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Wang, Haibo. "Hydroxyapatite degradation and biocompatibility". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1087238429.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiv, 190 p.; also includes graphics. Includes bibliographical references (p. 166-190).
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Roka, Eszter. "Biocompatibility evaluation and synthesis of macrocyclic compounds". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1027/document.
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La faible solubilité de certains médicaments cause des problèmes majeurs dans les formulations pharmaceutiques, puisque la solubilité dans l'eau est un critère indispensable pour la biodisponibilité. Les composés macrocycliques tels que les CDs et les calixarènes ont une cavité relativement hydrophobe, leur permettant ainsi d'encapsuler de nombreuses molécules. Les CDs ont déjà été utilisées comme excipients pharmaceutiques pour l'amélioration de la solubilité. La structure de ces macrocycles permet d'effectuer de nombreuses modifications, qui causent des changements tant au niveau de leurs caractéristiques physico-chimiques que sur leurs effets sur les organismes vivants. Ainsi, l'évaluation de la biocompatibilité de ces dérivés est primordiale en vue de leur utilisation en pharmacie. Puisque l'étude de la biocompatibilité de plusieurs dérivés de β-CD a déjà été étudiée, l'objectif de cette recherche était d'étendre ces expériences à des dérivés de l'α-CD qui sont disponibles dans le commerce. Nous nous sommes intéressés aux relations entre structure et toxicité. Ainsi les dérivés alkyl éther d'α-CD, avec des chaînes alkyle de longueur croissante et substitués sur différentes positions, ont été synthétisés et leur toxicité étudiée. Les para-sulphonato-calix[n]-arènes quant à eux, ont souvent été étudiés et ont montré une forte capacité à complexer de nombreux médicaments. Ils ont aussi démontré une activité biologique polyvalente. Néanmoins, leurs effets sur le mécanisme de transport paracellulaire n'a jamais été évaluée. Les tests de viabilité cellulaire et d'hémolyse nous ont permis d'une part de classer les α-CDs et de choisir les dérivés les plus sûrs, et d'autre part de comparer leur effets toxiques dans des systèmes différents. La comparaison des α- et ß-CDs portant les mêmes modifications chimiques nous a montré l'importance du nombre d'unités de construction. Le rapport entre l'effet cytotoxique et le nombre de groupes hydroxyles libres est également très important. Les dérivés portant de longues chaînes alkyles possèdent une faible solubilité, ce qui nous a conduits vers d'autres modifications chimiques : la sulfonation de ces derniers dérivés semble avoir un impact bénéfique sur la biocompatibilité de CDs. Elle a aussi amélioré la solubilité des calixarènes. Les calix[4] et [8]arène sulphonates ont prouvé leur effet positif sur l'absorption paracellulaire, tandis que le calix[6]arène sulphonate n'a pas eu d'effet similaire. Notre recherche conclut que les changements structurels sur les anneaux macrocycliques peuvent avoir un impact majeur sur la biocompatibilité. Comme les possibilités de modification sont pratiquement illimitées, l'évaluation de la structure et de l'activité est indispensable pour faciliter les choix les plus sûrs dans les applications pharmaceutiques à venirThe low solubility of drug candidates cause a major problem in pharmaceutical formulations, as the aqueous solubility is an indispensable criterion for appropriate bioavailability. Macrocyclic compounds possess a relatively hydrophobic cavity, which is suitable for guest molecule inclusion. Cyclodextrins and calixarenes are widely studied organic host-compounds, and CDs have already been used as pharmaceutical excipients for solubility enhancement. The macrocycles’ chemical structure allows their versatile modification, which eventuates changes not only in physicochemical characteristics, but in their effects on living organisms, as well. Thus, the biocompatibility evaluation of the derivatives is fundamental. Owing to the already performed assessment of numerous β-CD derivatives’ biocompatibility, the aim of this research was to extend these experiments to commercially available α-CDs. They have been used less frequently, however several derivatives, which have not been tested yet in vitro, have the possibility of future pharmaceutical use. Their importance is also certified by their benefits in nanoparticle formation. We have been interested in concrete structure-toxicity correlations, thus alkyl ether α-CD derivatives were synthetized bearing increasing length alkyl chains, in different positions. Para-sulphonato-calix[n]-arenes have already been widely examined due to their efficient drug complexation and versatile biological activity, however, their effects on paracellular transport mechanism have not been evaluated until now.The cell viability and hemolysis tests have allowed us to rank the α-CDs and to choose the safest derivatives, also to compare their toxic effects in different systems. The comparison of α- and β-CDs bearing the same chemical modifications highlighted the importance of the number of building units. Important information has been evaluated regarding the connection between the cytotoxic effect and the number of free hydroxyl groups. Derivatives with long alkyl chains possess low solubility, which led us towards further chemical modifications. Sulfonation seemed to have beneficial impact on the biocompatibility. Sulfonation also improved the solubility of calixarenes. C4S and C8S proved their positive effect on paracellular absorption in a non-toxic concentration range, however C6S had no similar effect, thus their behaviour in in vitro absorption model system arose forward-looking questions.Our research concludes, that the structural changes on the macrocyclic rings may have major impact on the biocompatibility. As the modification possibilities are practically unlimited, the evaluation of structure and activity cannot be avoided, facilitating the safest choice for further pharmaceutical use
A gyógyszerhatóanyagok rossz vízoldékonysága nagy kihívást jelent formulálásuk során, ugyanis a vízoldékonyság elengedhetetlen feltétele a megfelelő biohasznosulásnak. A makrociklusos vegyületek belső ürege viszonylag hidrofób, ez alkalmassá teszi őket vendégmolekulákkal való komplexképzésre. A ciklodextrinek és kalixarének széles körben tanulmányozott vegyületek, egyes CD-ek bejegyzett oldékonyságnövelő segédanyagok. A makrociklusok felépítése számos kémiai módosításra ad lehetőséget, amelyek nem csupán a fiziko-kémiai tulajdonságok változását eredményezik, hanem az élő organizmusokra kifejtett hatásokat is módosítják. Ezen származékok biokompatibilitás vizsgálata tehát elengedhetetlen. Számos β-CD származék biokompatibilitása ismert már, így kutatásunk célul tűzte ki ezen vizsgálatok α-CD-ekre történő kiterjesztését. Az α-CD-ek alkalmazása ritkább, azonban vannak származékok, amelyek in vitro vizsgálata még nem történt meg, de jelentőségük a nanopartikulum-képzésben már igazolt. A szerkezet-toxicitás összefüggések feltárása érdekében olyan alkil-éter CD származékokat szintetizáltunk, amelyek növekvő szénatomszámú alkil-csoportokkal rendelkeznek, eltérő pozíciókban. A para-szulfonáto-kalix[n]aréneket hatóanyag-komplexáló tulajdonságuk, valamint sokoldalú biológiai aktivitásuk miatt széles körben tanulmányozták már, azonban a paracelluláris anyagtranszportra gyakorolt hatásuk ezidáig még nem volt ismert. A sejtéletképességi és hemolízis vizsgálatok hozzásegítettek az egyes α-CD-ek rangsorolásához, továbbá a vegyületek különböző rendszerekben mért toxikussága is összevethetővé vált. A megegyező kémiai módosításokon átesett α- és β-CD-ek biokompatibilitása rávilágított a CD-gyűrű mértének jelentőségére. Egyértelmű összefüggést fedeztünk fel a toxicitás és a szabad hidroxil-csoportok száma között. A hosszú alkil-csoporttal rendelkező CD-ek rossz oldékonysága további kémiai módosításokat tett szükségszerűvé; a szulfát csoportok jelenléte jótékony hatással volt az oldhatóságra, és a citotoxicitásra is. A szulfatálás a kalixarének oldékonyságát is növelte. A C4S és C8S vegyületek növelték a paracelluláris felszívódás mértékét szubtoxikus koncentrációban, azonban a C6S nem mutatott hasonló hatást. Ezen eredmények további kérdéseket vetnek fel a pontos hatásmechanizmusról. Eredményeink rávilágítanak a makrociklusok szerkezetének és biokompatibilitásának összefüggéseire, valamint ezen ismeretek fontosságára annak érdekében, hogy minden formulációban a legbiztonságosabb segédanyagok legyenek alkalmazhatóak
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Sun, Tao, e 孙韬. "Surface modification of titanium metal for medical applications". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45457694.
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Reverte, Maëva. "Etude de la biocompatibilité d acides nucléiques modifiés par des acides boroniques : développement de nouveaux outils de diagnostic". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT236.
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La modification d’oligonucléotides est un domaine attrayant de la chimie organique. De nombreuses études se sont intéressées à la génération de liens internucléosidiques artificiels à visée thérapeutique, diagnostic ou encore pour des applications en chimie prébiotique. Ce manuscript de thèse rapporte la synthèse et l’étude de biocompatibilité d’acides nucléiques modifiés à leurs extrémités 5’ par un acide boronique. Les comportement des oligomères boroniques a été évalué en présence de différentes classes d’enzymes telles que les ligases, les polymérases ou encore les phosphodiestérases. Les résultats de biocompatibilité obtenus en présence de ces enzymes nous ont permis d’utiliser ces acides nucléiques modifiés comme de réels outils de diagnostic pour réaliser de la détection de point de mutation ou encore de la détection de péroxynitrite in-celluloThe modification of oligonucleotides is an attractive field of organic chemistry. Many studies have focused on the generation of artificial internucleoside linkages for therapeutic, diagnostic or for applications in prebiotic chemistry. This thesis manuscript reports the synthesis and study of nucleic acids biocompatibility modified at their 5 'ends by a boronic acid function. The behavior of boronic oligomers was assessed in the presence of different classes of enzymes, such as ligases, polymerases or phosphodiesterases. The biocompatibility results obtained in the presence of these enzymes allowed us to use these modified nucleic acids as real diagnostic tools to achieve mutation point detection or detection of peroxynitrite in-cellulo
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Le, Coadou Cécile. "Caractérisation de films de zircone yttriée et développement d’un procédé de brasage avec du TA6V pour des applications biomédicales". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI041/document.
