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Kohles SS. Application of flexural and membrane stress analysis to distinguish tensile and compressive moduli of biologic materials. J Mech Behav Biomed Mater 2021; 119:104474. [PMID: 33887626 DOI: 10.1016/j.jmbbm.2021.104474] [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: 08/10/2020] [Revised: 03/07/2021] [Accepted: 03/13/2021] [Indexed: 10/21/2022]
Abstract
Three-point bending is often used during the mechanical determination of tissue material properties. When taken to failure, the test samples often experience high deformations. The objective of this study was to present beam and plate theories as analytical tools for determining tensile and compressive elastic moduli during the transition from flexure to membrane stress states. Samples of cartilage, a highly flexible connective tissue having differing tensile and compressive moduli, were tested. Three-point bending tests were conducted on auricular (ear) and costal (rib) cartilage harvested from pigs. The influence of span length variation and Poisson's ratio assumptions were statistically assessed. Tensile elastic moduli of the ear (3.886 MPa) and rib (6.131 MPa) were derived from high-deformation bending tests. The functional assessment described here can be applied as a design input approach for tissue reconstruction and tissue engineering, considering both hard and soft tissue applications.
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Affiliation(s)
- Sean S Kohles
- Kohles Bioengineering,Portland, OR, USA; Division of Biomaterials & Biomechanics, School of Dentistry And Department of Emergency Medicine, School of Medicine, Oregon Health & Science University, Portland, OR, USA; Department of Human Physiology, University of Oregon, Eugene, OR, USA.
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Burkert J, Kochová P, Tonar Z, Cimrman R, Blassová T, Jashari R, Fiala R, Špatenka J. The time has come to extend the expiration limit of cryopreserved allograft heart valves. Cell Tissue Bank 2020; 22:161-184. [PMID: 32583302 DOI: 10.1007/s10561-020-09843-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 06/13/2020] [Indexed: 12/12/2022]
Abstract
Despite the wide choice of commercial heart valve prostheses, cryopreserved semilunar allograft heart valves (C-AHV) are required, and successfully transplanted in selected groups of patients. The expiration limit (EL) criteria have not been defined yet. Most Tissue Establishments (TE) use the EL of 5 years. From physiological, functional, and surgical point of view, the morphology and mechanical properties of aortic and pulmonary roots represent basic features limiting the EL of C-AHV. The aim of this work was to review methods of AHV tissue structural analysis and mechanical testing from the perspective of suitability for EL validation studies. Microscopic structure analysis of great arterial wall and semilunar leaflets tissue should clearly demonstrate cells as well as the extracellular matrix components by highly reproducible and specific histological staining procedures. Quantitative morphometry using stereological grids has proved to be effective, as the exact statistics was feasible. From mechanical testing methods, tensile test was the most suitable. Young's moduli of elasticity, ultimate stress and strain were shown to represent most important AHV tissue mechanical characteristics, suitable for exact statistical analysis. C-AHV are prepared by many different protocols, so as each TE has to work out own EL for C-AHV.
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Affiliation(s)
- Jan Burkert
- Department of Transplantation and Tissue Banking, Czech National Allograft Heart Valve Bank, Department of Cardiovascular Surgery, Motol University Hospital, and Second Faculty of Medicine Charles University in Prague, V Úvalu 84, 150 06, Prague, Czech Republic
| | - Petra Kochová
- Department of Transplantation and Tissue Banking, Czech National Allograft Heart Valve Bank, Department of Cardiovascular Surgery, Motol University Hospital, and Second Faculty of Medicine Charles University in Prague, V Úvalu 84, 150 06, Prague, Czech Republic. .,NTIS - New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Technická 8, Pilsen, Czech Republic.
| | - Zbyněk Tonar
- NTIS - New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Technická 8, Pilsen, Czech Republic.,Department of Histology and Embryology, Biomedical Centre, Faculty of Medicine in Pilsen, Charles University in Prague, Karlovarská 48, 301 66, Pilsen, Czech Republic
| | - Robert Cimrman
- NTIS - New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Technická 8, Pilsen, Czech Republic
| | - Tereza Blassová
- Department of Histology and Embryology, Biomedical Centre, Faculty of Medicine in Pilsen, Charles University in Prague, Karlovarská 48, 301 66, Pilsen, Czech Republic
| | - Ramadan Jashari
- European Homograft Bank, Saint-Jean Clinic, Rue du Meridien 100, 1210, Brussels, Belgium
| | - Radovan Fiala
- Department of Transplantation and Tissue Banking, Czech National Allograft Heart Valve Bank, Department of Cardiovascular Surgery, Motol University Hospital, and Second Faculty of Medicine Charles University in Prague, V Úvalu 84, 150 06, Prague, Czech Republic
| | - Jaroslav Špatenka
- Department of Transplantation and Tissue Banking, Czech National Allograft Heart Valve Bank, Department of Cardiovascular Surgery, Motol University Hospital, and Second Faculty of Medicine Charles University in Prague, V Úvalu 84, 150 06, Prague, Czech Republic
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Murdock K, Martin C, Sun W. Characterization of mechanical properties of pericardium tissue using planar biaxial tension and flexural deformation. J Mech Behav Biomed Mater 2017; 77:148-156. [PMID: 28915471 DOI: 10.1016/j.jmbbm.2017.08.039] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 08/21/2017] [Accepted: 08/25/2017] [Indexed: 11/26/2022]
Abstract
Flexure is an important mode of deformation for native and bioprosthetic heart valves. However, mechanical characterization of bioprosthetic leaflet materials has been done primarily through planar tensile testing. In this study, an integrated experimental and computational cantilever beam bending test was performed to characterize the flexural properties of glutaraldehyde-treated bovine and porcine pericardium of different thicknesses. A strain-invariant based structural constitutive model was used to model the pericardial mechanical behavior quantified through the bending tests of this study and the planar biaxial tests previously performed. The model parameters were optimized through an inverse finite element (FE) procedure in order to describe both sets of experimental data. The optimized material properties were implemented in FE simulations of transcatheter aortic valve (TAV) deformation. It was observed that porcine pericardium TAV leaflets experienced significantly more flexure than bovine when subjected to opening pressurization, and that the flexure may be overestimated using a constitutive model derived from purely planar tensile experimental data. Thus, modeling of a combination of flexural and biaxial tensile testing data may be necessary to more accurately describe the mechanical properties of pericardium, and to computationally investigate bioprosthetic leaflet function and design.
