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Sreeram, Attiganal Narayanaswamy. "Topological disorder in phosphate and other ceramics." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32679.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.Includes bibliographical references (leaves 146-157).
by Attiganal Narayanaswamy Sreeram.
Sc.D.
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Jensen, Amy S. "Phosphate bonding of ceramic hollow sphere foams." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19444.
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Langstaff, Sarah Dorthea. "Calcium phosphate ceramics capable of supporting osteoclastic resorption." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42953.pdf.
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Walsh, Pamela Judith. "Natural calcium phosphate ceramics for tissue engineering application." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486236.
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There is a great need for new bone graft materials. Bone related problems have increased considerably over the last few decades, owing to an ageing populate and the associated prevalence of bone disease. The traditional method of grafting to bridge bone defects are still widely used, despite a wide selection of new synthetic alternatives materials becoming available. These tend to lack the physical properties, such as porosity, interconnective and mechanical strength required for bone repair. Coral derived CaP ceramics have shown good potential, as substitute materials, offering the desirable physiochemical characteristics required for bone repair. This study investigated the development of a bioceramic from marine origins for use in bone tissue applications. Algae species were specifically selected to take account of their fast growth rate and aquaculture potential, which would minimise the environmental impact of harvesting. The conversion of alga was achieved through a novel technique, involving well controlled thermal processing followed by low pressure temperature hydrothermal synthesis technique. Using this technique, the original skeletal morphology of the alga was retained throughout processing. The resultant material was found to be a tri-phasic ceramic, with a > 90% composition of HA. Calcite and 13-TCP were the other two phases identified in the material. Cell studies confirmed the material to have good biocompatibility. A preliminary scaffold fabrication study incorporated the CaP material into a polymeric scaffold. The study found that the CaP material was robust and capable of withstanding rigorous processing. The work presented in this thesis indicates that this novel process is capable of synthesising a reproducible CaP material, which possesses suitable physiochemical properties for use in bone tissue engineering applications.
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De, Mestral François. "Calcium phosphate glasses and glass-ceramics for medical applications." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65405.
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Qadri, Syed Jalaluddin. "Phosphate and vanadate ceramics with xenotime and monazite structures." Thesis, University of Warwick, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406808.
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Lloyd, Michael Charles. "The dissolution of soluble phosphate glasses." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293799.
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Shaw, Lindsey Ann. "The development of chemical bonding systems for refractories/ceramics." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341290.
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Berg, Camilla. "Influence of Magnesium in theFormation of Phosphate Spheres : A simple method for the fabrication of sphericalparticles of calcium and magnesium phosphate." Thesis, Uppsala universitet, Oorganisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326255.
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Calcium phosphates and recently also magnesium phosphates, are used for medical applications, due to their biocompatibility and bioactivity. These properites makes spherical particles of calcium and magnesium phosphate suitable for carrier materials for drug delivery applications. By creating porous and/or hollow particles itis possible to load the particles with a drug and control therelease of the active substance. In this work, an ion-induced method for the synthesis of spherical calcium and magnesium phosphates was developed. A simple precipitation reaction was used, where substituting magnesium ions could replace the function of templates, such as surfactants or micelles, to induce the formation of spheres of a certain size and morphology. Experimental results showed that magnesium had an inhibitory effect on the nucleation and crystal growth of calcium phosphates. By using substituting ions as a structural regulator, it was possible to alter the size, morphology and phase composition of the spheres. At low magnesium concentrations, the spheres had a smooth surface andwere between 200 nanometer to 1 micrometer in diameter and composed of hydroxyapatite and/or magnesium-substituted beta-TCP. At higher magnesium concentrations, the spheres were about 10-50 micrometer with a rough, flaky surface. Results also proved that calcium ionshave the same effect on the crystallisation and self-assembly of magnesium phosphates. Apart from the magnesium concentration, reaction temperature proved to have a high influence on the sphereformation, whereas Ca/P ratio and reaction times above three hours did not affect the sphere formation to the same extent.
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Gallinetti, Sara. "New approaches in calcium phosphate cements and ceramics for bone regeneration." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/279558.
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Bone is among the most frequently transplanted tissues in the body. In Europe, about one million patients encounter a surgical bone reconstruction annually. The worldwide market of bone replacement materials is currently estimated at 5 billion Euros, with a 10% growth due to the ageing of the population. Natural grafts present several drawbacks which pushed scientists to investigate synthetic biomaterials. Although most synthetic bone substitutes available possess some of the positive properties of autografts, none yet have all the benefits of one's own bone. Among the available biomaterials, Calcium Phosphates (CaPs) are of great interest. Nonetheless, these materials can still be improved in several respects.
The main aim of this PhD Thesis is to contribute to the improvement of the properties of CaPs for bone regeneration with primary regard to Calcium Phosphate Cements (CPCs). The Thesis is divided in three main parts: i) Biphasic Calcium Phosphate Cements (BCPCs) with modified solubility and ion release; ii) Fibre Reinforced Calcium Phosphate cements (FRCPCs) with improved mechanical properties; iii) Macroporous CaP scaffolds for simvastatin acid release.
In the first part novel biphasic CDHA/ß-TCP cements were obtained by mixing two Tricalcium Phosphate (TCP) polymorphs with different solubility (a-TCP and ß-TCP) at different a-TCP/ß-TCP ratios, and characterised in terms of setting properties, mechanical properties, and degradation.
In the second part of this manuscript, new FRCPCs were fabricated with a focus on improving the adhesion fibres/matrix, in order to enhance the load transfer and, thus, the toughness of the material and their physico-chemical properties were investigated. Different approaches were studied. The first approach was to increase the chemical affinity of the fibres towards the matrix, adding an element in the matrix with high affinity to the fibres. In the first approach, TryMethyl Chitosan (TMC) was introduced in the liquid phase of a matrix reinforced with chitosan fibres. In the same line, lactic acid (LA) was added in the liquid phase of cements reinforced with Poly-L-lactic acid (PLLA) yarns. The biological characterisation of FRCPCs was explored using human osteoblastic-like cells MG63 . Another approach was to investigate the potential of low temperature plasma surface modification of PLLA yarns for reinforcement of CPCs. Oxygen low pressure plasma was employed at different treatment times and the surface properties of the untreated and plasma-treated PLLA were evaluated.
