Tissue Engineering
Sara Zadegan; Bahman Vahidi; Nooshin Haghighipour
Volume 16, Issue 3 , December 2022, , Pages 289-299
Abstract
Repairing osteochondral defects (OCD) remains a formidable challenge due to the high complexity of native osteochondral tissue and the limited self-repair capability of cartilage. In this regard, the development of osteochondral tissue engineering with scaffolds seeded with stem cells along with mechanical ...
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Repairing osteochondral defects (OCD) remains a formidable challenge due to the high complexity of native osteochondral tissue and the limited self-repair capability of cartilage. In this regard, the development of osteochondral tissue engineering with scaffolds seeded with stem cells along with mechanical stimulation has been considered by the researchers as a new proposed technique for the repair of this tissue. In this study, at first we fabricated an integrated and biomimetic trilayered Silk Fibroin (SF) scaffold containing SF nano fibers in each layer. Then fluid wall shear stress in different areas of the scaffold was predicted in dynamic cell culture condition under the inlet velocity of 0.4 ml/min in a perfusion bioreactor using finite elements and fluid-structure interactions methods. Finally, using the simulation results, osteogenesis and chondrogenesis of rabbit adipose derived stem cells (RADSCs) were analyzed. The results showed that this novel osteochondral graft has a seamlessly integrated layer structure and a high degree of pore interconnectivity. The average size of the pores in the bone layer, middle layer, and cartilage were 76, 152, and 102 microns, respectively. In addition, this biomimetic scaffold presented compressive moduli of 0.4 MPa and uitimate tensile strength of 10 MPa in the wet state. Also, based on the simulation analyses, the shear stress distribution is more uniform if the bone layer is exposed to the fluid inlet path which facilitates bone differentiation. Good adhesion and infiltration of cells were observed after 14 days dynamic culture. The results of expression analysis of differentiated genes in bone and cartilage layer containing RADSc after 21 days of culture under static and dynamic conditions showed that perfusion flow significantly upregulated the expression of bone and cartilage genes in the respective layers and downregulated the hypertrophy gene expression in intermediate layer of scaffold.
Tissue Engineering
Shahryar Ramezani Bajgiran; Maryam Saadatmand
Volume 11, Issue 3 , September 2017, , Pages 211-218
Abstract
Despite the advancements made in the tissue engineering, one of the obstacles in producing thick tissues is the means of oxygen transport to the deep layered cells of the engineered tissue and creating the network of veins inside the tissue. One way to overcome this problem is to create a microfluidic ...
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Despite the advancements made in the tissue engineering, one of the obstacles in producing thick tissues is the means of oxygen transport to the deep layered cells of the engineered tissue and creating the network of veins inside the tissue. One way to overcome this problem is to create a microfluidic network of channels inside the porous scaffold. These channels can both enhance the oxygenation and produce a mold for the natural vessels created by the angiogenesis cells. In this paper the dissolved oxygen distribution inside a 2D scaffold, which contains bifurcation based microfluidic channels, has been simulated by the means of computational fluid dynamics. To achieve this, the liquid flow and oxygen transport equations have been solved with considerations to the boundary conditions and suitable parameters. The oxygen transport has been found for the static scaffold, and the scaffolds made from the 0 order to third order of bifurcation with a bifurcation angle of 45 degrees. The results have shown that the scaffold with the second order of bifurcation has a better oxygen distribution and also more free area for the cell proliferation, which is consistent with the references. Next, the bifurcation angle was reduced to 35 degrees for the second order scaffold which resulted in an increase in the non-hypoxic area. Generally, by designing optimized angle of bifurcation based channels, a significant area can be oxygenated, while there will be sufficient surface available for cell proliferations.
Tissue Engineering
Mehdi Navidbakhsh; Mehdi Sajjadi; Simzar Hosseinzade
Volume 11, Issue 1 , May 2017, , Pages 51-61
Abstract
Tissue engineering is a promising approach for developing viable alternative for current treatments of cardiovascular diseases such as autologous vessel and synthetic bypass graft transplantation. One of the major challenges in development of an applicable tissue engineered vessel is proper design of ...
