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Böl M, Leichsenring K, Kohn S, Ehret AE. The anisotropic and region-dependent mechanical response of wrap-around tendons under tensile, compressive and combined multiaxial loads. Acta Biomater 2024; 183:157-172. [PMID: 38838908 DOI: 10.1016/j.actbio.2024.05.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 05/20/2024] [Accepted: 05/30/2024] [Indexed: 06/07/2024]
Abstract
The present work reports on the multiaxial region and orientation-dependent mechanical properties of two porcine wrap-around tendons under tensile, compressive and combined loads based on an extensive study with n=175 samples. The results provide a detailed dataset of the anisotropic tensile and compressive longitudinal properties and document a pronounced tension-compression asymmetry. Motivated by the physiological loading conditions of these tendons, which include transversal compression at bony abutments in addition to longitudinal tension, we systematically investigated the change in axial tension when the tendon is compressed transversally along one or both perpendicular directions. The results reveal that the transversal compression can increase axial tension (proximal-distal direction) in both cases to orders of 30%, yet by a larger amount in the first case (transversal compression in anterior-posterior direction), which seems to be more relevant for wrap-around tendons in-vivo. These quantitative measurements are in line with earlier findings on auxetic properties of tendon tissue, but show for the first time the influence of this property on the stress response of the tendon, and may thus reveal an important functional principle within these essential elements of force transmission in the body. STATEMENT OF SIGNIFICANCE: The work reports for the first time on multiaxial region and orientation-dependent mechanical properties of wrap-around tendons under various loads. The results indicate that differences in the mechanical properties exist between zones that are predominantly in a uniaxial tensile state and those that experience complex load states. The observed counterintuitive increase of the axial tension upon lateral compression points at auxetic properties of the tendon tissue which may be pivotal for the function of the tendon as an element of the musculoskeletal system. It suggests that the tendon's performance in transmitting forces is not diminished but enhanced when the action line is deflected by a bony pulley around which the tendon wraps, representing an important functional principle of tendon tissue.
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Affiliation(s)
- Markus Böl
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany.
| | - Kay Leichsenring
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany
| | - Stephan Kohn
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany
| | - Alexander E Ehret
- Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland; Institute for Mechanical Systems, ETH Zurich, Zürich, CH-8092, Switzerland
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2
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Witt NJ, Woessner AE, Herrmann J, Quinn KP, Sander EA. Mechanical Models of Collagen Networks for Understanding Changes in the Failure Properties of Aging Skin. J Biomech Eng 2024; 146:071002. [PMID: 38183223 PMCID: PMC10983714 DOI: 10.1115/1.4064406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 12/19/2023] [Accepted: 12/27/2023] [Indexed: 01/07/2024]
Abstract
Skin undergoes mechanical alterations due to changes in the composition and structure of the collagenous dermis with aging. Previous studies have conflicting findings, with both increased and decreased stiffness reported for aging skin. The underlying structure-function relationships that drive age-related changes are complex and difficult to study individually. One potential contributor to these variations is the accumulation of nonenzymatic crosslinks within collagen fibers, which affect dermal collagen remodeling and mechanical properties. Specifically, these crosslinks make individual fibers stiffer in their plastic loading region and lead to increased fragmentation of the collagenous network. To better understand the influence of these changes, we investigated the impact of nonenzymatic crosslink changes on the dermal microstructure using discrete fiber networks representative of the dermal microstructure. Our findings suggest that stiffening the plastic region of collagen's mechanical response has minimal effects on network-level stiffness and failure stresses. Conversely, simulating fragmentation through a loss of connectivity substantially reduces network stiffness and failure stress, while increasing stretch ratios at failure.