The third part of this Thesis consisted in producing low temperature (CDHA) or high temperature (ß-TCP) macroporous scaffolds as carriers for Simvastatin acid (SVA), an osteogenic and angiogenic promoter. In order to modulate the drug release beyond the intrinsic capacity of the material, plasma polymerisation with PCL:PEG copolymers was used to dry-coat the CaP scaffolds. The material properties, the plasma polymer layer and the drug release from the scaffold were characterised.El hueso es uno de los tejidos más trasplantados del cuerpo. Sólo en Europa, se cuentan alrededor de un millón de cirugías de reconstrucción ósea anualmente. La estimación del mercado global de los sustitutos óseos es aproximadamente de cinco billones de Euros por año, con un 10% de crecimiento anual debido al envejecimiento de la población. Debido a los problemas asociados a los injertos biológicos, la investigación y el desarrollo de materiales sintéticos y biocompatibles (Biomateriales) ha experimentado un gran auge. Aunque la mayoría de sustitutos sintéticos disponibles poseen algunas de las características de los autoinjertos, hasta el momento ninguno reúne todos los beneficios del hueso del propio individuo. Dentro de los biomateriales para regeneración ósea, los fosfatos de calcio han sido de gran interés debido a su composición química similar a la del hueso. Sin embargo, aún se requieren mejoras en distintos aspectos de estos materiales. El objetivo principal de esta Tesis Doctoral es contribuir a la mejora de las propiedades de los fosfatos de calcio para la regeneración ósea, con un interés especial en los cementos de fosfato de calcio. La Tesis investiga diferentes estrategias para el desarrollo de materiales para la sustitución ósea, novedosos y con propiedades mejoradas respecto a los actuales. La Tesis comprende tres partes principales: i) Cementos bifásicos de fosfato de calcio (BCPCs), constituidos por materiales con diferente solubilidad; ii) Fosfatos de calcio reforzados con fibras (FRCPCs), para la mejora de las propiedades mecánicas; iii) Andamios macroporosos para la liberación de una sal de simvastatina. En la primera parte de la Tesis, se describe el desarrollo de BCPCs compuestos por hidroxiapatita deficiente en calcio (CDHA) y fosfato tricálcico ß (ß-TCP). Estos materiales derivan de la reacción de las mezclas de dos polimorfos de fosfato tricalcico (TCP) con diferente solubilidad (a-TCP y ß-TCP) y, en esta tesis, se caracterizan su fraguado, sus propiedades mecánicas y degradación. En la segunda parte, se han desarrollado nuevos FRCPCs con especial atención hacia la mejora de la adhesión entre fibras y matriz, con el objetivo de mejorar la transferencia de carga entre ellos y por tanto, las propiedades mecánicas del compuesto. Se han investigado distintas estrategias. La primera de ellas basada en la investigación de materiales con una fase común (o con alta afinidad química) entre las fibras y la fase liquida del cemento; de esta manera se pretende crear un enlace más fuerte entre las fibras y la matriz. En un primer material se incorporó un 1 w/v% de Trimetilo de quitosán (TMC) en la fase líquida del cemento que a su vez se reforzó con fibras de quitosán. En un segundo grupo de materiales, se añadió un 10 v/v% de ácido láctico (LA) a la matriz del cemento junto con hilos discontinuos de ácido poliláctico (PLLA). Estos cementos también se caracterizaron biológicamente por medio de células osteoblásticas MG63. La segunda estrategia investigada en los FRCPCs se basa en la modificación superficial de las fibras de PLLA con plasma de baja temperatura con el fin de mejorar sus propiedades de mojado. Las fibras se trataron con plasma de oxigeno de baja presión a distintos tiempos y se incorporaron a la matriz de cemento, y se caracterizaron tanto las modificaciones superficiales de las fibras como las propiedades del cemento. La tercera parte ha consistido en el desarrollo de andamios macroporosos obtenidos a baja (CDHA) o alta (ß-TCP) temperatura para ser utilizados como formas de liberación de una sal de simvastatina (SVA), con propiedades osteogénicas y angiogénicas. Para conseguir modular la liberación del fármaco se recubrieron los andamios cargados con SVA con un copolímero de PCL:PEG mediante polimerización por plasma. Se caracterizaron las propiedades tanto del material como del recubrimiento y se evaluó la liberación del fármaco.
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Zhang, Xing. "Preparation and characterization of calcium phosphate ceramics and Composites as bone substitutes." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3294744.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed January 11, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 143-155).
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Martin, Richard Alan. "Properties of rare earth phosphate glasses and rare-earth halide liquids." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248113.
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Olsson, Mirja. "Chemical stability of grain boundariesin β-tricalcium phosphate ceramics : β-TCP as bone substitute material." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173285.
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β – Tricalcium phosphate (β-TCP, Ca3(PO4)2) is a commonly used bone substitute material due to its biocompatibility and resorption. This study focused on the production of almost fully dense β-TCP ceramics with varying degrees of impurities (Ca/PO4 ratio, addition of 5% Mg). Three methods were used to produce the β-TCP ceramics, uniaxial pressing, slip-casting and isostatic pressing. In this study the isostatic pressing and sintering at 1150ºC for 20h and 15min, resulted in the densest β-TCP ceramics (97.7-99.2%). No significant differences of grain size and density could be detected between the samples produced with various compositions. These isostatically pressed samples sintered at 1150ºC were then dissolved in 0.08M aceticacid solution to simulate the in vivo resorption. It was found that the samples containing extra Mg dissolved slower. Attempts to determine the chemical composition of the grain boundaries were made without success. However, SEM observations of partly dissolved β-TCP ceramics revealed that the grain boundaries dissolved faster than the grains. The study was performed at the RMS foundation in Switzerland.
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Zhou, Gang. "ZnSe ceramics and phosphate glasses for optical applications in the visible and infrared ranges." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S071/document.
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Une étude en deux parties a été effectuée sur la préparation et la caractérisation de céramiques de ZnSe et de verres de phosphate à des fins optiques. Pour préparer des poudres de ZnSe, deux voies de synthèse ont été utilisées: i) hydrothermales; ii) le broyage à billes. La taille des particules ainsi que leur morphologie a été analysée par différentes techniques (DRX, MEB…). Ensuite, deux technologies de frittage, pressage à chaud (HP) et frittage flash (SPS), ont été mises en œuvre pour obtenir des échantillons massifs de ZnSe optiquement transparents. La meilleure transmission obtenue dans le domaine du moyen infrarouge, pour les échantillons HP et SPS, est supérieure à 50% et 40% respectivement. Pour obtenir des verres de phosphate avec une grande durabilité chimique, des cations avec une intensité de champ élevée tels que Nb5+ et Ti4+ ont été incorporés dans un verre de phosphate. La transparence dans le domaine du visible a été obtenue en utilisant de petites quantités d'agents d'oxydation tels que les sulfates ou les nitrates. L’utilisation de la spectroscopie par réflectance diffuse a permis de déterminer les coordonnées chromatiques afin d’évaluer le bénéfice de ces ajoutsA two-part study was conducted on the preparation and characterization of ZnSe ceramic and phosphate glasses for optical applications in the visible and infrared range. To prepare ZnSe powders, two synthetic routes were used: i) hydrothermal; ii) ball milling. The size and morphology of synthesized powders were analyzed using different techniques (XRD, SEM…). Then two sintering technologies, hot pressing (HP) sintering and spark plasma sintering (SPS) sintering have been implemented to obtain optically transparent ZnSe bulk samples. The best transmission obtained in the mid-infrared range, using HP and SPS, is greater than 50% and 40% respectively. To synthesize phosphate glasses with a high chemical durability, cations with high field strength such as Nb5+ and Ti4+ were incorporated into a phosphate matrix. The transparency in the visible range was obtained using small amounts of oxidation agents such as sulfates or nitrates. The use of diffuse reflectance spectroscopy led to determination of the chromaticity coordinates to evaluate the benefit of these additions
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Hadzifejzovic, Emina. "Electrical and structural aspects of Li-ion conducting phosphate based glasses and glass ceramics." Thesis, Queen Mary, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408396.
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Hassan, Senin Bin. "The elastic and nonlinear acoustic vibrational properties of vitreous SiO2 and rare earth phosphate glasses." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238739.
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Schlosser, Margarete [Verfasser], Hans-Joachim [Akademischer Betreuer] Kleebe, and Christoph [Akademischer Betreuer] Schüth. "Vapor transport sintering of calcium phosphate ceramics / Margarete Schlosser. Betreuer: Hans-Joachim Kleebe ; Christoph Schüth." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/1106453352/34.
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Lee, Goonhee. "Selective laser sintering of calcium phosphate materials for orthopedic implants /." Digital version accessible at:, 1997. http://wwwlib.umi.com/cr/utexas/main.
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Casey, Brian Paul. "Novel fabrication techniques for the production of porous biphasic calcium phosphate ceramics for bone substitute application." Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760834.
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Metsger, Dean Scott. "The characterization of the biological and mechanical properties of porous calcium phosphate ceramics used as bone implants /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487759055156703.
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Bhatt, Himesh A. "Synthesis and Characterization of Nanocrystalline Hydroxyapatite Powder; And the Effects of Oxide-Based Sintering Additives on Tricalcium Phosphate." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3567.
