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Luchette M, Helmke K, Maissan IM, Hansen HC, Stolker RJ, Tasker RC, Akhondi-Asl A. Optic Nerve Sheath Viscoelastic Properties: Re-Examination of Biomechanical Behavior and Clinical Implications. Neurocrit Care 2022; 37:184-189. [PMID: 35237919 DOI: 10.1007/s12028-022-01462-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 02/01/2022] [Indexed: 10/19/2022]
Abstract
BACKGROUND Meta-analyses show a variable relationship between optic nerve sheath diameter (ONSD) and the presence of raised intracranial pressure (ICP). Because optic nerve sheath (ONS) tissue can be deformed, it is possible that ONSD reflects not only the current ICP but also prior deforming biomechanical exposures. In this post hoc analysis of two published data sets, we characterize ONS Young's modulus (E, mechanical stress per unit of strain) and calculate threshold pressure for plastic deformation. METHODS The authors of two previously published articles contributed primary data for these unique post hoc analyses. Human cadaveric ex vivo measurements of ONSD (n = 10) and luminal distending pressure (range 5 to 65 mm Hg) were used to calculate E and the threshold pressure for plastic deformation. Clinical in vivo measurements of ONSD and ICP during endotracheal tube suction from patients with traumatic brain injury (n = 15) were used to validate the ex vivo cadaveric findings. RESULTS Ex vivo ONS estimate of E was 140 ± 1.3 mm Hg (mean ± standard error), with evidence of plastic deformation occurring with distending pressure at 45 mm Hg. Similar E (71 ± 10 mm Hg) was estimated in vivo with an average ICP of 34 ± 2 mm Hg. CONCLUSIONS Ex vivo, ONS plastic deformation occurs at levels of pressure commonly seen in patients with raised ICP, leading to distortion of the ICP-ONSD relationship. This evidence of plastic deformation may illustrate why meta-analyses fail to identify a single threshold in ONSD associated with the presence of raised ICP. Future studies characterizing time-dependent viscous characteristics of the ONS will help determine the time course of ONS tissue biomechanical behavior.
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Affiliation(s)
- Matthew Luchette
- Division of Critical Care, Department of Anesthesiology, Critical Care, and Pain Medicine, Boston Children's Hospital, Boston, MA, USA.
| | - Knut Helmke
- Department of Neurology, Friedrich-Ebert-Hospital Neumuenster, University of Hamburg, Hamburg, Germany
| | - Iscander M Maissan
- Department of Anesthesiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Hans-Christian Hansen
- Department of Neurology, Friedrich-Ebert-Hospital Neumuenster, University of Hamburg, Hamburg, Germany
| | - Robert Jan Stolker
- Department of Anesthesiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Robert C Tasker
- Division of Critical Care, Department of Anesthesiology, Critical Care, and Pain Medicine, Boston Children's Hospital, Boston, MA, USA.,Selwyn College, Cambridge, UK
| | - Alireza Akhondi-Asl
- Division of Critical Care, Department of Anesthesiology, Critical Care, and Pain Medicine, Boston Children's Hospital, Boston, MA, USA
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2
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Jin Y, Wang X, Irnadiastputri SFR, Mohan RE, Aung T, Perera SA, Boote C, Jonas JB, Schmetterer L, Girard MJA. Effect of Changing Heart Rate on the Ocular Pulse and Dynamic Biomechanical Behavior of the Optic Nerve Head. Invest Ophthalmol Vis Sci 2020; 61:27. [PMID: 32315378 PMCID: PMC7401455 DOI: 10.1167/iovs.61.4.27] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Purpose To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model. Methods In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates. Results With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate. Conclusions In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology.
