philipp J Thurner
- Institute for Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29 A-1040, Vienna, Austria,
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Lange AW, Haitchi HM, LeCras TD, Sridharan A, Xu Y, Wert SE, James J, Udell N, Thurner PJ, Whitsett JA. Sox17 is required for normal pulmonary vascular morphogenesis. Dev Biol 2014; 387:109-20. [PMID: 24418654 DOI: 10.1016/j.ydbio.2013.11.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 11/14/2013] [Accepted: 11/16/2013] [Indexed: 11/19/2022]
Abstract
The SRY-box containing transcription factor Sox17 is required for endoderm formation and vascular morphogenesis during embryonic development. In the lung, Sox17 is expressed in mesenchymal progenitors of the embryonic pulmonary vasculature and is restricted to vascular endothelial cells in the mature lung. Conditional deletion of Sox17 in splanchnic mesenchyme-derivatives using Dermo1-Cre resulted in substantial loss of Sox17 from developing pulmonary vascular endothelial cells and caused pulmonary vascular abnormalities before birth, including pulmonary vein varices, enlarged arteries, and decreased perfusion of the microvasculature. While survival of Dermo1-Cre;Sox17Δ/Δ mice (herein termed Sox17Δ/Δ) was unaffected at E18.5, most Sox17Δ/Δ mice died by 3 weeks of age. After birth, the density of the pulmonary microvasculature was decreased in association with alveolar simplification, biventricular cardiac hypertrophy, and valvular regurgitation. The severity of the postnatal cardiac phenotype was correlated with the severity of pulmonary vasculature abnormalities. Sox17 is required for normal formation of the pulmonary vasculature and postnatal cardiovascular homeostasis.
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Affiliation(s)
- Alexander W Lange
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
| | - Hans Michael Haitchi
- Clinical and Experimental Sciences, Faculty of Medicine, and National Institute for Health Research Respiratory Biomedical Research Unit, Southampton General Hospital, United Kingdom
| | - Timothy D LeCras
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
| | - Anusha Sridharan
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
| | - Yan Xu
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
| | - Susan E Wert
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
| | - Jeanne James
- Heart Institute, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, OH 45229-3039, United States
| | - Nicholas Udell
- Bioengineering Sciences Research Group, Faculty of Engineering and the Environment, University of Southampton, United Kingdom
| | - Philipp J Thurner
- Bioengineering Sciences Research Group, Faculty of Engineering and the Environment, University of Southampton, United Kingdom
| | - Jeffrey A Whitsett
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States.
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41
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Evans ND, Oreffo ROC, Healy E, Thurner PJ, Man YH. Epithelial mechanobiology, skin wound healing, and the stem cell niche. J Mech Behav Biomed Mater 2013. [PMID: 23746929 DOI: 10.1016/jjmbbm.2013.04.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Skin wound healing is a vital process that is important for re-establishing the epithelial barrier following disease or injury. Aberrant or delayed skin wound healing increases the risk of infection, causes patient morbidity, and may lead to the formation of scar tissue. One of the most important events in wound healing is coverage of the wound with a new epithelial layer. This occurs when keratinocytes at the wound periphery divide and migrate to re-populate the wound bed. Many approaches are under investigation to promote and expedite this process, including the topical application of growth factors and the addition of autologous and allogeneic tissue or cell grafts. The mechanical environment of the wound site is also of fundamental importance for the rate and quality of wound healing. It is known that mechanical stress can influence wound healing by affecting the behaviour of cells within the dermis, but it remains unclear how mechanical forces affect the healing epidermis. Tensile forces are known to affect the behaviour of cells within epithelia, however, and the material properties of extracellular matrices, such as substrate stiffness, have been shown to affect the morphology, proliferation, differentiation and migration of many different cell types. In this review we will introduce the structure of the skin and the process of wound healing. We will then discuss the evidence for the effect of tissue mechanics in re-epithelialisation and, in particular, on stem cell behaviour in the wound microenvironment and in intact skin. We will discuss how the elasticity, mechanical heterogeneity and topography of the wound extracellular matrix impact the rate and quality of wound healing, and how we may exploit this knowledge to expedite wound healing and mitigate scarring.
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Affiliation(s)
- Nicholas D Evans
- Bioengineering Sciences Group, Faculty of Engineering and the Environment, University of Southampton, Highfield Campus, Highfield, Southampton, SO17 1BJ, United Kingdom; Centre for Human Development, Stem Cells and Regeneration, Institute for Developmental Sciences, University of Southampton Faculty of Medicine, Tremona Road, Southampton, SO16 6YD, United Kingdom.