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Calcium phosphate (CP) materials have been used extensively for bone replacement and augmentation due to their similarity to the mineral component of bone. In addition to being non-toxic, they are biocompatible, not recognized as foreign materials in vivo, and most importantly, exhibit osteoconductive behavior, being able to help in bone formation during healing. CPs form an intimate physicochemical bond with the host tissue, termed osseointegration. However the main limitation of calcium phosphates is their inherent brittle nature and poor mechanical performance under complex stress states. As a result, these materials have been used clinically only in non-load-bearing applications, primarily as granules. The primary goal of this research was to enhance mechanical performance of CPs, tricalcium phosphate (TCP) and hydroxyapatite (HAp) to be precise, in an attempt to develop controlled strength-loss resorbable/ bioactive ceramic bone-grafts for hard tissue engineering. In my work on TCP, I selected and introduced small quantities of single and multi-oxide sintering additives in TCP, to study their influence on sintering behavior, densification, mechanical properties and biodegradation/ biomechanical properties in vitro. Through this research, I could improve mechanical performance of [Beta]-tricalcium phosphate ([beta]-TCP) and controlled its rate of biodegradation by introducing of certain additives. In my second work, I improved mechanical performance of HAp (Ca10(PO4)6(OH)2 by reducing particle-size of the powder through the synthesis of stoichiometric, nanocrystalline, single phase HAp powder in the range of 2-20 nm. Synthesis of powder was accomplished via a modified low temperature sol-gel technique using ethanol/ water as solvent.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Kim, Hyunbin. "Synthesis and control of microstructure, mechanical properties, and bioactivity in biphasic and preferentially oriented calcium phosphate bioceramics." Birmingham, Ala. : University of Alabama at Birmingham, 2007. http://www.mhsl.uab.edu/dt/2007p/kim.pdf.
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Bernard, Sheldon Ainsworth. "Influence of silicon dioxide, magnesium oxide and zinc oxide on resorbable tricalcium phosphate based bioceramics." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/s%5Fbernard%5F083005.pdf.
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Rewinkel, Scott Everett. "The effects of SiO₂, ZnO, and MgO doping on the mechanical and biological properties of beta-tricalcium phosphate bioceramics for bone tissue engineering, in vitro and in vivo analysis." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Fall2009/s_rewinkel_100909.pdf.
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Thesis (M.S. in mechanical engineering)--Washington State University, December 2009.Title from PDF title page (viewed on Jan. 22, 2010). "School of Mechanical and Materials Engineering." Includes bibliographical references (p. 123-128).
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Dasgupta, Sudip. "Nanostructured hydroxyapatite and tricalcium phosphate based ceramics for bovine serum albumin protein delivery and bone implants using microwave sintering." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Dissertations/Summer2008/S_Dasgupta_073008.pdf.
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Karvat, Franciele. "Elaboração e caracterização de biomateriais : matriz de cálcio e compósitos fosfato de cálcio/Al2O3a Sol-Gel para aplicação como implante e regeneração óssea." Universidade do Estado de Santa Catarina, 2005. http://tede.udesc.br/handle/handle/1661.
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Bone defects arise from many causes including traumas, infections, tumors and congenital deformations. They are the main problems in orthodontic and orthopedic surgical clinics. In the last few years it was verified that porous ceramics are more and more used in medical applications such as substitution and regeneration of bone tissues, mainly the ceramic formed by Ca/P composition (calcium phosphates). These ceramic are broadly used in biomedical applications due to their mineralogical characteristics, which are similar to the biological apatite (bones of human skeleton), and also because they have an excellent biocompatibility. The aim of this work was focused on the optimization of the elaboration process by aqueous suspension and on the characterization of biomaterials composed of calcium phosphate and composites (calcium phosphate plus alumina). The purpose was to improve the mechanical properties of the calcium phosphate by incorporation of 5%, 10%, 20% and 30% in volume of micrometrics particles of sol-gel Al2O3-a, preserving its biocompatibility. The characterization was performed through morphological, microestrutural, physical, chemistry, and mechanical investigations, as well as by biocompatibility and thermal behavior. The results showed that the bioceramic powders obtained from calcination at 900ºC are formed by small agglomerated particles, in the size bellow 200 nm, for the calcium phosphate, and for the composite powders it was observed debris of sol-gel alumina particles dispersed inside the powders of the calcium phosphate. Evidences from X-ray diffraction showed that the powders, after calcination, are constituted of hydroxyapatite and calcium oxide for calcium phosphate, and for the composites it was found the same phases plus sol-gel alumina. On the biomaterials obtained by thermal treatment of the powders at 1300ºC and sintered at 1300ºC/2 hours, the present phases are hydroxyapatite and calcium oxide for calcium phosphate, and calcium aluminate oxide and tricalcium aluminate for the composites. Higher mechanical strength were observed on calcium phosphate containing 5 and 10% of sol-gel alumina. Complementally "in vitro" study of citotoxity enhanced the biocompatibility of the materials where the best results were obtained on the composite containing 20% of sol-gel alumina.
Os defeitos ósseos são resultados apresentados por diferentes causas incluindo traumas, infecções, tumores e deformações congênitas. Estes são os principais problemas nas clínicas cirúrgicas ortopédicas e odontológicas. No decorrer dos últimos anos, constatou-se que as cerâmicas microporosas destacam-se em aplicações de substituição e regeneração de tecidos ósseos, principalmente as cerâmicas formadas pela composição Ca/P, os fosfatos de cálcio. Estas cerâmicas vêm tomando um espaço importante em aplicações biomédicas, em razão de suas características mineralógicas semelhantes às apatitas da estrutura óssea do esqueleto humano, e também por apresentarem boa biocompatíbilidade. O objetivo deste trabalho concentrou-se na otimização do método de elaboração via úmida e caracterização de biomateriais fosfato de cálcio e compósitos. Tendo como interesse melhorar as propriedades mecânicas da matriz fosfato de cálcio, pela incorporação de partículas micrométricas de Al2O3-α sol-gel nas concentrações de 5%, 10%, 20% e 30% em volume e preservar as características de biocompatíbilidade destes biomateriais. Os estudos de caracterização foram realizados em nível morfológico, microestrutural, física, química, das propriedades mecânicas, do comportamento térmico e da biocompatíbilidade. Os resultados destes estudos, mostraram que, os pós biocerâmicos obtidos a partir da calcinação a 900ºC, são formados por finas partículas aglomeradas, apresentando tamanho (d < 200nm) para a matriz fosfato de cálcio, já para os pós compósitos, constatou-se a presença dos fragmentos de alumina-a sol-gel, dispersos dentro do pó da matriz. Os resultados obtidos pela técnica de difractometria de Raios X para os pós obtidos da calcinação, mostraram em seus espectros a presença da fase hidroxiapatita e óxido de cálcio para a matriz e para os compósitos, mais a presença da alumina-a sol-gel. Para os pós biocerâmicos obtidos do tratamento térmico a 1300ºC e biomateriais sinterizados a 1300ºC/2 horas, apresentaram em seus espectros as fases de hidroxiapatita, óxido de cálcio para a matriz e óxido aluminato de cálcio e aluminato tricálcico para os compósitos. Os ensaios mecânicos mostram claramente maior valor da tensão de ruptura flexão três pontos, para os compósitos fosfato de cálcio/5% e 10% de Al2O3-a sol-gel em volume em suas composições. O estudo complementar de citotoxidade in vitro , colocou em evidência a biocompatíbilidade das diferentes composições, observando melhor resultado para o pó compósito com 20% em volume de Al2O3-a sol-gel.
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Švec, Jiří. "Fosfátová pojiva v žáruvzdorné aplikaci." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2015. http://www.nusl.cz/ntk/nusl-234573.
