Academic literature on the topic 'Scaffold Permeability'
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Journal articles on the topic "Scaffold Permeability"
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Prakoso, Akbar Teguh, Hasan Basri, Dendy Adanta, Irsyadi Yani, Muhammad Imam Ammarullah, Imam Akbar, Farah Amira Ghazali, Ardiyansyah Syahrom, and Tunku Kamarul. "The Effect of Tortuosity on Permeability of Porous Scaffold." Biomedicines 11, no. 2 (February 1, 2023): 427. http://dx.doi.org/10.3390/biomedicines11020427.
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In designing porous scaffolds, permeability is essential to consider as a function of cell migration and bone tissue regeneration. Good permeability has been achieved by mimicking the complexity of natural cancellous bone. In this study, a porous scaffold was developed according to the morphological indices of cancellous bone (porosity, specific surface area, thickness, and tortuosity). The computational fluid dynamics method analyzes the fluid flow through the scaffold. The permeability values of natural cancellous bone and three types of scaffolds (cubic, octahedron pillar, and Schoen’s gyroid) were compared. The results showed that the permeability of the Negative Schwarz Primitive (NSP) scaffold model was similar to that of natural cancellous bone, which was in the range of 2.0 × 10−11 m2 to 4.0 × 10−10 m2. In addition, it was observed that the tortuosity parameter significantly affected the scaffold’s permeability and shear stress values. The tortuosity value of the NSP scaffold was in the range of 1.5–2.8. Therefore, tortuosity can be manipulated by changing the curvature of the surface scaffold radius to obtain a superior bone tissue engineering construction supporting cell migration and tissue regeneration. This parameter should be considered when making new scaffolds, such as our NSP. Such efforts will produce a scaffold architecturally and functionally close to the natural cancellous bone, as demonstrated in this study.
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Rasheed, Shummaila, Waqas Lughmani, Muhannad Obeidi, Dermot Brabazon, and Inam Ahad. "Additive Manufacturing of Bone Scaffolds Using PolyJet and Stereolithography Techniques." Applied Sciences 11, no. 16 (August 9, 2021): 7336. http://dx.doi.org/10.3390/app11167336.
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In this study, the printing capability of two different additive manufacturing (3D printing) techniques, namely PolyJet and micro-stereolithography (µSLA), are investigated regarding the fabrication of bone scaffolds. The 3D-printed scaffold structures are used as supports in replacing and repairing fractured bone tissue. Printed bone scaffolds with complex structures produced using additive manufacturing technology can mimic the mechanical properties of natural human bone, providing lightweight structures with modifiable porosity levels. In this study, 3D scaffold structures are designed with different combinations of architectural parameters. The dimensional accuracy, permeability, and mechanical properties of complex 3D-printed scaffold structures are analyzed to compare the advantages and drawbacks associated with the two techniques. The fluid flow rates through the 3D-printed scaffold structures are measured and Darcy’s law is applied to calculate the experimentally measured permeability. The Kozeny–Carman equation is applied for theoretical calculation of permeability. Compression tests were performed on the printed samples to observe the effects of the printing techniques on the mechanical properties of the 3D-printed scaffold structures. The effect of the printing direction on the mechanical properties of the 3D-printed scaffold structures is also analyzed. The scaffold structures printed with the µSLA printer demonstrate higher permeability and mechanical properties as compared to those printed using the PolyJet technique. It is demonstrated that both the µSLA and PolyJet printing techniques can be used to print 3D scaffold structures with controlled porosity levels, providing permeability in a similar range to human bone.
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Shi, Chenglong, Nana Lu, Yaru Qin, Mingdi Liu, Hongxia Li, and Haichao Li. "Study on mechanical properties and permeability of elliptical porous scaffold based on the SLM manufactured medical Ti6Al4V." PLOS ONE 16, no. 3 (March 4, 2021): e0247764. http://dx.doi.org/10.1371/journal.pone.0247764.
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In this paper, we take the elliptical pore structure which is similar to the microstructure of cancellous bone as the research object, four groups of bone scaffolds were designed from the perspective of pore size, porosity and pore distribution. The size of the all scaffolds were uniformly designed as 10 × 10 × 12 mm. Four groups of model samples were prepared by selective laser melting (SLM) and Ti6Al4V materials. The statics performance of the scaffolds was comprehensively evaluated by mechanical compression simulation and mechanical compression test, the manufacturing error of the scaffold samples were evaluated by scanning electron microscope (SEM), and the permeability of the scaffolds were predicted and evaluated by simulation analysis of computational fluid dynamics (CFD). The results show that the different distribution of porosity, pore size and pores of the elliptical scaffold have a certain influence on the mechanical properties and permeability of the scaffold, and the reasonable size and angle distribution of the elliptical pore can match the mechanical properties and permeability of the elliptical pore scaffold with human cancellous bone, which has great potential for research and application in the field of artificial bone scaffold.
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Jusoh, Norhana, Muhammad Aqil Mustafa Kamal Arifin, Muhammad Hamizan Hilmi Sulaiman, Muhammad Aiman Mohd Zaki, Nurul Ammira Mohd Noh, Nur Afiqah Ahmad Nahran, Koshelya Selvaganeson, and Amy Nurain Syamimi Ali Akbar. "Permeability of Bone Scaffold with Different Pore Geometries Based on CFD Simulation." Journal of Medical Device Technology 1, no. 1 (October 8, 2022): 45–49. http://dx.doi.org/10.11113/jmeditec.v1n1.16.
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Scaffold plays a significant role in promoting cells proliferation and differentiation in bone regeneration. Permeability is one of the factors that affect the function as it is able to extract waste and supply nutrients or oxygen. The aim of this study was to design different pore shapes and to simulate its fluid model in order to predict permeability value of the scaffold. There were few steps in this project which were scaffold design, fluid simulation analysis and permeability calculation. Three different pore shapes were designed, which were circle, triangle, and hexagon by using the Solidworks software. Each scaffold was designed by the combination of three unit cells. Then, Computational Fluid Dynamics (CFD) simulation in the Ansys Fluent software was conducted to obtain the pressure drop from the pressure distribution within the pores. The permeability of scaffold was obtained by applying Darcy's permeability formula at inlet velocity of 0.001 m/s, 0.01 m/s and 0.1 m/s. Based on the calculation, the permeability for hexagon pore shape were 3.96691x10-07 m2, 3.52 x10- 07 and 1.92 x10-07 for 0.001 m/s, 0.01 m/s and 0.1 m/s inlet velocity, respectively. Therefore, by increasing the inlet velocities, permeability decreased for all types of scaffolds. Furthermore. hexagon pore shape showed the highest permeability value when compared with triangle and circle’s pore shape. Nevertheless, all pore shapes demonstrated permeability values that within the range of natural bone permeability.