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Les maladies neurodégénératives sont en forte progression dans nos sociétés, mais elles sont également mieux connues et mieux soignées. Par exemple, la stimulation cérébrale profonde est de nos jours utilisée pour lutter contre des maladies comme la maladie de Parkinson. Pour cela, un boitier semblable à celui d'un pacemaker, placé sous la clavicule, est habituellement utilisé pour délivrer des impulsions électriques dans des zones spécifiques du cerveau grâce à des électrodes. Afin d'éviter certaines complications, un boitier ultrafin a été imaginé. Il peut être placé directement au niveau du crâne, au plus proche de la zone à traiter. Les matériaux composant ce boitier doivent présenter certaines caractéristiques. Nous avons choisi de travailler avec des feuilles de TA6V et de zircone yttriée et avons réalisé un assemblage hermétique par l'obtention d'une brasure fine en Ti2Ni.Les feuilles de zircone yttriée présentent des propriétés remarquables mais elles sont notoirement dégradées par un vieillissement hydrothermal. Une étude en vieillissement accéléré a été réalisée sur les feuilles de zircone telles que reçues mais également dans des conditions proches de l'utilisation. Le vieillissement mesuré est suffisamment limité pour envisager une utilisation in vivo, avec cependant une réserve concernant les zircones sous-stœchiométriques. Enfin, le profil de vieillissement et sa vitesse de progression ont pu être précisés.L'assemblage TA6V-zircone a été réalisé par brasage réactif in situ via l'apport initial en nickel pur et la création d'un joint de brasage en Ti2Ni. Le système TA6V-Ni-ZrO2 met en jeu plusieurs phénomènes, que nous avons cherché à déconvoluer : diffusion (solide et liquide), formation et croissance d'intermétalliques et réactions d'oxydo-réduction. La croissance des intermétalliques à partir du couple TA6V-Ni a été particulièrement étudiée. Cela a permis de relier certains événements à la température et de préciser les vitesses de croissance du Ti2Ni (selon son état physique). Grâce à l'ensemble des résultats, un procédé de brasage métal-céramique adapté aux matériaux ultrafins a été d'identifié et réalisé sur système avec succèsNeurodegenerative diseases are increasingly present in our society but they are also better known and treated. For example, deep brain stimulation is nowadays used to treat diseases such as Parkinson disease. For this purpose, a pacemaker-like device localized in the infraclavicular region is commonly used to deliver electrical pulses in concerned area of the brain thanks to electrodes. In order to avoid some complications, an ultrathin housing was designed. It could be directly implanted under the scalp, close to the area to be treated. Materials of the housing have to be display some features. TA6V, yttria-stabilized zirconia sheets and a hermetic brazing with a Ti2Ni joint were selected to develop this housing.Yttria-stabilized zirconia sheets have remarkable properties but they undergo a degradation caused by hydrothermal aging. An accelerated aging study was done on pristine sheets but also under near-reality conditions. The observed aging is sufficiently limited to consider an in vivo application, subject to one reservation for the under-stoichiometric zirconia. Finally, the aging profile and the propagation rate were specified.The TA6V-zirconia joining was obtained by an in situ reactive brazing, thanks to a filler metal in pure nickel and the formation of a Ti2Ni joint. Several phenomena occur in the TA6V-Ni-ZrO2 system, which were separately studied: (solid and liquid) diffusion, formation and growth of intermetallic compounds and redox reactions. The intermetallic compounds growth from the TA6V-Ni couple was studied in detail. Thanks to all of the results, a metal-ceramic brazing process for ultrathin materials was identified and successfully achieved on our system
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Bentley, P. K. "Biocompatibility assessment of novel perfluorochemical emulsions". Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293632.
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Campoccia, Davide. "Aspects of biocompatibility of hyaluronan derivatives". Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295835.
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Blanquer, Jerez Andreu. "Biocompatibility of new biomaterials for orthopaedic applications". Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/386500.
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L’ús de materials biocompatibles ha assolit una importància creixent en aplicacions ortopèdiques i quirúrgiques, degut a l’envelliment de la població. Els aliatges metàl·lics que s’empren actualment en medicina presenten propietats físiques i mecàniques diferents a les de l’os humà, incrementant la probabilitat de pèrdua de l’implant. Per aquesta raó, s’estan desenvolupant nous aliatges metàl·lics amb millors propietats. En aquest sentit, la present tesi té com objectiu l’anàlisi de la biocompatibilitat de nous aliatges pel seu ús en implants ortopèdics. En primer lloc, s’ha demostrat la biocompatibilitat del vidre metàl·lic massís TiZrCuPd en termes de citotoxicitat, i d’adhesió i de diferenciació d’osteoblasts. En segon lloc, s’ha avaluat l’efecte de dues modificacions de superfície, anodització electroquímica i modificació física, dels aliatges TiZrCuPd i Ti-6Al-4V sobre el comportament dels osteoblasts. En aquest cas, no hem observat cap efecte de la topografia en la proliferació, l’adhesió i la diferenciació. En tercer lloc, hem demostrat que els aliatges TiZrPdSi i TiZrPdSiNb són biocompatibles i afavoreixen l’adhesió, la proliferació i la diferenciació d’osteoblasts. Finalment, hem avaluat l’efecte electroestimulador de dos nous nanogeneradors piezoelèctrics, basats en ZnO, emprant dues línies cel·lulars implicades en la regeneració òssia (osteoblasts i macròfags). Els resultats observats indiquen que els nanogeneradors són biocompatibles i que la seva interacció amb les cèl·lules produeix un camp elèctric local que estimula la motilitat dels macròfags i l’augment de la concentració intracel·lular de Ca2+ en osteoblasts. Aquests nous materials intel·ligents presenten propietats força interessants pel seu ús en aplicacions biomèdiques. En conjunt, els resultats obtinguts en els nostres estudis contribueixen en el desenvolupament de materials per millorar la reparació i la regeneració òssia.The use of biocompatible materials has attained an increasing importance for medical surgery and orthopaedics due to population aging. Metallic alloys currently used in bone implants have physical and mechanical properties different from those of the bone, which increases the probability of implant loosening. For this reason, new metallic alloys with better properties are being developed. In this regard, the present thesis aims to analyse the biocompatibility of new biomaterials for orthopaedic applications. First, we demonstrated the biocompatibility of TiZrCuPd bulk metallic glass in terms of cytotoxicity, and osteoblast adhesion and differentiation. Second, we assessed the effect of surface modification of TiZrCuPd and Ti-6Al-4V alloys by electrochemical anodization and physical modification on osteoblast behaviour. Differences in topography did not cause changes on osteoblasts adhesion, proliferation and differentiation. Third, we demonstrated that TiZrPdSi and TiZrPdSiNb alloys are also biocompatible and enhance osteoblasts adhesion, spreading, proliferation and differentiation. Fourth, we evaluated the electrostimulation effect of two new ZnO piezoelectric nanogenerators using two cell lines involved in bone regeneration (osteoblasts and macrophages). We observed that both nanogenerators are biocompatible and that their interaction with cells produces a local electric field that stimulate macrophages motility and the increase in intracellular Ca2+ concentration in osteoblasts. Thus, these new smart materials have interesting properties for their use in biomedical devices. Collectively, the results obtained in our studies contribute to the progress in the development of better materials for bone repair and regeneration.
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Zeng, Muling. "Bacterial cellulose: fabrication, characterization and biocompatibility studies". Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/284146.
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En marzo de 2011, apliqué a una beca del CSC (Consejo de Becas de China), en cooperación con la Universitat Autònoma de Barcelona (UAB). Después de medio año, conseguí la beca y comencé mi tesis doctoral bajo la supervisión de la Dra. Anna Roig y la Dra. Anna Laromaine. Mi proyecto asignada era en celulosa bacteriana: su síntesis, caracterización y estudios de biocompatibilidad.
La celulosa bacteriana es un polisacárido de fuentes renovables, y puede ser producida por algunos tipos de bacterias en la naturaleza. Presenta propiedades químicas y físicas notables, incluyendo una alta pureza química y cristalinidad, una red de nanofibras, porosa, alta capacidad de absorción de agua y resistencia mecánica. La celulosa bacteriana se utiliza para una amplia variedad de aplicaciones comerciales. Por otra parte, la celulosa bacteriana es biocompatible con afinidad biológica y biodegradabilidad, que suscita la atención de investigadores en el área de la biomedicina.
El primer objetivo de mi tesis fue aprender a producir películas de celulosa bacteriana y encontrar estrategias para controlar sus propiedades. Un segundo objetivo fue el desarrollo de métodos para la fabricación de nanocompuestos basedos con celulosa bacteriana. El objetivo final estudia la biocompatibilidad de las capas de celulosa bacteriana que hemos producido y su utilidad como soportes tridimensionales para el crecimiento celular. Así se pretende establecer una plataforma para el estudio de la interacción de células y nanopartículas en un entorno 3D más realista.
Durante el primer año, se realizó la puesta a punto en el laboratorio del sistema para producir capas de celulosa bacteriana a partir de dos cepas bacterianas y secarlas a partir de tres métodos de secado:a temperatura ambiente, secado por liofilización y secado supercrítico. Por otra parte, se realizó la caracterización completa de las capas de celulosa bacteriana: su porosidad, la transparencia, la capacidad de absorción de agua y las propiedades mecánicas que se podían controlar seleccionando la cepa bacteriana y el método de secado. En el segundo año, se sintetizó la celulosa bacteriana compuesta con nanopartículas por el método asistida por microondas como materiales de celulosa funcionales novedosos. Este método es eficiente y rápido, forma un recubrimiento de las capas de celulosa bacteriana por nanopartículas de forma homogénea y controlable. Secando las capas de celulosa utilizando diferentes rutas, se puede controlar la cantidad final del contenido de las nanopartículas en los materiales compuestos. Así capas con dominios hidrófobos / hidrófilos favorecían el anclaje de nanopartículas de forma selectiva para crear materiales de celulosa más complejos y funcionales. En este último año, se ha llevado a cabo el estudio de la biocompatibilidad de las capas de celulosa bacteriana in vitro. Aunque la celulosa bacteriana se considera generalmente un material no citotóxico, su biocompatibilidad es un requisito importante para su uso en aplicaciones biológicas y médicas y no ha sido evaluado completamente. Además se fabricó una estructura de celulosa bacteriana 3D mejorada.