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The doctoral thesis is focused on the study, research and development of refractories with phosphate bonding. Primary motivation is preparation of phosphate-based binders that can be applied for non-shaped insulating material fabricated by “in situ” foaming. The phosphate binders based on Al2O3-H3PO4 system are one of the most common in refractory technology. The amphoteric nature of the aluminium and its oxides require the setting of Al2O3-H3PO4 binders under the higher temperatures. Application of higher temperatures is necessary to obtain the minimal manipulation strength of as-prepared green bodies. The main goal of the work is preparation of ytrium phosphate-based binders via different preparation techniques. Yttrium based binders would allow phosphate refractory preparation by standard way, i.e via reaction between binder and reactive aggregate, without structural disintegration of foamed material even before getting manipulation strength or the final firing procedure. Yttrium is more basic than aluminium and therefore more reactive in Y2O3-H3PO4 system.. Yttrium oxide is highly refractory material and sintered yttrium monophosphate has excellent properties from the thermal and corrosive stability point of view. This fact should compensate higher price of this material. Experimental part of this work studies the possibilities of binders preparation in Y2O3-H3PO4 system. The mixtures were designed to prepare binding phase Y(H2PO4)3. Products of these reactions were characterized in phase and chemical point of view. In order to study and describe setting and hardening processes of phosphate binders, the products were “in situ” analyzed by the thermal analyses and high-temperature diffraction analysis up to the 1300 °C. High temperature products were then characterized by means of phase and chemical composition and morphology.
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Garcia, Perez Delabat Javier. "PCL-Calcium Phosphate 3D Printed Scaffolds For Bone Tissue Regeneration." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81735.
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The design and selection of a biomaterial will depend on its specific application and the required properties for that application, both mechanical physicochemical properties. Biomaterials can be extremely helpful in order to treat and help the human body to heal and repair faster any kind of fracture produced in bones. Calcium phosphate scaffolds produced by sol-gel procedures have been used for this purpose with a great success regarding mechanical properties and biocompatibility. This is the reason why new techniques needs to be developed to be able to produce scaffolds in a faster way and to reach a personalized treatment to each patient. By using 3D printing techniques, a new and promising scope is open for bone tissue engineering due to the possibility of printing scaffolds with any shape and complexity through CAD design and modelling. In this project 3D printed scaffolds with a matrix combination of polymers and calcium phosphate will be produced and studied for bone tissue regeneration. Self-setting alpha tricalcium phosphate (α-TCP) based cement inks combined with polycaprolactone (PCL) were optimized, and 3D printed structure scaffolds were successfully generated by direct ink writing. Afterwards, the scaffolds were subjected to different hardening processes in order to obtain different hydroxyapatite microstructure morphologies and were characterised by different methodologies. It was demonstrated the important effect of obtaining a complete transformation from the α-TCP into hydroxyapatite in the mechanical properties. An improvement in the mechanical properties at compression was achieved with the addition of PCL within the scaffold ́s structure and a different fracture mode of the scaffolds was observed.
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Leal, Claudenete Vieira 1972. "Desenvolvimento e avaliação 'in vitro' de um cimento de fosfato de calcio." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263426.
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Orientador: Cecilia Amelia de Carvalho ZavagliaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Os cimentos ósseos a base de fosfato de cálcio são materiais cerâmicos que apresentam biocompatibilidade devido a sua composição química semelhante à dos ossos, e bioatividade, promovendo a osteocondução. Com essas características, é possível a utilização desses materiais como implantes ósseos ou como preenchimento. Os cimentos de fosfato de cálcio são materiais constituídos por um pó e um líquido, que, ao serem misturados formam uma pasta que endurece espontaneamente à temperatura ambiente ou corpórea como resultado da precipitação de um ou vários fosfatos de cálcio. O pó pode ser composto por um ou vários fosfatos de cálcio, outros sais de cálcio e aditivos orgânicos. O líquido pode ser água ou soluções aquosas de compostos de cálcio ou fosfato. A proposta desse trabalho foi estudar a síntese de monólitos de fosfatos de cálcio baseado no sistema ß-Fosfato Tricálcio/Ácido Fosfórico (ß-TCP/H3PO4), que produz hidrogeno fosfato de cálcio dihidratado (DCPD), um cimento de fosfato de cálcio que possui como principal vantagem baixo custo e a desvantagem de possuir pH ácido, podendo causar necrose em tecidos. Para contornar esse problema, o DCPD foi convertido em apatita pela hidrólise em solução alcalina. O estudo envolveu a síntese do ß-TCP, a preparação do cimento, caracterizações físicas e químicas e o estudo do cimento em Fluido Corpóreo Simulado (FCS), solução que simula o plasma sanguíneo humano, para avaliar seu comportamento in vitro
Abstract: Calcium phosphate bone cements are ceramics materials that present biocompatibility because of their chemical composition similar to the human bone, and bioactivity, promoting osteocunduction. Due to these characteristics, it is possible the use of these materials as bone implants. Calcium phosphate cements are composed of a powder and liquid phases, which, when mixed form a paste that hardens spontaneously as result of the precipitation of one or more calcium phosphates. The powder may be composed of one or some calcium phosphates, others salts and organics additives. The liquid may be water or calcium phosphates aqueous solutions. The purpose of this work is the synthesis of calcium phosphate monoliths based on ß-tricalcium phosphate/ortho-phosphoric acid (ß-TCP, Ca3(PO4)2/H3PO4), that produce dicalcium phosphate dehydrate (DCPD, CaHPO4.2H2O) as phase precipitated as a result of the setting reaction. DCPD is inexpensive, but is quite soluble and has an acidic hydrolysis, which may cause necrosis in vivo. To resolve this problem, DCPD was converted in apatite phase by hydrolysis in NaOH aqueous solution. This study included ß-TCP synthesis, cement preparation, chemical and physical characterizations and the study of the cement in Simulated Body Fluid (SBF), with ion concentrations nearly equal to those of human blood plasma, to evaluate the in vitro behavior
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Ajaxon, Ingrid. "Can Bone Void Fillers Carry Load? : Behaviour of Calcium Phosphate Cements Under Different Loading Scenarios." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-316656.
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Calcium phosphate cements (CPCs) are used as bone void fillers and as complements to hardware in fracture fixation. The aim of this thesis was to investigate the possibilities and limitations of the CPCs’ mechanical properties, and find out if these ceramic bone cements can carry application-specific loads, alone or as part of a construct. Recently developed experimental brushite and apatite cements were found to have a significantly higher strength in compression, tension and flexion compared to the commercially available CPCs chronOS™ Inject and Norian® SRS®. By using a high-resolution measurement technique the elastic moduli of the CPCs were determined and found to be at least twice as high compared to earlier measurements, and closer to cortical bone than trabecular bone. Using the same method, Poisson's ratio for pure CPCs was determined for the first time. A non-destructive porosity measurement method for wet brushite cements was developed, and subsequently used to study the porosity increase during in vitro degradation. The compressive strength of the experimental brushite cement was still higher than that of trabecular bone after 25 weeks of degradation, showing that the cement can carry high loads over a time span sufficiently long for a fracture to heal. This thesis also presents the first ever fatigue results for acidic CPCs, and confirms the importance of testing the materials under cyclic loading as the cements may fail at stress levels much lower than the material’s quasi-static compressive strength. A decrease in fatigue life was found for brushite cements containing higher amounts of monetite. Increasing porosity and testing in a physiological buffer solution (PBS), rather than air, also decreased the fatigue life. However, the experimental brushite cement had a high probability of surviving loads found in the spine when tested in PBS, which has previously never been accomplished for acidic CPCs. In conclusion, available brushite cements may be able to carry the load alone in scenarios where the cortical shell is intact, the loading is mainly compressive, and the expected maximum stress is below 10 MPa. Under such circumstances this CPC may be the preferred choice over less biocompatible and non-degradable materials.
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Cardoso, Hugo Ananias Inacio 1987. "Cimento de Alfa-TCP com diferentes aditivos = cinética da reação de cura, propriedades mecânicas e avaliação da citotoxicidade." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263531.
