Scaffolding / Bio-Scaffolds
Seyedeh Sara Kamali; Haniye Abdi Kordlar; Maryam Saadatmand; Shohreh Mashayekhan
Volume 14, Issue 1 , May 2020, , Pages 43-53
Abstract
Successful cell culture in large scale 3D scaffolds in tissue engineering is still challenging and requires full control over physical, chemical and mechanical properties of the applied scaffolds. Recently, using printers for the fabrication of 3D scaffold with a structural arrangement of fibers has ...
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Successful cell culture in large scale 3D scaffolds in tissue engineering is still challenging and requires full control over physical, chemical and mechanical properties of the applied scaffolds. Recently, using printers for the fabrication of 3D scaffold with a structural arrangement of fibers has been extensively developed, because it is possible to define the structure of scaffold geometry before manufacturing. The aim of this study was the investigation of the effective geometrical parameters on the 3D symmetric porous scaffold from the mass and momentum transport phenomena point of view. In this way, the mass and momentum transfer equations were solved using COMSOL Multiphysics software. In 3D scaffolds, the optimum model is the one that can provide a more appropriate environment for the cultured cells leading an increase in the attached cell number. The oxygen concentration reaching the bone cells should be greater than 0.02 mol/m3 in order to prevent cell death. Moreover, the fluid shear stress regime must be such that (between 10-5 to 10-3 Pa) it could not cause cell detachment. After studying the results of the simulation and changing the different parameters such as fiber diameter, fiber distance and the width of the channels, the appropriate structure was obtained regarding maximum shear stress and minimum oxygen concentration, and then the effect of fluid flow rate on maximum shear stress was examined for the appropriate structure. The optimized model with a fiber diameter of 0.25 mm, a fiber distance of 0.25 mm, and a channel width of 0.25 mm was proposed that fluid flow inlet velocity was 5×10-5 m/s.
Nano-Biomaterials
Mohammad Nazari; Razieh Solgi; Ghazale Graily; Seyed Rabi Mahdavi; Alireza Shirazi
Volume 12, Issue 1 , June 2018, , Pages 11-23
Abstract
In clinical studies, it is difficult to determine the temperature distribution throughout both tumor and normal tissue during hyperthermia treatment, since temperatures are sampled at only a limited number of locations with conventional sensors. Simulation studies can help physicians understand better ...
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In clinical studies, it is difficult to determine the temperature distribution throughout both tumor and normal tissue during hyperthermia treatment, since temperatures are sampled at only a limited number of locations with conventional sensors. Simulation studies can help physicians understand better the effects of the treatment. In this study, three 2D tumor models are built in the COMSOL software environment based on the images of nano-particle distributions in sliced PC3, DU145 and LAPC4 tumors. The images are pre-processed in MATLAB before being imported into COMSOL. A uniform distribution model is added as a control group. Temperature distribution, maximum temperature, time to reach steady state, CEM43, iso-effective dose and heat flux at tumor-tissue boundary are analyzed to evaluate the effect of the nano-particle distribution on hyperthermia treatment. The results indicate that a more concentrated nano-particle distribution is better in damaging diseased tissue than the uniform distribution under high heating power. A more uniform distribution is better than the concentrated distribution under low heating power. For concentrated nano-particle distributions, the location where the nano-particles are concentrated influences tissue damage: a more centered one has a better effect. Tumor tissue is more likely to be defective.
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.
Biomechanics / Biomechanical Engineering
Aminreza Noghrehabadi; Mohammad Hosein Heidarshenas; Reza Bahoosh
Volume 10, Issue 2 , August 2016, , Pages 123-136
Abstract
A two-dimensional-in-space mathematical model of amperometric micro biosensors with selective and perforated membranes has been proposed and analyzed. The model involves the geometry of micro or nano meter holes partially or fully filled with an enzyme. The model is based on a system of the reaction-diffusion ...
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A two-dimensional-in-space mathematical model of amperometric micro biosensors with selective and perforated membranes has been proposed and analyzed. The model involves the geometry of micro or nano meter holes partially or fully filled with an enzyme. The model is based on a system of the reaction-diffusion equations containing a nonlinear term related to the Michaelis-Menten enzymatic reaction. In this study, in order to generate general equation, first, dimensionless parameters are introduced and then by replacing them into governing equation are converted to dimensionless equations.The general equations have been solved numerically in 2D space.. Using numerical simulation of the biosensor action, the influence of the geometry of the holes as well as of the filling level of the enzyme in the holes on the biosensor response was investigated. For this purpose three different geometries including cylindrical, upright circular and downright circular cone for cavities are considered and the impact of these geometries on the response of the biosensor in different levels of enzyme are obtained. Biosensor's respond based on rate of enzyme level variations to slope of the cone variations are determined. In the biosensor, as the level of enzyme rises in all three geometries, the biosensor output current increases. Under the same conditions, the sensitivity of biosensor in upright circular cone is more than the other two geometries and increases with a decrease in conical gradient. As long as the enzymatic properties are the same, the more biosensor's number, the more sensitivity.Moreover, a concept known as reduced dimensionless current is introduced by providing and calculating dimensionless current in the biosensor.