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Tissue engineering is a promising approach for developing viable alternative for current treatments of cardiovascular diseases such as autologous vessel and synthetic bypass graft transplantation. One of the major challenges in development of an applicable tissue engineered vessel is proper design of scaffold. Scaffolds are served to mimic the natural in vivo environment of cells where they interact and behave according to the mechanical cues obtained from the surrounding extracellular matrix. In recent studies alginate hydrogels containing silk fibroin protein have shown sufficient biological capability for vascular cells attachment, spreading, growth and metabolic activity. The purpose of this study was to evaluate the mechanical properties of mentioned hydrogels as scaffolds for vascular tissue engineering. Elastic modulus of linear region, yield strain and stress and compliance of three types of Alginate based hydrogel with different synthesis procedures were obtained via uniaxial tensile test of dogbone shaped specimens and thick-wall cylinders stress-strain equations. Results were compared to find the optimal formulation and synthesis process for mimicing mechanical properties of native tissue. Results of this study shows that while the proposed formulation of alginate/fibroin hydrogel lacks required mechanical stiffness, flexibility and strength; hybrid dual-network hydrogels of alginate/fibroin/polyacrylamide with a two-steps synthesis process and cross-linked by Fe3+ and Ca2+ cations promote suitable mechanical properties to be used as vascular tissue engineering scaffolds. Adding polyacrylamide to alginate-firoin hydrogels increased its elastisity modulus from 46 kPa to 480 kPa with a two step gelation process which makes it more similar to arteries wall tissue mechanically.
Tissue Engineering
Farnaz Ghorbani; Ali Zamanian; Hanie Noje Dehian
Volume 8, Issue 4 , February 2015, , Pages 399-409
Abstract
In this study, we fabricated 3-dimentional PLGA-gelatin scaffolds with aligned-oriented pores by freeze casting technique which is similar to Extra Cellular Matrix (ECM), and evaluated its effect on both physical and mechanical features. Dissolving synthetic (PLGA) and natural (Gelatin) polymers in common ...
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In this study, we fabricated 3-dimentional PLGA-gelatin scaffolds with aligned-oriented pores by freeze casting technique which is similar to Extra Cellular Matrix (ECM), and evaluated its effect on both physical and mechanical features. Dissolving synthetic (PLGA) and natural (Gelatin) polymers in common solvent was one of the strengths of this investigation. Scanning electron microscopy (SEM) micrographs indicated that scaffolds contained 95% interconnected pores with diameter about 50-400 µm in horizontal direction and 50-200 µm in vertical direction. Moreover, the results of mercury intrusion porosimetry represented diameter of pores in range of 100–300 µm. According to fourieres transform infrared (FTIR) spectrum there was no inappropriate interactions during processing. Additionally, mechanical analysis (3.2 MPa) of PLGA-gelatin constructs illustrated that polymeric scaffolds can withstand mechanical loads in freezing direction. Based on the water absorption (950%) and biodegradation results, samples can support cellular interactions and prevent their integrity during tissue regeneration. In brief, freeze casted PLGA-gelatin scaffolds can provide unidirectional matrix with desired physical and mechanical characters to regenerate lesions.
Tissue Engineering
Zakieh Alihemmati; Bahman Vahidi; Nooshin Haghighipour
Volume 8, Issue 2 , June 2014, , Pages 135-149
Abstract
Body cells, including mesenchymal stem cells are subject to a lot of mechanical forces. The type and magnitude of these forces are different in different physiological and pathological conditions. They cause a wide variety of cell responses and are able to change metabolisms and functions of the cell. ...
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Body cells, including mesenchymal stem cells are subject to a lot of mechanical forces. The type and magnitude of these forces are different in different physiological and pathological conditions. They cause a wide variety of cell responses and are able to change metabolisms and functions of the cell. Analysis of stem cell response to mechanical stimulation is very important in recognizing healthy and diseased condition of tissues and cells. Differentiation potential of mesenchymal stem cells to specialized cells makes them important cell sources in tissue engineering. In this study, atomic force microscopy and finite element method and used mechanical effects on a stem cellaresimulated which includes cell behavior due to strain andstress distributions in internal components of the cell. In this study, the ADINA software used to simulate mechanical behavior of the cell components (cell membrane, cytoplasm and nucleus) under a compressiveload. Results indicate mechanical response of stem cells in the body through which they can differentiate into bone cells and cartilage under compressive loads in the physiological range. This study has some considerable innovations as compared with the similar studies in the literature which is because of the kind of cells has been used (adipose-derived stem cells) as well as and also using precise material models for cell components based on the data extracted from laboratory tests for mechanical properties of the cell. Furthermore, this study can be considered as an important initial step for future studies on different patho-cells and analyzing their responses to mechanical loading using a similar method of this study to find new diagnostic methods. Also, it can be used to deepen pathological studies of the cells and the tissues.
Tissue Engineering
Zahra Saghaei Noosh Abadi; Atefe Aghajani; Mohammad Haghpanahi
Volume 7, Issue 1 , June 2013, , Pages 1-11
Abstract
We introduce how we may produce an experimental phantom for modeling the mechanical properties of soft tissue. Gelatin materials are used to construct the phantom. Our phantom comprises of two different types of tissue; tumor and background normal tissue. Weight ratio of the dry gelatin and deionized ...