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Orientador: Cecília Amélia de Carvalho ZavagliaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Os cimentos ósseos à base de fosfato de cálcio são biomateriais cerâmicos biorreabsorvíveis utilizados na substituição e no reparo de tecido ósseo danificado. Apresentam uma série de atrativos, como excelente biocompatibilidade e capacidade de serem moldados em cavidades pequenas e complexas. Porém, sua aplicação é restringida pela sua baixa resistência mecânica e sua cinética da reação lenta. O objetivo principal deste trabalho foi desenvolver cimentos de fosfato de cálcio, baseado no sistema do alfa-fosfato tricálcico, com melhores propriedades mecânicas e cinética da reação acelerada. Para isso, obteve-se o pó de alfa-fosfato tricálcico a partir de reagentes sintetizados em laboratório a fim de se obter pureza elevada; utilizou-se hidrogeno fosfato de sódio, ácido cítrico e ácido tânico como aditivos na solução de pega a fim de melhorar suas propriedades. O método de obtenção dos reagentes mostrou-se eficaz, obtendo-se pó de alfa-fosfato tricálcico com pureza elevada. Todas as combinações de aditivos utilizadas aceleraram a cinética da reação e aumentaram a resistência mecânica do cimento de fosfato de cálcio, obtendo-se valores superiores aos reportados na literatura
Abstract: The calcium phosphate bone cements are resorbable bioceramics used for replacement and repair of damaged bone tissue. Such material has many benefits, such as excellent biocompatibility and ability to be molded into complex and small cavities. However, its application is restricted by their low mechanical strength and slow reaction kinetics. The main objective of this study was to develop calcium phosphate bone cements, based on alpha-tricalcium phosphate system, with better mechanical properties and faster reaction kinetics. Hence, the powder of alpha-tricalcium phosphate was obtained from reagents synthesized in the laboratory to get high purity powder; disodium hydrogen phosphate, citric acid and tannic acid are used as additive on setting liquid to improve the cement properties. The method to obtain the reagents was effective, resulting in a powder of alpha-tricalcium phosphate with high purity. All combinations of additives accelerated the reaction kinetics and increased the mechanical strength of the calcium phosphate cement, resulting in higher values than those reported in the literature
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Wijesinghe, Dayanjan. "Ceramide Kinase and Ceramide-1-Phosphate." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1621.
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Ceramide-1-phosphate (C1P) is a bioactive lipid that has been implicated in many biological processes. Our laboratory has conclusively demonstrated its role in inflammation via activation of cPLA2α. The only known enzyme to date responsible for direct synthesis of C1P is ceramide kinase. Very little was known about this enzyme in terms of its enzyme kinetics and substrate specificity. As CERK is an enzyme that acts on membrane lipids, its kinetics cannot be studied using standard bulk dilutions methods. Thus we developed a surface dilution approach using Triton X 100 mixed micelles for studying the kinetics of CERK. We discovered that ceramide kinase has an affinity for naturally occurring long chain ceramides while ceramides containing shorter than 8 carbons are very poor substrates for the enzyme. Also of note is the discovery that there is no discrimination between the naturally occurring long chain ceramides leading to the conclusion that the preponderance of D-e-C16 C1P in cells are due to an availability effect. We also investigated the chain length specificity of interaction between C1P and cPLA2α. Our data indicate that cPLA2α is activated by C1P’s containing acyl chains longer than two carbons. The study showed C2 C1P as being unable to activate cPLA2α thus establishing a tool for the investigation of cPLA2α dependent and independent effects of C1P. In the course of the study we investigated the ethanol/dodecane delivery system as a means of safely delivering lipids to cells. Our data conclusively demonstrate that this delivery system successfully delivers lipids to the internal membranes where their biological action takes place and that at low lipid concentration (<1µM), is non toxic to cells. A significant technical hurdle in the study of C1P was the lack of accurate and reproducible method of quantitatively and qualitatively analyzing the lipid. Using a mass spectrometric approach we developed an accurate technique that now allows us to quantify the lipids in cells. Using this and radiolabeling studies we discovered evidence for production of C1P from S1P via an acyl transferase pathway. Further studies are currently being carried out to identify the enzyme/s responsible for this pathway.
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Duarte, Cláudia Regina Appio. "Avaliação da citotoxicidade in vitro de composições de fosfato de cálcio para uso em reparação óssea." Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/950.
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Previous issue date: 2015-07-20The nanostructured calcium phosphate bioceramics have shown importance in bone repair biomaterials for its chemical and crystallographic similarity with bone tissue crystalline structure, increasing their relevance in orthopedics, dentistry and bone healing. These biomaterials have interconnected microporous nanostructure, made of thin grains and micropores, which favor their use as synthetic matrix in recuperation of injure bone. In vitro cell culture is a value tool for studying the mechanisms whereby biomaterials can cause adverse reactions in cell level, indicating their potential use at medical practice. The aim of this study was to evaluate the biocompatibility of porous calcium phosphate bioceramics with different morphology of grains and microporous by MTT assay, cell growth curve and cell-material interaction study by scanning electron microscope (SEM). The cell-material interaction study by SEM showed fibroblasts adhesion and proliferation in the biomaterials surface. In the results of MTT assay and cell growth curve it was found that the tested biomaterials were biocompatible, making them suitable candidates as bone substitutes. The biomaterial composed by 80% TCP-β/20% HA (1,67M/1100 °C/2h) showed cell viability less than 70% and descendant growth curve, indicating certain level of cytotoxicity
As biocerâmicas nanoestruturadas de fosfato de cálcio tem se destacado na área de biomateriais de reconstituição óssea pela sua semelhança química e cristalográfica com a apatita óssea do esqueleto humano, reforçando sua importância na ortopedia, odontologia, fixação de implantes e reparação do tecido ósseo. Estes biomateriais apresentam micro e nanoestruturas microporosas interconectadas, formada por finos grãos e microporos, características estas que favorecem seu uso como matriz sintética na recuperação de tecido ósseo lesado. O cultivo de células in vitro é uma valiosa ferramenta para se estudar os mecanismos pelos quais os biomateriais podem produzir reações adversas em nível celular, indicando seu potencial para uso na prática médica. Este trabalho teve como objetivo avaliar a biocompatibilidade das cerâmicas porosas de fosfato de cálcio em condições diferenciadas de morfologia de grãos e de microporos por meio do teste de citotoxicidade MTT, análise da curva de crescimento celular e estudo da interação célula-material por microscopia eletrônica de varredura (MEV). A análise da interação célula-material por MEV mostrou a adesão e proliferação dos fibroblastos na superfície das diferentes biocerâmicas de fosfato de cálcio testadas. Nos resultados obtidos por meio do ensaio colorimétrico MTT e curva de crescimento constatou-se que os biomateriais testados se mostraram biocompatíveis, possuindo grande potencial como substitutos ósseos. O biomaterial composto por 80% TCP-β/20% HA (1,67M/1100 °C/2h) apresentou viabilidade celular abaixo de 70% e curva de crescimento descendente, demonstrando grau de citotoxicidade
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Khan, Yusuf M. Laurencin Cato T. "Development of a polymer/ceramic composite scaffold for bone tissue engineering /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/470.
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Cassiano, Gaspar Stefania. "Mise en forme par extrusion de supports de catalyseurs à base d'alumine et à microstructure multi-échelles : Effet de la composition granulaire et du liant sur les propriétés des matériaux." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0056/document.