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Shin A, Park J, Le A, Poukens V, Demer JL. Bilaminar Mechanics of the Human Optic Nerve Sheath. Curr Eye Res 2020; 45:854-863. [PMID: 31821056 PMCID: PMC7286774 DOI: 10.1080/02713683.2019.1701689] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 11/18/2019] [Accepted: 11/22/2019] [Indexed: 10/25/2022]
Abstract
PURPOSE/AIM The adult human optic nerve (ON) sheath has recently been recognized to be bilaminar, consisting of inner layer (IL) and outer layer (OL). Since the ON and sheath exert tension on the globe in large angle adduction as these structures transmit reaction force of the medial rectus muscle to the globe, this study investigated the laminar biomechanics of the human ON sheath. MATERIALS AND METHODS Biomechanical characterization was performed in ON sheath specimens from 12 pairs of fresh, post-mortem adult eyes. Some ON sheath specimens were tested completely, while others were separated into IL and OL. Uniaxial tensile loading under physiological temperature and humidity was used to characterize a linear approximation as Young's modulus, and hyperelastic non-linear behavior using the formulation of Ogden. Micro-indentation was performed by imposing small compressive deformations with small, hard spheres. Specimens of the same sheaths were paraffin embedded, sectioned at 10 micron thickness, and stained with van Gieson's stain for anatomical correlation. RESULTS Mean (± standard error of the mean, SEM) tensile Young's modulus of the inner sheath at 19.8 ± 1.6 MPa significantly exceeded that for OL at 9.7 ± 1.2 MPa; the whole sheath showed intermediate modulus of 15.4 ± 1.1 MPa. Under compression, the inner sheath was stiffer (7.9 ± 0.5 vs 5.2 ± 0.5 kPa) and more viscous (150.8 ± 10.6 vs 75.6 ± 6 kPa s) than outer sheath. The inner sheath had denser elastin fibers than outer sheath, correlating with greater stiffness. CONCLUSIONS We conclude that maximum tensile stiffness occurs in the elastin-rich ON sheath IL that inserts near the lamina cribrosa where tension in the sheath exerted during adduction tethering may be concentrated adjacent the ON head.
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Affiliation(s)
- Andrew Shin
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles
- Wellman Center for Photomedicine, Harvard Medical School & Massachusetts General Hospital, Boston
| | - Joseph Park
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles
- Department of Bioengineering, University of California, Los Angeles
| | - Alan Le
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles
- Department of Bioengineering, University of California, Los Angeles
| | - Vadims Poukens
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles
| | - Joseph L. Demer
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles
- Biomedical Engineering Interdepartmental Program, University of California, Los Angeles
- Neuroscience Interdepartmental Program, University of California, Los Angeles
- Department of Neurology, University of California, Los Angeles
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GRAMIGNA VERA, FRAGOMENI GIONATA, FONTANELLA CHIARAGIULIA, STEFANINI CESARE, CARNIEL EMANUELELUIGI. A COUPLED EXPERIMENTAL AND NUMERICAL APPROACH TO CHARACTERIZE THE ANISOTROPIC MECHANICAL BEHAVIOR OF AORTIC TISSUES. J MECH MED BIOL 2020. [DOI: 10.1142/s021951942050027x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nowadays, the investigation of aortic wall biomechanics is a fundamental tool in clinical research and vascular prosthesis design. This study aims at analyzing the biomechanical behavior of aortic tissues using a coupled experimental and computational approach. Considering the typical fiber-reinforced configuration of aortic tissues, uni-axial tensile tests along six different loading directions were performed on specimens from pig aorta. Starting from the obtained experimental data, a suitable constitutive framework was defined and a methodology for the identification of the constitutive parameters was developed using the inverse analysis of mechanical tests. Transversal stretch versus loading stretch and nominal stress versus loading stretch curves were evaluated, showing the anisotropic and nonlinear mechanical behavior determined by tissue conformation with fibers distributed along preferential directions. In detail, experimental data showed different mechanical responses between longitudinal and circumferential directions, with a greater tissue stiffness along the longitudinal one. The reliability of the developed constitutive framework was evaluated by the comparison between experimental data and model results. The mentioned analysis can be considered as a useful tool for the development of reliable computational models, which allow a better understanding of the pathophysiology of cardiovascular diseases and can be applied for a proper planning of surgical procedures.