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We introduce how we may produce an experimental phantom for modeling the mechanical properties of soft tissue. Gelatin materials are used to construct the phantom. Our phantom comprises of two different types of tissue; tumor and background normal tissue. Weight ratio of the dry gelatin and deionized water are obtained for producing the young’s modulus of 21 kPa and 102 kPa for the normal tissue and tumor, respectively. This phantom is used in ultrasound elastography with external excitation less than 5%.
Nano-Biomaterials
Zeynab Fereshteh; Mohammad Hossein Fathi; Reza Mozaffarinia
Volume 6, Issue 3 , June 2012, , Pages 177-193
Abstract
The aim of this study was to prepare and characterize the novel poly (ε-caprolactone) / Mg-doped fluorapatite nanoparticles (PCL / nMg-FA) composite scaffolds by electrospinning method. The optimized composite was achieved by changing of electrospinning parameters such as solvent, polymer concentration, ...
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The aim of this study was to prepare and characterize the novel poly (ε-caprolactone) / Mg-doped fluorapatite nanoparticles (PCL / nMg-FA) composite scaffolds by electrospinning method. The optimized composite was achieved by changing of electrospinning parameters such as solvent, polymer concentration, applied voltage, nozzle to collector distance and content of ceramic. It was shown that the diameter size of fibers decreased by adjusting the viscosity and conductivity solution. Optimal samples were studied with transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and thermogravimetric analysis (TGA). According to TEM and the X-ray maps of the scaffolds, Mg-FA particles were homogeneously dispersed into the nanofibers without any agglomeration. It is noteworthy that was not any surfactant in this study. Also results of XRD show no chemical reactions between polymeric solution components. Mechanical properties of the scaffolds were also evaluated. Results showed that tensional strength of scaffolds and also thermal stability increased by increasing the weight ratio of nanoparticles up to 5 wt. %.
Biomedical Image Processing / Medical Image Processing
Effat Yahaghi; Yashar Nohi; Amir Movafeghi; Hamid Soltanian Zadeh
Volume 4, Issue 1 , June 2010, , Pages 1-11
Abstract
Magnetic resonance imaging (MRI) is a non-ionizing method for identification and evaluation of soft tissue lesions. Perfusion MRI evaluates soft tissues by measuring changes in magnetization of water molecules due to a contrast agent. To this end, concentration curves in the plasma and tissue are estimated ...
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Magnetic resonance imaging (MRI) is a non-ionizing method for identification and evaluation of soft tissue lesions. Perfusion MRI evaluates soft tissues by measuring changes in magnetization of water molecules due to a contrast agent. To this end, concentration curves in the plasma and tissue are estimated by MRI and effective longitudinal relaxation time (T1eff) of the tissue was calculated. To interpret the results, the effects of water exchange on the effective longitudinal relaxation time should be studied. This work presents such a study in which the equations of two- and three-compartmental models of rat brain tissue are solved using Hion and Runge-Kutta numerical methods for different input functions and simulated by Monte Carlo method. Since the exchange of water and contrast agent among different tissue compartments is a diffusion phenomenon, Monte Carlo method is applicable. Results of the numerical methods were compared with those of Monte Carlo simulation. The results of the two methods were almost identical with a maximum relative difference of less than 1%. In this work, concentration of contrast agent in plasma is estimated from MRI of a rat brain tissue. This data is used in the Monte Carlo method to obtain T1eff and exchange rate constants. An advantage of our method is that T1eff is obtained from real data and not from the curve fitting method as commonly used. We derive concentration of contrast agent as a function of time in extravascular space for different constants (K). Then, the curves of simulated and real data were compared to obtain the exchange rate constant of each compartment. The results showed that K of an abnormal tissue was larger than that of the normal tissues. As such, this parameter may be used for diagnosis and treatment of the soft tissue diseases.
Tissue Engineering
Jafar Ai; Saeed Sarkar; Mohammad Ali Oghabian
Volume 4, Issue 2 , June 2010, , Pages 161-166
Abstract
Various reviews have shown that strong electromagnetic fields have negative effects on human health. This study focused on the effect of MRI radiation on liver functional test histometery of liver in adult male rats. For this purpose, we used an MRI device that could produce 1.5 T electromagnetic radiations, ...