La tesis se estructura en seis capítulos. Capítulo 1 proporciona una introducción a la celulosa bacteriana. Capítulo 2 ofrece una descripción detallada de la fabricación de capas de celulosa bacteriana (BCF). Capítulo 3 se centra en la síntesis de compuestos de celulosa bacteriana funcionales que incorporan nanopartículas. Capítulo 4 presenta estudios de biocompatibilidad de la celulosa bacteriana como estructura 2D y 3D para estudios celulares in vitro. Capítulo 5 se enumeran las principales conclusiones derivadas de la presente tesis y algunas sugerencias para el trabajo futuro.Capítulo 6 recoge información sobre el autor y las publicaciones durante el doctorado.In March 2011, I started the application of a scholarship from CSC (Chinese Scholarship Council), which cooperated with the Universitat Autònoma de Barcelona (UAB). After about half year, I secured the scholarship and began my doctoral thesis under the supervision of Dr. Anna Roig and Dr. Anna Laromaine. My project assignment was on bacterial cellulose: fabrication, characterization and biocompatibility studies. Bacterial cellulose is a renewable polysaccharide, which is produced by some types of bacteria in nature. It presents remarkable chemical and physical properties, including high chemical purity and crystallinity, nano-scale fibre network, porosity, high water absorption capacity and mechanical strength. Bacterial cellulose is being used for a wide variety of commercial applications, for example textiles, cosmetics, food products and other technical areas. Furthermore, bacterial cellulose is also biocompatible with excellent biological affinity and biodegradability, which is drawing immense attention from the bio and medical area researchers. The objective of my thesis was to learn how to produce bacterial cellulose films and find strategies to control their properties. A second objective was to developed methods to fabricate nanocomposites based on bacterial cellulose. The final objective was related to prove the biocompatibility of the in-house produced bacterial cellulose films and to be able to use them as three-dimensional scaffolds for cell in-growth. In this way setting up a platform that will allow us to study the interaction of cells and nanoparticles in a realistic 3D environment. During the first year, a lab set-up was successfully built to produce bacterial cellulose from two bacterial strains and three methods of drying were accessed to dry the thin films; at room temperature, freeze drying and supercritical drying. Moreover, the full characterization of bacterial cellulose films was accomplished: their porosity, transparency, water absorption capacity and mechanical properties were tuned by selecting the bacterial strain and the drying method. In the second year, bacterial cellulose composited with nanoparticles as novel functional cellulose materials were synthesized by microwave-assisted method. This method is efficient and fast to form a homogenous conformal and controllable coating of nanoparticles on the bacterial cellulose films. By drying the cellulose films using different routes, the final amount of the nanoparticles content in the composites can be controlled. Furthermore, those films were patterned with hydrophobic/hydrophilic domains and selectively anchored nanoparticles to create more complex and functional cellulose composites. During the last year, an investigation of the biocompatibility of the bacterial cellulose films in vitro was performed. Although bacterial cellulose is generally considered non-cytotoxic material, its biocompatibility as a major requirement for the use in biological and medical applications has not been fully evaluated. Furthermore, an improved 3D bacterial cellulose scaffold was fabricated. The thesis is organized into six chapters. Chapter 1 provides an introduction to bacterial cellulose. Chapter 2 describes a detailed description of the fabrication of bacterial cellulose films (BCFs). Chapter 3 focuses on the synthesis of functional bacterial cellulose composites incorporating nanoparticles. Chapter 4 presents the studies of bacterial cellulose biocompatibility as 2D and 3D scaffold for cell studies in vitro. Chapter 5 lists the main conclusions derived from the present thesis and some suggestions for the future work. Chapter 6 gathers information about the author and the publications during the Ph.D. studies.
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Somayajula, Dilip Ayyala. "Biocompatibility of osteoblast cells on titanium implants". Cleveland, Ohio : Cleveland State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1207322725.
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Thesis (M.S.)--Cleveland State University, 2008.Abstract. Title from PDF t.p. (viewed on May 8, 2008). Includes bibliographical references (p. 72-76). Available online via the OhioLINK ETD Center. Also available in print.
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Suwannasom, Nittiya [Verfasser]. "Biocompatibility of Biopolymer Submicron Particles / Nittiya Suwannasom". Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1202044433/34.
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Fretwell, Grant Michael. "On the biocompatibility of nickel titanium alloys". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366485.
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Frykstrand, Ångström Sara. "Mesoporous magnesium carbonate : Synthesis, characterization and biocompatibility". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-281522.
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Mesoporous materials constitute a promising class of nanomaterials for a number of applications due to their tunable pore structure. The synthesis of most mesoporous materials involves a surfactant liquid crystal structure to form the pores. As well as the many advantages associated with this method of synthesis, there are disadvantages such as high production costs and a substantial environmental impact which limit the possibilities for large scale production. Therefore there is a need for other synthesis routes. The aim of the work described herein was to contribute to this field by developing a synthesis route that does not rely on surfactants for pore formation. A mesoporous magnesium carbonate material was therefore formed by self-assemblage of the particles around carbon dioxide gas bubbles, which functioned as pore templates. It was also possible to vary the pore diameter between 3 and 20 nm. The biocompatibility of the formed magnesium carbonate material was evaluated in terms of in vitro cytotoxicity and hemocompatibility, in vivo skin irritation and acute systemic toxicity. The results from the in vitro cytotoxicity, in vivo skin irritation and acute systemic toxicity test using a polar extraction vehicle showed that the material was non-toxic. While signs of toxicity were observed in the acute systemic toxicity test using a non-polar solvent, this was attributed to injection of particles rather than toxic leachables. In the in vitro hemocompatibility test, no hemolytic activity was found with material concentrations of up to 1 mg/ml. It was further shown that the material had anticoagulant properties and induced moderate activation of the complement system. The anticoagulant properties were ascribed to uptake of Ca2+. Finally, the ability of the material to increase the dissolution rate of the poorly soluble drug itraconazole was analyzed. Itraconazole was dissolved up to 23 times faster from the magnesium carbonate pores than when the free drug was used. The release rate from the delivery vehicle was dependent on the pore diameter. The work presented herein is expected to be useful for the development of alternative synthesis routes for mesoporous materials and also for encouraging the development of biomedical applications for these materials.
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Brendel, Christopher M. "Biocompatibility of Polymer Implants for Medical Applications". University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1246892895.
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Christenson, Elizabeth. "Biostability and Biocompatibility of Modified Polyurethane Elastomers". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1118268387.
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Ayyala, Somayajula Dilip. "Biocompatibility of osteoblast cells on titanium implants". Cleveland State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1207322725.
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Abraham, Nicole M. "Evaluation of Blood Vessel Mimic Scaffold Biocompatibility". DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2313.
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The Tissue Engineering Research Lab at California Polytechnic State University, San Luis Obispo focuses on creating tissue-engineered blood vessel mimics (BVMs) for use in preclinical testing of vascular devices. These BVMs are composed of electrospun scaffolds made of an assortment of polymers that are seeded with different cell types. This integration of polymers with cells leads to the need for biocompatibility testing of the polymer scaffolds. Many of the lab’s newest scaffolds have not been fully characterized for biologic interactions. Therefore, the first aim of this thesis developed methods for in vitro cytotoxicity testing of polymers used in the fabrication of BVMs. This included cytotoxicity testing using direct contact and elution-based methods, along with fluorescent staining to visualize the scaffold effects on cells.
The second aim of this thesis implemented the newly developed cytotoxicity protocols to evaluate the biocompatibility of existing polymers, ePTFE and PLGA, used in the tissue engineering lab. The results demonstrated that ePTFE and PLGA were noncytotoxic to cells. The third aim of this thesis evaluated the biocompatibility of novel polymers used to fabricate BVMs: PLGA with salt, PLLA, and PCL. Elution-based methods concluded that PLGA with salt, PLLA, and PCL were noncytotoxic to cells; however, the direct contact method illustrated PLGA with salt and PCL were mildly cytotoxic at 24 and 48 hours. Potential causes of this variability include the addition of salt to PLGA, dissolving PCL in dichloromethane, inadequate sample sizing, and the inherent differences between the test methods. Overall, this thesis developed and implemented methods to evaluate the biocompatibility of polymer scaffolds used in the BVM model, and found that ePTFE, PLGA, and PLLA scaffold materials were biocompatible and could be implemented in future BVM setups without concerns. Meanwhile, PLGA with salt and PCL’s toxicity was mild enough to urge future cytotoxicity testing on PLGA with salt and PCL before further use in the lab.
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Félix, Pedro Tiago Albergaria. "Assessment of biocompatibility of selected ferroelectric ceramics". Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/10711.
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Mestrado em Materiais e Dispositivos BiomédicosDesde há muitas décadas que é sabido que os organismos vivos, em especial os tecidos, reagem fisicamente a estímulos eléctricos, podendo esses efeitos reproduzirem-se numa libertação de químicos endógenos, ou deformar a sua estrutura física. O tecido ósseo por si só é considerado um material/tecido piezoeléctrico, deformando-se mecanicamente quando lhe é induzido um estímulo eléctrico e vice-versa, ou seja, produz um potencial eléctrico quando sofre uma tracção ou compressão mecânica. A hipótese de que um material ferroeléctrico possa vir a produzir efeitos no desempenho deste tipo de tecidos é então proposta, como por exemplo, para uma melhor, mais rápida e eficaz regeneração óssea. Estes mesmos materiais ferroeléctricos podem porventura alterar as cargas de superfície dos tecidos vivos de modo a atrair, atrasar ou até impedir o fluxo iónico de elementos químicos específicos responsáveis pelo processo de regeneração. São escolhidos então o niobato de lítio e o tantalato de lítio como cerâmicos ferroeléctricos e foi estudada pela primeira vez a sua bioactividade in vitro, esperando-se encontrar pistas relativas à sua bioactividade in vivo. Estes cerâmicos ferroeléctricos foram seleccionados devido às suas importantes propriedades piezoeléctricas e ferroeléctricas. Estas propriedades podem abrir um novo e importante leque de aplicações biomédicas caso estes cerâmicos sejam bioactivos. Este trabalho foi dividido em 3 fases: (i) sintetização dos pós de niobato de lítio e tantalato de lítio, (ii) caracterização dos pós e (iii) preparação das amostras e (iv) estudo da bioactividade destes cerâmicos ferroeléctricos. Os pós foram produzidos através de um processo simples de mistura/moagem seguido de calcinação. Foram estudadas as fases cristalinas presentes através de Difracção de raios-X (DRX) e avaliadas as características morfológicas destes pós, nomeadamente o diâmetro de partículas e área superficial específica. De modo a simular o ambiente do plasma humano, foi produzido sinteticamente um “Simulated Body Fluid” (SBF). Seguidamente as amostras foram imersas nesse ambiente líquido por 1, 3, 7, 15 e 21 dias. Após remoção dos pós foram realizadas uma série de análises de modo a estudar a sua bioactividade. De entre estes testes destacam-se a microscopia electrónica de varrimento (SEM/EDS), DRX e espectroscopia de Infravermelho por transformada de Fourier com reflectância total atenuada (FTIR-ATR). Embora não tenham sido detectadas alterações no DRX realizado aos pós, verificou-se a formação de aglomerados de fosfato de cálcio na superfície dos pós através do SEM, resultados estes, reforçados pelo EDS e FTIR-ATR. Estes precipitados de fosfato de cálcio indiciam a capacidade destes pós cerâmicos ferroeléctricos se comportarem como bioactivos em contacto com tecidos ósseos in vivo.