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Affiliation(s)
- VERA GRAMIGNA
- Neuroscience Research Center, Magna Graecia University, Viale Europa, 88100 Catanzaro, Italy
| | - GIONATA FRAGOMENI
- Medical and Surgical Sciences, Magna Graecia University, Viale Europa, 88100 Catanzaro, Italy
| | - CHIARA GIULIA FONTANELLA
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Via Venezia 1, Padova I-35131, Italy
| | - CESARE STEFANINI
- The BioRobotics Institute, Scuola Superiore Sant’Anna, Viale Rinaldo Piaggio 34, Pontedera (Pisa) I-56025, Italy
- Healthcare Engineering Innovation Center, Khalifa University, Abu Dhabi, UAE
| | - EMANUELE LUIGI CARNIEL
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Via Venezia 1, Padova I-35131, Italy
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5
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Vargun E, Ozaltin K, Fei H, Harea E, Vilčáková J, Kazantseva N, Saha P. Biodegradable porous polylactic acid film as a separator for supercapacitors. J Appl Polym Sci 2020. [DOI: 10.1002/app.49270] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Elif Vargun
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
- Department of ChemistryMugla Sitki Kocman University Mugla Turkey
| | - Kadir Ozaltin
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
| | - Haojie Fei
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
| | - Evghenii Harea
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
| | - Jarmila Vilčáková
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
| | - Natalia Kazantseva
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
| | - Petr Saha
- Centre of Polymer SystemsTomas Bata University in Zlín Zlín Czech Republic
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Li RL, Russ J, Paschalides C, Ferrari G, Waisman H, Kysar JW, Kalfa D. Mechanical considerations for polymeric heart valve development: Biomechanics, materials, design and manufacturing. Biomaterials 2019; 225:119493. [PMID: 31569017 PMCID: PMC6948849 DOI: 10.1016/j.biomaterials.2019.119493] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 08/21/2019] [Accepted: 09/11/2019] [Indexed: 01/12/2023]
Abstract
The native human heart valve leaflet contains a layered microstructure comprising a hierarchical arrangement of collagen, elastin, proteoglycans and various cell types. Here, we review the various experimental methods that have been employed to probe this intricate microstructure and which attempt to elucidate the mechanisms that govern the leaflet's mechanical properties. These methods include uniaxial, biaxial, and flexural tests, coupled with microstructural characterization techniques such as small angle X-ray scattering (SAXS), small angle light scattering (SALS), and polarized light microscopy. These experiments have revealed complex elastic and viscoelastic mechanisms that are highly directional and dependent upon loading conditions and biochemistry. Of all engineering materials, polymers and polymer-based composites are best able to mimic the tissue-level mechanical behavior of the native leaflet. This similarity to native tissue permits the fabrication of polymeric valves with physiological flow patterns, reducing the risk of thrombosis compared to mechanical valves and in some cases surpassing the in vivo durability of bioprosthetic valves. Earlier work on polymeric valves simply assumed the mechanical properties of the polymer material to be linear elastic, while more recent studies have considered the full hyperelastic stress-strain response. These material models have been incorporated into computational models for the optimization of valve geometry, with the goal of minimizing internal stresses and improving durability. The latter portion of this review recounts these developments in polymeric heart valves, with a focus on mechanical testing of polymers, valve geometry, and manufacturing methods.
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Affiliation(s)
- Richard L Li
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA; Division of Cardiac, Thoracic and Vascular Surgery, Section of Pediatric and Congenital Cardiac Surgery, New-York Presbyterian - Morgan Stanley Children's Hospital, Columbia University Medical Center, New York, NY, USA
| | - Jonathan Russ
- Department of Civil Engineering and Engineering Mechanics, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Costas Paschalides
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Giovanni Ferrari
- Department of Surgery and Biomedical Engineering, Columbia University Medical Center, New York, NY, USA
| | - Haim Waisman
- Department of Civil Engineering and Engineering Mechanics, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA
| | - Jeffrey W Kysar
- Department of Mechanical Engineering, Fu Foundation School of Engineering and Applied Science, Columbia University, New York, NY, USA; Department of Otolaryngology - Head and Neck Surgery, Columbia University Medical Center, New York, NY, USA.
| | - David Kalfa
- Division of Cardiac, Thoracic and Vascular Surgery, Section of Pediatric and Congenital Cardiac Surgery, New-York Presbyterian - Morgan Stanley Children's Hospital, Columbia University Medical Center, New York, NY, USA.