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Various reviews have shown that strong electromagnetic fields have negative effects on human health. This study focused on the effect of MRI radiation on liver functional test histometery of liver in adult male rats. For this purpose, we used an MRI device that could produce 1.5 T electromagnetic radiations, and chose 22 Wistar rats as laboratory animal models. Rats were divided into two equal groups. The first group exposed to 1.5T electromagnetic radiation and RF radiation during a 30- minute MRI scan as experimental group. The control group experienced 1.5T electromagnetic radiation exposure without RF radiation by the same MRI device. The rats were anesthetized and blood samples were obtained from cardiac chambers to measure the serum levels of LDL, HDL, ALT, AST, ALP, total cholesterol, total protein, albumin, total billirobin, and direct bilirobin. Livers were then removed and the specimens fixed. Serial sections (5 μm thick) were prepared from livers and the diameter of hepatocytes and their nuclei were measured. The findings of the present study indicate that, there was a significant increase (P<0.5) in amount of HDL, ALT, AST, ALP, total billirobin, direct bilirobin and there was a significant decrease (P<0.5) in amount of total cholesterol, LDL, total protein, and albumin in experimental group by comparison with control group. But no significant differences were seen in the diameter of hepatocytes and their nuclei between both groups. The electromagnetic radiations of MRI device may influence the level of liver enzymes and liver function without any histomorphologically changes. Conducting clinical trial studies with human subjects is recommended.
Tissue Engineering
Fateme Shamsi; Mohsen Janmaleki; Nasser Fatouraee
Volume 3, Issue 4 , June 2009, , Pages 265-274
Abstract
In this study a mechanism was modeled to control the jet path of nanofibers produced by electrospinning through inducing a magnetic field over the jet path. Firstly, a model was developed for the jet path in which the fibers composed of a series of viscoelastic segments. Considering the mass and momentum ...
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In this study a mechanism was modeled to control the jet path of nanofibers produced by electrospinning through inducing a magnetic field over the jet path. Firstly, a model was developed for the jet path in which the fibers composed of a series of viscoelastic segments. Considering the mass and momentum conservation and maxwellian model of stretching viscoelastic segments using three equations governing the jet dynamics of the jet model in electrospinning, a program was developed in MATLAB with Runge–Kutta method. After ensuring the accuracy of the model, its behavior was evaluated in the presence of a magnetic field. The field induced a uniform force distribution over the jet. As the intensity of the magnetic field increased; the instability and bending radius of the jet reduced. The results of the research showed that utilizing a suitable mechanism for applying magnetic field can provide help in controlling the jet path and alignment of the nanofibers.
Biomechanics of Bone / Bone Biomechanics
Mahmoud Azami; Fathollah Moztarzadeh; Mohammad Rabiee
Volume 3, Issue 4 , June 2009, , Pages 275-284
Abstract
During past decade, using biomimetic approaches has received much attention by scientists in the field of tissue substitutes preparation. These approaches have been employed for synthesis of bone tissue engineering scaffolds in the case of either materials or synthesis methods. In this study, an apatite ...
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During past decade, using biomimetic approaches has received much attention by scientists in the field of tissue substitutes preparation. These approaches have been employed for synthesis of bone tissue engineering scaffolds in the case of either materials or synthesis methods. In this study, an apatite phase has been synthesized within gelatin hydrogel in biomimetic condition. The obtained composite hydrogel has changed to a porous scaffold with the application of freeze drying technique in order to be used in bone tissue engineering. To characterize the chemical composition and crystal structure of the synthesized precipitate within hydrogel, FTIR, XRD and TEM analysis were used. Surface morphology and porous structure of the scaffold were studied with SEM. SEM analysis was also used to investigate the quality of cultured osteoblast cells activity. Results approved formation of an apatite phase within gelatin hydrogel in biomimetic condition with crystallite size ranging between 7-10 nm. Porosity percentage of the obtained nanocomposite scaffold was about 82% with pores sizes in the range of 100-350μm. Young’s elastic modulus of the scaffold was comparable with that of the spongy bone. The osteoblast cells cultured on the scaffold showed adhesion, immigration and extracellular matrix excretion on the scaffold internal surfaces. Thus, obtained results indicated the potential ability of the prepared biomimetic bone tissue engineering scaffold to be used in bone tissue repair process.
Biomechanics of Bone / Bone Biomechanics
Masoume Haghbin Nazarpak; Farzane Pourasgari; Mohammad Nabi Sarbolouki
Volume 3, Issue 4 , June 2009, , Pages 291-298
Abstract
The scaffolds for bone tissue engineering should consider the functional requirements: porosity, biocompatibility, and biodegradability. In this study, porous Poly (lactic-co-glycolic acid)/Hydroxyapatite composites were prepared with different weight ratios. Porous samples were fabricated by freeze-extraction ...