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42
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Nobakhti S, Limbert G, Thurner PJ. Cement lines and interlamellar areas in compact bone as strain amplifiers - contributors to elasticity, fracture toughness and mechanotransduction. J Mech Behav Biomed Mater 2013; 29:235-51. [PMID: 24113298 DOI: 10.1016/j.jmbbm.2013.09.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 08/28/2013] [Accepted: 09/02/2013] [Indexed: 10/26/2022]
Abstract
Bone is multi-scale hierarchical composite material making the prediction of fragility, as well as pinning it to a certain cause, complicated. For proper mechanical simulation and reflection of bone properties in models, microscopic structural features of bone tissue need to be included. This study sets out to gain a mechanistic insight into the role of various microstructural features of bone tissue in particular cement lines and interlamellar areas. Further the hypothesis that compliant interlamellar areas and cement lines within osteonal bone act as strain amplifiers was explored. To this end, a series of experimentally-based micromechanical finite element models of bovine osteonal bone were developed. Different levels of detail for the bone microstructure were considered and combined with the results of physical three-point bending tests and an analytical composite model of a single osteon. The objective was to examine local and global effects of interface structures. The geometrical and microstructural characteristics of the bone samples were derived from microscopy imaging. Parametric finite element studies were conducted to determine optimal values of the elastic modulus of interstitial bone and interlamellar areas. The average isotropic elastic modulus of interfaces suggested in this study is 88.5MPa. Based on the modelling results, it is shown that interfaces are areas of accumulated strain in bone and are likely to act as potential paths for crack propagation. The strain amplification capability of interface structures in the order of 10 predicted by the models suggests a new explanation for the levels of strain required in bone homoeostasis for maintenance and adaptation.
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Affiliation(s)
- Sabah Nobakhti
- Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK.
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43
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Ridha H, Thurner PJ. Finite element prediction with experimental validation of damage distribution in single trabeculae during three-point bending tests. J Mech Behav Biomed Mater 2013; 27:94-106. [PMID: 23890577 DOI: 10.1016/j.jmbbm.2013.07.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 07/01/2013] [Accepted: 07/04/2013] [Indexed: 01/22/2023]
Abstract
There is growing evidence that information on trabecular microarchitecture can improve the assessment of fracture risk. One current strategy is to exploit finite element (FE) analysis applied to experimental data of mechanically loaded single trabecular bone tissue obtained from non-invasive imaging techniques for the investigation of the damage initiation and growth of bone tissue. FE analysis of this type of bone has mainly focused on linear and non-linear analysis to evaluate the bone's failure properties. However, there is a lack of experimentally validated FE damage models at trabecular bone tissue level allowing for the simulation of the progressive damage process (initiation and growth) till complete fracture. Such models are needed to perform enhanced prediction of the apparent failure mechanical properties needed to assess the fracture risk of bone organs. In the current study, we develop a FE model based on a continuum damage mechanics (CDM) approach to simulate the damage initiation and propagation of a single trabecula till complete facture in quasi-static regime. Three-point bending experiments were performed on single bovine trabeculae and compared to FE results. In order to validate the proposed FE mode, (i) the force displacement curve was compared to the experimental one and (ii) the damage distribution was correlated to the measured one obtained by digital image correlation based on stress whitening in bone, reported to be correlated to microdamage. A very good agreement was obtained between the FE and experimental results, indicating that the proposed damage investigation protocol based on FE analysis and testing is reliable to assess the damage behavior of bone tissue and that the current damage model is able to accurately simulate the damaging and fracturing process of single trabeculae under quasi static load.
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Affiliation(s)
- Hambli Ridha
- Prisme Institute - MMH, 8, Rue Leonard de Vinci, 45072 Orleans cedex 2, France.
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44
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Evans ND, Oreffo ROC, Healy E, Thurner PJ, Man YH. Epithelial mechanobiology, skin wound healing, and the stem cell niche. J Mech Behav Biomed Mater 2013; 28:397-409. [PMID: 23746929 DOI: 10.1016/j.jmbbm.2013.04.023] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 04/23/2013] [Accepted: 04/29/2013] [Indexed: 12/25/2022]
Abstract
Skin wound healing is a vital process that is important for re-establishing the epithelial barrier following disease or injury. Aberrant or delayed skin wound healing increases the risk of infection, causes patient morbidity, and may lead to the formation of scar tissue. One of the most important events in wound healing is coverage of the wound with a new epithelial layer. This occurs when keratinocytes at the wound periphery divide and migrate to re-populate the wound bed. Many approaches are under investigation to promote and expedite this process, including the topical application of growth factors and the addition of autologous and allogeneic tissue or cell grafts. The mechanical environment of the wound site is also of fundamental importance for the rate and quality of wound healing. It is known that mechanical stress can influence wound healing by affecting the behaviour of cells within the dermis, but it remains unclear how mechanical forces affect the healing epidermis. Tensile forces are known to affect the behaviour of cells within epithelia, however, and the material properties of extracellular matrices, such as substrate stiffness, have been shown to affect the morphology, proliferation, differentiation and migration of many different cell types. In this review we will introduce the structure of the skin and the process of wound healing. We will then discuss the evidence for the effect of tissue mechanics in re-epithelialisation and, in particular, on stem cell behaviour in the wound microenvironment and in intact skin. We will discuss how the elasticity, mechanical heterogeneity and topography of the wound extracellular matrix impact the rate and quality of wound healing, and how we may exploit this knowledge to expedite wound healing and mitigate scarring.