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Bidhendi AJ, Geitmann A. Methods to quantify primary plant cell wall mechanics. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:3615-3648. [PMID: 31301141 DOI: 10.1093/jxb/erz281] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 06/26/2019] [Indexed: 05/23/2023]
Abstract
The primary plant cell wall is a dynamically regulated composite material of multiple biopolymers that forms a scaffold enclosing the plant cells. The mechanochemical make-up of this polymer network regulates growth, morphogenesis, and stability at the cell and tissue scales. To understand the dynamics of cell wall mechanics, and how it correlates with cellular activities, several experimental frameworks have been deployed in recent years to quantify the mechanical properties of plant cells and tissues. Here we critically review the application of biomechanical tool sets pertinent to plant cell mechanics and outline some of their findings, relevance, and limitations. We also discuss methods that are less explored but hold great potential for the field, including multiscale in silico mechanical modeling that will enable a unified understanding of the mechanical behavior across the scales. Our overview reveals significant differences between the results of different mechanical testing techniques on plant material. Specifically, indentation techniques seem to consistently report lower values compared with tensile tests. Such differences may in part be due to inherent differences among the technical approaches and consequently the wall properties that they measure, and partly due to differences between experimental conditions.
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Affiliation(s)
- Amir J Bidhendi
- Department of Plant Science, McGill University, Macdonald Campus, Lakeshore, Ste-Anne-de-Bellevue, Québec, Canada
- Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montreal, Quebec, Canada
| | - Anja Geitmann
- Department of Plant Science, McGill University, Macdonald Campus, Lakeshore, Ste-Anne-de-Bellevue, Québec, Canada
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Shin A, Yoo L, Park J, Demer JL. Finite Element Biomechanics of Optic Nerve Sheath Traction in Adduction. J Biomech Eng 2018; 139:2648719. [PMID: 28787473 DOI: 10.1115/1.4037562] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Indexed: 02/01/2023]
Abstract
Historical emphasis on increased intraocular pressure (IOP) in the pathogenesis of glaucoma has been challenged by the recognition that many patients lack abnormally elevated IOP. We employed finite element analysis (FEA) to infer contribution to optic neuropathy from tractional deformation of the optic nerve head (ONH) and lamina cribrosa (LC) by extraocular muscle (EOM) counterforce exerted when optic nerve (ON) redundancy becomes exhausted in adduction. We characterized assumed isotropic Young's modulus of fresh adult bovine ON, ON sheath, and peripapillary and peripheral sclera by tensile elongation in arbitrary orientations of five specimens of each tissue to failure under physiological temperature and humidity. Physical dimensions of the FEA were scaled to human histological and magnetic resonance imaging (MRI) data and used to predict stress and strain during adduction 6 deg beyond ON straightening at multiple levels of IOP. Young's modulus of ON sheath of 44.6 ± 5.6 MPa (standard error of mean) greatly exceeded that of ON at 5.2 ± 0.4 MPa, peripapillary sclera at 5.5 ± 0.8 MPa, and peripheral sclera at 14.0 ± 2.3 MPa. FEA indicated that adduction induced maximum stress and strain in the temporal ONH. In the temporal LC, the maximum stress was 180 kPa, and the maximum strain was ninefold larger than produced by IOP elevation to 45 mm Hg. The simulation suggests that ON sheath traction by adduction concentrates far greater mechanical stress and strain in the ONH region than does elevated IOP, supporting the novel concept that glaucomatous optic neuropathy may result at least partly from external traction on the ON, rather than exclusively on pressure on the ON exerted from within the eye.