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The scaffolds for bone tissue engineering should consider the functional requirements: porosity, biocompatibility, and biodegradability. In this study, porous Poly (lactic-co-glycolic acid)/Hydroxyapatite composites were prepared with different weight ratios. Porous samples were fabricated by freeze-extraction method, coated with triblock copolymer and sterilized by UV. Then, human mesenchymal stem cells were cultured on scaffolds. Microstructural studies with SEM suggest the formation of about 50 micrometer size porous structure and interconnected porosity so that cells adhesion within the structure is well in depth in coated samples. DAPI fluorescence microscopy showed cells adhesion to the coated scaffolds and cells diffusion into the pores. Also, direct assay of cell proliferation performed with MTT test showed that, cells grew on the scaffold similar to or more than control samples result. Therefore, these findings suggest that the triblock-coated Poly (lactic-coglycolic acid)/ Hydroxyapatite porous composite scaffolds could provide cells adhesion and proliferation and are appropriate matrices for bone tissue engineering.
Tissue Engineering
Mehdi Navidbakhsh; Milade Jafarnejad
Volume 3, Issue 4 , June 2009, , Pages 299-306
Abstract
The cancer changes the cytoskeleton of the cells .This change has some effects on the cell mechanobiology and will lead to some changes in the deformability of the cells. The moving ability of the cancer cells would be more than healthy cells. Thus, they can migrate through the tissue in human body. ...
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The cancer changes the cytoskeleton of the cells .This change has some effects on the cell mechanobiology and will lead to some changes in the deformability of the cells. The moving ability of the cancer cells would be more than healthy cells. Thus, they can migrate through the tissue in human body. In this survey, a valid FEM of a cancer cell is presented. Then the effects of various factors such as membrane thickness, elasticity, strain, and frequency response are studied during a process of being converted from normal cells into cancerous malignant cells. Besides, the initial mathematical models are provided. The results clarify that an increase in membrane elasticity, strain, and frequency would lead to increase in the reaction force. However, an increase in the membrane thickness decreases the reaction force.
Tissue Engineering
Mohsen Rabbani; Mohammad Tafazzoli Shadpour; Zahra Goli Malekabadi; Mohsen Janmaleki; Mohammad Taghi Khorasani; Mohammad Ali Shokrgozar
Volume 3, Issue 4 , June 2009, , Pages 307-314
Abstract
Vital function of the cell is correlated with the mechanical loads that the cell experiences. The cell shape and morphology are also related to its mechanical environments. Different methods have been proposed to obtain cell groups with the same morphology and alignment which considered desirable features ...
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Vital function of the cell is correlated with the mechanical loads that the cell experiences. The cell shape and morphology are also related to its mechanical environments. Different methods have been proposed to obtain cell groups with the same morphology and alignment which considered desirable features in tissue engineering applications. For instance, applying cyclic loading makes cells elongated and aligned as bundles in a specific direction to the tension axis. Applying static stretches also affect the cells morphology, extra-cellular matrix, enzymes secretion and genes expression. The effect of applying in vivo static stretch on cellular alignment was evaluated in this study. Human mesenchymal stem cells (hMSCs) were cultured on the elastic membrane, and then subjected to static stretch. The results demonstrated that applying a 10% static stretch for 24 hours aligns intra-structure actin filaments and applying a 20% static stretch had a significant effect on the arrangement of the oriented fibers.
Tissue Engineering
Rana Imani; Parisa Rahnama Moshtaq; Shahriar Hojati Emami; Sasan Jalili; Ali Mohammad Sharifi
Volume 3, Issue 4 , June 2009, , Pages 315-324
Abstract
Cell therapy based on cell encapsulation technology holds out the promise of the treatment of many diseases. The technology of cell encapsulation represents a strategy in which cells that secrete therapeutic products are immobilized and immunoprotected within polymeric and biocompatible carriers. Hydrogels ...
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Cell therapy based on cell encapsulation technology holds out the promise of the treatment of many diseases. The technology of cell encapsulation represents a strategy in which cells that secrete therapeutic products are immobilized and immunoprotected within polymeric and biocompatible carriers. Hydrogels - highly hydrated polymer networks- have ideal characteristics for this application because of good biocompatibility and mimicking natural ECM properties. They can homogeneously incorporate and suspend cells, growth factors, and other bioactive compounds. Temperature-sensitive hydrogels, which can form implants in situ in response to temperature change, from ambient to body temperature, have been extensively used in various cell encapsulation, and tissue repair. The objective of this study was preparation, Characterization and selection the optimum composition of agarose-gelatin blend hydrogel, for cell encapsulation application. In order to obtain hydrogel with appropriate properties, rheological, mechanical, and structural characteristics of obtained hydrogels were examined. Furthermore, the stability of samples was characterized by degradation and gelatin release measurements under physiological condition. Cell attachment and cytotoxicity analysis were also performed. Based on the results, hydrogel containing a 1:1 mixture of gelatin and agarose exhibited sol-to-gel transition near body temperature. Samples contain 50% agarose and more, exhibited mechanical integrity under physiological condition. Indentation test of the mechanical properties demonstrated viscoelastic behavior of the blend gelatin-agarose hydrogels under static load; however by increasing the agarose portion, hydrogel behaved more elastically. In vitro biocompatibility experiments showed undetectable cytotoxicity of the hydrogels. Also adding gelatin to agarose modified cell attachment behavior. The results of this study indicate the possibility of the potential use of prepared thermo-responsive agarose/gelatin conjugate with nearly same portion of two components as cell encapsulation carrier.