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Affiliation(s)
- Nathan J. Witt
- Roy J. Carver Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, IA 52240
| | - Alan E. Woessner
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR 72701
| | - Jacob Herrmann
- Roy J. Carver Department of Biomedical Engineering, College of Engineering, University of Iowa, Iowa City, IA 52242
| | - Kyle P. Quinn
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR 72701
| | - Edward A. Sander
- Roy J. Carver Department of Biomedical Engineering, College of Engineering, University of Iowa, 5629 Seamans Center, Iowa City, IA 52242; Department of Orthopedics and Rehabilitation, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
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3
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Létocart AJ, Svensson RB, Mabesoone F, Charleux F, Marin F, Dermigny Q, Magnusson SP, Couppé C, Grosset JF. Structure and function of Achilles and patellar tendons following moderate slow resistance training in young and old men. Eur J Appl Physiol 2024:10.1007/s00421-024-05461-y. [PMID: 38649478 DOI: 10.1007/s00421-024-05461-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 03/05/2024] [Indexed: 04/25/2024]
Abstract
The aim of this study was to investigate the effect of aging and resistance training with a moderate load on the size and mechanical properties of the patellar (PT) and Achilles tendon (AT) and their associated aponeuroses; medial gastrocnemius (MG) and vastus lateralis (VL). Young (Y55; 24.8 ± 3.8 yrs, n = 11) and old men (O55; 70.0 ± 4.6 yrs, n = 13) were assigned to undergo a training program (12 weeks; 3 times/week) of moderate slow resistance training [55% of one repetition maximum (RM)] of the triceps surae and quadriceps muscles. Tendon dimensions were assessed using 1.5 T magnetic resonance imaging before and after 12 weeks. AT and PT cross sectional area (CSA) were determined every 10% of tendon length. Mechanical properties of the free AT, MG aponeurosis, PT, and VL aponeurosis were assessed using ultrasonography (deformation) and tendon force measurements. CSA of the AT but not PT was greater in O55 compared with Y55. At baseline, mechanical properties were generally lower in O55 than Y55 for AT, MG aponeurosis and VL aponeurosis (Young's modulus) but not for PT. CSA of the AT and PT increased equally in both groups following training. Further, for a given force, stiffness and Young's modulus also increased equally for VL aponeurosis and AT, for boths groups. The present study highlights that except for the PT, older men have lower tendon (AT, MG aponeurosis, and VL aponeurosis) mechanical properties than young men and 12-weeks of moderate slow resistance training appears sufficient to improve tendon size and mechanical adaptations in both young and older men. New and Noteworthy: These novel findings suggest that short-term moderate slow resistance training induces equal improvements in tendon size and mechanics regardless of age.
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Affiliation(s)
- Adrien J Létocart
- UMR CNRS 7338 Biomécanique et Bioingénierie, Sorbonne Universités, Université de Technologie de Compiègne, 60205, Compiègne Cedex, France.
| | - René B Svensson
- Department of Physical and Occupational Therapy, Bispebjerg-Frederiksberg Hospitals, Copenhagen, Denmark
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital-Bispebjerg and Frederiksberg, Copenhagen, Denmark
- Center for Healthy Aging, Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Frédéric Marin
- UMR CNRS 7338 Biomécanique et Bioingénierie, Sorbonne Universités, Université de Technologie de Compiègne, 60205, Compiègne Cedex, France
| | - Quentin Dermigny
- UMR CNRS 7338 Biomécanique et Bioingénierie, Sorbonne Universités, Université de Technologie de Compiègne, 60205, Compiègne Cedex, France
| | - S Peter Magnusson
- Department of Physical and Occupational Therapy, Bispebjerg-Frederiksberg Hospitals, Copenhagen, Denmark
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital-Bispebjerg and Frederiksberg, Copenhagen, Denmark
- Center for Healthy Aging, Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Christian Couppé
- Department of Physical and Occupational Therapy, Bispebjerg-Frederiksberg Hospitals, Copenhagen, Denmark
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital-Bispebjerg and Frederiksberg, Copenhagen, Denmark
| | - Jean-François Grosset
- UMR CNRS 7338 Biomécanique et Bioingénierie, Sorbonne Universités, Université de Technologie de Compiègne, 60205, Compiègne Cedex, France.
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4
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Barrett JM, Callaghan JP. Strain inhibition of bacterial collagenase is consistent with a collagen fibril uncrimping mechanism in rat tail tendons. J Biomech 2024; 162:111892. [PMID: 38061208 DOI: 10.1016/j.jbiomech.2023.111892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 11/23/2023] [Accepted: 11/28/2023] [Indexed: 01/16/2024]
Abstract
Mechanical strain inhibits bacterial collagenase from cleaving collagen. Additionally, the toe region of a soft tissue's force-elongation curve arises from sequentially engaging collagen fibrils as the tissue lengthens. Together, these phenomena suggest that mechanical strain may gradually inhibit collagenase activity through a soft tissue's toe region. Therefore, this investigation sought to test this hypothesis. 92 rat tail tendon fascicles from 3 female sentinel animals underwent preliminary stiffness tests, and their force-elongation curves were fit to a collagen distribution model. This distribution-based model calculated the force magnitude corresponding to p% of collagen fibril engagement. Specimens were separated into one of five levels of p, and that level of force was maintained for two hours while being exposed to 0.054 U/mL of bacterial collagenase from C. histolyticum. The specimens were strained to failure following the creep test, and the relative reduction in stiffness was quantified to estimate the fraction of digested fibrils. Every 10% additional collagen engagement corresponded to a 6.3% (97% highest density interval: 4.3 - 8.4%) retention of stiffness, which indicated collagenase inhibition. The results of this investigation were consistent with a strain-inhibition hypothesis along with the established uncrimping mechanism in the toe region. These results support an interaction between mechanical strain and collagenolysis, which may be valuable for disease prevention or treatment.
