On the Bio-Mechanical Properties of a Dual-Porous Osteochondral Scaffold

2008 ◽  
Author(s):  
Hajar Sharif ◽  
Yaser Shanjani ◽  
Mihaela Vlasea ◽  
Ehsan Toyserkani
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Porous Scaffold ◽  
Element Model ◽  
Homogeneous Distribution ◽  
Porous Scaffolds ◽  
Osteochondral Scaffold ◽  
Apparent Stiffness

This work is concerned with the finite element modeling of a dual-porous scaffold including both fine and coarse pores. The layer with coarse pores is suitable for bone in vivo ingrowth and the finer pore layer is appropriate for in vitro cartilage culturing. Such scaffolds can be extensively used for repairing of osteochondral defects. The bio-mechanical properties of the proposed scaffold, including apparent stiffness and strain-based capability of the cell ingrowth, are identified using a 3D Finite Element Model. Moreover, to study the effect of the second layer on the strength of the whole scaffold, the stiffness of the dual and single-porous scaffolds was compared. The result of this study shows that the stiffness decreases by adding the second layer to a single-porous scaffold. Additionally, principal strain histograms of the single and the dual-porous scaffolds are compared to assess the effect of added layer on the capability for cell ingrowth stimulation of the whole structure. According to the results, the dual-porous scaffold provides more homogeneous distribution but a smaller amount of micro-strains which may cause different cell-growth behavior.

A Finite Element Prediction of Strain on Cells in a Highly Porous Collagen-Glycosaminoglycan Scaffold

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
A. J. F. Stops ◽  
L. A. McMahon ◽  
D. O’Mahoney ◽  
P. J. Prendergast ◽  
P. E. McHugh
Keyword(s):  
Tissue Engineering ◽  
Finite Element ◽  
Load Transfer ◽  
Porous Scaffold ◽  
Computational Prediction ◽  
Element Model ◽  
Porous Scaffolds ◽  
Wide Range ◽  
A Cell

Tissue engineering often involves seeding cells into porous scaffolds and subjecting the scaffold to mechanical stimulation. Current experimental techniques have provided a plethora of data regarding cell responses within scaffolds, but the quantitative understanding of the load transfer process within a cell-seeded scaffold is still relatively unknown. The objective of this work was to develop a finite element representation of the transient and heterogeneous nature of a cell-seeded collagen-GAG-scaffold. By undertaking experimental investigation, characteristics such as scaffold architecture and shrinkage, cellular attachment patterns, and cellular dimensions were used to create a finite element model of a cell-seeded porous scaffold. The results demonstrate that a very wide range of microscopic strains act at the cellular level when a sample value of macroscopic (apparent) strain is applied to the collagen-GAG-scaffold. An external uniaxial strain of 10% generated a cellular strain as high as 49%, although the majority experienced less than ∼5% strain. The finding that the strain on some cells could be higher than the macroscopic strain was unexpected and proves contrary to previous in vitro investigations. These findings indicate a complex system of biophysical stimuli created within the scaffolds and the difficulty of inducing the desired cellular responses from artificial environments. Future in vitro studies could also corroborate the results from this computational prediction to further explore mechanoregulatory mechanisms in tissue engineering.

Strain Measurement in Coronary Arteries Using Intravascular Ultrasound and Deformable Images

2002 ◽  
Vol 124 (6) ◽  
pp. 734-741 ◽  
Author(s):  
Alexander I. Veress ◽  
Jeffrey A. Weiss ◽  
Grant T. Gullberg ◽  
D. Geoffrey Vince ◽  
Richard D. Rabbitt
Keyword(s):  
Finite Element ◽  
Intravascular Ultrasound ◽  
Coronary Arteries ◽  
Strain Distribution ◽  
Plaque Rupture ◽  
Element Model ◽  
Cross Sectional ◽  
Image Pairs