For many decades it is known that living organisms, especially living tissues, physically react to electrical stimuli, and these effects may result in a release of endogenous chemicals, or deform its physical structure. The bone tissue itself is considered a piezoelectric material/tissue deforming mechanically when induced by an electrical stimulus and vice-versa, in other words, it produces an electric potential when it is submitted to a mechanical deformation. The hypothesis that a ferroelectric material is likely to have an effect on the performance of this type of tissue is then proposed for, as an example, better, faster and more effective bone regeneration. These same ferroelectric materials may possibly change the surface of living tissues to attract, delay or even prevent the flow of specific ions responsible for the tissue regeneration process. Lithium niobate and lithium tantalate were selected as ferroelectric ceramics and its bioactivity was studied in vitro and it is expected to find clues concerning its bioactivity in vivo. These ferroelectric ceramics were selected due to their important piezoelectric and ferroelectric properties. These properties may open up a new and important range of biomedical applications if they are proven to be viable bioactive ferroelectric ceramics. This work is divided into three phases: (i) synthesis of lithium niobate and lithium tantalate powders, (ii) characterization of powders and (iii) sample preparation and (iv) study of the bioactivity of these ferroelectric ceramics. The powders were produced through a simple process of mixing/milling followed by calcination. Studies regarding the crystalline phases, particle size and specific surface area were made. In order to simulate the environment of human plasma, a "Simulated Body Fluid" (SBF) was synthetically prepared. Thereafter, the samples were immersed in the liquid environment for 1, 3, 7, 15 and 21 days. After removal of the powders, a series of tests, namely SEM/EDS, XRD and FTIR-ATR were conducted to these powders in order to study its bioactivity. From these tests consisted mainly on SEM/EDS, XRD and FTIR-ATR. Although no changes were detected in the powders XRD, it was visualized by SEM the formation of agglomerates of calcium phosphate on the surface and these results were corroborated by EDS and FTIR-ATR. These precipitates of calcium phosphate suggest the ability of the ferroelectric ceramics to behave as bioactive in contact in bone tissue in vivo.
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Yamamoto, Akiko. "Biocompatibility evaluation of metallic biomaterials in vitro". Kyoto University, 1998. http://hdl.handle.net/2433/182365.
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Yu, Young. "Enhancing the biocompatibility of coronary artery stents". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/16472.
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Cardiovascular disease, in particular coronary artery disease is a leading cause of morbidity and mortality worldwide. Coronary artery disease occurs as a consequence of atherosclerosis. Impediment to coronary blood flow causes myocardial ischemia, manifesting clinically as angina. Plaque rupture can lead to rapid vessel occlusion and myocardial necrosis. Revascularization (restoration of normal blood flow) can be achieved percutaneously with balloon angioplasty and coronary stent placement. Coronary stents are the most commonly implanted medical prostheses. To date the majority of commercially available stents are constructed from metallic alloys. Implantation of stents in the vasculature has two main biocompatibility issues 1) metals are thrombogenic, 2) stent deployment injures the vessel wall. Stent thrombosis and in stent restenosis are clinical consequences of stent thrombogenicity and vessel injury, respectively. Potent anti‐platelet agents and use of anti‐proliferative drug eluting stents reduce thrombogenicity and restenosis at the cost of increased bleeding and retardation of stent strut endothelialization leading to very late stent thrombosis. The interaction of biological systems with biomaterials is highly dependent on surface properties. Modification of the physical and chemical properties of the surface offers a simple and effective meanings to modulate the biological response to stents without altering the mechanical benefits that metallic alloys offer. Recently, plasma polymer deposition of thin films has been adapted for metallic substrates and three dimensional structures. These films reduce thrombogenicity and can attach biomolecules. One such molecule, recombinant human tropoelastin (rhTE) when attached to the films has been shown to enhance endothelial activity. Increasingly endothelial progenitor cells (EPCs) have been implicated in the maintenance of vascular health. Of particular interest is the capacity of these cells to participate in the healing of injured endothelium. Animal models demonstrate the ability of these cells to home in to sites of iatrogenic vessel injury and contribute to re‐endothelialisation. The goal of this thesis is to design a reproducible and scalable biocompatible coating platform for coronary stents. We explored the capacity of rhTE to support EPC activity followed by a mechanistic study of the nature of this interaction. Following this, we purpose built a plasma polymer film deposition chamber, optimizing for consistent and predictable film production. Nitrogen content of the plasma polymer films were progressively increased. A detailed physical, chemical and biological characterization of these nitrogenized films was carried out. There were several key findings from this thesis. We found rhTE supported EPC attachment, spreading and proliferation via an integrin mediated process. Using truncated rhTE constructs we were able to narrow down the site of interaction on rhTE to a region between N‐terminal domains 10 and 18. By increasing the flow of nitrogen during plasma film deposition we successfully created films with increasing concentration of nitrogen. Physical and chemical analyses demonstrated an amorphous carbon structure with smooth topography, containing nanoscale p‐conjugated graphite‐ like clusters, independent of nitrogen content. In contrast, nitrogen doping increased surface wettability and the amount of polar functional groups. In thrombogenicity assays lower thrombus formation, platelet adhesion and activation correlated with higher nitrogen concentration. Surprisingly, highly nitrogenized films also enhanced endothelial cell and EPC attachment and proliferation independent of rhTE functionalization. Nitrogenization of the plasma polymers did not impact on the capacity to covalently attach proteins. Nitrogenized plasma films is a promising platform to improve the biocompatibility of existing coronary stents.
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Barraud, Joanne Elizabeth. "The biocompatibility of novel phosphorylcholine based biomaterials". Thesis, University of Brighton, 2001. https://research.brighton.ac.uk/en/studentTheses/6dcb572f-e393-4a65-8c76-80c490a5d4f4.
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Many conventional biomaterials fail to meet the demands required of them with respect to their surface and bulk properties. This problem can be addressed by developing novel biomaterials that have the desired bulk properties and increased biocompatibility. Alternatively the surfaces of biomaterials which have the desired bulk properties can be modified to increase their biocompatibility without compromising these bulk properties. Phosphorylcholine (PC) based coatings mimic the surface of biological membranes and so offer a novel method for modifying bulk materials, or can be incorporated into novel bulk biomaterials. One of the key issues of biocompatibility is the continual stimulation of the inflammatory response by biomaterials characterised in part by complement activation, macrophage adhesion and granulocyte activation.
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Gladwin, Karen M. "Carbon nanotube biocompatibility with primary sensory neurons". Thesis, University of Brighton, 2010. https://research.brighton.ac.uk/en/studentTheses/7de21b7a-9c7c-4367-8e1c-ddbd347fd0c9.
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The repair of peripheral nerve lesions presents a common clinical challenge, with those injured suffering from an array of debilitating symptoms and sensory or motor handicaps. The current method of repairing peripheral nerve lesions involves the use of nerve autografts or artificial nerve repair conduits to bridge the gap between the two ends of the damaged nerve. However, results from the use of these techniques rarely produce full functional recovery. Several studies have shown that carbon nanotubes (CNTs) can be used as a successful substrate for the growth and guidance of neurons. These data suggest CNTs could be used as a neural tissue scaffold that may be incorporated into the lumen of existing nerve repair conduits to enhance axonal guidance at the nanoscale. Despite the substantial interest in the use of CNTs as a biomaterial in neurobiology, very little is understood about the interactions of CNT’s with neurons. The aim of this research project is to 1) provide an assessment of CNT biocompatibility with cells of the peripheral nervous system and 2) assess the ability of a CNT substrate to support neurite outgrowth.
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Nouman, Micheal. "Effet de l'exsudation des additifs sur les propriétés d'usage d'un dispositif médical implantable (cathéter)". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS056/document.
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L'état de surface est l'un des paramètres les plus importants pour déterminer la biocompatibilité d'un dispositif médical implantable, tout changement à la surface une fois en contact avec les tissus corporels peut avoir un impact sur la réponse biologique (cytotoxicité, inflammation, irritation, thrombose ... etc.). Pendant le stockage, l’exsudation des additifs peut se produire à la surface des polymères et modifier leurs propriétés. Dans cette étude, nous utilisons du polyuréthane à base de cathéter (Pellethane®), en raison de ses nombreuses applications dans le domaine des dispositifs médicaux, pour évaluer l'impact d’exsudation des additifs sur la biocompatibilité. L'impact des traitements de stérilisation et d'oxydation sur le phénomène d’exsudation a été étudié. L'étude a été réalisée sur du polyuréthane utilisé dans la fabrication de cathéters sur lesquels l’exsudation de cristaux d’additifs a déjà été observée. La stérilisation par rayonnements ionisants (bêta, gamma) a été réalisée sur ce matériau et les échantillons ont été soumis à différents types de processus d'oxydation (UV, H2O2 et action des macrophages). La viabilité des cellules endothéliales a été étudiée. Une évaluation préliminaire de l'hémocompatibilité a été réalisée par la mesure de l'hémolyse du sang total, ainsi que par l'adhésion des plaquettes en contact avec les différents échantillons de PU. L'étude de la production pro-inflammatoire d'IL-alpha; et de TNF-alpha; par des macrophages en contact avec des échantillons a également été rapportéeSurface state is one of the most important parameter determining the biocompatibility of animplantable medical device, any change on the surface once in contact with body tissues canimpact the biological response (Cytotoxicity, inflammation, irritation, thrombosis …etc). During storage, the blooming of additives may occur on the surface of polymers and modify their properties. In this study, we use (Pellethane®) catheter-based polyurethane, because of its many applications in the field of medical devices, to evaluate the impact of additives blooming on the biocompatibility. The impact of sterilizing and oxidation treatments on blooming was studied. The study was realized on polyurethane used in the fabrication of catheters on which the blooming of antioxidant crystals has been previously observed. Sterilization by ionizing radiations (beta, gamma) was performed on this material and samples were submitted to different kinds of oxidation process (UV, H2O2 and macrophages action). Endothelial cells viability was studied. A preliminary haemocompatibility evaluation was performed through the measurement of whole blood hemolysis, as well as platelet adhesion in contact with the different PU samples. The study of the pro-inflammatory IL-alpha; and TNF-alpha; production by macrophages in contact with samplesis also reported
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González, Paz Rodolfo Jesús. "Polyurethanes based on fatty acids with improved biocompatibility". Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/96663.
