Development of Anisotropy in Fibroblast Populated Collagen Gels

2002 ◽  
Author(s):  
Stavros Thomopoulos ◽  
Vedran Knezevic ◽  
Kevin D. Costa ◽  
Jeffrey W. Holmes
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Load ◽  
The Other ◽  
Collagen Structure ◽  
Collagen Gels ◽  
Specific Loading ◽  
Anisotropic Mechanical Properties ◽  
Muscle Loading ◽  
Heart Wall

The development of anisotropic mechanical properties is critical for the successful tissue engineering of many soft tissues. Load bearing tissues naturally develop varying degrees of anisotropy, presumably in response to their specific loading environment. For example, the heart wall develops a collagen structure that varies in a predictable manner through its depth [1]. Tendon, on the other hand, develops a matrix that does not vary much in orientation and is highly aligned in the direction of muscle loading [2]. These varied levels of anisotropy may be due to inherent differences between the cells in each tissue, to differences in the mechanical load and boundary conditions seen by the cells, or to a combination of these factors.

A Structural Basis for Anisotropy in Cardiac Fibroblast Populated Collagen Gels

2004 ◽  
Author(s):  
Stavros Thomopoulos ◽  
Jeffrey W. Holmes
Keyword(s):  
Myocardial Infarction ◽  
Mechanical Properties ◽  
Collagen Fiber ◽  
Collagen Gel ◽  
Mechanical Anisotropy ◽  
Control Individual ◽  
Structural Basis ◽  
Collagen Gels ◽  
Specific Loading ◽  
Anisotropic Mechanical Properties

The development of anisotropic mechanical properties is critical for the successful function of many soft tissues. Load bearing tissues naturally develop varying degrees of anisotropy, presumably in response to their specific loading environment. For example, the scar tissue that forms after a myocardial infarction is structurally and mechanically anisotropic. To better understand the scar mechanics, we first need to develop structure-function relationships for collagen fiber networks. In order to improve the healing after myocardial infarction, a better understanding of the mechanical anisotropy is necessary. An in vitro collagen gel system can be used to control individual fiber network components and to determine the effect of each component on the mechanical properties of the gel. Previously, we demonstrated the ability to promote two different collagen gel structures, with two different levels of mechanical anisotropy [1]. The goal of the current study was to quantitatively relate the observed mechanical anisotropy to the collagen fiber structure. It was hypothesized that the anisotropy could be explained with a simple structural model, where the gel behavior is derived from the behavior of the individual fibers within the gel (i.e., the properties of the fibers, their orientation, and their level of slack).

scholarly journals An Investigation on the Correlation between the Mechanical Properties of Human Skull Bone, Its Geometry, Microarchitectural Properties, and Water Content

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Jik Hang Clifford Lee ◽  
Benjamin Ondruschka ◽  
Lisa Falland-Cheung ◽  
Mario Scholze ◽  
Niels Hammer ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Soft Tissues ◽  
Mechanical Load ◽  
Bone Microarchitecture ◽  
Mechanical Analysis ◽  
Assessment Criteria ◽  
Skull Bone ◽  
Human Skull ◽  
Detailed Imaging

With increasingly detailed imaging and mechanical analysis, modalities need arises to update methodology and assessment criteria for skull bone analysis to understand how bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The main aim was to analyze the effect of macroscopic and microstructural features, as well as periosteal attachment, on the mechanical properties of human skull bone. Fifty-six skull specimens from ethanol-phenoxyethanol-embalmed cadavers were prepared from two human cadavers. Assuming symmetry of the skull, all samples from one-half each were stripped of periosteum and dura mater, while the soft tissues were kept intact on the remaining samples on the contralateral side. The specimens were analyzed using microcomputed tomography to assess trabecular connectivity density, total surface area, and volume ratio. The specimens were loaded under three-point bend tests until fracture with optical co-registration. The bone fragments were then lyophilized to measure their water content. With increasingly detailed imaging and mechanical analysis modalities, there is a need to update methodology and assessment criteria for skull bone analysis to understand how the bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The mechanical properties were negatively correlated to bone thickness and water content. Conversely, most microarchitectural features did not influence either mechanical parameter. The correlation between mechanical response data and morphologic properties remains similar between the results of embalmed tissues presented here and fresh osseous tissue from literature data. The findings presented here add to the existing methodology to assess human skull for research purposes. The interaction between most microarchitectural features in ethanol-phenoxyethanol-embalmed embalmed skull samples and bending stress appear to be minute.