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L'empilement maîtrisé de granules de différentes tailles est un concept utilisé dans la plupart de procédés de mise en forme de matériau. Cette organisation hiérarchique est connue pour améliorer les propriétés d'écoulement à l'étape de mise en forme et les caractéristiques mécaniques du matériau final. Il est apparu intéressant d'appliquer ce concept à la mise en forme par extrusion de supports de catalyseurs avec des petites (2 µm) et grosses (19 µm) granules d'alumine poreuse dont l'assemblage est assurée par un liant traditionnel, la boehmite peptisée et neutralisée, ou par un liant plus original, le phosphate d'aluminium. L'étude vise ainsi à évaluer l'effet du liant et de la microstructure multi-échelles apportée par l'organisation hiérarchique des granules, sur les propriétés texturales et mécaniques des supports. Le contrôle des conditions de mise en forme et l'optimisation de la formulation des deux liants ont permis d'obtenir des extrudés à microstructure comparable entre la boehmite et le phosphate d'aluminium et variable en fonction de la proportion de petites. Cette population remplit les espaces entre les grosses granules de manière optimale entre 40 et 60% pds et les desserre aux plus fortes teneurs. La rétraction du liant au cours des traitements thermiques génère un volume de macropores qui est minimisé lorsque les petites granules comblent les espaces formés par les grosses. La macroporosité minimale conduit à de meilleures résistances à la rupture (par tests d'écrasement de type brésilien) et les matériaux les plus résistants sont ceux mis en forme avec le phosphate d'aluminium. Ce résultat est expliqué par la nature très cohésive de ce liant formée in situ par réaction de l'acide phosphorique avec la boehmite et la périphérie des granules d'alumine. Dans ce cas, la rupture a lieu au sein des granules différemment des supports mis en forme avec la boehmite peptisée à l'acide nitrique qui présentent une rupture à l'interface granule-liant. Les matériaux à microstructure multi-échelles présentent également une meilleure ténacité déterminée par des essais de flexion trois points. Le phosphate d'aluminium étant un liant non-poreux conduit à des supports avec une mésoporosité plus faible. Les nouveaux supports à microstructure multi-échelles semblent prometteurs pour des nombreuses applications catalytiques sensibles aux propriétés diffusionnelles et mécaniquesThe controlled packing of different sized-granules is a concept widely used in most of the shaping material processes. This hierarchical organization is known to improve the flow properties during shaping and the mechanical characteristics of the finished material. It seemed interesting to apply this concept in order to prepare catalyst supports by extrusion containing small (2 µm) and large (19 µm) porous alumina granules assembled by a traditional binder, the peptized and neutralized boehmite, or by a more original, an aluminum phosphate binder. This study aims to investigate the effect of binder type and of the multiscale microstructure achieved by the packing of different granules size on textural and mechanical support properties. The control of kneading and extrusion conditions associated with the optimized binder formulation, conducted to similar microstructures with both binders according to the amount of each granular population. Small granules fills better the residual spaces between the larges between 40 and 60 wt.% and loosens them with strongest contents. Binder shrinkage during heat treatment generates a macroporosity which is minimized when small granules fills the voids formed by the larger ones. Minimal macroporosity leads to better crushing resistance (by Brazilian test) and the most resistant materials are the ones shaped with the aluminum phosphate. This result is explained by the high cohesive capacity of this binder obtained in situ by reaction of the phosphoric acid with the boehmite and the border of the alumina granules. In this case, the breakage takes place inside the granules differently from the supports shaped with the peptized boehmite by nitric acid which present a breakage at the granule-binder interface. Also, the multiscale microstructure materials present a better tenacity determined by three point bending. Aluminum phosphate being a non-porous binder, leads to supports with a weaker mesoporosity. The new multiscale microstructure supports seem interesting for several catalytic applications that are sensitive to diffusivity and mechanical properties
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Hill, Alexandra. "Thermodynamic and Morphological Properties of Ceramide-1-Phosphate Model Monolayer Systems." Kent State University Honors College / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1291831964.
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Leerssen, Robert Douglas. "Iron phosphate glass for the vitrification of INEEL sodium bearing waste and Hanford low activity waste." Diss., Rolla, Mo. : University of Missouri-Rolla, 2002. http://scholarsmine.mst.edu/thesis/pdf/Leerssen_Thesis_09007dcc805618fa.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2002.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 25, 2008) Includes bibliographical references.
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RIBEIRO, CHRISTIANE. "Processamento e caracterizacao de ceramicas a base de hidroxiapatita e fosfato-tricalcico." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11058.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/11693-7
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Loutou, Mohamed. "Granulats à base de boues de phosphates : transformations thermiques, propriétés physiques et application." Thesis, Toulon, 2015. http://www.theses.fr/2015TOUL0016/document.
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Des agrégats à base des boues de phosphate de la zone de Gantour ( Youssoufia,Maroc) sont cuits à des températures comprises entre 900 et 1200°C, et examinés par différentes techniques (DRX, MEB, analyses thermique et dilatométrique, et spectroscopie d’impédance). Les propriétés physiques des agrégats (retrait, absorption d’eau et résistance à la compression) sont mesurées et corrélées, dans certains cas, aux facteurs expérimentaux(température, temps de cuisson, teneur de l’additif), et ce en utilisant la méthodologie de la recherche expérimentale.Les agrégats amendés à l’argile smectitique sont le siège de formation de la gehlénite. Dans ce cas, la fluorapatite a partiellement résisté au traitement thermique, et a été le siège d’une ségrégation localisée. Les mesures d'impédance ont bien mis en évidence l'étape principale du frittage, lequel s’est produit par écoulement de la masse fondue. En se basant sur les valeurs de la densité, les granulats cuits à 900 et à 1100°C pouvaient bien être considérés comme des agrégats légers.Les études menées sur les agrégats des mélanges : argile kaolinitique-boue, cendre boue,et argile kaolinitique-cendre-boue ont montré la présence de la labradorite, et d’une masse fondue, qui semblait se former, entre autres, de la fusion de la fluorapatite. Par ailleurs,l'utilisation de la méthodologie de la recherche expérimentale a permis d'évaluer le poids des effets des facteurs expérimentaux sur les propriétés physiques des agrégats. Des granulats légers (1,02 < densité < 2,1 g/cm3) et résistants sont préparés avec succès dans les conditions expérimentales adoptées. Les granulats ayant le meilleur rapport résistance / densité sont ceux du mélange ternaire.Concernant le volet application, les résultats ont montré que l’utilisation des agrégats en construction est possible et que l’association d’agrégats légers au sol a permis d’activer la croissance des plants de la luzerne. D’un autre côté, l'absorption du phosphore par les racines(1,45 mg/g maximum) des plantes était meilleure dans le cas du mélange contenant de l’argilePhosphate sludge generated from beneficiation plants of Moroccan phosphate rocks was investigated at the range [900-1200°C] by X-ray diffraction, scanning electron microscopy, thermal analysis dilatometric analysis and impedance spectroscopy. Mixtures of the phosphates ludge and amendments such as a swelling clay (up to 30 wt.% of the clay), a kaolinitic clay (up to 40 wt.% of the sludge) and a fly ash (65.5 wt.% of the ash) were investigated and their properties (shrinkage, density, water absorption and compressive strength) were measured as a function of temperature and clay addition. The results showed that gehlénite neoformed from lime of decomposed carbonates and breakdown products of clay minerals in the first mixture while labradorite/anorthite was the only neoformed phase in the other blends. Also fluoroapatite (original mineral) resisted heating until fusion in almost samples. A new approach based on the methodology of the experimental design was adopted to assess the effect of the processing factors on the studied properties. The measured properties were mainly controlled by temperature, and the effect of clay addition was less regular. Considering the mixtures densities lightweight agglomerates can be produced at specific conditions. On the other hand, the release ability of phosphorus by LWAs in the presence ofalfalfa plants has been performed. It was found that due to the release of phosphorus by soil embedded pellets the growth of alfalfa plants improved. The sintering process of blends of phosphate sludge and a naturally occurring clay material (0-30 wt.%) was investigated in the range 650-1100°C by using impedance spectroscopy. The results showed that the sintering process was effective between 750 and 1000°C and occurred by melt flow
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Hassan, S. M. Mahmudul. "Development of Novel High Strength Composite Calcium Phosphate Cement for Orthopedic Applications." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533212629435654.