Tissue Engineering
Mohammad Haghpanahi; Mohammad Nikkhoo; Habibollah Peirovi
Volume 2, Issue 1 , June 2008, , Pages 47-56
Abstract
According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. ...
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According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. Then the standard Galerkin weighted residual method was used to form the finite element model. The implicit time integration schemes were applied to solve the nonlinear equations. The formulation accuracy and convergence for one dimensional case were examined with Simon's and Sun's analytical solutions and also Drost's experimental Data. It was shown that the mathematical model is in excellent agreement and has the capability to simulate the intervertebral disc response under different types of mechanical and electrochemical loading conditions. Finally, to have a short review of the capability of the model, a homogenous two dimensional version of the model was applied to simulate the response of a simple sagittal slice of the intervertebral disc.
Biomechanics of Bone / Bone Biomechanics
Seyed Mahmoud Rabiei; Fathollah Moztarzadeh; Mehran Solati Hashjin; Saeed Hesaraki
Volume 1, Issue 2 , June 2007, , Pages 105-110
Abstract
In this research, the influence of NaH2PO4.2H2O with different concentrations on setting time and compressive strength of bone cement based on hydroxyapatite was investigated. Hydroxyapatite cement is of calcium phosphate bone cements, which can be considered as the best substitute for hard tissues. ...
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In this research, the influence of NaH2PO4.2H2O with different concentrations on setting time and compressive strength of bone cement based on hydroxyapatite was investigated. Hydroxyapatite cement is of calcium phosphate bone cements, which can be considered as the best substitute for hard tissues. The powder phase of the cement was prepared from various compositions of calcium phosphates such: tricalcium phosphate (TCP), calcium carbonate (CaCO3) and montite (CaHPO4) as constant and the liquid part using NaH2PO4.2H2O solution with different concentrations. The influences of liquid/powder ratio L/P (ml/g) was investigated on the initial and final setting times and compressive strengths of the cement. According to the obtained results, with optimum concentrations of the liquid phase, this cement seems suitable for clinical applications.
Tissue Engineering
Farhad Farmanzad; Siamak Najarian; Mohammad Reza Eslami; Amir Saeed Seddighi
Volume 1, Issue 4 , June 2007, , Pages 281-288
Abstract
Two different types of computer modeling, i.e., the elastic and hyperelastic plane strain models were employed and compared with each other. Using finite element analysis, we determined a suitable model for describing the biomechanical behavior of the brain, especially the deformation and displacement ...
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Two different types of computer modeling, i.e., the elastic and hyperelastic plane strain models were employed and compared with each other. Using finite element analysis, we determined a suitable model for describing the biomechanical behavior of the brain, especially the deformation and displacement of the brain ventricles. The CT-Scan of an epidural hematoma patient was modeled using both approaches. Then, by varying the mechanical parameters of the tissue (i.e., C10, C01, E, and v) and the internal ventricular pressure, the displacement rate of the corresponding points in the ventricles was simulated. Finally, the results of the simulation were compared with those of the actual ventricles, and then, the data set with the least amount of error was identified. For various types of loadings and with different pressure gradients, the results of the simulation show that if the effect of an increase in the internal pressure of the ventricles is neglected, it will lead to unrealistic results. Particularly, in unidirectional strain loading with a pressure gradient of zero (AP= 0), the walls of the ventricle adjacent to the hematoma will collapse completely. The best results were obtained for the elastic model where ΔP = 9.4 mmHg (1.25 kPa) and for the hyperelastic model where ΔP = 7.5 mmHg (1.00 kPa). These findings are consistent with the clinical conditions of the patient. In the plane strain biomechanical modeling, for unidirectional strain loading (conditions which are similar to the application of navigation systems in surgeries), neglecting the geometry and the variation of the internal pressure of the ventricles will not lead to acceptable results. Taking into account the abovementioned parameters in describing the mechanical behavior of the brain (for epidural hematoma lesions), the elastic model (88.7% average relative accuracy) brings about better results compared with those of the hyperclastic model (86.9% average relative accuracy).
Biomechanics of Bone / Bone Biomechanics
Abdorreza Sheikh Mehdi Mesgar; Zahra Mohammadi; Fathollah Moztarzadeh; Mahtab Ashrafi Khouzani; Zeinab Sadat Mohammadi
Volume 1, Issue 1 , June 2007, , Pages 39-51
Abstract
Amorphous carbonated calcium phosphates (ACCPs) with different carbonate contents and Ca/P ratios were reproducible synthesized by the reaction parameters as low temperature, high pH value, using initial solutions of calcium and phosphate at low concentrations, and various amounts of carbonate, as well ...