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Affiliation(s)
- Andrew Shin
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095
| | - Lawrence Yoo
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095; Intelon Optics Inc., Cambridge, MA 02138-4430
| | - Joseph Park
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095; Department of Mechanical Engineering, University of California, Los Angeles, CA 90095
| | - Joseph L Demer
- Arthur L. Rosenbaum Professor of Pediatric Ophthalmology Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095 e-mail: ; Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, CA 90095;Neuroscience Interdepartmental Program, University of California, Los Angeles, CA 90095; Department of Neurology, University of California, Los Angeles, CA 90095
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Opto-mechanical characterization of sclera by polarization sensitive optical coherence tomography. J Biomech 2018; 72:173-179. [PMID: 29580690 DOI: 10.1016/j.jbiomech.2018.03.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 01/23/2018] [Accepted: 03/06/2018] [Indexed: 11/20/2022]
Abstract
Polarization sensitive optical coherence tomography (PSOCT) is an interferometric technique sensitive to birefringence. Since mechanical loading alters the orientation of birefringent collagen fibrils, we asked if PSOCT can be used to measure local mechanical properties of sclera. Infrared (1300 nm) PSOCT was performed during uniaxial tensile loading of fresh scleral specimens of rabbits, cows, and humans from limbal, equatorial, and peripapillary regions. Specimens from 8 human eyes were obtained. Specimens were stretched to failure at 0.01 mm/s constant rate under physiological conditions of temperature and humidity while birefringence was computed every 117 ms from cross-sectional PSOCT. Birefringence modulus (BM) was defined as the rate of birefringence change with strain, and tensile modulus (TM) as the rate of stress change between 0 and 9% strain. In cow and rabbit, BM and TM were positively correlated with slopes of 0.17 and 0.10 GPa, and with correlation coefficients 0.63 and 0.64 (P < 0.05), respectively, following stress-optic coefficients 4.69, and 4.20 GPa-1. In human sclera, BM and TM were also positively correlated with slopes of 0.24 GPa for the limbal, 0.26 GPa for the equatorial, and 0.31 GPa for the peripapillary regions. Pearson correlation coefficients were significant at 0.51, 0.58, and 0.69 for each region, respectively (<0.001). Mean BM decreased proportionately to TM from the limbal to equatorial to peripapillary regions, as stress-optic coefficients were estimated as 2.19, 2.42, and 4.59 GPa-1, respectively. Since birefringence and tensile elastic moduli correlate differently in cow, rabbit, and various regions of human sclera, it might be possible to mechanically characterize the sclera in vivo using PSOCT.
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10
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Haslach HW, Gipple JM, Leahy LN. Influence of high deformation rate, brain region, transverse compression, and specimen size on rat brain shear stress morphology and magnitude. J Mech Behav Biomed Mater 2017; 68:88-102. [PMID: 28157598 DOI: 10.1016/j.jmbbm.2017.01.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/03/2017] [Accepted: 01/23/2017] [Indexed: 11/26/2022]
Abstract
An external mechanical insult to the brain, such as a blast, may create internal stress and deformation waves, which have shear and longitudinal components that can induce combined shear and compression of the brain tissue. To isolate the consequences of such interactions for the shear stress and to investigate the role of the extracellular fluid in the mechanical response, translational shear stretch at 10/s, 60/s, and 100/s translational shear rates under either 0% or 33% fixed transverse compression is applied without preconditioning to rat brain specimens. The specimens from the cerebrum, the cerebellum grey matter, and the brainstem white matter are nearly the full length of their respective regions. The translational shear stress response to translational shear deformation is characterized by the effect that each of four factors, high deformation rate, brain region, transverse compression, and specimen size, have on the shear stress magnitude averaged over ten specimens for each combination of factors. Increasing the deformation rate increases the magnitude of the shear stress at a given translational shear stretch, and as tested by ANOVAs so does applying transverse fixed compression of 33% of the thickness. The stress magnitude differs by the region that is the specimen source: cerebrum, cerebellum or brainstem. The magnitude of the shear stress response at a given deformation rate and stretch depends on the specimen length, called a specimen size effect. Surprisingly, under no compression a shorter length specimen requires more shear stress, but under 33% compression a shorter length specimen requires less shear stress, to meet a required shear deformation rate. The shear specimen size effect calls into question the applicability of the classical shear stress definition to hydrated soft biological tissue.