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Subramanian, Preeti. "Role of Ceramide-1-Phosphate as a Specific and Potent Activator of Group IVA Cytosolic Phospholipase A2 Alpha." VCU Scholars Compass, 2007. http://hdl.handle.net/10156/1404.
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Cordaro, Nicholas Michael. "Accelerated bone bonding to calcium phosphate ceramic coated strain gauges: An experimental and computational study." Thesis, The University of Arizona, 2000. http://hdl.handle.net/10150/278724.
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Calcium phosphate ceramic (CPC) coated strain gauges have been used for long term in vivo bone strain measurements but require 6 to 9 weeks for sufficient bonding. PepTite2000™, OP-1, TGF-β1, Ca₂SO₄·2H₂O, and an endothelial cell layer with and without TGF-β1 were examined as enhancements to accelerate bone to CPC bonding. Young male Sprague-Dawley rats were implanted with gauges for three weeks and calcein labeled. Following euthanasia, their femurs were explanted and mechanically tested. Histology was completed. Optical Coherence Tomography (OCT) was studied as an alternative to histology. A finite element analysis (FEA) examined bone to gauge strain transfer. Mechanical testing indicated increased sensing accuracy with TGF-β1 and OP-1 enhancements versus unenhanced gauges. PepTite2000™ and endothelial enhanced gauges displayed lower sensing accuracy and contained vasculature near CPC. TGF-β1 increased bonding with endothelial cells. Ca₂SO₄·2H₂O inhibited bone bonding. OCT unsuccessfully imaged bone to CPC contact. FEA identified geometric and material parameters for improved gauge design.
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Gariboldi, Maria Isabella. "Effect of calcium phosphate ceramic architectural features on the self-assembly of microvessels in vitro." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283005.
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One of the greatest obstacles to clinical translation of bone tissue engineering is the inability to effectively and efficiently vascularise scaffolds. This limits the size of defects that can be repaired, as blood perfusion is necessary to provide nutrient and waste exchange to tissue at the core of scaffolds. The goal of this work was to systematically explore whether architecture, at a scale of hundreds of microns, can be used to direct the growth of microvessels into the core of scaffolds. A pipeline was developed for the production of hydroxyapatite surfaces with controlled architecture. Three batches of hydroxyapatite were used with two different particle morphologies and size distributions. On sintering, one batch remained phase pure and the other two batches were biphasic mixtures of α-tricalcium phosphate (α-TCP) and hydroxyapatite. Sample production methods based on slip casting of a hydroxyapatite-gelatin slurry were explored. The most successful of these involved the use of curable silicone to produce moulds of high-resolution, three dimensional (3D) printed parts with the desired design. Parts were dried and sintered to produce patterned surfaces with higher resolution than obtainable through conventional 3D printing techniques. Given the difficulties associated with the structural reproducibility of concave pores architectures in 3D reported in the literature, in this work, a 2.5D model has been developed that varies architectural parameters in a controlled manner. Six contrasting architectures consisting of semi-circular ridges and grooves were produced. Grooves and ridges were designed to have widths of 330 μm and 660 μm, with periodicities, respectively, of 1240 μm and 630 μm. Groove depth was varied between 150 μm and 585 μm. Co-cultures of endothelial cells and osteoblasts were optimised and used to grow microcapillary-like structures (referred to as "microvessels") on substrates. Literature shows that these precursors to microcapillaries contain lumina and can produce functional vasculature, demonstrating their clinical promise. The effects of the composition and surface texture of grooved samples on microvessel formation were studied. It was found that surface microtopography and phase purity (α-TCP content) did not affect microvessel formation. However, hydroxyapatite architecture was found to significantly affect microvessel location and orientation. Microvessels were found to form predominantly in grooves or between convexities. Two metrics - the degree of alignment (DOA) and the degree of containment (DOC) - were developed to measure the alignment of endothelial cell structures and their localisation in grooves. For all patterned samples, the CD31 (an endothelial cell marker) signal was at least 2.5 times higher along grooves versus perpendicular to grooves. In addition, the average signal was at least two times higher within grooves than outside grooves for all samples. Small deep grooves had the highest DOA and DOC (6.13 and 4.05 respectively), and individual, highly aligned microvessels were formed. An image analysis method that compares sample X-ray microtomography sections to original designs to quantify architectural distortion was developed. This method will serve as a useful tool for improvements to architectural control for future studies. This body of work shows the crucial influence of architecture on microvessel self-assembly at the hundreds of micron scale. It also highlights that microvessel formation has a relatively low sensitivity to phase composition and microtopography. These findings have important implications for the design of porous scaffolds and the refinement of fabrication technologies. While important results were shown for six preliminary architectures, this work represents a toolkit that can be applied to screen any 2.5D architecture for its angiogenic potential. This work has laid the foundations that will allow elucidating the precise correspondence between architecture and microvessel organisation, ultimately enabling the "engineering" of microvasculature by tuning local scaffold design to achieve desirable microvessel properties.
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Santos, Rodrigo Brandão Medeiros dos. "Síntese e caracterização de pós nanoestruturados de fosfato de cálcio e nanocompósitos hidroxiapatita/sílica-gel." Universidade do Estado de Santa Catarina, 2009. http://tede.udesc.br/handle/handle/1750.
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Previous issue date: 2009-12-18Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The loss of an organ or a part of the body generates, besides the loss of function, social and psychological disorders. The materials used to replace bone fall into a class called biomaterials and should have physical and biological properties compatible with living tissue hosts. The objective of this study is to optimize the method of synthesis and characterization of a bone matrix of calcium phosphate nanostructured and nanocomposite calcium phosphate /SiO2n at concentrations of 1%, 2%, 3% and 5% by volume. Were carried out morphological characterization of nanoparticles, nanostructured mineral powders and biomaterials obtained by sintering at 1200 C/2h. Finally, studies were performed on the mechanical behavior of nanostructured biomaterials. The process of synthesis of nanostructured powders proved to be efficient and optimized, allowing to obtain the matrix of calcium phosphate and nanocomposites with silica gel. Silica gel influence the surface energy of the matrix of calcium phosphate and this phenomenon has influenced the particle size of the nanocomposites, phase transformation and sinterability of the matrix of calcium phosphate. Tests of mechanical properties showed that the increase in percentual silica gel in the phosphate matrix tends to reduce the mechanical strength (hardness, strength and fracture toughness). Only the nanocomposite with 1% silica showed improvement in mechanical properties after annealing.
A perda de um órgão ou de uma parte do corpo humano gera, além da perda da função, transtornos sociais e psicológicos. Os materiais utilizados na substituição de ossos enquadram-se em uma classe denominada de biomateriais e devem apresentar propriedades físicas e biológicas compatíveis com os tecidos vivos hospedeiros. Esse trabalho tem como objetivo otimizar o método de síntese e caracterização de uma matriz óssea de fosfato de cálcio nanoestruturada e de nanocompósitos fosfato de cálcio/SiO2n, nas concentrações de 1%, 2%, 3% e 5% em volume. Foram realizadas caracterizações morfológicas das nanopartículas, mineralógica dos pós nanoestruturados e dos biomateriais obtidos da sinterização a 1200ºC/2h. Por fim, foram realizados estudos sobre o comportamento mecânico dos biomateriais nanoestruturados. O processo de síntese de pós nanoestruturados mostrou-se eficiente e otimizado, permitindo a obtenção da matriz de fosfato de cálcio e dos nanocompósitos com sílica gel. A sílica gel influenciou na energia de superfície da matriz de fosfato de cálcio e esse fenômeno influenciou no tamanho de partícula dos nanocompósitos, transformação de fase e sinterabilidade da matriz de fosfato de cálcio. Os ensaios de propriedades mecânicas mostraram que o aumento do percentual de sílica gel na matriz de fosfato tende a reduzir a resistência mecânica (microdureza, flexão e tenacidade à fratura). Apenas o nanocompósito com 1% de sílica apresentou melhora nas propriedades mecânicas após o recozimento.