Characterizing the Influence of Scaffold Anisotropy on Engineered Heart Valve Leaflet Function

2009 ◽  
Author(s):  
David E. Schmidt ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Large Deformations ◽  
Pulmonary Valve ◽  
Mechanical Anisotropy ◽  
Prosthetic Valves ◽  
Anisotropic Mechanical Properties ◽  
Cell Sources ◽  
Biaxial Mechanical Properties ◽  
The Impact

Tissue engineered pulmonary valves (TEPV) represent a conceptually appealing alternative to current non-viable prosthetic valves and valved conduits for the repair of congenital or acquired lesions in pediatric patients. In addition to the identification of clinically feasible cell sources, engineered soft tissues such as the TEPV require scaffolds with anisotropic mechanical properties that undergo large deformations (not possible with current PGA/PLLA non-wovens) coupled with controllable biodegradative and cell-adhesive characteristics. Electrospun PEUU (ES-PEUU) scaffolds have been produced with tensile biaxial mechanical properties remarkably similar to the native pulmonary valve (Fig. 1-a), including the ability to undergo large physiologic strains and exhibit pronounced mechanical anisotropy. Moreover, a novel cell micro-integration technique has been developed that allows for successful cell integration directly into the scaffolds at the time of fabrication, eliminating cellular penetration problems. These encouraging results suggest that ES-PEUU scaffolds micro-integrated with the appropriate cells and can serve as successful TEPV scaffolds. In the present study, we conducted a finite element based analysis of TEPV leaflets (Fig. 1-b) under quasi-static transvalvular pressure to demonstrate the impact of ES-PEUU mechanical anisotropy on scaffold strain distributions.

Anisotropic Mechanical Properties of Soft Tissues by Magnetic Resonance Elastography

2009 ◽  
Author(s):  
Ravi Namani ◽  
Matthew Wood ◽  
Shelly E. Sakiyama-Elbert ◽  
Philip V. Bayly
Keyword(s):  
Mechanical Properties ◽  
Magnetic Resonance ◽  
Elastic Properties ◽  
Soft Tissues ◽  
Magnetic Resonance Elastography ◽  
Tissue Response ◽  
Noninvasive Technique ◽  
Empirical Measures ◽  
Anisotropic Mechanical Properties ◽  
Propagating Shear

Structure-function relationships incorporate anisotropy of soft tissues, to account for their direction-dependent loading response [1]. Empirical measures: fiber alignment and distribution have been used to describe soft tissue response due to cell-matrix interactions and applied loads [2, 3]. To complement these measures, noninvasive estimation of anisotropic mechanical properties is essential. Magnetic resonance elastography (MRE) is a noninvasive technique to obtain elastic properties form propagating shear waves [4]. Wave propagation patterns in MRE were found to vary with direction of tissue excitation and fiber orientation [5]. Accurate estimates of anisotropic elastic properties of soft tissues have yet to be obtained by MRE.