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El objetivo principal de esta tesis ha sido el desarrollo de nuevos poliuretanos a partir de ácidos grasos como fuentes renovables, utilizando química “click” en la síntesis de los dioles y polioles correspondientes. La primera parte del trabajo describe la preparación de los monómeros “vía” acoplamiento tiol-eno ó tiol-ino, su caracterización y las propiedades de los poliuretanos sintetizados. Como los polímeros a partir de ácidos grasos provienen de macromoléculas biológicas y pueden ser potencialmente biocompatibles, la segunda parte del trabajo está dirigida a incrementar la biocompatibilidad de los poliuretanos a través de diversas estrategias de funcionalización con moléculas bioactivas, para su implementación en ingeniería de tejidos. Tres metodologías fueron investigadas: mezclas con gelatina; inmovilización covalente de colágeno sobre la superficie mediante plasma; e inmovilización iónica de sulfato de condroitina sobre la superficie mediante aminólisis.The main objective of this thesis has been the development of new polyurethanes from renewable sources such as fatty acids, using "click" chemistry in the synthesis of the corresponding diols and polyols. The first part of this study describes the preparation of monomers "via" thiol-ene or thiol-yne coupling, characterization and properties of the synthesized polyurethanes. As the polymers from fatty acids derived from biological macromolecules and can be potentially biocompatible, the second part of this work is focused on the enhancement of polyurethanes biocompatibility through bioactive molecules functionalization strategies, for tissue engineering purposes. Three approaches have been investigated: blends of polyurethanes and gelatin; covalent surface modification of polyurethanes with collagen by plasma treatment; and ionic surface modification of polyurethanes with chondroitin sulfate by aminolysis treatment.
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Kapanen, A. (Anita). "Biocompatibility of orthopaedic implants on bone forming cells". Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:9514266064.
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Abstract
Reindeer antler was studied for its possible use as a bone implant material. A
molecular biological study showed that antler contains a growth factor promoting
bone formation. Ectopic bone formation assay showed that antler is not an equally
effective inducer as allogenic material.
Ectopic bone formation assay was optimised for biocompatibility studies of
orthopaedic NiTi implants. Ti-6Al-4V and stainless steel were used as reference
materials. The assay showed differences in bone mineral densities, with superior
qualities in NiTi. The rate of endochondral ossification varied between the
implants, NiTi ossicles had larger cartilage and bone areas than ossicles of the
two other materials.
The cytocompatibility of NiTi was studied with three different methods. Cell
viability, cell adhesion and TGF-β1 concentration were assessed in
ROS-17/2.8 cell cultures. Cells grown on NiTi had better viability than cells
grown on pure nickel or stainless steel. Cell attachment on the materials was
studied with paxillin staining of focal contacts. The number of focal contacts
was clearly higher in cells grown on NiTi than in cells grown on pure titanium,
pure nickel or stainless steel. TGF-β1 concentration was measured with
ELISA. The results showed that there was only some minor variation between NiTi,
pure titanium and stainless steel. Nickel showed a lower TGF-β1
concentration. Taken together, these results suggest that NiTi is well tolerated
by ROS-17/2.8 cells. The cytocompatibility of stainless steel is not so good as
that of NiTi.
The same tests were used to study the effects of the surface roughness of the
implant on cytocompatibility. Three different surface roughness grades were
compared in cell cultures on NiTi and titanium alloy discs. Titanium alloy was
subjected to two different heat treatments, to compare the effects of the
treatments on cytocompatibility. The studies showed that NiTi had a lesser impact
on cell viability and attachment than titanium alloy. Further, rough NiTi was
found to be a better tolerated surface than the others. In this study, heat
treatment of titanium alloy at +850° C did not interfere with cell viability
or attachment, as did the +1050° C treatment of the alloy. On the contrary,
TGF-β1 concentrations decreased on the +850° C treated alloy and were
approximately same on the +1050° C treated alloy and on NiTi.
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Pulletikurthi, Chandan. "Biocompatibility Assessment of Biosorbable Polymer Coated Nitinol Alloys". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1552.
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Owing to an increased risk of aging population and a higher incidence of coronary artery disease (CAD), there is a need for more reliable and safer treatments. Numerous varieties of durable polymer-coated drug eluting stents (DES) are available in the market in order to mitigate in-stent restenosis. However, there are certain issues regarding their usage such as delayed arterial healing, thrombosis, inflammation, toxic corrosion by-products, mechanical stability and degradation. As a result, significant amount of research has to be devoted to the improvement of biodegradable polymer-coated implant materials in an effort to enhance their bioactive response.
In this investigation, magneto-electropolished (MEP) and a novel biodegradable polymer coated ternary Nitinol alloys, NiTiTa and NiTiCr were prepared to study their bio and hemocompatibility properties. The initial interaction of a biomaterial with its surroundings is dependent on its surface characteristics such as, composition, corrosion resistance, work of adhesion and morphology. In-vitro corrosion tests such as potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were conducted to determine the coating stability and longevity. In-vitro hemocompatibility studies and HUVEC cell growth was performed to determine their thrombogenic and biocompatibility properties. Critical delamination load of the polymer coated Nitinol alloys was determined using Nano-scratch analysis. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions leached from Nitinol alloys on the viability of HUVEC cells. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), contact angle meter and X-ray diffraction (XRD) were used to characterize the surface of the alloys.
MEP treated and polymer coated (PC) Nitinol alloys displayed a corrosion resistant polymer coating as compared to uncoated alloys. MEP and PC has resulted in reduced Ni and Cr ion leaching from NiTi5Cr and subsequently low cytotoxicity. Thrombogenicity tests revealed significantly less platelet adhesion and confluent endothelial cell growth on polymer coated and uncoated ternary MEP Nitinol alloys. Finally, this research addresses the bio and hemocompatibility of MEP + PC ternary Nitinol alloys that could be used to manufacture blood contacting devices such as stents and vascular implants which can lead to lower U.S. healthcare spending.
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McDougall, Kathleen Emma. "Evaluation of biocompatibility using human craniofacial bone cells". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368260.
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Cohen, Sarah J. (Sarah Jennifer). "Biocompatibility of an implantable ophthalmic drug delivery device". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39871.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 90-94).
Diseases of the posterior eye present clinicians with a treatment challenge mainly due to the region's inaccessible location. Several drugs, including those available for the treatment of exudative age-related macular degeneration, are currently delivered by periodic injection into the eyeball. To avoid the risks and complications associated with this method, several implantable, timed release devices have been investigated to deliver these drugs directly to affected areas. Draper Laboratory and Massachusetts Eye and Ear Infirmary have proposed an implantable, fully programmable, mechanical device for long-term drug delivery to the eye wall. To investigate the biocompatibility of this solution, test devices containing gears or a ball bearing were designed to mimic elements of its moving parts, geometry and materials. Cell culture studies identified a polytetrafluoroethylene filter with 100m pores as a promising addition to seal devices from interaction with fibroblasts. Test devices with or without this membrane were implanted on the rabbit eye for 2 or 10 week periods. They were evaluated mechanically after implant, and surrounding tissues were inspected histologically. Gross observation revealed a significant amount of tissue formation around the devices, especially in the conjunctiva.
(cont.) Devices had to be cut away from the eye surface, and there was a significant amount of tissue inside the gear devices. Notably less tissue surrounded and invaded the ball bearing devices. Histological evaluation identified the invading tissue as fibrotic at both time points, though significantly more was seen at longer implant times. Eye wall tissue was typically unharmed during implant, though an additional layer of fibrosis between the eye and the device was common. Mechanical testing of long-term gear devices after implant revealed a 1000 fold increase in torque required to turn the elements, but long-term ball bearing devices were significantly less affected (100 fold increase). Torque also increased in devices with membrane covers, due to similar fibrosis. However, in these implants, tissue was forced to enter through only the 0.002in. openings around the base of the devices. Biocompatibility for this device may best be achieved by minimizing the amount of relative micro motion allowed between the device and the eye and by sealing all openings with a porous polytetrafluoroethylene filter.
by Sarah J. Cohen.
S.M.
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William, V. G., Володимир Миколайович Дейнека, Владимир Николаевич Дейнека, Volodymyr Mykolaiovych Deineka, R. Gwendolen, Максим Володимирович Погорєлов, Максим Владимирович Погорелов e Maksym Volodymyrovych Pohorielov. "In-vivo testing of spongy titanium implant biocompatibility". Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/31970.
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The conducted experiment shows porous titanium implant biocompatibility and existence of conductive features. This results leads to further research concerning this materials possible usage in osteoplasty.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/31970
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Bernard, Mélisande. "Etude de biocompatibilité des films à base de COC en tant que matériaux implantables". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS378.
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L’objet de ce travail est l’étude de la biocompatibilité in vitro des matériaux à base de COC, afin d’évaluer leur potentiel de biomatériaux implantables.Cette évaluation est réalisée par le suivi de plusieurs paramètres : viabilité cellulaire/cytotoxicité, évaluation des phénomènes de stress oxydant, inflammatoires et hémocompatibilité. Une relation entre ces réponses biologiques et les propriétés physico chimiques des matériaux étudiés a été appréhendée.Les résultats montrent une bonne biocompatibilité des films testés avec un impact significatif de la présence des additifs (anti-oxydant et lubrifiant) sur les paramètres biologiques et physico-chimiques évalués.L’effet simulé du vieillissement biologique de ces matériaux sur leur biocompatibilité et leurs caractères physico-chimiques a également été étudié. Des conditions de pH et d’oxydation extrêmes, ainsi que le contact avec des macrophages pendant 1 mois, ont un effet sur la surface et sur l’interaction des films de COC avec l’environnement biologique sans compromettre leur biocompatbilité. La présence d’additifs a également eu un impact sur ces modifications.En suivant une logique de management du risque, la systématisation de l’ensemble des méthodes développées a permis d’obtenir une approche simplifiée et validée au sein du laboratoire, applicable à l’ensemble des matériaux naturels ou synthétiques susceptibles d’être utilisés dans la fabrication des DM implantablesAbstract : The purpose of this work is the study of the in vitro biocompatibility of COC-based materials in order to evaluate their potential as implantable biomaterials.This evaluation is carried out by monitoring several parameters: cell viability / cytotoxicity, evaluation of oxidative stress, inflammatory reactions and hemocompatibility. A relationship between these biological responses and physicochemical properties of the studied materials has been apprehended.Results show a good biocompatibility of the tested films with a significant impact of the presence of additives (anti-oxidant and lubricant) on the evaluated biological and physicochemical parameters.The simulated effect of biological aging of these materials on their biocompatibility and physico-chemical characteristics has also been studied. Extreme pH and oxidation conditions, as well as contact with macrophages during 1 month, affect the surface and interaction of COC films with the biological environment without compromising their biocompatibility. The presence of additives also had an impact on these changes.Following a risk management logic, the systematization of the developed methods within the laboratory made it possible to obtain a simplified and validated approach, applicable to all natural or synthetic materials that could be used for manufacturing implantable medical devices
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Beaufils, Sylvie. "Synthèse électrochimique et caractérisation de nanoparticules d'hydroxypatite, mise en charge de matrices extracellulaires d'hydrogel et leurs caractérisations mécaniques et biologiques". Thesis, Reims, 2018. http://www.theses.fr/2018REIMS031/document.