Atherosclerotic plaque rupture is responsible for the majority of myocardial infarctions and acute coronary syndromes. Rupture is initiated by mechanical failure of the plaque cap, and thus study of the deformation of the plaque in the artery can elucidate the events that lead to myocardial infarction. Intravascular ultrasound (IVUS) provides high resolution in vitro and in vivo cross-sectional images of blood vessels. To extract the deformation field from sequences of IVUS images, a registration process must be performed to correlate material points between image pairs. The objective of this study was to determine the efficacy of an image registration technique termed Warping to determine strains in plaques and coronary arteries from paired IVUS images representing two different states of deformation. The Warping technique uses pointwise differences in pixel intensities between image pairs to generate a distributed body force that acts to deform a finite element model. The strain distribution estimated by image-based Warping showed excellent agreement with a known forward finite element solution, representing the gold standard, from which the displaced image was created. The Warping technique had a low sensitivity to changes in material parameters or material model and had a low dependency on the noise present in the images. The Warping analysis was also able to produce accurate strain distributions when the constitutive model used for the Warping analysis and the forward analysis was different. The results of this study demonstrate that Warping in conjunction with in vivo IVUS imaging will determine the change in the strain distribution resulting from physiological loading and may be useful as a diagnostic tool for predicting the likelihood of plaque rupture through the determination of the relative stiffness of the plaque constituents.

scholarly journals Applicability assessment of a stent-retriever thrombectomy finite-element model

2020 ◽  
Vol 11 (1) ◽  
pp. 20190123 ◽  
Author(s):  
Giulia Luraghi ◽  
Jose Felix Rodriguez Matas ◽  
Gabriele Dubini ◽  
Francesca Berti ◽  
Sara Bridio ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Blood Circulation ◽  
Blood Clot ◽  
Invasive Procedure ◽  
Element Model ◽  
Stent Deployment ◽  
Numerical Finite Element

An acute ischaemic stroke appears when a blood clot blocks the blood flow in a cerebral artery. Intra-arterial thrombectomy, a mini-invasive procedure based on stent technology, is a mechanical available treatment to extract the clot and restore the blood circulation. After stent deployment, the clot, trapped in the stent struts, is pulled along with the stent towards a receiving catheter. Recent clinical trials have confirmed the effectiveness and safety of mechanical thrombectomy. However, the procedure requires further investigation. The aim of this study is the development of a numerical finite-element-based model of the thrombectomy procedure. In vitro thrombectomy tests are performed in different vessel geometries and one simulation for each test is carried out to verify the accuracy and reliability of the proposed numerical model. The results of the simulations confirm the efficacy of the model to replicate all the experimental setups. Clot stress and strain fields from the numerical analysis, which vary depending on the geometric features of the vessel, could be used to evaluate the possible fragmentation of the clot during the procedure. The proposed in vitro / in silico comparison aims at assessing the applicability of the numerical model and at providing validation evidence for the specific in vivo thrombectomy outcomes prediction.

Inverse Estimation of the In Vivo Mechanical Properties of the Human Cornea

2000 ◽  
Author(s):  
Shou-sung Chang ◽  
Peter M. Pinsky
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Human Cornea ◽  
Corneal Tissue ◽  
Shear Moduli ◽  
Inverse Estimation ◽  
Nonlinear Finite Element Model

Abstract Various forms of refractive surgery for vision correction have come into clinical practice in which the corneal tissue is either incised, removed, added to, or redistributed. The outcomes of these procedures must be to a large extent determined by the intrinsic mechanical properties of the major structural layer of the cornea, the stroma1. If these mechanical properties, principally the Young’s modulus and shear modulus, are established for the human cornea, it will be possible to include them in a finite element model of the stroma that can help predict the outcome of keratorefractive procedures. In this study an opto-mechanical testing device was developed to measure the contour of a cornea deformed in situ by a mechanical probe. A nonlinear finite element model of the cornea was then constructed to simulate the experiment for use in inverse estimation of the in vivo Young’s and shear moduli of an individual eye.

scholarly journals Measurement of the Persistence Length of Cytoskeletal Filaments using Curvature Distributions

2018 ◽  
Author(s):  
Pattipong Wisanpitayakorn ◽  
Keith J. Mickolajczyk ◽  
William O. Hancock ◽  
Luis Vidali ◽  
Erkan Tüzel
Keyword(s):  
Mechanical Properties ◽  
Actin Filaments ◽  
Imaging System ◽  
Average Length ◽  
Persistence Length ◽  
Small Data ◽  
Data Sets ◽  
Apparent Stiffness

AbstractCytoskeletal filaments such as microtubules and actin filaments play important roles in the mechanical integrity of cells and the ability of cells to respond to their environment. Measuring the mechanical properties of cytoskeletal structures is crucial for gaining insight into intracellular mechanical stresses and their role in regulating cellular processes. One of the ways to characterize these mechanical properties is by measuring their persistence length, the average length over which filaments stay straight. There are several approaches in the literature for measuring filament deformations, including Fourier analysis of images obtained using fluorescence microscopy. Here, we show how curvature distributions can be used as an alternative tool to quantify bio-filament deformations, and investigate how the apparent stiffness of filaments depends on the resolution and noise of the imaging system. We present analytical calculations of the scaling curvature distributions as a function of filament discretization, and test our predictions by comparing Monte Carlo simulations to results from existing techniques. We also apply our approach to microtubules and actin filaments obtained fromin vitrogliding assay experiments with high densities of non-functional motors, and calculate the persistence length of these filaments. The presented curvature analysis is significantly more accurate compared to existing approaches for small data sets, and can be readily applied to bothin vitroorin vivofilament data through the use of an ImageJ plugin we provide.