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Cui, Yuantao [Verfasser], and H. J. [Akademischer Betreuer] Seifert. "Phosphate based ceramic as solid-state electrolyte for lithium ion batteries / Yuantao Cui ; Betreuer: H. J. Seifert." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1170230482/34.
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Lacerda, Kassio André. "Obtenção de matrizes bioabsorvíveis à base de hidroxiapatita para aplicação em braquiterapia." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2006. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=2.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoO objetivo deste trabalho foi a síntese e a caracterização físico-química e microestrutural de matrizes cerâmicas porosas à base de hidroxiapatita de cálcio, bem como a avaliação de um pó de hidroxiapatita comercial, com potencialidade para atuarem como matrizes para incorporação de radionuclídeos de fontes radioativas para uso em braquiterapia. Pós de hidroxiapatita de cálcio foram sintetizados por via co-precipitativa de soluções precursoras de cálcio e fosfato em meio básico. As matrizes correspondentes foram obtidas a partir da compactação axial dos pós à baixa pressão e sinterizadas ao ar. Difração de raios X, fluorescência de raios X, espectrofotometria de infravermelho, análise BET, análise térmica TG-DTA e microscópia eletrônica de varredura foram realizadas para caracterização dos pós e matrizes. O iodo foi incorporado nas matrizes através de um inpregnação de solução aquosa de iodeto de sódio. Foi realizada a quantificação de iodo (simulador de radionuclídeo) nas matrizes através da técnica de análise por ativação neutrônica. Verificou-se que as hidroxiapatitas sintetizada e comercial têm características de hidroxiapatitas bioabsorvíveis. As matrizes de hidroxiapatita apresentaram uma baixa densificação. A porosidade total é da ordem de 55%, e a porosidade aberta de 54%. Comparações feitas entre os resultados de incorporação de iodo e as atividades das fontes de braquiterapia comerciais mostram que a matrizes bioabsorvíveis à base de hidroxiapatita têm grande potencial, porque elas podem ser carregadas com uma ampla faixa de atividade.
The aim of this work was the synthesis and physico-chemical and microstructural characterization of pores ceramic matrices of calcium hydroxyapatites, and also the evaluation of a commercial hydroxyapatite powder, and both with the potency do in view of their possible use act as matrices for radionuclide incorporation of bioresorbable radioactive sources for the use of brachytherapy. Calcium hydroxyapatite powders were synthesized by co-precipitation of precursor solutions of calcium and phosphate in basic environment. The corresponding matrices were obtained for uniaxial compaction of powders at low pressure and sinterized in air. X-rays diffraction and fluorescence, infrared spectrphotometry, surface area (BET), thermal analysis (TG-DTA), and scanning electron microscopy were carried out to characterize the powders and the matrices. Iodine was incorporated in the matrices through impregnation of sodium iodine aqueous solution. The amount of incorporated iodine (radionuclide simulator) was done by neutron activation. Both hydroxyapatites have characteristics for bioabsorption. The matrices showed a low densification with total porosity of about 55%, and open porosity of about 54%. Through comparisons done between the results of incorporated iodine and the activities of the commercial brachytherapy sources show that the bioresorbable matrices of hydroxyapatites have great potential.
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Jiang, Zhiping. "CHARACTERIZATION OF PHOSPHOINOSITIDE AND SPHINGOLIPID DOMAIN FORMATION IN MODEL MEMBRANES." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1291046490.
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Rieck, Michael [Verfasser]. "The role of ceramide synthase 2 in sphingosine-1-phosphate-mediated thymic egress / Michael Rieck." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1149154152/34.
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Saito, Lia 1989. "Estudo da biocompatibilidade in-vitro e In-vivo de cimento de [Alfa]-fosfato tricálcico : diferentes tempos e processos de moagem." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263501.
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Orientador: Cecília Amélia de Carvalho ZavagliaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: A necessidade de substituintes ósseos está crescendo rapidamente no campo da cirurgia reconstrutiva. Os cimentos à base de fosfato de cálcio são largamente empregados no reparo do tecido ósseo devido a uma série de propriedades atrativas, como excelente bioatividade e biocompatibilidade. São muitos os estudos feitos em busca da otimização das propriedades desses materiais ou a análise do comportamento biológico desses substitutos, entretanto esses estudos analisam essas propriedades isoladamente, sem se atentar para que as duas variáveis devem ser analisadas simultaneamente. O objetivo deste trabalho foi avaliar a influência da distribuição granulométrica do pó de ?-TCP no comportamento biológico do cimento ósseo que utiliza este pó precursor através de uma análise simultânea de propriedades físico-químicas, mecânicas e morfológicas e do comportamento biológico do material. Para isso, o pó de ?-TCP foi obtido em laboratório a fim de se alcançar elevada pureza de fase. Este mesmo pó passou por diferentes protocolos de moagem a fim de se obter duas faixas de distribuição granulométrica. Finalmente, os cimentos que apresentaram potencial para aplicação como implantes de acordo com as caracterizações prévias do material passaram por avaliação das suas propriedades biológicas através de testes in-vitro e in-vivo. Ambos as amostras apresentaram pureza de fase, livres de contaminações. Além disso, obtiveram valores de resistências mecânicas semelhantes ou maiores do que consta na literatura e resultados positivos em relação à biocompatibilidade
Abstract: Bone substitutes are largely used in reconstructive medicine, especially calcium phosphate cements to repair bone tissue due to its attractive properties as excellent bioactivity and biocompatibility. There are several studies about the increase of these materials¿ properties or the analysis of biological behavior from these substitutes, however the researches only show the properties separately, instead of analyze the two variables simultaneously. The aim of this project was to analyze the influence of two different particle size distribution of ?-TCP powder on biological behavior of its bone cement through simultaneous analysis of physical-chemical, mechanical and morphological properties and biological behavior of the material. Thus, ?-TCP powder was obtained in laboratory to reach the maximum purity level. The same powder was processed by different milling protocols to obtain two distinct ranges of particle size distribution. Finally, the cements that presented high potential application as implants from its characterization methods were evaluated by in vitro and in vivo essays. Both samples presented phase purity without contamination, mechanical resistance similar or superior than described on literature and positive results in biocompatibility tests
Mestrado
Materiais e Processos de Fabricação
Mestra em Engenharia Mecânica
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MacKnight, Patrick. "The interaction between ceramide-1-phosphate and Group IVA cytosolic phospholipase A2 and its role in wound healing." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5633.
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The sphingolipid, ceramide-1-phosphate (C1P), directly binds and activates Group IVA cytosolic phospholipase A2 (cPLA2a) to generate eicosanoids. Due to the role of eicosanoids in wound healing, we choose to use our novel genetic mouse model expressing cPLA2a with an ablated C1P interaction site (KI) to examine the cPLA2a/C1P interaction in wound healing. Wound closure rate was not affected, but wound maturation was dramatically enhanced by loss of the C1P/cPLA2α interaction based on the following findings. Wounds in KI mice displayed: i) increased infiltration of dermal fibroblasts into the wound environment; ii) increased wound tensile strength; and iii) higher Type I/Type III collagen ratios. These findings were recapitulated in vitro as primary dermal fibroblasts (pDFs) from KI mice showed significantly increased collagen deposition and migration velocity compared to WT and KO pDFs. Additionally, the KI showed an altered eicosanoid profile of reduced pro-inflammatory prostaglandins (e.g., PGE2) and increased levels of specific HETE species (e.g., 5-HETE). Elevated 5-HETE levels promoted increased dermal fibroblast migration and collagen deposition. This “gain of function” role for the mutant cPLA2a was also linked to differential cellular localization of cPLA2α and 5-HETE biosynthetic factors. These studies demonstrate regulation of key in vivo biological mechanisms by a defined protein:lipid interaction and provide new insights into cPLA2a function.