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Dans le but de réduire la morbidité et la durée d’hospitalisation, la médecine régénérative progresse de nos jours vers le développement de techniques chirurgicales moins invasives. Cette recherche en chirurgie mini-invasive a motivé le développement de matrices injectables pour l’ingénierie tissulaire osseuse. Ces matrices doivent aussi être capables de durcir une fois injectées in situ, acquérir la forme souhaitée ainsi que des propriétés mécaniques compatibles avec le tissu hôte qu’elles doivent réparer. De nombreux hydrogels sont déjà employés pour cette application mais aucun ne remplit complètement les propriétés requises. L’objectif de cette thèse est de développer de nouveaux substituts de greffe osseuse : des hydrogels à base de biopolymères associés à des cellules osseuses pour obtenir des greffons mi-synthétiques, mi-biologiques. Des nanoparticules de phosphates de calcium sont ajoutées pour améliorer les propriétés biologiques et mécaniques des hydrogels. L’hydroxyapatite, le phosphate de calcium choisi, est attrayante à cause de ses similitudes chimiques et structurales au constituent minéral de l’os humain. Le but de ce travail est de synthétiser des nanofils d’hydroxyapatite par la méthode template et des nanopoudres d’hydroxyapatite de taille contrôlée par sonoélectrochimie pulsée déphasée. Ensuite pour améliorer les propriétés intrinsèques des structures 3D, ces nanoparticules de phosphates de calcium seront insérées dans des matrices d’hydrogel synthétisées par le laboratoire d’ingénierie ostéo-articulaire et dentaire (LIOAD) de Nantes. Des mesures de coefficient de diffusion seront suivies par des tests de cytotoxicité et de biocompatibilité de ces matériaux. Des études en sous-cutané et après implantation en milieu osseux suivrontIn order to reduce morbidity and hospital stay, regenerative medicine is nowadays moving towards the development of less invasive surgical techniques. This search for a minimally invasive surgery has motivated the development of injectable matrices for bone tissue engineering. These matrices must also be able to harden in situ once injected, acquire the desired shape and mechanical properties compatible with the host tissue it intends to repair. Many hydrogels are already used for this application but none fully meets the required properties. The objective of this thesis is to develop new bone graft substitutes: hydrogels based on biopolymers associated with bone cells to achieve half synthetic and half biological grafts. Nanoparticles of calcium phosphates are added to improve the biological and mechanical properties of hydrogels. Hydroxyapatite, calcium phosphate chosen, has attracted much attention because of its chemical and structural similarity to the mineral constituent of human bone. The aim of this work is to synthesize firstly hydroxyapatite nanowires by the template method and secondly size controlled hydroxyapatite nanopowders by out-of-phase pulsed sonoelectrochemistry. Thirdly to improve the intrinsic properties of these three-dimensional structures, those nanoparticles of calcium phosphates will be added in the matrices of hydrogel synthesized by the LIOAD. Measurements of diffusion coefficient will be followed by testing cytotoxicity and biocompatibility of those materials. A subcutaneous study and bone model study will follow
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Ryhänen, J. (Jorma). "Biocompatibility evaluation of nickel-titanium shape memory metal alloy". Doctoral thesis, Oulun yliopisto, 1999. http://urn.fi/urn:isbn:9514252217.
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Abstract
The shape memory effect, superelasticity, and good damping properties, uncommon in other implant alloys, make the nickel-titanium shape memory metal alloy (Nitinol or NiTi) a fascinating material for surgical applications. It provides a possibility to make self-locking, self-expanding and self-compressing implants. The purpose of this work was to determine if NiTi is a safe material for surgical implant applications.
The primary cytotoxicity and the corrosion rate of NiTi were assessed in human osteoblast and fibroblast cell cultures. Comparisons were made with 316 LVM stainless steel (StSt) and pure titanium. The metal ions present in the media were analyzed using atomic absorption spectrometry (GFAAS). Despite the higher initial nickel dissolution, NiTi induced no toxic effects, decrease in cell proliferation or inhibition in the growth of cells in contact with the metal surface.
The general soft tissue responses to NiTi were compared to corresponding responses to StSt and Ti-6Al-4V alloy in rats during a follow-up of 26 weeks. The muscular tissue response to NiTi was clearly non-toxic and non-irritating, as were also the neural and perineural responses. The overall inflammatory response and the presence of immune cells, macrophages and foreign body giant cells were similar compared to the other test materials. At 8 weeks, histomorphometry showed that the encapsule membrane of NiTi was thicker than that of stainless steel, but at 26 weeks the membrane thicknesses were equal.
A regional acceleratory phenomenon (RAP) model was used to evaluate new bone formation, bone resorption and bone (re)modeling after periosteal implantation of NiTi, StSt or Ti-6Al-4V in rats using histomorphometry. Maximum new woven bone formation started earlier in the Ti-6Al-4V group than in the NiTi group, but also decreased earlier, and at 8 weeks the NiTi and StSt groups had greater cortical bone width. Later, no statistical differences were seen. NiTi had no negative effect on total new bone formation or normal RAP during a 26-week follow-up.
The ultrastructural features of cell-NiTi adhesion were analyzed with scanning electron microscopy (FESEM). Cell adhesion and focal contacts showed a good acceptance of NiTi.
Femoral osteotomies of rats were fixed with either NiTi or StSt intramedullary nails. Bone healing was examined with radiographs, peripheral quantitative computed tomography (pQCT) and histologically. The maximum follow-up was 60 weeks. There were more healed bone unions in the NiTi than the StSt group at early time points. Callus size and bone mineral density did not differ between the NiTi and StSt groups. Mineral density in both groups was lower in the osteotomy area than in the other areas along the nail. Density in the nail area was lower than in the proximal part of the operated femur or the contralateral femur. Bone contact to NiTi was close, indicating good tissue tolerance. Determination of trace metals from several organs was done by GFAAS or inductively coupled plasma-atomic emission spectrometry (ICP-AES). There were no statistically significant differences in nickel concentration between the NiTi and StSt groups in distant organs. The FESEM assessment showed surface corrosion changes to be more evident in the StSt implants.
On the basis of this study, the biocompatibility of NiTi seems to be similar to or better than that of stainless steel or Ti-6Al-4V alloy. NiTi appears to be suitable for further use as a biomaterial, because its biocompatibility is good. When NiTi is intended to be used in long-term implants, optimal surface treatment must consider.
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Long, Susanna. "Factors affecting the biocompatibility of novel phosphorylcholine based biomaterials". Thesis, University of Brighton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405288.
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Phosphorylcholine (PC) based polymers have been used in medical devices to improve biocompatibility. In this study, PC based polymers were modified with either a cationic charge or combined with poly(butylmethacrylate) (PBMA) and their biocompatibility assessed through a series of biological assays. Protein adsorption assays revealed that the presence of a cationic charge significantly increased the number of proteins adsorbed. The total amount of protein adsorbed to PC with 30% cationic charge was considerably more then that adsorbed to the other samples. Fibronectin, albumin, complement factor B and immunoglobulins were found adsorbed to all samples. Clq however, was only adsorbed on samples containing 10% cationic charge or more. The presence of a cationic charge increased cell adhesion for both the fibroblast cells and the epithelial cells. Adhesion did not increase linearly with cationic charge, possibly due to alterations in protein adsorption, coating stability, and or cytotoxicity. Endothelial cells showed little to no cell adhesion on any of the PC cationic samples. Pre-coating materials in fibronectin increased endothelial cell adhesion, although this effect generally decreased as serum concentration increased. Pre-coating samples in laminin facilitated cell adhesion on PC with 20% cationic charge but not on PET or PC with 0% cationic charge. The combination of cationic charge and laminin may encourage cell adhesion, possibly through alterations in conformation of adsorbed proteins. Serum type affected adhesion and activation of mononuclear cells and granulocytes. The presence of a cationic charge increased the adhesion and activation of these two cell types. Adhesion and activation did not increase linearly with cationic charge, possibly due to differences in protein adsorption, coating stability and or cytotoxicity. The biocompatibility of PC and PBMA copolymer samples were assessed, looking at adhesion of corneal epithelial cells and macrophage cells. Adhesion of both of these cell these cell types increased as PBMA content increased and PC decreased. This is probably due to alterations in protein adsorption as a result of changes in surface hydrophobicity.
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Martines, Elena. "Surfaces with periodic nano-features : physical properties and biocompatibility". Thesis, University of Glasgow, 2006. http://theses.gla.ac.uk/3900/.
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The behaviour of animal cells in vitro is affected by both the chemistry and the shape of the surface (“topography”) to which they adhere. Culturing animal cells on nanopatterns of different shape, dimensions and chemistry considerably modifies cell attachment, spreading, proliferation, migration and gene expression. This work was primarily aimed at elucidating the influence of nanopatterning on some physical properties of the substrate. The contact angle of water on nanopatterned silicon was measured, and the predicted DLVO (Derjaguin-Landau-Verweey-Overbeek) interaction between a nanopatterned silica plate and a microsphere was calculated. After the physical measurements, the silicon nanopatterns were replicated into a biocompatible polymer, and further experimental investigations of the response of biological cells to nano-pillared samples were carried out. Finally, in the last chapter a flow system was designed, in order to determine the influence of a nano-pitted interface on the initial adhesion of cells subjected to hydrodynamic forces. Surface texture has a great influence on both the wetting and the interfacial properties of the substrate. In this thesis, I show that the contact angles on nano-topographies are linked to the geometry and chemistry of the pattern by defined analytical rules. Contact angle measurements also proved that air-trapping can happen at a nanopatterned biomaterial surface. On the other hand, a SEI (Surface Element Integration) study predicts that the adhesion of a microsphere onto a plate should be strongly favoured by nanopatterned regular protrusions, and that the shape of the protrusions is a determining factor in this process. My results on cell behaviour confirm previous observations that some particular nano-patterns can inhibit the proliferation of fibroblasts in vitro. It is also shown how cell-specific this response can be, and possible explanations for this behaviour, including air-trapping at the interface, are discussed.