scholarly journals Characterization and in vitro assessment of three-dimensional extrusion Mg-Sr codoped SiO2-complexed porous microhydroxyapatite whisker scaffolds for biomedical engineering

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Chengyong Li ◽  
Tingting Yan ◽  
Zhenkai Lou ◽  
Zhimin Jiang ◽  
Zhi Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Proliferation ◽  
Pore Size ◽  
Osteogenic Differentiation ◽  
Bone Repair ◽  
Porous Scaffold ◽  
Porous Scaffolds ◽  
Sprague Dawley ◽  
Active Elements

Abstract Background Large bone defects have always been a great challenge for orthopedic surgeons. The use of a good bone substitute obtained by bone tissue engineering (BTE) may be an effective treatment method. Artificial hydroxyapatite, a commonly used bone defect filler, is the main inorganic component of bones. Because of its high brittleness, fragility, and lack of osteogenic active elements, its application is limited. Therefore, its fragility should be reduced, its osteogenic activity should be improved, and a more suitable scaffold should be constructed. Methods In this study, a microhydroxyapatite whisker (mHAw) was developed, which was doped with the essential trace active elements Mg2+ and Sr2+ through a low-temperature sintering technique. After being formulated into a slurry, a bionic porous scaffold was manufactured by extrusion molding and freeze drying, and then SiO2 was used to improve the mechanical properties of the scaffold. The hydrophilicity, pore size, surface morphology, surface roughness, mechanical properties, and release rate of the osteogenic elements of the prepared scaffold were detected and analyzed. In in vitro experiments, Sprague–Dawley (SD) rat bone marrow mesenchymal stem cells (rBMSCs) were cultured on the scaffold to evaluate cytotoxicity, cell proliferation, spreading, and osteogenic differentiation. Results Four types of scaffolds were obtained: mHAw-SiO2 (SHA), Mg-doped mHAw-SiO2 (SMHA), Sr-doped mHAw-SiO2 (SSHA), and Mg-Sr codoped mHAw-SiO2 (SMSHA). SHA was the most hydrophilic (WCA 5°), while SMHA was the least (WCA 8°); SMHA had the smallest pore size (247.40 ± 23.66 μm), while SSHA had the largest (286.20 ± 19.04 μm); SHA had the smallest Young's modulus (122.43 ± 28.79 MPa), while SSHA had the largest (188.44 ± 47.89 MPa); and SHA had the smallest compressive strength (1.72 ± 0.29 MPa), while SMHA had the largest (2.47 ± 0.25 MPa). The osteogenic active elements Si, Mg, and Sr were evenly distributed and could be sustainably released from the scaffolds. None of the scaffolds had cytotoxicity. SMSHA had the highest supporting cell proliferation and spreading rate, and its ability to promote osteogenic differentiation of rBMSCs was also the strongest. Conclusions These composite porous scaffolds not only have acceptable physical and chemical properties suitable for BTE but also have higher osteogenic bioactivity and can possibly serve as potential bone repair materials.

scholarly journals Three dimensional porous scaffolds derived from collagen, elastin and fibrin proteins orchestrate adipose tissue regeneration

2021 ◽  
Vol 12 ◽  
pp. 204173142110192
Author(s):  
Prasad Sawadkar ◽  
Nandin Mandakhbayar ◽  
Kapil D Patel ◽  
Jennifer Olmas Buitrago ◽  
Tae Hyun Kim ◽  
...  
Keyword(s):  
Stem Cells ◽  
Soft Tissue ◽  
Porous Scaffold ◽  
Pathological Condition ◽  
Donor Site ◽  
Porous Scaffolds ◽  
Adipose Derived Stem Cells ◽  
Natural Polymers