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Madurantakam, Parthasarathy A., Isaac A. Rodriguez, Koyal Garg, Jennifer M. McCool, Peter C. Moon, and Gary L. Bowlin. "Compression of Multilayered Composite Electrospun Scaffolds: A Novel Strategy to Rapidly Enhance Mechanical Properties and Three Dimensionality of Bone Scaffolds." Advances in Materials Science and Engineering 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/561273.
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One major limitation of electrospun scaffolds intended for bone tissue engineering is their inferior mechanical properties. The present study introduces a novel strategy to engineer stiffer scaffolds by stacking multiple layers and cold welding them under high pressure. Electrospun polydioxanone (PDO) and PDO:nanohydroxyapatite (PDO:nHA) scaffolds (1, 2, or 4 layered stacks) were compressed either before or after mineralizing treatment with simulated body fluid (SBF). After two weeks in SBF, scaffolds were analyzed for total mineral content and stiffness by Alizarin red S and uniaxial tensile testing, respectively. Scaffolds were also analyzed for permeability, pore size, and fiber diameter. Results indicated that compression of multiple layers significantly increased the stiffness of scaffolds while reducing mineralization and permeability. This phenomenon was attributed to increased density of fibers and loss of surface area due to fiber welding. Statistics revealed, the 4-layered PDO:nHA scaffold compressed first followed by mineralization in revised SBF had maximal stiffness, low permeability and pore size, and mineralization second only to noncompressed scaffolds. Within the limitations of permeability and pore size, this scaffold configuration represents an optimal midway for desired stiffness and mineral content for bone tissue engineering.
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Lü, Lanxin, Hongxian Shen, Daichi Kasai, and Ying Yang. "Fabrication and Characterization of Alveolus-Like Scaffolds with Control of the Pore Architecture and Gas Permeability." Stem Cells International 2022 (January 20, 2022): 1–12. http://dx.doi.org/10.1155/2022/3437073.
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The micrometer scale sac-like alveoli are the most important and essential unit for gas exchange in the lung. Thus, design and fabrication of scaffolds for alveoli regeneration by tissue engineering approach should meet a few topography and functional requests such as large surface area, flexibility, and high gas permeability to their native counterpart. Testing the gas permeability of scaffolds through a fast and simple technique is also highly demanded to assist new scaffold development. This study fabricated alveolus-like scaffolds with regular pore shape, high pore connectivity, and high porosity produced by inverse opal technique alongside randomly distrusted porous scaffolds by salt leaching technique from two different materials (polyurethane and poly(L-lactic acid)). The scaffold surface was modified by immobilization of VEGF. A facile and new technique based on the bubble meter principle enabling to measure the gas permeability of porous scaffolds conveniently has been developed specifically. The cellular response of the scaffolds was assessed by culturing with bone marrow mesenchymal stem cells and coculturing with lung epithelial NL20 and endothelial HUVECs. Our results showed that the newly designed gas permeability device provided rapid, nondestructive, reproducible, and accurate assessment of gas permeability of different scaffolds. The porous polyurethane scaffolds made by inverse opal method had much better gas permeability than other scaffolds used in this study. The cellular work indicated that with VEGF surface modification, polyurethane inverse opal scaffolds induced alveolus-like tissues and have promising application in lung tissue engineering.
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Ghasemi-Mobarakeh, Laleh, Mohammad Morshed, Khadijeh Karbalaie, Mehr-Afarin Fesharaki, Marziyeh Nematallahi, Mohammad-Hossein Nasr-Esfahani, and Hossein Baharvand. "The Thickness of Electrospun Poly (ε-Caprolactone) Nanofibrous Scaffolds Influences Cell Proliferation." International Journal of Artificial Organs 32, no. 3 (March 2009): 150–58. http://dx.doi.org/10.1177/039139880903200305.
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Nanofibrous scaffolds have morphological similarities to native extracellular matrix and have been considered as candidate scaffolds in tissue engineering. However, there is no report on the effect of the thickness of nanofibrous scaffold on cell behavior. In this study poly (∊-caprolactone) (PCL) nanofibrous scaffolds with thicknesses of 0.1 and 0.6 mm were fabricated by electrospinning. Properties of PCL nanofibrous scaffolds were measured by contact angle and air permeability measurements while the morphology of the nanofibers was observed by SEM. Mouse embryonal carcinoma stem cells (P19), monkey epithelial kidney cells (Vero), Chinese hamster ovary cells (CHO) and mouse mesenchymal stem cells (MSCs) were seeded on PCL nanofibrous scaffolds with thicknesses of 0.1 and 0.6 mm. Air permeability measurements showed that air permeability decreases with the increase in the thickness of nanofibrous scaffolds, and contact angle measurements revealed a contact angle of 118° for electrospun PCL nanofibers. The MTT assays showed that the proliferation of the cells was influenced by the thickness of the nanofibrous scaffold. Scaffolds with a thickness of 0.6 mm were found to provide a better substrate for cell proliferation, possibly due to more dimensional stability. Therefore, regardless of cell origin, thicker scaffolds provide a better substrate for cell proliferation, possibly due to the higher dimensional stability and tightness of thicker scaffolds.
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Boschetti, Pedro J., Orlando Pelliccioni, Mariángel Berroterán, María V. Candal, and Marcos A. Sabino. "Fluid flow in a Porous Scaffold for Microtia by Lattice Boltzmann Method." International Journal of Advances in Medical Biotechnology - IJAMB 2, no. 1 (March 1, 2019): 46. http://dx.doi.org/10.25061/2595-3931/ijamb/2019.v2i1.35.
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The birth deformity of ear, known as microtia, varies from a minimal deformed ear to the absence of auricular tissue or anotia. This malformation has been treated by reconstructing the external ear, mainly by autogenous rib cartilage in auricular repair. The fabrication of the ear framework is a prolonged reconstructive procedure and depends of the surgeon’s skill. In order to avoid these inconveniences and reduce surgery time, it was proposed in a previous work to use implants made with biocompatible materials. One of these is a scaffold made by fused deposition modeling using PLA based in the three-dimensional geometry of the ear cartilage. The aim of this work is to evaluate the feasibility of this scaffold to perform cell culture in a perfusion biorreactor by estimating the flow transport characteristics in porous media using a scaffold with the porous geometry of the human auricular cartilage for microtia. Flow and heat transfer through the scaffold were simulated by the lattice Boltzmann method, and permeability and shear stress distribution were obtained at different Reynolds numbers. The permeability values of the scaffold achieved are in the order of magnitude of scaffolds used for cell culture. Linear dependencies between maximum shear stress and Reynolds number, and between maximum shear stress and permeability were obtained. The values of shear stress achieved correspond to high percentage of cell viability. The scaffolds for microtia treatment with the proposed filling pattern select is appropriate for cell culture in a perfusion bioreactor with characteristics similar to those described herein.