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Affiliation(s)
- Nicholas D Evans
- Bioengineering Sciences Group, Faculty of Engineering and the Environment, University of Southampton, Highfield Campus, Highfield, Southampton, SO17 1BJ, United Kingdom; Centre for Human Development, Stem Cells and Regeneration, Institute for Developmental Sciences, University of Southampton Faculty of Medicine, Tremona Road, Southampton, SO16 6YD, United Kingdom.
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Brennan MA, Gleeson JP, Browne M, O'Brien FJ, Thurner PJ, McNamara LM, McNamara LM. Site specific increase in heterogeneity of trabecular bone tissue mineral during oestrogen deficiency. Eur Cell Mater 2011; 21:396-406. [PMID: 21574136 DOI: 10.22203/ecm.v021a30] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Although osteoporosis reduces overall bone mass causing bone fragility, recent studies report that the remaining bone tissue is significantly stiffer. Preliminary studies indicate that alterations in bone tissue mineral content might explain these changes, albeit that other studies report conflicting observations. The objective of this study is to quantify whether the distribution of bone tissue mineral is altered during oestrogen deficiency. Individual trabeculae were harvested from the proximal femur of 7 ovariectomised sheep (OVX), sacrificed 12 months post-surgery, and 5 age-matched controls. Mineral content (wt% Ca) was determined using a quantitative backscattered scanning electron microscopy imaging approach. Mineral heterogeneity within individual trabeculae was compared by calculating the full width at half maximum (FWHM) of mineral density distributions. Mean calcium content, the spatial distribution of mineral within trabeculae and the inter-trabecular variation between regions of proximal femora were also compared. Oestrogen deficiency increased mineral heterogeneity within individual trabeculae compared to healthy controls, as measured by FWHM (3.57 ± 0.68 vs. 3.17 ± 0.36 wt% Ca, p = 0.04). In particular mineral variability increased between superficial and deep regions of trabeculae of OVX animals (p = 0.04). Interestingly, mineralisation variability between greater and lesser trochanters (i.e. intertrochanteric fracture line) was increased in OVX compared to CON, as indicated by a greater % difference in the standard deviation of trabecular mineral content (77.11 ± 11.70 vs. 45.64 ± 23.70 %, p = 0.03). Such changes are undetectable by evaluating the mean mineral content of bone tissue, but may contribute to changes in bone mechanical strength following osteoporotic bone loss.
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Affiliation(s)
- M A Brennan
- Bioengineering Sciences Research Group, School of Engineering Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
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Thurner PJ, Erikson B, Schriock Z, Langan J, Scott J, Zhao M, Fantner GE, Turner P, Kindt JH, Schitter G, Hansma PK. High-Speed Photography of Human Trabecular Bone during Compression. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-874-l1.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractThe mechanical properties of healthy and diseased bone tissue are extensively studied in mechanical tests. Most of this research is motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates simulating conditions experienced in individuals during falls. Apparent strains were found to translate to a broad range of local strains. Moreover, strained trabeculae were seen to whiten with increasing strain. We hypothesize that the effect seen is due to microcrack formation in these areas, similar to stress whitening seen in synthetic polymers. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also of high deformation. We believe that this method will allow further insights into bone failure mechanisms, and help toward a better understanding of the processes involved in bone failure.
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Kindt JH, Fantner GE, Thurner PJ, Schitter G, Hansma PK. A new technique for imaging Mineralized Fibrils on Bovine Trabecular Bone Fracture Surfaces by Atomic Force Microscopy. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-874-l5.12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractHigh resolution atomic force microscopy (AFM) images of bovine trabecular bone fracture surfaces reveal individual fibrils coated with extrafibrillar mineral particles. The mineral particles are distinctly different in different regions. In some regions the particles have average dimensions of (70 ± 35) nm along the fibrils and about half that across the fibrils. In other regions they are smaller and rounder, of order (53 ± 14) nm both along and across the fibrils. In other regions they are smaller and rounder, of order (25 ± 15) nm both along and across the fibrils, with more rounded top surfaces.Significantly, we rarely observed bare collagen fibrils. If the observed particles can be verified to be native extrafibrillar mineral, this could imply that the fractures which created the observed areas propagated within the mineralized extrafibrillar matrix.