Current gold standard to treat soft tissue injuries caused by trauma and pathological condition are autografts and off the shelf fillers, but they have inherent weaknesses like donor site morbidity, immuno-compatibility and graft failure. To overcome these limitations, tissue-engineered polymers are seeded with stem cells to improve the potential to restore tissue function. However, their interaction with native tissue is poorly understood so far. To study these interactions and improve outcomes, we have fabricated scaffolds from natural polymers (collagen, fibrin and elastin) by custom-designed processes and their material properties such as surface morphology, swelling, wettability and chemical cross-linking ability were characterised. By using 3D scaffolds, we comprehensive assessed survival, proliferation and phenotype of adipose-derived stem cells in vitro. In vivo, scaffolds were seeded with adipose-derived stem cells and implanted in a rodent model, with X-ray microtomography, histology and immunohistochemistry as read-outs. Collagen-based materials showed higher cell adhesion and proliferation in vitro as well as higher adipogenic properties in vivo. In contrast, fibrin demonstrated poor cellular and adipogenesis properties but higher angiogenesis. Elastin formed the most porous scaffold, with cells displaying a non-aggregated morphology in vitro while in vivo elastin was the most degraded scaffold. These findings of how polymers present in the natural polymers mimicking ECM and seeded with stem cells affect adipogenesis in vitro and in vivo can open avenues to design 3D grafts for soft tissue repair.

scholarly journals Poly(lactide- co -glycolide) porous scaffolds for tissue engineering and regenerative medicine

2012 ◽  
Vol 2 (3) ◽  
pp. 366-377 ◽  
Author(s):  
Zhen Pan ◽  
Jiandong Ding
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Regenerative Medicine ◽  
Porous Scaffolds ◽  
Plga Scaffold ◽  
Degradation Rates ◽  
Long Time ◽  
Facile Fabrication

Porous scaffolds fabricated from biocompatible and biodegradable polymers play vital roles in tissue engineering and regenerative medicine. Among various scaffold matrix materials, poly(lactide- co -glycolide) (PLGA) is a very popular and an important biodegradable polyester owing to its tunable degradation rates, good mechanical properties and processibility, etc. This review highlights the progress on PLGA scaffolds. In the latest decade, some facile fabrication approaches at room temperature were put forward; more appropriate pore structures were designed and achieved; the mechanical properties were investigated both for dry and wet scaffolds; a long time biodegradation of the PLGA scaffold was observed and a three-stage model was established; even the effects of pore size and porosity on in vitro biodegradation were revealed; the PLGA scaffolds have also been implanted into animals, and some tissues have been regenerated in vivo after loading cells including stem cells.

Finite element model of mechanical properties of human skin in vivo under indentation coupled with MRI technique

2006 ◽  
Vol 39 ◽  
pp. S395
Author(s):  
V. Tran ◽  
F. Charleux ◽  
D. Capron ◽  
A. Ehrlacher ◽  
M.C. Hobatho
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Model ◽  
Human Skin ◽  
Element Model

Finite-element analysis of stress in the canine diaphragm

1994 ◽  
Vol 76 (5) ◽  
pp. 2070-2075 ◽  
Author(s):  
S. S. Margulies ◽  
G. T. Lei ◽  
G. A. Farkas ◽  
J. R. Rodarte
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Model ◽  
Biaxial Stress ◽  
Principal Stresses ◽  
Element Analysis ◽  
Transdiaphragmatic Pressure ◽  
Sigma 1

Stress in the diaphragm, transdiaphragmatic pressure, and diaphragm shape are interrelated by a balance of forces. Using precise in vivo measurements of diaphragm shape and transdiaphragmatic pressure distribution in combination with finite-element analysis (ANSYS), we determined the direction and magnitude of stress in the passive diaphragm at relaxation volume. Lead spheres sutured along muscle bundles identified muscle bundle location and orientation in vivo. The x, y, and z coordinates of the lead spheres and entire surface of the diaphragm, excluding the zone of apposition, were determined to within 1.4 mm. Thin shell elements were used to construct a finite-element model of the diaphragm with a 2.1- to 4.2-mm internodal spacing. The diaphragm was assumed to have a uniform thickness of 2.5 mm, and magnitude and direction of the principal stresses were computed. The results show that 1) diaphragm stress is nonuniform and anisotropic (i.e., varies both with location on diaphragm surface and direction examined), 2) largest stress (sigma 1) is aligned with muscle bundles and is two to four times larger than sigma 2 (perpendicular to sigma 1 in diaphragm plane), and 3) stress along the muscle bundles is larger in vivo under conditions of biaxial stress than at same length in vitro under uniaxial stress. Although diaphragm stress and tension have often been assumed to be uniform, our finding that stress is oriented primarily along the muscle fibers should be considered in future models of the diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

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