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Affiliation(s)
- Jeff M Barrett
- Department of Kinesiology and Health Sciences, University of Waterloo, Canada.
| | - Jack P Callaghan
- Department of Kinesiology and Health Sciences, University of Waterloo, Canada.
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5
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Mohammadkhah M, Klinge S. Review paper: The importance of consideration of collagen cross-links in computational models of collagen-based tissues. J Mech Behav Biomed Mater 2023; 148:106203. [PMID: 37879165 DOI: 10.1016/j.jmbbm.2023.106203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/25/2023] [Accepted: 10/17/2023] [Indexed: 10/27/2023]
Abstract
Collagen as the main protein in Extra Cellular Matrix (ECM) is the main load-bearing component of fibrous tissues. Nanostructure and architecture of collagen fibrils play an important role in mechanical behavior of these tissues. Extensive experimental and theoretical studies have so far been performed to capture these properties, but none of the current models realistically represent the complexity of network mechanics because still less is known about the collagen's inner structure and its effect on the mechanical properties of tissues. The goal of this review article is to emphasize the significance of cross-links in computational modeling of different collagen-based tissues, and to reveal the need for continuum models to consider cross-links properties to better reflect the mechanical behavior observed in experiments. In addition, this study outlines the limitations of current investigations and provides potential suggestions for the future work.
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Affiliation(s)
- Melika Mohammadkhah
- Technische Universität Berlin, Institute of Mechanics, Chair of Structural Mechanics and Analysis, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany.
| | - Sandra Klinge
- Technische Universität Berlin, Institute of Mechanics, Chair of Structural Mechanics and Analysis, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
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6
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Leighton MP, Kreplak L, Rutenberg AD. Torsion and bistability of double-twist elastomers. SOFT MATTER 2023; 19:6376-6386. [PMID: 37577969 DOI: 10.1039/d3sm00554b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
We investigate the elastic properties of anisotropic elastomers with a double-twist director field, which is a model for collagen fibrils or blue phases. We observe a significant Poynting-like effect, coupling torsion (fibril twist) and extension. For freely-rotating boundary conditions, we identify a structural bistability at very small extensional strains which undergoes a saddle-node bifurcation at a critical strain - at approximately 1% strain for a parameterization appropriate for collagen fibrils. With clamped boundary conditions appropriate for many experimental setups, the bifurcation is not present. We expect significant helical shape effects when fixed torsion does not equal the equilibrium torsion of freely-rotating boundary conditions, due to residual torques.
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Affiliation(s)
- Matthew P Leighton
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Andrew D Rutenberg
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
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7
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Single collagen fibrils isolated from high stress and low stress tendons show differing susceptibility to enzymatic degradation by the interstitial collagenase matrix metalloproteinase-1 (MMP-1). Matrix Biol Plus 2023; 18:100129. [PMID: 36915648 PMCID: PMC10006499 DOI: 10.1016/j.mbplus.2023.100129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 02/10/2023] [Accepted: 02/20/2023] [Indexed: 02/25/2023] Open
Abstract
Bovine forelimb flexor and extensor tendons serve as a model for examining high stress, energy storing and low stress, positional tendons, respectively. Previous research has shown structural differences between the collagen fibrils of these tissues. The nanoscale collagen fibrils of flexor tendons are smaller in size, more heavily crosslinked, and respond differently to mechanical loading. Meanwhile, energy storing tendons undergo less collagen turnover compared to positional tendons and are more commonly injured. These observations raise the question of whether collagen fibril structure influences the collagen degradation processes necessary for remodelling. Atomic force microscopy was used to image dry collagen fibrils before and after 5-hour exposure to matrix metalloproteinase-1 (MMP-1) to detect changes in fibril size. Collagen fibrils from three tissue types were studied: bovine superficial digital flexor tendons, matched-pair bovine lateral digital extensor tendons, and rat tail tendons. Compared to control fibrils exposed only to buffer, a significant decrease in fibril cross-sectional area (CSA) following MMP-1 exposure was observed for bovine extensor and rat tail fibrils, with larger fibrils experiencing a greater magnitude of CSA decrease in both fibril types. Fibrils from bovine flexor tendons, on the other hand, showed no decrease in CSA when exposed to MMP-1. The result did not appear to be linked to the small size of flexor fibrils, as equivalently sized extensor fibrils were readily degraded by the enzyme. Increased proteolytic resistance of collagen fibrils from high stress tendons may help to explain the longevity of collagen within these tissues in vivo.