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Dias, Marta, Paulo Fernandes, José Guedes, and Scott Hollister. "SCAFFOLD DESIGN WITH CONTROLLED PERMEABILITY." Journal of Biomechanics 45 (July 2012): S661. http://dx.doi.org/10.1016/s0021-9290(12)70662-0.
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Normahira, Mamat, Razali Khairul Raimi, Fazli Mohd Nashrul Nasir, Abd Razak Norazian, and Hashim Adilah. "Biomimetic Porosity of Gelatin-Hydroxyapatite Scaffold for Bone Tissue." Advanced Materials Research 970 (June 2014): 3–6. http://dx.doi.org/10.4028/www.scientific.net/amr.970.3.
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Biomimetic Porosity of Gelatin/hydroxyapatite (HA) scaffold was fabricated by using solvent casting method and particulate leaching technique. The composite solution were prepared by adding fixed weight percentages of HA (30wt%) with different concentration a gelatin solution (0.25wt%, 0.30wt%, 0.35wt%, 0.40wt% and 0.50wt%) . Five different composites polymers were poured into a mold with size of 15mm x 15mm x 10mm cube and dried in the oven dryer under 60°C to 90°C. After that, the dry composite scaffolds were immersed in the 8% of glutaraldehyde (GA) solution in a few minute for crosslinking process. Porosity of the scaffold is obtained by doing liquid displacement method. Meanwhile, the mechanical properties (Youngs Modulus) of the scaffolds are obtained by doing compressive test on the scaffold. Lastly, the microstructure and morphology of the composite scaffolds were observed under Scanning Electron Microscope (SEM). It was found that, when gelatin concentration were increased in the composite scaffold, percentages of liquid adsorption will increase, thus indicate that, the scaffold which has high percentage of liquid adsorption has poor mechanical properties and excellent permeability. Besides, SEM result shows that, the scaffolds have pore size in the range of 3 μm - 22μm. and do not exhibit uniform pores distribution. Pore size of the scaffold depends upon the sizes of the NaCl particles.
Dissertations / Theses on the topic "Scaffold Permeability"
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Reinwald, Yvonne. "Investigation of interconnectivity and permeability in correlation with scaffold structural properties." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574659.
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It is widely accepted that pore interconnectivity and permeability are important characteristics effecting cell migration and cell response as well as the transport of nutrients, oxygen and cellular waste products throughout porous tissue engineering scaffolds. Furthermore, it was hypothesized that limited mass transport throughout three-dimensional structures resulted in diminished cell survival and cell distribution being restricted to the scaffold periphery. Several approaches were described for the quantification of scaffold permeability for liquid systems. Up to date, there are only a limited number of quantitative approaches to determine three-dimensional scaffold interconnectivity. This study aims to investigate interconnectivity and permeability in correlation with pore size and porosity. Therefore, tissue engineering scaffolds were fabricated by solvent casting/particulate leaching, supercritical fluid technology and particle sintering. In order to obtain different scaffold architectures, processing conditions were modified. Pore size, pore size distribution and porosity were quantified by MicroCT, and pore windows were analyzed using SEM. A novel interconnectivity algorithm was developed, which allowed the quantification of interconnectivity in 3D throughout the entire scaffold. Permeability of pre-wet scaffolds was determined. Results suggested that scaffolds with larger pore sizes and porosities also exhibited highest interconnectivities and permeabilities. However, these scaffolds showed a heterogeneous pore structure and pore distribution. The distribution of 3T3 fibroblasts through scC02-foamed scaffolds and particulate scaffolds was investigated by MicroCT and MTT staining. Homogenous cell distributions and largest cell volumes were observed on scaffolds with homogenous pore structure and hence smallest pore sizes, porosities, interconnectivities and permeabilities. This study might enable the tailoring of scaffold interconnectivity and permeability by altering scaffold processing conditions. Further, this study might allow the investigation of a minimum interconnectivity that is required for cell migration and proliferation in to order to generate tissues such as bone and cartilage; as well as to promote vascularization.
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Mohee, Lakshana. "Collagen scaffolds for tissue engineering : the relationship between microstructure, fluid dynamics, mechanics and scaffold deformation." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276980.
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Collagen scaffolds are porous structures which are used in bioreactors and in a wide range of tissue engineering applications. In these contexts, the scaffolds may be subjected to conditions in which fluid is forced through the structure and the scaffold is simultaneously compressed. It is clear that fluid transport within collagen scaffolds, and the inter-relationships between permeability, scaffold structure, fluid pressure and scaffold deformation are of key importance. However, these relationships remain poorly understood. In this thesis, a series of isotropic collagen structures were produced using a freeze-drying technique from aqueous slurry concentrations 0.5, 0.75 and 1 wt%, and fully characterised using X-ray micro-tomography and compression testing. It was found that collagen wt% influenced structural parameters such as pore size, porosity, relative density and mechanical properties. Percolation theory was used to investigate the pore interconnectivity of each scaffold. Structures with lower collagen fraction resulted in larger percolation diameters, but lower mechanical stiffness. Aligned collagen scaffolds were also produced by altering the freeze-drying protocol and using different types of mould materials and designs. It was found that a polycarbonate mould with stainless base resulted in vertically aligned structures with low angular variation. When compared with isotropic scaffolds from slurry of the same concentration, aligned scaffolds had a larger percolation diameter. Tortuosity was used as a mathematical tool to characterise the interconnected pathways within each porous structure. The effect of the size of the region of interest (ROI) chosen and the size of the virtual probe particle used in the analysis on the values of tortuosity calculated were determined and an optimised calculation methodology developed. Increasing the collagen fraction within isotropic scaffolds increased the tortuosity, and aligned structures had smaller tortuosity values than their isotropic counterparts. Permeability studies were conducted using two complementary experimental rigs designed to cover a range of pressure regimes and the results were compared with predictions from mathematical models and computational simulations. At low pressures, it was found that the lower collagen fraction structures, which had more open morphologies, had higher permeabilities. Alignment of the structure also enhanced permeability. The scaffolds all experienced deformation at high pressures resulting in a restriction of fluid flow. The lower collagen fraction scaffolds experienced a sharper decrease in permeability with increased pressure and aligned structures were more responsive to deformation than their isotropic counterparts. The inter-relationships between permeability, scaffold structure, fluid pressure and deformation of collagen scaffolds were explored. For isotropic samples, permeability followed a broad $(1- \epsilon)^2$ behaviour with strain as predicted by a tetrakaidecahedral structural model, with the constant of proportionality changing with collagen fraction. In contrast, the aligned structures did not follow this behaviour with the permeability dropping much more sharply in the early stages of compression. Open-cell polyurethane (PU) foams, sometimes used as dressings in wound healing applications, are often compared with collagen scaffolds in permeability models and were used in this thesis as a comparison structure. The foam had a higher permeability than the scaffolds due to its larger pore sizes and higher interconnectivity. In the light of the effects of compression on permeability, the changes in porous structure with compression were explored in isotropic and aligned 0.75 wt% scaffolds. Unlike the fluid flow experiments, these experiments were carried out in the dry state. Deformation in simple linear compression and in step-wise compression was studied, and the stress relaxation behaviour of the scaffolds characterised. A methodology was developed to characterise the structural changes accompanying compression using X-ray micro-tomography with an in situ compression stage. The methodology accounted for the need for samples to remain unchanged during the scan collection period for stable image reconstruction. The scaffolds were studied in uniaxial compression and biaxial compression and it was found that pore size and percolation diameter decreased with increasing compressive strain, while the tortuosity increased. The aligned structure was less affected than the isotropic at low compressions, in contrast to the results from the permeability study in which the aligned structure was more responsive to strain. This suggests that the degree of hydration may affect the structural changes observed. The insights gained in this study of the inter-relationships between microstructure, fluid dynamics and deformation in collagen scaffolds are of relevance to the informed design of porous structures for medical applications.
