Dissertations / Theses: 'Biodegradable materials'

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Tolentino, Chivite Ainhoa. "Ionic complexes of biodegradable polyelectrolytes." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/144662.

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Biopolymers are polymers produced by living organisms. A more broad classification would embrace also those polymers synthesized from renewable sources which are able to display biodegradability. The demand of biopolymers has been continuously growing along these last decades. The main reason for such increasing interest is their sustainability; the renewable origin of biopolymers makes them inexhaustible in contrast with synthetic polymers produced from finite fossil sources. Biodegradability is a second advantage; due to the presence in the nature of enzymes able to degrade biopolymers under environmental conditions to give non-toxic products, their impact on the environment is basically trivial. Finally, the use of more or less modified biopolymers as biomaterials, owing to their unique properties of biocompatibility and biodegradability, has aroused their interest in several disciplines. As a result of all these considerations, great efforts in biopolymers research including chemical modification, characterization and property evaluation are today being carried out to develop new materials able to replace traditional plastics in a wide diversity of applications. In the present Thesis, a selection of carboxylic biopolymers has been studied for their capacity to form stable ionic complexes with cationic surfactants suitable to render new materials with advanced properties. Previous studies on polyelectrolytesurfactant complexes carried out in our group have demonstrated that these coupled systems tend to be self-assembled in well-ordered structures that can be exploited for building films and particles with singular properties as biomaterials. The main goal of this Thesis is the study of polyelectrolyte-ionic complexes based on naturally occurring polyacids and cationic surfactants. One part of the work delves into the complexes of poly(g-glutamic acid), a system that has been object of continuous research in our group from 90s. The aim is to progress in the development by making them "greener" through coupling with bio-based surfactants, and by improving their basic properties through blending with nanoclays. The other part is dedicated to explore the ionic complexes made from poly(uronic acid)s and cationic surfactants. This is the first time that such complexes are examined and their structural features and properties compared to those displayed by complexes based on poly(glutamic acid). Experimentally, the Thesis embodies a multidisciplinary task work including preparation, structural characterization and evaluation of thermal properties of a series of ionic complexes, as well as a preliminary valuation of the suitability of some of them to be used as drug delivery systems. Hence, the specific objectives in this Thesis are enumerated as follows: 1. Synthesis and chemical characterization of ionic complexes of poly(uronic acid)s (pectinic, alginic and hyaluronic acids), with trimethylalkylammonium surfactants of n= 18, 20 and 22. Structural and thermal analysis of these complexes and critical comparison of results with those available for complexes made of poly(glutamic acid). 2. Synthesis and characterization of choline-based surfactants for the preparation of fully bio-based polyglutamic complexes as an alternative to complexes based on trimethylalkylammonium surfactants in their potential use as biomaterials. Structural and thermal analysis of these complexes and their preliminary evaluation as nano-particulated drug delivery systems. 3. Preparation of composites of poly(glutamic acid)-cationic surfactant complexes with organo-modified nanoclays, their extensive structural characterization and the evaluation of their thermal and mechanical properties compared to those displayed by the neat complexes. The Thesis is organized in five Chapters. After a very brief summary of the whole work with explicit definition of the objectives, Chapter I is an introduction to the subject, in which an extensively referenced account of the main hints previously achieved in the field is provided and the state-of-art is described. The following three Chapters correspond to the three specific objectives enumerated above. Chapter II gathers the synthesis, characterization and properties evaluation study carried out on ionic complexes of poly(uronic acid)s. Chapter III is focused on the study of ionic complexes of polyglutamic and alkanoylcholines, the synthesis and characterization of the surfactants, the preparation of their complexes with poly(glutamic acid) and their possibilities as potential biomaterials. Chapter IV covers the preparation of the composites made of Cloisite 30B and poly(glutamic acid) complexes along with a detailed study of their structure by X-ray diffraction, electron microscopy and modeling, and a correlative analysis of their structure with their thermal and mechanical properties. Chapter V contains the whole collection of conclusions that have been drawn from the Thesis. The author’s profile and published scientific production coming out from the Thesis constitute the body of the closing part.

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Mylonakis, Andreas Wei Yen. ""Biodegradable polymer adhesives, hybrids and anomaterials" /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2911.

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Gioffré, Michela <1984&gt. "Biodegradable systems for the development of functional materials." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5418/.