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48
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Jungmann R, Szabo ME, Schitter G, Tang RYS, Vashishth D, Hansma PK, Thurner PJ. Local strain and damage mapping in single trabeculae during three-point bending tests. J Mech Behav Biomed Mater 2010; 4:523-34. [PMID: 21396601 DOI: 10.1016/j.jmbbm.2010.12.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 12/07/2010] [Accepted: 12/11/2010] [Indexed: 10/18/2022]
Abstract
The use of bone mineral density as a surrogate to diagnose bone fracture risk in individuals is of limited value. However, there is growing evidence that information on trabecular microarchitecture can improve the assessment of fracture risk. One current strategy is to exploit finite element analysis (FEA) applied to 3D image data of several mm-sized trabecular bone structures obtained from non-invasive imaging modalities for the prediction of apparent mechanical properties. However, there is a lack of FE damage models, based on solid experimental facts, which are needed to validate such approaches and to provide criteria marking elastic-plastic deformation transitions as well as microdamage initiation and accumulation. In this communication, we present a strategy that could elegantly lead to future damage models for FEA: direct measurements of local strains involved in microdamage initiation and plastic deformation in single trabeculae. We use digital image correlation to link stress whitening in bone, reported to be correlated to microdamage, to quantitative local strain values. Our results show that the whitening zones, i.e. damage formation, in the presented loading case of a three-point bending test correlate best with areas of elevated tensile strains oriented parallel to the long axis of the samples. The average local strains along this axis were determined to be (1.6±0.9)% at whitening onset and (12±4)% just prior to failure. Overall, our data suggest that damage initiation in trabecular bone is asymmetric in tension and compression, with failure originating and propagating over a large range of tensile strains.
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Affiliation(s)
- R Jungmann
- Physics Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
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Thurner PJ, Chen CG, Ionova-Martin S, Sun L, Harman A, Porter A, Ager JW, Ritchie RO, Alliston T. Osteopontin deficiency increases bone fragility but preserves bone mass. Bone 2010; 46:1564-73. [PMID: 20171304 PMCID: PMC2875278 DOI: 10.1016/j.bone.2010.02.014] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 02/08/2010] [Accepted: 02/09/2010] [Indexed: 12/17/2022]
Abstract
The ability of bone to resist catastrophic failure is critically dependent upon the material properties of bone matrix, a composite of hydroxyapatite, collagen type I, and noncollagenous proteins. These properties include elastic modulus, hardness, and fracture toughness. Like other aspects of bone quality, matrix material properties are biologically-defined and can be disrupted in skeletal disease. While mineral and collagen have been investigated in greater detail, the contribution of noncollagenous proteins such as osteopontin to bone matrix material properties remains unclear. Several roles have been ascribed to osteopontin in bone, many of which have the potential to impact material properties. To elucidate the role of osteopontin in bone quality, we evaluated the structure, composition, and material properties of bone from osteopontin-deficient mice and wild-type littermates at several length scales. Most importantly, the results show that osteopontin deficiency causes a 30% decrease in fracture toughness, suggesting an important role for OPN in preventing crack propagation. This significant decline in fracture toughness is independent of changes in whole bone mass, structure, or matrix porosity. Using nanoindentation and quantitative backscattered electron imaging to evaluate osteopontin-deficient bone matrix at the micrometer level, we observed a significant reduction in elastic modulus and increased variability in calcium concentration. Matrix heterogeneity was also apparent at the ultrastructural level. In conclusion, we find that osteopontin is essential for the fracture toughness of bone, and reduced toughness in osteopontin-deficient bone may be related to the increased matrix heterogeneity observed at the micro-scale. By exploring the effects of osteopontin deficiency on bone matrix material properties, composition and organization, this study suggests that reduced fracture toughness is one mechanism by which loss of noncollagenous proteins contribute to bone fragility.
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Affiliation(s)
- Philipp J. Thurner
- Department of Orthopaedic Surgery, University of California San Francisco, CA, USA
- School of Engineering Sciences, University of Southampton, UK
| | - Carol G. Chen
- Department of Orthopaedic Surgery, University of California San Francisco, CA, USA
| | - Sophi Ionova-Martin
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | - Luling Sun
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | | | | | - Joel W. Ager
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Robert O. Ritchie
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California San Francisco, CA, USA
- Department of Bioengineering and Therapeutic Sciences, Department of Otolaryngology, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California San Francisco, CA, USA
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