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Notara, Maria D. "Characterisation and biocompatibility of novel chitosan-alginata blend membranes". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423279.
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Seamen, P. J. "Investigation into the biocompatibility of modified synthetic polymer surfaces". Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381699.
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Watkins, Lucy. "Radio frequency plasma treatment of polymers for improved biocompatibility". Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441055.
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Hua, Kai. "Nanocellulose for Biomedical Applications : Modification, Characterisation and Biocompatibility Studies". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267301.
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In the past decade there has been increasing interest in exploring the use of nanocellulose in medicine. However, the influence of the physicochemical properties of nanocellulose on the material´s biocompatibility has not been fully investigated. In this thesis, thin films of nanocellulose from wood (NFC) and from Cladophora algae (CC) were modified by the addition of charged groups on their surfaces and the influence of these modifications on the material´s physicochemical properties and on cell responses in vitro was studied. The results indicate that the introduction of charged groups on the surface of NFC and CC results in films with decreased surface area, smaller average pore size and a more compact structure compared with the films of unmodified nanocelluloses. Furthermore, the fibres in the carboxyl-modified CC films were uniquely aggregated and aligned, a state which tended to become more prevalent with increased surface-group density. The biocompatibility studies showed that NFC films containing hydroxypropyltrime-thylammonium (HPTMA) groups presented a more cytocompatible surface than unmodified NFC and carboxymethylated NFC regarding human dermal fibroblasts. Carboxymethyl groups resulted in NFC films that promoted inflammation, while HPTMA groups had a passivating effect in terms of inflammatory response. On the other hand, both modified CC films behaved as inert materials in terms of the inflammatory response of monocytes/macrophages and, under pro-inflammatory stimuli, they suppressed secretion of the pro-inflammatory cytokine TNF-α, with the effects of the carboxylated CC film more pronounced than those of the HPTMA CC material. Carboxyl CC films showed good cytocompatibility with fibroblasts and osteoblastic cells. However, it was necessary to reach a threshold value in carboxyl-group density to obtain CC films with cytocompatibility comparable to that of commercial tissue culture material. The studies presented here highlight the ability of the nanocellulose films to modulate cell behaviour and provide a foundation for the design of nanocellulose-based materials that trigger specific cell responses. The bioactivity of nanocellulose may be optimized by careful tuning of the surface properties. The outcomes of this thesis are foreseen to contribute to our fundamental understanding of the biointerface phenomena between cells and nanocellulose as well as to enable engineering of bioinert, bioactive, and bioadaptive materials.
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Zhu, Lin. "Biocompatibility of Carbon Nanomaterials: Materials Characterization and Cytotoxicity Evaluation". University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343744183.
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Huber, Daniel Edward. "Structure and Properties of Titanium Tantalum Alloys for Biocompatibility". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480589088123473.
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Jeewandara, Thamarasee M. "Bioengineering Stents for Proactive Biocompatibility: From Biomaterials to Stents". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14974.
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The thesis describes methods to characterize modified biomaterial surfaces in vitro, and investigate its short term implications at the artery interface in vivo. Plasma activated coating (PAC) technology has been previously deposited on a stainless steel biomaterial (316LSS), investigated in the stent form in vivo. Initial histopathology characterizations conducted with resin-artery-stents evaluate artery-stent interface interactions in vivo. The 7 day pilot study was followed by detailed material characterization and biofunctionalization on a modified cobalt chromium metal alloy L605, for the first time herein. The outcome of this study, is to transfer optimized plasma technology to new generation cobalt chromium stents (Multi Link 8, Abbott Vascular); currently in use to treat coronary artery disease (CAD). Plasma technology is unique for its ability to not delaminate from a biomaterial, while providing surface hemocompatibility, cytocompatibility, and controlled covalent attachment of protein tropoelastin (TE), in its native conformation. The present study addressed three key questions: 1. Do PAC 316LSS stents engineered with TE improve in vivo biocompatibility at 7 days? 2. How does PAC adhere to cobalt chromium alloy L605 (novel biomaterial) to prevent delamination under stress? 3. How does PAC-L605 maintain superior hemocompatibility and promote homogenous cell culture compared to alloy L605.
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Källrot, Martina. "Covalent Surface Modification of Degradable Polymers for Increased Biocompatibility". Licentiate thesis, KTH, Fiber- och polymerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-579.
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Degradable polymers have gained an increased attention in the field of biomedical applications over the past decades, for example in tissue engineering. One way of improving the biocompatibility of these polymers is by chemical surface modification, however the risk of degradation during the modification procedure is a limiting factor. In some biomedical applications, for example in nerve guides, a patterned surface is desired to improve the cell attachment and proliferation. In this thesis a new non-destructive, single-step, and solvent free method for surface modification of degradable polymers is described. Poly(L-lactide) (PLLA) substrates have been functionalized with one of the following vinyl monomers; N-vinylpyrrolidone (VP), acrylamide (AAm), or maleic anhydride (MAH) grafts. The substrates were subjected to a vapor phase atmosphere constituted of a mixture of a vinyl monomer and a photoinitiator (benzophenone) in a closed chamber at very low pressure and under UV irradiation. Poly(ε-caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), and poly(trimethylene carbonate) (PTMC) have been surface modified with VP using the same procedure to show the versatility of the method. The wettability of all of the four substrates increased after grafting. The surface compositions were confirmed by ATR-FTIR and XPS. The VP grafted PLLA, PTMC and PLGA substrates have been shown to be good substrates for the normal human cells i.e. keratinocytes and fibroblasts, to adhere and proliferate on. The topography of substrates with well defined nano patterns was preserved during grafting, since the grafted layer is very thin. We have also shown that the method is useful for a simultaneous chemical and topographical modification of substrates by masked vapor phase grafting. The surface topography was determined with SEM and AFM.Intresset för användningen av nedbrytbara polymerer till biomedicinska applikationer som till exempel vävnads rekonstruktion har ökat avsevärt de senaste decennierna. Ett sätt att öka biokompatibiliteten hos dessa polymerer är genom kemisk ytmodifiering, men risken för nedbrytning under själva modifieringen är en begränsande faktor. I vissa biomedicinska applikationer, till exempel nervguider, är det önskvärt att ha en väldefinierad ytstruktur för att öka vidhäftningen och tillväxten av celler. I den här avhandlingen presenteras en ny ickeförstörande, lösningsmedelsfri enstegsprocess för ytmodifiering av nedbrytbara polymerer. Substrat av poly(L-laktid) (PLLA) har ytfunktionaliserats med var och en av följande vinylmonomerer, N-vinylpyrrolidon (VP), akrylamid (AAm) eller maleinsyraanhydrid (MAH). Substraten har exponerats för en gasfasatmosfär av en blandning av en vinylmonomer och en fotoinitiator (bensofenon) i en tillsluten reaktor vid mycket lågt tryck och under UV-strålning. Metodens mångsidighet har även påvisats genom att ytmodifiera substrat av poly(ε-kaprolakton) (PCL), poly(laktid-co-glykolid) (PLGA) och poly(trimetylen karbonat) (PTMC) med VP. Vätbarheten ökade för alla fyra materialen efter ympning med en vinylmonomer. Ytsammansättningen fastställdes med ATR-FTIR och XPS. De VP ympade filmerna av PLLA, PLGA och PTMC visade sig vara bra substrat för mänskliga celler, i detta fall keratinocyter och fibroblaster, att vidhäfta och växa på. Yttopografin hos filmer med väldefinierade nanomönstrade ytor kunde bevaras efter ympning, tack vare att det ympade lagret är så tunt. Gasfas metoden har också visat sig användbar för att simultant ytmodifiera både kemiskt och topografiskt genom maskad gasfasympning. Yttopografin bestämdes med SEM och AFM.
QC 20101014
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Chan, Yee-loi, e 陳以來. "Surface modification of NiTi for long term orthopedic applications". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557406.
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Lakbakbi, Souad. "Adhésion et activation des cellules sanguines par une membrane d'hémodialyse (AN-69ST) : conséquence sur l'expression de facteur tissulaire et la thrombogénecité de la membrane". Thesis, Reims, 2014. http://www.theses.fr/2014REIMS012/document.
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L'objectif de ce travail est d'évaluer le rôle du facteur tissulaire (FT) dans l'initiation de la coagulation d'un circuit d'hémodialyse. A partir de l'analyse des membranes d'hémodialyse, nous avons observé que les leucocytes et, majoritairement les polynucléaires neutrophiles (PNN) adhéraient aux membranes hémocompatibles (de type AN69ST). Ces cellules expriment un FT fonctionnel. Nous avons développé différents modèles d'étude de l'expression du FT par les PNN. A partir de PNN humains obtenus chez des sujets sains, nous montrons que les PNN expriment le FT après stimulation par le TNF. L'IL-8, chemokine chimioattractante des PNN augmentent, par un effet de priming, l'expression de FT en réponse au TNF. L'inhibition de l'adhésion par un anticorps dirigé contre les β2-intégrines, induit une diminution de l'expression de FT en réponse au TNF. L'inhibition de la voie de signalisation MEK1/2, la p38 MAPK, et des radicaux libres oxygénés, inhibe également cette expression. A partir de PNN provenant de péritonites secondaires à une dialyse péritonéale, nous avons mis en évidence une forte expression de FT par ces PNN (ARNm et protéine). Le FT possède un fort potentiel pro-coagulant. Ce modèle physiopathologique est la conséquence d'une migration et d'une activation inflammatoire comparable au modèle que nous avons développé in-vitro. Dans l'objectif de faire la preuve de ce nouveau concept, nous avons évalué un facteur VII humain recombinant inactivé (FVIIai) dans un modèle d'hémodialyse chez le mouton. Nos résultats sont en faveur d'un effet anticoagulant du circuit d'hémodialyse, sans effet anticoagulant mesurable chez l'animalThe objective of this study is to analyse the role of Tissue Factor, the unique physiological trigger on thrombin generation. Analysing haemodialysis membranes, we found that leukocytes, mainly polymorphonuclear neutrophils (PMN) adhere to hemocompatible (AN69ST) membranes. These cells express a functional TF. We next showed that human PMN obtained from healthy subjects expressed TF in response to TNF. IL-8, a major chemokine involved in PMN chemoattraction primed TNF-induced TF by PMN. TF expression was down regulated when 2 integrins were blocked by a potent antibody. The inhibition of MEK1/2, p38 MAPK and free radicals reduced TF expression. We observed, that PMN obtained from patients experiencing peritonitis, expressed high levels of TF (mRNA and protein). Functional assays measuring Xa generation and kinetics of thrombinn generation (thrombinography) indicate the stong procoagulant potential of these cells. This physiopathological model is close to our in vitro model as it results from PMN migration and inflammatoty activation. For proof of concept, we evaluated the effect of an inactivated human recombinant factor VIIa ( FVIIai) in a sheep model of hemodialysis. Our results show that FVIIai limits haemodialysis circuit coagulation without any measurable systemic anticoagulant effect
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Cottance, Myline. "Contribution au développement d'interfaces neuro-électroniques". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1105/document.