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Affiliation(s)
- Henry W Haslach
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.
| | - Jenna M Gipple
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Lauren N Leahy
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
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11
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Hasan A, Saliba J, Pezeshgi Modarres H, Bakhaty A, Nasajpour A, Mofrad MRK, Sanati-Nezhad A. Micro and nanotechnologies in heart valve tissue engineering. Biomaterials 2016; 103:278-292. [PMID: 27414719 DOI: 10.1016/j.biomaterials.2016.07.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/26/2016] [Accepted: 07/01/2016] [Indexed: 02/04/2023]
Abstract
Due to the increased morbidity and mortality resulting from heart valve diseases, there is a growing demand for off-the-shelf implantable tissue engineered heart valves (TEHVs). Despite the significant progress in recent years in improving the design and performance of TEHV constructs, viable and functional human implantable TEHV constructs have remained elusive. The recent advances in micro and nanoscale technologies including the microfabrication, nano-microfiber based scaffolds preparation, 3D cell encapsulated hydrogels preparation, microfluidic, micro-bioreactors, nano-microscale biosensors as well as the computational methods and models for simulation of biological tissues have increased the potential for realizing viable, functional and implantable TEHV constructs. In this review, we aim to present an overview of the importance and recent advances in micro and nano-scale technologies for the development of TEHV constructs.
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Affiliation(s)
- Anwarul Hasan
- Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, Doha 2713, Qatar; Department of Mechanical Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut 1107 2020, Lebanon; Biomaterials Innovation Research Center, Division of Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA.
| | - John Saliba
- Department of Mechanical Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut 1107 2020, Lebanon
| | - Hassan Pezeshgi Modarres
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada; Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, 208A Stanley Hall, Berkeley, CA 94720-1762, USA
| | - Ahmed Bakhaty
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, 208A Stanley Hall, Berkeley, CA 94720-1762, USA
| | - Amir Nasajpour
- Biomaterials Innovation Research Center, Division of Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California Berkeley, 208A Stanley Hall, Berkeley, CA 94720-1762, USA; Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Amir Sanati-Nezhad
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada.
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12
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Biomechanical properties of native and tissue engineered heart valve constructs. J Biomech 2014; 47:1949-63. [DOI: 10.1016/j.jbiomech.2013.09.023] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
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13
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Huang S, Huang HYS. Virtualisation of stress distribution in heart valve tissue. Comput Methods Biomech Biomed Engin 2013; 17:1696-704. [PMID: 23477432 DOI: 10.1080/10255842.2013.763937] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This study presents an image-based finite element analysis incorporating histological photomicrographs of heart valve tissues. We report stress fields inside heart valve tissues, where heterogeneously distributed collagen fibres are responsible for transmitting forces into cells. Linear isotropic and anisotropic tissue material property models are incorporated to quantify the overall stress distributions in heart valve tissues. By establishing an effective predictive method with new computational tools and by performing virtual experiments on the heart valve tissue photomicrographs, we clarify how stresses are transferred from matrix to cell. The results clearly reveal the roles of heterogeneously distributed collagen fibres in mitigating stress developments inside heart valve tissues. Moreover, most local peak stresses occur around cell nuclei, suggesting that higher stress may be mediated by cells for biomechanical regulations.