Directional, Regional, and Layer Variations of Mechanical Properties of Esophageal Tissue and its Interpretation Using a Structure-Based Constitutive Model

2005 ◽  
Vol 128 (3) ◽  
pp. 409-418 ◽  
Author(s):  
W. Yang ◽  
T. C. Fung ◽  
K. S. Chian ◽  
C. K. Chong
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Mechanical Behavior ◽  
Soft Tissues ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Material Parameters ◽  
Esophageal Tissue ◽  
Anisotropic Mechanical Properties ◽  
Mucosal Layer

The esophagus, like other soft tissues, exhibits nonlinear and anisotropic mechanical properties. As a composite structure, the properties of the outer muscle and inner mucosal layer are different. It is expected that the complex mechanical properties will induce nonhomogeneous stress distributions in the wall and nonuniform tissue remodeling. Both are important factors which influence the function of mechanosensitive receptor located in various layers of the wall. Hence, the characterization of the mechanical properties is essential to understand the neuromuscular motion of the esophagus. In this study, the uniaxial tensile tests were conducted along two mutually orthogonal directions of porcine esophageal tissue to identify the directional (circumferential and axial), regional (abdominal, thoracic, and cervical), and layer (muscle and mucosa) variations of the mechanical properties. A structure-based constitutive model, which took the architectures of the tissue’s microstructures into account, was applied to describe the mechanical behavior of the esophagus. Results showed that the constitutive model successfully described the mechanical behavior and provided robust estimates of the material parameters. In conclusion, the model was demonstrated to be a good descriptor of the mechanical properties of the esophagus and it was able to facilitate the directional, layer, and regional comparisons of the mechanical properties in terms of the associated material parameters.

Physical and Mechanical Properties of Tenun Pahang Fabrics using Alternative Yarns

2016 ◽  
Vol 13 (2) ◽  
pp. 67
Author(s):  
Engku Liyana Zafirah Engku Mohd Suhaimi ◽  
Jamil Salleh ◽  
Suzaini Abd Ghani ◽  
Mohamad Faizul Yahya ◽  
Mohd Rozi Ahmad
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Silk Fabrics ◽  
Recovery Angle ◽  
Made In

An investigation on the properties of Tenun Pahang fabric performances using alternative yarns was conducted. The studies were made in order to evaluate whether the Tenun Pahang fabric could be produced economically and at the same time maintain the fabric quality. Traditional Tenun Pahang fabric uses silk for both warp and weft. For this project, two alternative yarns were used which were bamboo and modal, which were a little lower in cost compared to silk. These yarns were woven with two variations, one with the yarns as weft only while maintaining the silk warp and the other with both warp and weft using the alternative yarns. Four (4) physical testings and three (3) mechanical testings conducted on the fabric samples. The fabric samples were evaluated including weight, thickness, thread density, crease recovery angle, stiffness and drapability. The results show that modal/silk and bamboo silk fabrics are comparable in terms of stiffness and drapability, hence they have the potential to replace 100% silk Tenun Pahang.

scholarly journals Influence of artificial aging: mechanical and physicochemical properties of dental composites under static and dynamic compression

2021 ◽  
Author(s):  
D. C. Gornig ◽  
R. Maletz ◽  
P. Ottl ◽  
M. Warkentin
Keyword(s):  
Mechanical Properties ◽  
Water Sorption ◽  
Artificial Aging ◽  
Filler Content ◽  
Dynamic Compression ◽  
The Other ◽  
Chemical Degradation ◽  
Dental Composites ◽  
Compression Tests ◽  
Acid Ph

Abstract Objective The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods Specimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F =  ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C). Results Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended.

scholarly journals The Effect of Different Annealing Strategies on the Microstructure Development and Mechanical Response of Austempered Steels

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1041
Author(s):  
Eliseo Hernandez-Duran ◽  
Luca Corallo ◽  
Tanya Ros-Yanez ◽  
Felipe Castro-Cerda ◽  
Roumen H. Petrov
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Mechanical Response ◽  
Steel Grade ◽  
The Other ◽  
Microstructure Development ◽  
Microstructural Refinement ◽  
Heterogeneous Distribution ◽  
Parent Austenite ◽  
Conventional Annealing