Nano-Biomaterials
Sahar Rezaei; Nader Riahi Alam
Volume 8, Issue 2 , June 2014, , Pages 151-158
Abstract
Detection of tumors at an early stage is important for the diagnosis of cancer. Therefore, to detect cancer cells it is necessary to distinguish between metastases from normal cells at an early stage. Due to the large size and coverage necessary to prevent chemical reactions of the current contrast agents ...
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Detection of tumors at an early stage is important for the diagnosis of cancer. Therefore, to detect cancer cells it is necessary to distinguish between metastases from normal cells at an early stage. Due to the large size and coverage necessary to prevent chemical reactions of the current contrast agents in the body, they are just applicable to the extracellular space. Due to the small size of nanoparticles in comparison to cells, it is possible for them to enter the cells. Therefore, these materials are used for molecular imaging. In this paper, variations in the external magnetic field (Tesla) due to magnetic nanoparticles in homogeneous tissue were studied by the finite element method. For this purpose, a simulation was performed in the presence of magnetic nanoparticles and without it. By the finite element method, conversion of differential and integral governing equations to simple and solvable equations that are numerically stable was made possible. The results obtained indicate that the external magnetic field is intensified by the presence of magnetic nanoparticles.
Mehran Baboli; Seyed Ali Ghorashi; Namdar Saniei; Alireza Ahmadian
Volume 2, Issue 4 , June 2008, , Pages 297-303
Abstract
Ultra Wide Band (UWB) signals are widely used in medical applications. In this paper, we developed a novel non-contact monitoring system to measure the heart rates of patients using UWB signals. The work is performed in two stages. First, a simulated UWB system including a model for human body is developed, ...
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Ultra Wide Band (UWB) signals are widely used in medical applications. In this paper, we developed a novel non-contact monitoring system to measure the heart rates of patients using UWB signals. The work is performed in two stages. First, a simulated UWB system including a model for human body is developed, where heart is simulated using simple layered model, and then its rate is detected. In second stage, real experiments are carried out on human body using UWB radar with 3.2 GHz bandwidth, and a new practical wavelet based algorithm is proposed to detect heart rate. The proposed algorithm has a high precision (98%) and accuracy (92%) and appears to be promising for future monitoring systems.
Neuro-Muscular Engineering
Mehrak Mahmoudi; Mohammad Jafar Abd Khodaei; Saeide Khatibirad
Volume -2, Issue 1 , July 2005, , Pages 9-16
Abstract
A mathematical model is presented for simulation of neurotransmitter release in the synaptic cleft of a neuromuscular junction. Chaudhuri's model is improved by adding calcium diffusion effect on the neurotransmitter release. When an action potential occurs, the calcium channels on presynaptic membrane ...
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A mathematical model is presented for simulation of neurotransmitter release in the synaptic cleft of a neuromuscular junction. Chaudhuri's model is improved by adding calcium diffusion effect on the neurotransmitter release. When an action potential occurs, the calcium channels on presynaptic membrane will open and allow calcium ions to enter in presynaptic terminal. Then, these ions diffuse between calcium channels and release sites, where clearance mechanisms remove some of them. The model is defined by some partial differential equations which are solved by numerical methods. Solving these equations, the temporal changes of calcium concentration in the release sites and the amount of neurotransmitter release at each time are obtained. Finally, the effect of two consecutive action potential pulses on the above mechanisms is studied.
Neuro-Muscular Engineering
Ali Esteki
Volume -1, Issue 1 , June 2004, , Pages 15-23
Abstract
Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired ...
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Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired posture of the hand to assist the implementation of FNS systems. The hand was treated as a multi-body system including rigid segments connected by joints. Each joint was subjected to a total moment including muscle active and joint passive components. The forward approach, in which the equilibrium equations are solved for joint positions as a function of muscle moments, was used. The results showed that at the base joint of the index finger, flexion effect of the extrinsic flexor muscles was about two times of that of the intrinsic muscles. It was also shown that each muscle of the extensor system is individually more effective than the extrinsic flexor muscles. At the more distal joints, intrinsic muscles acted as feeble extensors. At the base joint of the thumb, extensor muscles were much more powerful than the flexor and flexor effect of adductor muscles. Also, abductor muscles were much more effective than the adductors. It was revealed that flexor muscles of the more distal joints are as strong as the extensor muscles. The conclusions are that: the minimum required muscles for appropriate positioning of the hand and for grasp and applying force to objects are limited.