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Sell, Scott Allen. "Scaffold Permeability as a Means to Determine Fiber Diameter and Pore Size of Electrospun Fibrinogen." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1311.
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The purpose of this study was to construct a flowmeter that could accurately measure the hydraulic permeability of electrospun fibrinogen scaffolds, providing insight into the transport properties of electrospun scaffolds while making the measurement of their topographical features (fiber and pore size) more accurate. Three different concentrations of fibrinogen were used (100, 120, and 150mg/ml) to create scaffolds with three different fiber diameters and pore sizes. The fiber diameters and pore sizes of the electrospun scaffolds were analyzed through scanning electron microscopy and image analysis software. The permeability of each scaffold was measured and used to calculate permeability-based fiber diameters and pore sizes, which were compared to values obtained through image analysis. Permeability measurement revealed scaffold permeability to increase linearly with fibrinogen concentration, much like average fiber diameter and pore size. Comparison between the two measurement methods proved the efficacy of the flowmeter as a way to measure scaffold features.
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Serpooshan, Vahid. "Control of dense collagen gel scaffolds for tissue engineering through measurement and modeling of hydraulic permeability." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97117.
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Among various natural biopolymers, type I collagen gels have demonstrated the highest potential as biomimetic scaffolds for tissue engineering (TE). However, the successful application of collagen gels requires a greater understanding of the relationship between their microstructure and physical-mechanical properties. Therefore, a precise method to modulate collagen gel microstructure in order to attain optimal scaffold properties for diverse biomedical applications is necessary. This dissertation describes a new approach to produce collagen gels with defined microstructures, quantified by hydraulic permeability (k), in order to optimize scaffold properties for TE applications. It was hypothesized that the measurement of k can be used to study the role of microstructure in collagen gel properties, as well as cell function and cell-scaffold interactions. Applying increasing levels of plastic compression (PC) to the highly hydrated collagen gels resulted in an increase in collagen fibrillar density, reduced Happel model derived k values, increased gel stiffness, promoted MSC metabolic activity, osteogenic differentiation, and mineral deposition, while cell-induced gel contraction diminished. Thus, collagen gels with lower k and higher stiffness values exhibited greater potential for bone tissue engineering.Correlating between collagen gel microstructure, k, and fibroblast function within collagen gels indicated that increasing the level of PC yielded a reduction in pore size and an increase in fibril bundle diameter. Decrease in k values resulted in a decrease in gel contraction and an increase in cell metabolic activity. An increase in cell density accelerated contraction. Therefore, fibroblast function within collagen gels can be optimised by a balance between the microstructure, k, and cell seeding density.Developing a micromechanical model to measure experimental k of collagen gels during confined compression revealed the formation of a dense collagen lamella at the fluid expulsion boundary, thereby generating a two-layer model. By applying gel mass loss into Darcy's law, experimental k values of the lamella, along with the thickness of lamella (c) and hydrated gel layer (b) were measured. An increase in either compression level or compression time resulted in a decrease in k, decrease in b, and an increase in c. In conclusion, controlled compression of collagen gels can be used to produce multi-layered biomimetic scaffolds with defined microstructures and k in order to attain optimal properties for tissue engineering applications.Parmi les biopolymères naturels couramment utilisés, les gels de collagène de type I se sont révélés être parmi les matrices biomimétiques les plus prometteuses pour l'ingénierie tissulaire. Cependant, le succès des applications thérapeutiques des matrices collagéniques nécessite une meilleure compréhension de la relation entre leur microstructure et leurs propriétés mécaniques. C'est pourquoi une méthode précise permettant de moduler la microstructure du gel de collagène est nécessaire pour pouvoir espérer atteindre les propriétés optimales de la matrice pour des applications médicales diverses. Cette thèse de doctorat décrit le développement et l'évaluation d'une nouvelle approche pour produire des gels de collagène avec une microstructure définie. Cette méthode permet de quantifier la perméabilité hydraulique (k) afin d'optimiser les propriétés de la matrice pour des applications en ingénierie tissulaire. Il a émis l'hypothèse que la mesure de k peut être utilisée pour étudier le rôle de la microstructure dans les propriétés du gel de collagène ainsi que la fonction cellulaire et les interactions matrice-cellules a été formulée.Appliquant des différents niveaux de compression plastique (PC) à des gels de collagène a entraîné une augmentation de la densité de fibrillaire, réduit les valeurs de k dérivées du modèle de Happel, augmentation de la rigidité du gel, stimulé l'activité métabolique des MSC, la différenciation ostéogénique et le dépôt de minéral, alors que la contraction du gel induite par les cellules a été réduite. Ainsi, les gels de collagène qui présentent une valeur de k plus faible et des valeurs de rigidité plus élevées ont présenté un potentiel plus élevé pour des applications en ingénierie tissulaire osseuse. Corréler la microstructure du gel de collagène, la perméabilité, et la fonction des fibroblastes cultivés dans des gels de collagène a indiqué que l'augmentation du niveau de PC résultait en la diminution de la taille des pores et une augmentation du diamètre des faisceaux de fibres. Diminution des valeurs de k résultait en une diminution de la contraction du gel et une augmentation de l'activité cellulaire métabolique. C'est pourquoi la fonction des fibroblastes, cultivés à l'intérieur de matrices de collagène, peut être optimisée en réalisant une balance entre les propriétés de microstructure, définie par k et par la densité cellulaire.Développement d'un modèle micromécanique pour mesurer la valeur expérimentale de k des gels de collagène pendant l'auto-compression radiaire confinée (SC) a révélé la formation d'une lamelle de collagène dense à la limite de l'expulsion de fluide, générant ainsi un model à deux couches. En appliquant la perte de masse de gel à la loi de Darcy, les valeurs expérimentales de k de la lamelle, ainsi que l'épaisseur de la lamelle (c) et hydratée couche de gel (b) ont été mesurés. Une augmentation soit au niveau de compression ou de temps de compression résultait en une diminution de k, diminution de b, et une augmentation de c.En conclusion, la compression contrôlée des gels hydratés de collagène peut être utilisée afin de produire des matrices multicouches biomimétiques présentant une microstructure définie et des valeurs de perméabilité permettant d'atteindre des propriétés optimales pour des applications en ingénierie tissulaire.