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Affiliation(s)
- Siyao Huang
- a Mechanical and Aerospace Engineering Department , North Carolina State University , 3002 EBIII, Campus Box 7910, 911 Oval Drive, Raleigh , NC 27695-7910 , USA
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Weed BC, Borazjani A, Patnaik SS, Prabhu R, Horstemeyer MF, Ryan PL, Franz T, Williams LN, Liao J. Stress State and Strain Rate Dependence of the Human Placenta. Ann Biomed Eng 2012; 40:2255-65. [DOI: 10.1007/s10439-012-0588-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 05/04/2012] [Indexed: 11/28/2022]
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Lewinsohn AD, Anssari-Benham A, Lee DA, Taylor PM, Chester AH, Yacoub MH, Screen HRC. Anisotropic strain transfer through the aortic valve and its relevance to the cellular mechanical environment. Proc Inst Mech Eng H 2011; 225:821-30. [PMID: 21922958 DOI: 10.1177/0954411911406340] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aortic valve interstitial cells are responsible for maintaining the valve in response to their local mechanical environment. However, the complex organization of the extracellular matrix means cell strains cannot be directly derived from gross strains, and knowledge of tissue structure-function correlations is fundamental towards understanding mechanotransduction. This study investigates strain transfer through the valve, hypothesizing that organization of the valve matrix leads to non-homogenous local strains. Radial and circumferential samples were cut from aortic valve leaflets and subjected to quasi-static mechanical characterization. Further samples were imaged using confocal microscopy, to determine local strains in the matrix. Mechanical data demonstrated that the valve was significantly stronger and stiffer when loaded circumferentially, comparable with previous studies. Micromechanical studies demonstrated that strain transfer through the matrix is anisotropic and indirect, with local strains consistently smaller than applied strains in both orientations. Under radial loading, strains were transferred linearly to cells. However, under circumferential loading, strains were only one-third of applied values, with a less direct relationship between applied and local strains. This may result from matrix reorganization, and be important for preventing cellular damage during normal valve function. These findings should be taken into account when investigating interstitial cell behaviours, such as cell metabolism and mechanotransduction.
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Affiliation(s)
- A D Lewinsohn
- Medical Engineering Division, School of Engineering and Materials Science, Queen Mary, University of London, London, UK
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Khanafer K, Duprey A, Schlicht M, Berguer R. Effects of strain rate, mixing ratio, and stress–strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications. Biomed Microdevices 2008; 11:503-8. [DOI: 10.1007/s10544-008-9256-6] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Abstract
Incompetent inflow valves have been reported with clinical pulsatile left ventricular assist devices that use bioprosthetic valves. Suspected as the cause of premature valve failure within these devices, absolute pressures and instantaneous pressure changes were evaluated in the MagScrew total artificial heart (TAH). The MagScrew TAH is a passively filling pulsatile pump which uses a reciprocating magnetic actuating mechanism under various control modes to propel blood into circulation. Both right and left ejection speeds were modulated and optimized at the onset of hydraulic eject. These various speed profiles were evaluated in vitro at 220 beats per minute (bpm), 100% pump fill, mean aortic pressure of 100 mm Hg and mean pulmonary artery pressure of 20 mm Hg. The pressure inside the left and right pump chambers was measured with Millar Mikro-Tip catheter and captured using Power Lab at a rate of 40 kHz. The pump chamber peak pressure, operating with unmodified eject speeds, measured on average 183 mm Hg for the left and 133 mm Hg for the right. Eject speed profiling for both pumps reduced the peak pressure by 10% and 28% for the left and right pump, respectively. Future studies will assess software controlled optimization of the eject speed profiles under any operating condition and how effective it is in vivo.
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Brody S, Pandit A. Microarchitectural characterization of the aortic heart valve. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 553:167-86. [PMID: 15503455 DOI: 10.1007/978-0-306-48584-8_13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- Sarah Brody
- National Centre for Biomedical Engineering Science and Department of Mechanical and Biomedical Engineering, National University of Ireland, Galway, Ireland
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Abstract
Porcine aortic valve (PAV) cusps are folded and wrinkled in the in vitro state. In the tensile testing of PAV specimens, estimating gauge length (the length at which a specimen starts to offer measurable resistance to load) is often difficult and subjective. We have therefore developed a new method for estimating the gauge length of such tissues. The method is based on the observation that the specimen's gauge length can be associated with a stationary point on the slope of its load-length curve if loaded from a wrinkled state, or a state of slight compression. We represented the load-length response of test specimens in the low-load, high-compliance region by a cubic function and determined the stationary point on the slope of the function using elementary calculus. The cubic function representation is fine-tuned by reducing or expanding an originally selected "test region" until the correlation coefficient of the cubic fit is maximized. The new method was applied to data obtained from the tensile testing of strips of heart valve tissue and was found to be objective, repeatable and robust.
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Affiliation(s)
- Evelyn O Carew
- Department of Biomedical Engineering/ND 20, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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