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Les travaux menés au cours de cette thèse portent sur la microfabrication d'interfaces neuro-électroniques pour des applications en neurosciences. Nous avons choisi de nos focaliser sur la réhabilitation fonctionnelle motrice et sensorielle en développant différentes matrices de micro-électrodes (MEA) respectivement, des sondes neuronales rigides et des implants rétiniens souples. Selon les applications visées, deux types de substrats ont été utilisés pour concevoir ces MEA. Pour des analyses ou expériences in-vitro, les MEA (sondes neuronales) ont plutôt été réalisées sur des substrats rigides tels que le silicium ou le verre, tandis que pour les expériences in-vivo, les MEA (implants rétiniens) ont été réalisées sur des substrats souples tels que des polymères biocompatibles (polyimide ou parylène). Ces MEA ont été fabriquées avec différents matériaux d'électrodes (diamant dopé, platine, platine noir et or) qui ont également été testés afin de déterminer leur capacité en enregistrement et/ou stimulation. De plus, à l'aide de travaux de modélisation numérique, nous avons validé le concept d'une géométrie tridimensionnelle avec grille de masse permettant une stimulation plus focale des cellules. Cette thèse a ainsi contribué à stabiliser différents procédés de fabrication pour obtenir des MEA plus reproductibles ainsi que pour améliorer leur rendement. Elle a également permis d'établir un suivi et un protocole expérimental pour assurer une traçabilité des MEA et contrôler leur performances à toutes les étapes : depuis leur fabrication au moyen de techniques électrochimiques (CV, EIS) jusqu'aux expériences biologiques in-vitro et in-vivoThe work lead during this thesis deals with microfabrication of neuro-electronic interfaces for neuroscience applications. We have chosen to focus on motor and sensory function rehabilitations by developing Micro-Electrode Arrays (MEA) respectively, rigid neural probes and flexible retinal implants. According to the targeted applications, two types of substrates have been used to achieve these MEA. For analysis or in vitro experiments, neural probes MEA have been realized on rigid substrates such as silicon or glass whereas for in-vivo experiments, retinal implants MEA have been realized on flexible substrates such as biocompatible polymers (polyimide or parylene). These MEA were made with different electrode materials (boron doped diamond, platinum, black platinum and gold) which have been tested to determine their capability in recording and/or stimulation. Moreover, with numerical modelling work, we have validated a tridimensional geometry concept with a ground grid which permits a more local stimulation of cells. This thesis has contributed to stabilize different fabrication processes to obtain more repeatable MEA and also to improve their yield. It also allowed the set-up of a follow-up and an experimental protocol to insure MEA traceability and to monitor their performances at each step since their fabrication through means of electrochemical techniques (CV, EIS) to in vitro and in-vivo biological experiments
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Ljunggren, Lennart. "Biothermodynamic studies of blood components with special reference to biocompatibility". Lund : Dept. of Clinical Chemistry, University Hospital, 1994. http://catalog.hathitrust.org/api/volumes/oclc/39117042.html.
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Kujala, S. (Sauli). "Biocompatibility and biomechanical aspects of Nitinol shape memory metal implants". Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514271246.
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Abstract
Nickel-titanium shape memory metal Nitinol (NiTi) is a new kind of implant material, which provides a possibility to prepare functional implants activated at body temperature and withstands kinking better than conventional metals. Applications utilizing these unique properties are a target of active research interest. Host reactions to NiTi and to the forces created by functional implants should also be studied.
A functional NiTi intramedullary nail, which causes a bending force on the bone, was developed for correcting bone deformities. In the present studies, the action of the device was inverted to induce a bone deformity instead of correcting one, in order to test the hypothesis that bone modelling can be controlled using such functional nail. Implanting the nail into the medullary cavity of rat femur for twelve weeks caused bowing of the bone, retardation of its longitudinal growth, and thickening of the bone and the cortex. In another study the effects of functional and straight nails were compared. Bowing of the bone and significant overall thickening of the bone and the cortex were associated only with the functional nail, while the straight nail induced only minor thickening of the bone. Retardation of longitudinal growth was seen in both groups, and this may have been caused by perforating the distal epiphyseal plate during the nailing. Finite element model of the bone-nail combination was also created.
Porous NiTi was studied as a bone graft substitute by filling a bone defect in the distal femoral metaphysis of a rat bone with porous NiTi implants of different porosities. After 30 weeks, porosity of 66.1% (mean pore size (MPS) 259μm) showed the best bone-implant contact (51%). However, porosity of 46.6% (MPS 505μm) with 39% bone-implant contact was not significantly inferior in this respect and showed a significantly lower incidence of fibrosis within the implant and thus seemed to be the best choice for a bone graft substitute, out of the porosities tested here. The porosity of 59.2% (MPS 272μm) showed lower contact values.
NiTi tendon suture material was studied by implanting NiTi sutures into rabbit tendon and subcutaneous tissues for two, six, and twelve weeks. NiTi proved to be stronger than polyester, which served as control material. The encapsulating membrane was minimal with both materials, suggesting good biocompatibility in tendon tissue. The implantation did not affect the strength properties of either material.
On the basis of the present studies, NiTi provides a possibility to develop new kinds of implants for correcting bone deformities, for filling bone defects in weight-bearing locations and a good candidate for a tendon suture material.
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Haider, Waseem. "Enhanced Biocompatibility of NiTi (Nitinol) Via Surface Treatment and Alloying". FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/177.
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It is projected that by 2020, there will be 138 million Americans over 45, the age at which the increased incidence of heart diseases is documented. Many will require stents. This multi-billion dollar industry, with over 2 million patients worldwide, 15% of whom use Nitinol stents have experienced a decline in sales recently, due in part to thrombosis. It is a sudden blood clot that forms inside stents. As a result, the Food and Drug Administration and American Heart Association are calling for a new generation of stents, new designs and different alloys that are more adaptable to the arteries. The future of Nitinol therefore depends on a better understanding of the mechanisms by which Nitinol surfaces can be rendered stable and inert. In this investigation, binary and ternary Nitinol alloys were prepared and subjected to various surface treatments such as electropolishing (EP), magnetoelectropolishing (MEP) and water boiling & passivation (W&P). In vitro corrosion tests were conducted on Nitinol alloys in accordance with ASTM F 2129-08. The metal ions released into the electrolyte during corrosion tests were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Biocompatibility was assessed by observing the growth of human umbilical vein endothelial cells (HUVEC) on the surface of Nitinol alloys. Static and dynamic immersion tests were performed by immersing the Nitinol alloys in cell culture media and measuring the amount of metal ions released in solution. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions on the growth of HUVEC cells. The surfaces of the alloys were studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Finally, wettability and surface energy were measured by Contact Angle Meter, whereas surface roughness was measured by Atomic Force Microscopy (AFM). All the surface treated alloys exhibited high resistance to corrosion when compared with untreated alloys. SRB assays revealed that Ni and Cu ions exhibited greater toxicity than Cr, Ta and Ti ions on HUVEC cells. EP and MEP alloys possessed relatively smooth surfaces and some were composed of nickel oxides instead of elemental nickel as determined by XPS. MEP exhibited lowest surface energy and lowest surface roughness.
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Kidani, Derrick D. A. "Surface modifications to improve the biocompatibility of polymeric vascular prostheses". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11263.
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Ruan, Jianming. "Characterisation and biocompatibility evaluation of calcium phosphate biomaterials in vitro". Thesis, University of Strathclyde, 2000. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21172.
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Medical applications of calcium phosphate biomaterials are limited because of poor mechanical properties and acute inflammation reactions which take place occasionally in the clinic. To increase the usefulness of calcium phosphate biomaterials it is necessary to improve the mechanical properties and biological character. Processing and characterization of porous hydroxyapatite (HA) and dense composite (HA-Spinel) biomaterials have been performed in the present research. Biocompatibility of these biomaterials has been examined in vitro using human and rat immortalized osteoblast cells, and the advantages and limitations of cell culture biocompatibility tests are discussed. X-ray analysis of material structure demonstrated that after sintering at 1450°C, HA-Spinel was changed into tricalcium phosphate (TCP)-Spinel phase structure. Mechanical properties testing showed that the bending strength and compressive strength of HA may be improved by adding Spinel. Biocompatibility examination demonstrated that both human and rat osteoblast cells anchored to the surface of the porous and dense biomaterials in a short time, and subsequently, grew and proliferated normally on the surface of these biomaterials. Cytotoxicity evaluation in vitro by studying material extracts demonstrated that compared with the control group of cells cultured on polystyrene, HA-Spinel possessed slight toxicity. Cell growth in HA-Spinel first extracts was slightly impaired. Tritium labeling and immunofluorescent analysis proved that human osteoblast cells and rat osteoblast cells have normal expression of collagen synthesis on the above biomaterials. Confocal laser scanning microscopy (CLSM) observation showed that collagen fibers were produced on these materials, and the amount of the collagen synthesized on the materials increased with culture time. Subsequent analysis indicated that both HA and HA-Spinel can strongly adsorb serum and albumin proteins from culture media and the amount of protein adsorption was proportional to the porosity in the materials. Protein adsorption on the material surface was saturated usually in 2-4 hours, and 1/3-1/2 of the total protein adsorption was achieved in several minutes. In vitro assay also confirmed that human and rat osteoblast cells can be applied as an in vitro model to evaluate the biocompatibility, cytotoxicity and other biological characteristics. Compared with human osteoblast cells, rat osteoblast cells have a greater proliferation rate. In normal conditions, the proliferation rate of the rat osteoblast cells is 2-4 times that of the human osteoblast cells and for this reason rat osteoblasts seem more sensitive to material extracts.