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Serpooshan, Vahid. "Control of dense collagen gel scaffolds for tissue engineering through measurement and modelling of hydraulic permeability." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111921.
Full textAbstract:
Among various natural biopolymers, type I collagen gels have demonstrated the highest potential as biomimetic scaffolds for tissue engineering (TE). However, the successful application of collagen gels requires a greater understanding of the relationship between their microstructure and physical-mechanical properties. Therefore, a precise method to modulate collagen gel microstructure in order to attain optimal scaffold properties for diverse biomedical applications is necessary. This dissertation describes a new approach to produce collagen gels with defined microstructures, quantified by hydraulic permeability ( k), in order to optimize scaffold properties for TE applications. It was hypothesized that the measurement of k can be used to study the role of microstructure in collagen gel properties, as well as cell function and cell-scaffold interactions. Applying increasing levels of plastic compression (PC) to the highly hydrated collagen gels resulted in an increase in collagen fibrillar density, reduced Happel model derived k values, increased gel stiffness, promoted MSC metabolic activity, osteogenic differentiation, and mineral deposition, while cell-induced gel contraction diminished. Thus, collagen gels with lower k and higher stiffness values exhibited greater potential for bone tissue engineering.Correlating between collagen gel microstructure, k, and fibroblast function within collagen gels indicated that increasing the level of PC yielded a reduction in pore size and an increase in fibril bundle diameter. Decrease in k values resulted in a decrease in gel contraction and an increase in cell metabolic activity. An increase in cell density accelerated contraction. Therefore, fibroblast function within collagen gels can be optimised by a balance between the microstructure, k, and cell seeding density.
Developing a micromechanical model to measure experimental k of collagen gels during confined compression revealed the formation of a dense collagen lamella at the fluid expulsion boundary, thereby generating a two-layer model. By applying gel mass loss into Darcy's law, experimental k values of the lamella, along with the thickness of lamella (c) and hydrated gel layer (b) were measured. An increase in either compression level or compression time resulted in a decrease in k, decrease in b, and an increase in c. In conclusion, controlled compression of collagen gels can be used to produce multi-layered biomimetic scaffolds with defined microstructures and k in order to attain optimal properties for tissue engineering applications.
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Machado, Jeferson Luis de Moraes. "Desenvolvimento de cimento ósseo de fosfato de cálcio como suporte para o crescimento de tecidos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/17368.
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O crescimento de células em arcabouços tridimensionais porosos tem se tornado progressivamente ativo na engenharia de tecidos. Os arcabouços guiam o crescimento celular, sintetizam uma matriz extracelular e outras moléculas biológicas, e facilitam a formação de tecidos e órgãos funcionais. Um cimento deste tipo pode ser preparado misturando um sal de fosfato de cálcio com uma solução aquosa para que se forme uma pasta que possa reagir à temperatura corporal dando lugar a um precipitado que contenha hidroxiapatita (Ca10(PO4)6(OH)2). A similaridade química e morfológica entre este biomaterial e a parte mineral dos tecidos ósseos permite a osteocondução, sendo o cimento substituído por tecido ósseo novo com o tempo e com a vantagem de não desencadear processos inflamatórios e de corpo estranho, com eventual expulsão do material implantado. O objetivo do presente trabalho foi a obtenção e caracterização de suportes tridimensionais para a engenharia de tecido, com o uso de matérias-primas nacionais, por meio da utilização de microesferas de parafina como corpos geradores de poros. As microesferas foram produzidas por suspensão em solução aquosa de poli (álcool vinílico) (PVA) e sulfato de sódio (Na2SO4). Foram analisadas as fases presentes no cimento sintetizado e após a reação de cura do mesmo, a variação do tamanho de partícula e da resistência mecânica com o tempo de moagem. Foi analisada a porosidade dos suportes e a forma de extração da parafina daqueles que a utilizaram na sua formação. O tamanho de poro dos suportes gerados com a variação da quantidade de fase líquida ficou aquém do tamanho considerado ideal para o crescimento de tecido ósseo. A porosidade dos arcabouços fabricados com esferas de parafina foi observada por microscopia eletrônica de varredura (MEV), e seu comportamento foi analisado a partir de ensaios in vitro em solução SBF (simulated body fluid) e em cultura de células. A utilização de esferas de parafina permitiu a formação de poros com tamanho tal que possibilitam potencialmente o crescimento tecidual e celular.The growth of cells in three-dimensional porous scaffolds has been extensively studied for use in tissue engineering. They guide grow of cells, synthesize extra cellular matrix and other biological molecules, and facilitate the formation of functional tissues and organs. Bone cements has been developed for biomedical applications for a decade approximately. This kind of cement can be prepared mixing a calcium phosphate salt with aqueous solution forming a paste that can react at body temperature generating a hydroxyapatite precipitated (Ca10(PO4)6(OH)2). The chemical and morphological similarity between the cement composition and the mineral part of the bones allows osteoconduction in the tissue with replacement of cement by new bone formed with the advantage to not unchain inflammatory processes and of strange body. The objective of this work was the use of the α-TCP cement for making these scaffolds, through the variation of the amount of liquid phase in the cement and of the use of paraffin spheres as pore source. These spheres were produced by suspension in water solution of poly (vinyl alcohol) and sodium sulphate (Na2SO4). The phases had been analyzed in the synthesized cement and after the reaction of cure of cement, beyond variation of the particle size and the resistance mechanics with the milling time. It was analyzed the porosity of the scaffolds and the extraction of the paraffin in that supports. The pore size of the supports generated with the variation of the amount of liquid phase was on this side of the size considered ideal for the bone tissue growth. The porosity of scaffolds manufactured with paraffin spheres was observed by Scanning Electron Microscopy (SEM), and its behavior was analyzed from test in vitro in SBF solution (simulated body fluid). The use of paraffin spheres allowed the formation of pores size able to permit tissue growth.