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8
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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] [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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9
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Nozaki S, Kinugasa R, Yaeshima K, Hashimoto T, Jinzaki M, Ogihara N. Quantification of the in vivo stiffness and natural length of the human plantar aponeurosis during quiet standing using ultrasound elastography. Sci Rep 2022; 12:15707. [PMID: 36127445 PMCID: PMC9489693 DOI: 10.1038/s41598-022-20211-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 09/09/2022] [Indexed: 11/09/2022] Open
Abstract
This study aimed to identify the stiffness and natural length of the human plantar aponeurosis (PA) during quiet standing using ultrasound shear wave elastography. The shear wave velocity (SWV) of the PA in young healthy males and females (10 participants each) was measured by placing a probe in a hole in the floor plate. The change in the SWV with the passive dorsiflexion of the metatarsophalangeal (MP) joint was measured. The Young's modulus of the PA was estimated to be 64.7 ± 9.4 kPa, which exponentially increased with MP joint dorsiflexion. The PA was estimated to have the natural length when the MP joint was plantarflexed by 13.8°, indicating that the PA is stretched by arch compression during standing. However, the present study demonstrated that the estimated stiffness for the natural length in quiet standing was significantly larger than that in the unloaded condition, revealing that the PA during standing is stiffened by elongation and through the possible activation of intrinsic muscles. Such quantitative information possibly contributes to the detailed biomechanical modeling of the human foot, facilitating an improved understanding of the mechanical functions and pathogenetic mechanisms of the PA during movements.
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Affiliation(s)
- Shuhei Nozaki
- Laboratory of Human Evolutionary Biomechanics, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan.
| | - Ryuta Kinugasa
- Department of Human Sciences, Kanagawa University, Kanagawa, 221-8686, Japan
| | - Katsutoshi Yaeshima
- Department of Human Sciences, Kanagawa University, Kanagawa, 221-8686, Japan
| | - Takeshi Hashimoto
- Sports Medicine Research Center, Keio University, Kanagawa, 223-8521, Japan
| | - Masahiro Jinzaki
- Department of Radiology, Keio University School of Medicine, Tokyo, 160-8582, Japan
| | - Naomichi Ogihara
- Laboratory of Human Evolutionary Biomechanics, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan.
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10
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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. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:054103. [PMID: 35649813 DOI: 10.1063/5.0072123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [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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11
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Gouissem A, Mbarki R, Al Khatib F, Adouni M. Multiscale Characterization of Type I Collagen Fibril Stress–Strain Behavior under Tensile Load: Analytical vs. MD Approaches. Bioengineering (Basel) 2022; 9:bioengineering9050193. [PMID: 35621471 PMCID: PMC9138028 DOI: 10.3390/bioengineering9050193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 04/17/2022] [Accepted: 04/26/2022] [Indexed: 11/24/2022] Open
Abstract
Type I collagen is one of the most important proteins in the human body because of its role in providing structural support to the extracellular matrix of the connective tissues. Understanding its mechanical properties was widely investigated using experimental testing as well as molecular and finite element simulations. In this work, we present a new approach for defining the properties of the type I collagen fibrils by analytically formulating its response when subjected to a tensile load and investigating the effects of enzymatic crosslinks on the behavioral response. We reveal some of the shortcomings of the molecular dynamics (MD) method and how they affect the obtained stress–strain behavior of the fibril, and we prove that not only does MD underestimate the Young’s modulus and the ultimate tensile strength of the collagen fibrils, but also fails to detect the mechanics of some stretching phases of the fibril. We prove that non-crosslinked fibrils have three tension phases: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime related to the stretching of the backbone of the tropocollagen molecules, and (iii) a plastic regime dominated by molecular sliding. We also show that for crosslinked fibrils, the second regime can be subdivided into three sub-regimes, and we define the properties of each regime. We also prove, analytically, the alleged MD quadratic relation between the ultimate tensile strength of the fibril and the concentration of enzymatic crosslinks (β).
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Affiliation(s)
- Afif Gouissem
- Mechanical Engineering Department, Australian University, East Mishref, Kuwait City P.O. Box 1411, Kuwait; (A.G.); (R.M.); (F.A.K.)
| | - Raouf Mbarki
- Mechanical Engineering Department, Australian University, East Mishref, Kuwait City P.O. Box 1411, Kuwait; (A.G.); (R.M.); (F.A.K.)
| | - Fadi Al Khatib
- Mechanical Engineering Department, Australian University, East Mishref, Kuwait City P.O. Box 1411, Kuwait; (A.G.); (R.M.); (F.A.K.)
| | - Malek Adouni
- Mechanical Engineering Department, Australian University, East Mishref, Kuwait City P.O. Box 1411, Kuwait; (A.G.); (R.M.); (F.A.K.)
- Physical Medicine and Rehabilitation Department, Northwestern University, Chicago, IL 60611, USA
- Correspondence:
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