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Amorphous carbonated calcium phosphates (ACCPs) with different carbonate contents and Ca/P ratios were reproducible synthesized by the reaction parameters as low temperature, high pH value, using initial solutions of calcium and phosphate at low concentrations, and various amounts of carbonate, as well as freeze drying of the precipitates. The addition of carbonate to the solutions led to form precipitates with higher Ca/P ratios with respect to the initial solutions. Heat treatment of freezedried ACCPs at 500 °C had no influence on their amorphous structure. The results of elemental carbon and thermal analysis showed that the carbonate may be eliminated in a wide range of temperature (500−1150oC). Dissolution rate of ACCPs in the simulated bone resorption medium was dependent to the contents of carbonate and remaining water. Dissolution rate of the specimens with higher carbonate contents was controlled by the carbonate content, but the amount of remaining water had major influence on the dissolution rate of the precipitates with lower carbonate contents. The dissolution kinetics was found to follow a shrinking-core model, with product layer as the ratedetermining step. Formation of an amorphous calcium phosphate and/or thermodynamically desirable dicalcium phosphate dihydrate as possible product layer prevents complete resorption of ACCPs under bone resorption conditions, and promotes osteoblastic activation process through nucleation and growth of biological apatite.
Tissue Engineering
Giti Torkamaan; Ali Fallah; Mahmoud Mofid; Sedighe Ghiasi; Ghadam Ali Talebi
Volume 1, Issue 3 , June 2007, , Pages 215-225
Abstract
In this study 22 male Guinea Pigs, 4-6 months old, weighting 400-450 g were used. A computer controlled indentor system was used to apply a controlled pressure. The applied pressure was 291 mmHg for 3 hours over the trochanter region of animal hind limb. The animals were divided in three groups; in group ...
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In this study 22 male Guinea Pigs, 4-6 months old, weighting 400-450 g were used. A computer controlled indentor system was used to apply a controlled pressure. The applied pressure was 291 mmHg for 3 hours over the trochanter region of animal hind limb. The animals were divided in three groups; in group 1, pressure was applied 3 hours continuously, in group 2, pressure was applied 90 minutes at two days and in group 3, Pressure was applied in two cycles of 90 minutes with 15 minutes rest between them. To study the biomechanical and histological changes, tissue was removed 7 days after pressure application. Uniaxial tensile test was performed at a deformation rate of 20 mm/min. In this test, the contralateral site on the experimental animal served as intra-animal control. Tissue biopsy was taken and stained with H&E and Trichorome for histological examination. Continuous pressure induced muscle necrosis. Also ultimate stress, stiffness, ultimate strain and area under the load-deformation curve decreased significantly. These results suggest that application of continuous pressure is the major cause of ischemia and necrosis of soft tissue.
Nano-Biomaterials
Babak Mostaghasi; Mohammad Hossein Fathi; Mahmoud Sheikh Zeinaddin; Sabihe Soleimanianzad
Volume 1, Issue 2 , June 2007, , Pages 137-146
Abstract
Hydroxyapatite (HA) is a well known candidate for many applications in dentistry and medicine such as bone replacement and regeneration and coatings for medical implants. Nano-crystalline HA exhibits improved mechanical properties and biocompatibility. To optimize the benefits of nano-sized precursors, ...
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Hydroxyapatite (HA) is a well known candidate for many applications in dentistry and medicine such as bone replacement and regeneration and coatings for medical implants. Nano-crystalline HA exhibits improved mechanical properties and biocompatibility. To optimize the benefits of nano-sized precursors, the particles must be of a uniform shape and size and have minimum degree of agglomeration. The aim of this study was to synthesize of nano-crystalline HA via the biomineralization route. For this purpose, an Iranian strain of Serratia (Serratia marcescens PTCC 1187) was utilized for the synthesis of nano-crystalline HA. The strain was cultivated. Then the pellet of S. marcescens PTCC 1187 was separated and exposed to Glycerol 2-phosphate and Calcium chloride. After 14 days of incubation at 37oC, the white precipitated material was separated. After drying and calcination at 600oC the powder was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR) techniques. The results showed that nano-structured HA powder was synthesized and the crystallinity of the powder was relatively high according to the standard. The particles of the powder were single crystal with the size of 25-30 nm. Moreover, the shape and size of the particles were relatively uniform and the agglomeration was lower comparing to the conventional methods. This powder could be used in the regeneration of bone defects, fabrication of medical, dental implants and also as a vector for pharmaceuticals and biological materials such as the genes.