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Karande, Tejas Shyam. "Effect of scaffold architecture on diffusion of oxygen in tissue engineering constructs." Thesis, 2007. http://hdl.handle.net/2152/3270.
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Viable tissue formation is often observed in peripheral regions of tissue engineering scaffolds whereas the interior fails to support viable tissue. This could be attributed to the fact that as cells within the pores of the scaffold begin to proliferate and secrete extracellular matrix, they simultaneously begin to occlude the pores and decrease supply of nutrients to the interior. Since transport within the scaffold is mainly a function of diffusion, careful design of the diffusion characteristics of the scaffold is critical. These transport issues relate to oxygen and nutrient delivery, waste removal, protein transport and cell migration, which in turn are governed by scaffold porosity and permeability. The current study addresses these issues by evaluating the effect of these architectural parameters on oxygen concentration and cell behavior in the interior of scaffolds with different architectures. Cylindrical polycaprolactone (PCL) scaffolds fabricated using precision extrusion deposition and having the same pore size but different porosities and tortuosities, and hence different permeabilities, were statically seeded with MG63 cells. The bases of the scaffolds were sealed with an impermeable layer of PCL and the scaffolds were surrounded with a tubing of low air permeability to allow diffusion of air into the constructs mainly from the top. These constructs were evaluated at days 1 and 7 for cell viability and proliferation as well as oxygen concentration as a function of depth within the construct. A simple mathematical model was used to describe the process of diffusion of oxygen in these cell-seeded scaffolds of varying permeability. It was hypothesized that there would be better diffusion and cell function with increasing permeability. This was found to be true in case of cell viability. However, cell proliferation data revealed no significant differences as a function of depth, day or architecture. Oxygen concentration data revealed trends showing decreasing concentrations of oxygen as a function of depth across all architectures. Tortuosity had a greater influence on oxygen concentration profiles on day 1 compared to porosity, whose effect seemed to dominate on day 7. Overall, porosity seemed to play a greater role than tortuosity in supporting viability, proliferation and oxygen diffusion.text
Book chapters on the topic "Scaffold Permeability"
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Murata, Masaru, Toshiyuki Akazawa, Katsutoshi Ito, Tomoya Sasaki, Junichi Tazaki, and Makoto Arisue. "Blood Permeability of a Novel Ceramic Scaffold for BMP-2." In Bioceramics 18, 961–64. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-992-x.961.
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Oshi, Murtada A., Abdul Muhaymin, Ammara Safdar, Meshal Gul, Kainat Tufail, Fazli Khuda, Sultan Ullah, Fakhar-ud-Din, Fazli Subhan, and Muhammad Naeem. "Electrospun Nanofibers Scaffolds: Fabrication, Characterization and Biomedical Applications." In Biomaterial Fabrication Techniques, 103–32. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815050479122010008.
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The electrospinning (ES) technique in the fabrication of biomaterials-based electrospun nanofibers (ESNFs) has risen to prominence because of its accessibility, cost-effectiveness, high production rate and diverse biomedical applications. The ESNFs have unique characteristics, such as stability and mechanical performance, high permeability, porosity, high surface area to volume ratio, and ease of functionalization. The characteristics of ESNFs can be controlled by varying either process variables or biomaterial solution properties. The active pharmaceutical agents can be introduced into ESNFs by blending, surface modification, or emulsion formation. In this chapter, in the first part, we briefly discuss the fundamental aspects of the fabrication, commonly used materials, process parameters, and characterization of ESNFs. In the second part, we discuss in detail the biomedical applications of ESNFs in drug delivery, tissue engineering, and wound healings, cancer therapy, dentistry, medical filtration, biosensing and imaging of disease.
Conference papers on the topic "Scaffold Permeability"
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Egan, Paul F., Veronica C. Gonella, Max Engensperger, Stephen J. Ferguson, and Kristina Shea. "Design and Fabrication of 3D Printed Tissue Scaffolds Informed by Mechanics and Fluids Simulations." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67602.
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Advances in additive manufacturing are enabling the fabrication of lattices with complex geometries that are potentially advantageous as tissue scaffolds. Scaffold design for optimized mechanics and tissue growth is challenging, due to complicated trade-offs among scaffold structural properties including porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Here, a design for additive manufacturing approach is developed for tuning unit cell libraries as tissue scaffolds through (1) simulation, (2) design automation, and (3) fabrication. Finite element simulations are used to determine elastic and shear moduli of lattices as a function of porosity. Fluids simulations suggest that lattice permeability scales with porosity cubed over surface-volume ratio squared. The design automation approach uses simulation results to configure lattices with specified porosity and pore size. A cubic and octet lattice are fabricated with pore sizes of 1,000μm and porosities of 60%; these lattice types represent unit cells with high unidirectional elastic modulus/permeability and high shear modulus/surface-volume ratio, respectively. Imaging suggests the 3D printing process recreates the form accurately, but distorts microscale features. Future iterations are required to determine how lattices perform in comparison to computational predictions. The developed approach provides the foundations of a design automation approach for optimized 3D printed tissue scaffolds informed by simulation and experiments.
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Pennella, Francesco, Piergiorgio Gentile, Marco A. Deriu, Diego Gallo, Alessandro Schiavi, Gianluca Ciardelli, Eric Lorenz, Alfons G. Hoekstra, Alberto Audenino, and Umberto Morbiducci. "A Virtual Test Bench to Study Transport Phenomena in 3D Porous Scaffolds Using Lattice Boltzmann Simulations." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14489.