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Affiliation(s)
- Kyle Murdock
- Tissue Mechanics Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Caitlin Martin
- Tissue Mechanics Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Wei Sun
- Tissue Mechanics Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
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Brazile B, Wang B, Wang G, Bertucci R, Prabhu R, Patnaik SS, Butler JR, Claude A, Brinkman-Ferguson E, Williams LN, Liao J. On the bending properties of porcine mitral, tricuspid, aortic, and pulmonary valve leaflets. J Long Term Eff Med Implants 2015; 25:41-53. [PMID: 25955006 PMCID: PMC6721960 DOI: 10.1615/jlongtermeffmedimplants.2015011741] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The atrioventricular valve leaflets (mitral and tricuspid) are different from the semilunar valve leaflets (aortic and pulmonary) in layered structure, ultrastructural constitution and organization, and leaflet thickness. These differences warrant a comparative look at the bending properties of the four types of leaflets. We found that the moment-curvature relationships in atrioventricular valves were stiffer than in semilunar valves, and the moment-curvature relationships of the left-side valve leaflets were stiffer than their morphological analog of the right side. These trends were supported by the moment-curvature curves and the flexural rigidity analysis (EI value decreased from mitral, tricuspid, aortic, to pulmonary leaflets). However, after taking away the geometric effect (moment of inertia I), the instantaneous effective bending modulus E showed a reversed trend. The overall trend of flexural rigidity (EI: mitral > tricuspid > aortic > pulmonary) might be correlated with the thickness variations among the four types of leaflets (thickness: mitral > tricuspid > aortic > pulmonary). The overall trend of the instantaneous effective bending modulus (E: mitral < tricuspid < aortic < pulmonary) might be correlated to the layered fibrous ultrastructures of the four types of leaflets, of which the fibers in mitral and tricuspid leaflets were less aligned, and the fibers in aortic and pulmonary leaflets were highly aligned. We also found that, for all types of leaflets, moment-curvature relationships are stiffer in against-curvature (AC) bending than in with-curvature bending (WC), which implies that leaflets tend to flex toward their natural curvature and comply with blood flow. Lastly, we observed that the leaflets were stiffer in circumferential bending compared with radial bending, likely reflecting the physiological motion of the leaflets, i.e., more bending moment and movement were experienced in radial direction than circumferential direction.
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Affiliation(s)
- Bryn Brazile
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Bo Wang
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Guangjun Wang
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Robbin Bertucci
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Raj Prabhu
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Sourav S. Patnaik
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - J. Ryan Butler
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Andrew Claude
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Erin Brinkman-Ferguson
- Department of Clinical Sciences, College of Veterinary
Medicine, Mississippi State University, MS, 39762
| | - Lakiesha N. Williams
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
| | - Jun Liao
- Tissue Bioengineering Laboratory, Department of Biological
Engineering, Mississippi State University, MS, 39762
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Abstract
Shaped cartilage grafts can be used in the restoration of injured joints and the reconstruction of deformities of the head and neck. This study describes a novel method for altering cartilage shape, based on the hypothesis that mechanical loading coupled with in vitro tissue growth and remodeling facilitates tissue reshaping. Static bending deformations were imposed on strips of immature articular cartilage, and retention of the imposed shape and structural and biochemical measures of growth were assessed after 2, 4, and 6 days of incubation. The results show that mechanical reshaping of tissue is feasible, because shape retention was greater than 86% after 6 days of culture. The imposed mechanical deformations had little effect on measures of tissue viability or growth within the 6-day culture period. The addition of cycloheximide to the culture medium only slightly reduced the ability to reshape these tissues, but cycloheximide plus a lower culture temperature of 4 degrees C markedly inhibited the reshaping response. These results suggest a limited role for chondrocyte biosynthesis but a potentially important role for metabolic reactions in the cartilage matrix in the reshaping process. The ability to modulate cartilage shape in vitro may prove useful for tissue engineering of shaped cartilage grafts.
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Affiliation(s)
- Gregory M Williams
- Department of Bioengineering, University of California, San Diego, La Jolla 92093, USA
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