This study focuses on the effect of non-conventional annealing strategies on the microstructure and related mechanical properties of austempered steels. Multistep thermo-cycling (TC) and ultrafast heating (UFH) annealing were carried out and compared with the outcome obtained from a conventionally annealed (CA) 0.3C-2Mn-1.5Si steel. After the annealing path, steel samples were fast cooled and isothermally treated at 400 °C employing the same parameters. It was found that TC and UFH strategies produce an equivalent level of microstructural refinement. Nevertheless, the obtained microstructure via TC has not led to an improvement in the mechanical properties in comparison with the CA steel. On the other hand, the steel grade produced via a combination of ultrafast heating annealing and austempering exhibits enhanced ductility without decreasing the strength level with respect to TC and CA, giving the best strength–ductility balance among the studied steels. The outstanding mechanical response exhibited by the UFH steel is related to the formation of heterogeneous distribution of ferrite, bainite and retained austenite in proportions 0.09–0.78–0.14. The microstructural formation after UFH is discussed in terms of chemical heterogeneities in the parent austenite.

Ultrapurified Alginate Gel Containing Bone Marrow Aspirate Concentrate Enhances Cartilage and Bone Regeneration on Osteochondral Defects in a Rabbit Model

2021 ◽  
pp. 036354652110141
Author(s):  
Liang Xu ◽  
Atsushi Urita ◽  
Tomohiro Onodera ◽  
Ryosuke Hishimura ◽  
Takayuki Nonoyama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Marrow ◽  
Cell Transplantation ◽  
Cartilage Repair ◽  
Subchondral Bone ◽  
Bone Repair ◽  
Bone Marrow Aspirate ◽  
Defect Group ◽  
The Other ◽  
Osteochondral Defects

Background: Ultrapurified alginate (UPAL) gel implantation has been demonstrated as effective in cartilage repair for osteochondral defects; however, cell transplantation within UPAL gels would be required to treat larger defects. Hypothesis: The combination of UPAL gel and bone marrow aspirate concentrate (BMAC) would enhance cartilage repair and subchondral bone repair for large osteochondral defects. Study Design: Controlled laboratory study. Methods: A total of 104 osteochondral defects (1 defect per knee) of 52 rabbits were randomly divided into 4 groups (26 defects per group): defects without any treatment (Defect group), defects treated using UPAL gel alone (UPAL group), defects treated using UPAL gel containing allogenic bone marrow mesenchymal stromal cells (UPAL-MSC group), and defects treated using UPAL gel containing BMAC (UPAL-BMAC group). At 4 and 16 weeks postoperatively, macroscopic and histologic evaluations and measurements of repaired subchondral bone volumes of reparative tissues were performed. Collagen orientation and mechanical properties of the reparative tissue were assessed at 16 weeks. Results: The defects in the UPAL-BMAC group were repaired with hyaline-like cartilage with well-organized collagen structures. The histologic scores at 4 weeks were significantly higher in the UPAL-BMAC group (16.9 ± 2.0) than in the Defect group (4.7 ± 1.9; P < .05), the UPAL group (10.0 ± 3.3; P < .05), and the UPAL-MSC group (12.2 ± 2.9; P < .05). At 16 weeks, the score in the UPAL-BMAC group (24.4 ± 1.7) was significantly higher than those in the Defect group (9.0 ± 3.7; P < .05), the UPAL group (14.2 ± 3.9; P < .05), and the UPAL-MSC group (16.3 ± 3.6; P < .05). At 4 and 16 weeks, the macroscopic evaluations were significantly superior in the UPAL-BMAC group compared with the other groups, and the values of repaired subchondral bone volumes in the UPAL-BMAC group were significantly higher than those in the Defect and UPAL groups. The mechanical properties of the reparative tissues were significantly better in the UPAL-BMAC group than in the other groups. Conclusion: The implantation of UPAL gel containing BMAC-enhanced hyaline-like cartilage repair and subchondral bone repair of osteochondral defects in a rabbit knee model. Clinical Relevance: These data support the potential clinical application of 1-step treatment for large osteochondral defects using biomaterial implantation with cell transplantation.

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