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In tissue engineering (TE), scaffolds are widely used to provide a suitable and native-like environment for cell growth, organization, and proliferation. Microstructure of TE scaffolds is fundamental to the cell attachment and in-depth penetration, in conjunction with biological factors as cell seeding and nutrients supply. In particular, several studies have established that an adequate transport of nutrient through the scaffold is fundamental for culturing cells [1]. Hence, the easiness at which fluids/species move through the scaffold and friction forces exherted from fluid motion, have a marked impact in TE processes [2]. Mass transport through scaffolds is a phenomenon that can be described at different scales, the molecular level (nanoscale), the single-pore dimension level (microscale) and the whole-sample level (macroscale). In this work we present a virtual test bench where realistic 3D models of porous TE scaffolds are reconstructed from micro-CT images and the transport phenomena through them is simulated in silico by applying the Lattice Boltzmann Method (LBM). The final aim is to create an effective in silico tool suitable to study and optimize transport phenomena of porous scaffolds. The application of the LBM is justified by its versatility in simulating flows in irregular porous media (i.e. simplicity of handling complex boundaries) and in providing insights into transport properties such as permeability [3–4] and physical quantities as the shear stress, which are barely achievable experimentally [2]. Here, the virtual tool is applied to evaluate the performance of three biomimetic bioactive glass/polymer composite porous scaffolds for bone tissue regeneration with well-known mechanical and chemical properties, but never characterized in terms of transport phenomena. The in silico results are macroscopically validated in terms of permeability (kC) by comparison with experimental permeability (kE) measurements obtained by means of a dedicated test bench, very recently proposed for the characterization of porous media [5].
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Susa, Tomoya, Ryosuke Nansai, Norimasa Nakamura, and Hiromichi Fujie. "Influence of Permeability on the Compressive Property of Articular Cartilage: A Scaffold-Free, Stem Cell-Based Therapy for Cartilage Repair." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53365.
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Since the healing capacity of articular cartilage is limited, it is important to develop cell-based therapies for the repair of cartilage. Although synthetic or animal-derived scaffolds are frequently used for effective cell delivery long-term safety and efficiency of such scaffolds still remain unclear. We have been studying on a scaffold-free tissue engineered construct (TEC) bio-synthesized from synovium-derived mesenchymal stem cells (MSCs) [1]. As the TEC specimen is composed of cells with their native extracellular matrix, we believe that it is free from concern regarding long term immunological effects. our previous studies indicated that a porcine partial thickness chondral defect was successfully repaired with TEC but that the compressive property of the TEC-treated cartilage-like repaired tissue was different from normal cartilage in both immature and mature animals. Imura et al. found that the permeability of the immature porcine cartilage-like tissues repaired with TEC recovered to normal level for 6 months except the superficial layer [2]. Therefore, the present study was performed to determine the depth-dependent permeability of mature porcine cartilage-like tissue repaired with TEC. Moreover, we investigated the effect of difference of permeability on the compressive property of articular cartilage using a finite element analysis (FEM).
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Sahin, Mervenaz, Ahmet Fatih Tabak, and Gullu Kiziltas Sendur. "Initial Study Towards the Integrated Design of Bone Scaffolds Based on Cell Diffusion, Growth Factor Release and Tissue Regeneration." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23940.
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Abstract Three-dimensional (3D) porous tissue scaffolds combined with bioactive molecules and cells offer key advantages for bone repair mechanisms. A functional bone tissue scaffold should provide mechanical support with an adequate combination of porosity and permeability for nutrients, oxygen supply, waste removal, and growth factors release as well as controlled degradation. Although a vast amount of work exist to address these challenges, to the best of our knowledge, a design framework taking tissue differentiation, diffusion, and growth factor (GF) release into account in time-domain simultaneously does not exist. In this paper, we provide an initial effort to address such a need by laying down the foundations for a simulation framework incorporating these effects within a Finite Element Analysis (FEA) model in COMSOL Multiphysics® software. The effectiveness of the numerical model is demonstrated via preliminary mechano-biology analyses on a simulated 3D poroelastic bone scaffold. Initial time-dependent results demonstrate the suitability of this model for an optimization framework. More specifically, it is demonstrated that coupled Multiphysics equations of diffusion, GF release, and differentiation could provide valuable inputs for ideal bone scaffold systems for effective bone repair tasks in the future.
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Guarnera, Daniele, Federica Iberite, Marco Piazzoni, Irini Gerges, Tommaso Santaniello, Lorenzo Vannozzi, Cristina Lenardi, and Leonardo Ricotti. "Effects of the 3D Geometry Reconstruction on the Estimation of 3D Porous Scaffold Permeability." In 2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC). IEEE, 2021. http://dx.doi.org/10.1109/embc46164.2021.9629664.
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Finkbiner, J. J., K. L. Harrigan, K. C. Dee, and G. A. Livesay. "Fabrication and Properties of Collagen Fibers With Increased Surface Areas for Enhanced Fiber-Matrix Interactions." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176514.
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Collagen plays an important structural role in many natural tissues, such as ligaments and tendons. Due to its ubiquity in the human body and its commercial availability, biomaterials using collagen gel as a scaffold for an extracellular matrix are being developed as alternative treatments for soft tissue injuries [1]. The use of collagen fibers as a matrix in cell-seeded collagen gels has been shown to limit contraction of the gels as well as increase scaffold permeability and cell viability [2,3]. Additionally, it has been found that dehydration of collagen fibers increases fiber strength [4]. Therefore, investigating the effect of changing fiber shape to increase fiber surface and gel/fiber interaction is important.
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Dunkers, Joy P., Stefan D. Leigh, Marcus T. Cicerone, Forrest A. Landis, Francis W. Wang, and John A. Tesk. "NIST Development of Reference Material Scaffolds for Tissue Engineering." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82012.
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In consultation with ASTM and other stakeholders in Tissue-Engineered Medical Products (TEMPs) industry, the National Institute of Standards and Technology (NIST) initiated a project designed to produce Reference Material scaffolds for tissue engineering. The rationale for Reference Material scaffolds was developed through several NIST/Industry workshops. In brief, Reference Material scaffolds have multiple uses: facilitating the development and the validation of new test methods that measure interactions among various components of a TEMP; comparison with other scaffolds and scaffold materials in terms of cellular responses, biodegradation, and releases of growth factors; and comparisons of responses among various cell lines. The primary customers for Reference Material scaffolds are expected to be the TEMPs industry, academic researchers, regulators, and standards developing organizations. There are many properties of a TEMP that warrant development of multiple Reference Material scaffolds. Currently, NIST is defining a set of Reference Material scaffolds based on geometric descriptors such as permeability, pore volume, pore size distribution, interconnectivity, and tortuosity. In consultation with ASTM, NIST is testing three candidate scaffolds produced by: three dimensional (3-D) printing, stereolithography, and fused deposition modeling (FDM). Scaffolds made by these methods have been obtained from Mayo Clinic (Rochester, MN), Case Western Reserve University (CWRU) (Cleveland, OH), and Osteopore International (Singapore), respectively, for structural characterization. These prototype scaffolds, with well-defined architectures, have been selected to address the following items of interest: 1) establishment of useful functional definitions of porosity content, interconnectivity, and pores; 2) evaluation of testing methods listed in the Standard Guide for the Porosity of Polymeric Scaffolds for Use in Tissue-Engineered Medical Products, which is being drafted by ASTM. Currently, NIST and the Center for Devices and Radiological Health of the Food and Drug Administration, as well as other groups from US and foreign laboratories, are actively carrying out cross-validation test of these prototype scaffolds.