Tissue Engineering
Abdorreza Sheikh Mehdi Mesgar; Zahra Mohammadi
Volume -1, Issue 1 , June 2004, , Pages 47-55
Abstract
The conditions for synthesis of amorphous calcium phosphates (ACPs) according to the crystallization principles were described. By selecting reaction parameters correctly (low temperature, high pH, immediate removing of water and using solutions containing calcium cations and phosphate anions at low ...
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The conditions for synthesis of amorphous calcium phosphates (ACPs) according to the crystallization principles were described. By selecting reaction parameters correctly (low temperature, high pH, immediate removing of water and using solutions containing calcium cations and phosphate anions at low concentrations), full ACPs can be reproducibly synthesized. The X-ray diffraction patterns of synthesized amorphous specimens were showed a characteristic broad peak. The Ca/P ratio of the resulting precipitates was weakly dependent on the initial Ca/P ratio. Solubility of synthesized specimens in simulated osteoclastic activity conditions was showed that the rate of dissolution would be decreased with increasing crystallinity level. The synthesized amorphous calcium phosphates showed the highest dissolution rate in the simulated solution, and can be a suitable candidate for using in the field of hard tissue engineering applications.
Tissue Engineering
Karim Asgarzadeh Tabrizi; Fariba Ourang
Volume -1, Issue 1 , June 2004, , Pages 57-64
Abstract
Gelatin is a protein which is derived from the organic constituent of bone (collagen). Combination of this protein with the inorganic constituent of bone (hydroxyapatite) may provide closer properties to the natural bone. In this study, a biodegradable composite scaffold based on gelatin and hydroxyapatite ...
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Gelatin is a protein which is derived from the organic constituent of bone (collagen). Combination of this protein with the inorganic constituent of bone (hydroxyapatite) may provide closer properties to the natural bone. In this study, a biodegradable composite scaffold based on gelatin and hydroxyapatite was prepared as a substitute for bone tissue. To increase the biocompatibility of this, composite, its fabrication was carried out without using any organic solvent. Porosities obtained were spontaneously achieved without any porogen. The pore morphology indicated a high interconnectivity with diameters ranging from 50 to 200 micrometers, which seems appropriate for bone tissue engineering applications. In order to study the biocompatibility of the scaffolds, mouse fibroblastic cells were used. After 24-hour cell culture period in vitro, suitable cell attachment was observed showing high biocompatibility for all the samples. Further examinations demonstrated that the best biocompatibility is obtained for the composite of 50 wt% hydroxyapatite and 50 wt% gelatin.
Tissue Engineering
Giti Torkamaan; Ali Akbar Sharafi; Ali Fallah; Hamid Reza Katouzian; Mahmoud Mofid
Volume -1, Issue 1 , June 2004, , Pages 93-100
Abstract
Pressure ulcers are areas of tissue necrosis that tend to develop when tissue is compressed between a bony prominence and an external surface. Normal structure and physiological function of tissue viability are recognized but mechanism of tissue breakdown is unknown. In this study, an attempt has been ...
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Pressure ulcers are areas of tissue necrosis that tend to develop when tissue is compressed between a bony prominence and an external surface. Normal structure and physiological function of tissue viability are recognized but mechanism of tissue breakdown is unknown. In this study, an attempt has been made to recognize the tissue mechanical changes after pressure application using 61 male albino guinea pigs, 4-6 months old, weighing 300-450 g. A computer controlled indentor system was developed to induce pressure sore. This system is capable of monitoring and adjusting the applied pressure, friction and shearing force throughout the experiment. The applied force remained within ±10g of desired target force. The applied pressures were at 291 and 387 mmHg for 1,3 or 5 hours over the trochanter region of animal hind limb. The tissue was removed and blood was taken immediately, 2 and 7 days after pressure release. Uniaxial tensile test was performed using deformation rate of 20 mm/min. In this test, the contralateral site on the experimental animal served as intra-animal control. Full- thickness biopsy was taken and stained with H & E, trichrome and orcein for histological examination. Results of tensile tests showed that the maximum tensile strength (Fmax), stress and the area under load-deformation curve (work) have decreased significantly 7 days after pressure application (P<0.05). Histological study immediately and 2 days after force release, showed an increase in cellularity and inflammatory cells infiltration. Muscle necrosis and reduction of the skin fibers density were observed 7 days after load release. Serum CPK (2 days after) was increased. The amount of lactic acid as well as phosphorus immediately and 2 days after pressure also increased (P<0.05). Finally it was distinguished that pressure changed the biomechanical properties of skin and muscle. Decrease of tissue resistance was consistent with the histological findings as well as elevation of muscle specific enzymes in blood. It was also observed that pressure resulted in the tissue ischemia and breakdown.