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Xia, Chunguang, and Nicholas Fang. "Enhanced Mass Transport Through Permeable Polymer Microcirculatory Networks." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15408.
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One of the obstacles of culturing functioning vital tissues in vitro is to obtain a substantial biomass at a physiological cell density (>108cells/cm3). At this high density, the diffusion length of metabolites is limited to ~100um. As a matter of fact, in real tissue, almost all the cells are located within 100um distance from the capillaries [1]. Studies [2, 3] also confirmed that the cells in the artificial tissue cannot be properly cultured when they are further than 400um from the external nutrient source. Therefore, to culture three dimensional artificial tissue with substantial biomass, vascularization is necessary to enhance the metabolites transport. The short diffusion length of the metabolites requires high capillary density (>100/mm2) in vascularization. To meet this need, we have developed a novel high resolution and high speed 3D microfabrication technique, the projection microstereolithography[4] to explore microcirculatory networks with high density (>150/mm2). Using this technology we designed and fabricated the microreactors as shown in Figure 1. In our samples, 800um PEG microcapillaries with 20um inner radius and 40um outer radius with pitch of 96um are fabricated. Two rings as inlet and outlet are connected to external supply of culture medium. We designed the parameters of the vascularized microbioreactor based on the simulations of oxygen and carbon dioxide transport and metabolism in hepatocytes. As shown in Figure 2, the capillaries are arranged in a hexagonal way. According to the geometric symmetry, the final simulation domain is divided into 2 regions, the polymer capillary wall and the tissue. We assumed that a culture media with dissolved oxygen is pumped through the capillaries at 1.5mm/s rate and diffuses through the capillary wall, into the hepatocytes. The consumption of oxygen follows Michaelis-Menten kinetics [5, 6] and the metabolic rate of carbon dioxide is assumed to be proportional to that of oxygen by a fixed quotient (-0.81) which is addressed and studied by other groups [7]. The carbon dioxide diffuses into the capillaries and can be carried away through the flow of the culture medium. Our simulation indicates that the bottleneck of effective oxygen transport is the permeability of the polymer materials. The oxygen concentration drops off about 90% after diffusing through the capillary wall. It is predicted that the diffusion length at the inlet is 74um and 48um at the outlet; the rapid drop of carbon dioxide concentration also happens across the capillary wall. The predicted carbon dioxide concentration in the tissue is ~80nmol/cm3; this value is much smaller than the toxic value (100mmHg or 3umol/cm3) reported by David Gray and coworkers [8]. In Figure 2, we present the effect of the permeability of the capillary polymer materials on the diffusion length of oxygen and the concentration of carbon dioxide in the tissue. Our study indicates the existence of an optimal permeability for the capillary network, at which the overall diffusion length of oxygen is maximized. Interestingly, we also found a maximum concentration of carbon dioxide in the cultured tissue as the permeability of the polymer material changes. We attribute it to the competition between the tissue thickness and the permeability. Higher permeability increases the cultured tissue thickness, and also increases the ability of capillary to empty carbon dioxide. Not only is this model applicable for oxygen and carbon dioxide, but also for the transport of other metabolites. As an ongoing experimental effort, our fluorescent microscopy measurement validated the diffusion transport of fluorescent species from the capillary (Figure 3). Experiments are also in progress on the oxygen diffusion from the capillaries will cell cultures of high density on the PEG scaffold by introducing proper indicators. In summary, we have established a method to design and manufacture vascularized microcirculatory network to enhance the mass transport during the tissue culture. To ensure the effective nutrient delivery and wastes removal, our numerical simulation also confirms that it is essential to embed high density microcapillaries with optimal permeability.
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Soltz, Michael A., Anna Stankiewicz, Gerard Ateshian, Robert L. Mauck, and Clark T. Hung. "Direct Hydraulic Permeability Measurements of Agarose Hydrogels Used as Cell Scaffolds." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0461.
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Abstract The objective of this study was to determine the intrinsic hydraulic permeability of 2% agarose hydrogels. Two-percent agarose was chosen because it is a concentration typically used for encapsulation of chondrocytes in suspension cultures [3–5], Hydraulic permeability is a measure of the relative ease by which fluid can pass through a material. Importantly, it governs the level of interstitial fluid flow as well as the interstitial fluid pressurization that is generated in a material during loading. Fluid pressurization is the source of the unique load-bearing and lubrication properties of articular cartilage [1,17] and represents a major component of the in vivo chondrocyte environment. We have previously reported that 2% agarose hydrogels can support fluid pressurization, albeit to a significantly lesser degree than articular cartilage [18]. Interstitial fluid flow gives rise to convective transport of nutrients and ions [6,7] and matrix compaction [9] which may serve as important stimuli to chondrocytes. We report for the first time the strain-dependent hydraulic permeability of 2% agarose hydrogels.
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Owen, John R., and Jennifer S. Wayne. "Influence of the Superficial Tangential Zone for Cartilage Modeled in Finite Deformation and With Tension/Compression Nonlinearity." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-193180.
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Creation of replacement tissue to repair articular surface defects remains a challenge. Normal zonal characteristics of articular cartilage throughout its thickness, particularly the superficial tangential zone (STZ), and normal material properties have not been reproduced in vitro in scaffolds nor in vivo in repairing defects. Without sufficient quality, such transplanted scaffolds in vivo may be doomed mechanically from the outset. Removal of the STZ from normal cartilage negatively affects the remaining cartilage’s ability to support axial loads and retain fluids [1–3]. Previous studies have modeled excessive axial deformation of repair cartilage [4–5]. Studies have shown that modeling the STZ of normal cartilage as transversely isotropic provides better agreement with indentation experimental results than isotropic models [6–9]. Others have modeled experimental conditions by incorporating tension and compression nonlinearity [10]. Previous analyses have indicated that strain-dependent permeability within the STZ can positively affect the ability of free-draining normal and repair models to withstand imposed surface loads [11,12]. This finite element study further examined the role of an STZ with strain-dependent permeability on the behavior of normal and repaired articular surfaces under contact loading from rigid permeable and impermeable spheres. Nonlinear geometry permitted finite deformations to occur while the differential stiffness in tension and compression was also represented.