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This PhD work was aimed to design, develop, and characterize gelatin-based scaffolds, for the repair of defects in the muscle-skeletal system. Gelatin is a biopolymer widely used for pharmaceutical and medical applications, thanks to its biodegradability and biocompatibility. It is obtained from collagen via thermal denaturation or chemical-physical degradation. Despite its high potential as biomaterial, gelatin exhibits poor mechanical properties and a low resistance in aqueous environment. Crosslinking treatment and enrichment with reinforcement materials are thus required for biomedical applications. In this work, gelatin based scaffolds were prepared following three different strategies: films were prepared through the solvent casting method, electrospinning technique was applied for the preparation of porous mats, and 3D porous scaffolds were prepared through freeze-drying. The results obtained on films put into evidence the influence of pH, crosslinking and reinforcement with montmorillonite (MMT), on the structure, stability and mechanical properties of gelatin and MMT/gelatin composites. The information acquired on the effect of crosslinking in different conditions was utilized to optimize the preparation procedure of electrospun and freeze-dried scaffolds. A successful method was developed to prepare gelatin nanofibrous scaffolds electrospun from acetic acid/water solution and stabilized with a non-toxic crosslinking agent, genipin, able to preserve their original morphology after exposure to water. Moreover, the co-electrospinning technique was used to prepare nanofibrous scaffolds at variable content of gelatin and polylactic acid. Preliminary in vitro tests indicated that the scaffolds are suitable for cartilage tissue engineering, and that their potential applications can be extended to cartilage-bone interface tissue engineering. Finally, 3D porous gelatin scaffolds, enriched with calcium phosphate, were prepared with the freeze-drying method. The results indicated that the crystallinity of the inorganic phase influences porosity, interconnectivity and mechanical properties. Preliminary in vitro tests show good osteoblast response in terms of proliferation and adhesion on all the scaffolds.

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Kim, Jina 1984. "Lamination of a biodegradable polymeric microchip." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35137.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references (leaf 22).
This work builds on the initial design of a polymer microchip for controlled-release drug delivery. Currently, the microchip employs a nonbiodegradable sealant layer, and the new design aims to fabricate it only of biodegradable parts. Experiments were conducted to evaluate two potential designs that are fabricated via lamination, and a final design was proposed based on the results. Design 1 sought to replace the sealant directly with a PLA backing layer, but the laminated backing layer was found to leak in 14C-dextran release experiments. Design 2 used a laminated film instead of the original injected membrane. The laminated film was optimized to a 200- [mu]m thick poly(D,L-lactic-co-glycolic acid) 2A membrane, and the film-laminated microchip was shown to release 14C-dextran within a 40-day period. The final proposed design was based on Design 2, which demonstrated more potential as a future means of drug delivery.
by Jina Kim.
S.B.

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Kenar, Halime. "3d Patterned Cardiac Tissue Construct Formation Using Biodegradable Materials." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610315/index.pdf.

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The heart does not regenerate new functional tissue when myocardium dies following coronary artery occlusion, or is defective. Ventricular restoration involves excising the infarct and replacing it with a cardiac patch to restore the heart to a more efficient condition. The goal of this study was to design and develop a myocardial patch to replace myocardial infarctions. A basic design was developed that is composed of 3D microfibrous mats that house mesenchymal stem cells (MSCs) from umbilical cord matrix (Wharton&rsquo
s Jelly) aligned parallel to each other, and biodegradable macroporous tubings to supply growth media into the structure. Poly(glycerol sebacate) (PGS) prepolimer was synthesized and blended with P(L-D,L)LA and/or PHBV, to produce aligned microfiber (dia 1.16 - 1.37 &
#956
m) mats and macroporous tubings. Hydrophilicity and softness of the polymer blends were found to be improved as a result of PGS introduction. The Wharton&rsquo
s Jelly (WJ) MSCs were characterized by determination of their cell surface antigens with flow cytometry and by differentiating them into cells of mesodermal lineage (osteoblasts, adipocytes, chondrocytes). Cardiomyogenic differentiation potential of WJ MSCs in presence of differentiation factors was studied with RT-PCR and immunocytochemistry. WJ MSCs expressed cardiomyogenic transcription factors even in their undifferentiated state. Expression of a ventricular sarcomeric protein was observed upon differentiation. The electrospun, aligned microfibrous mats of PHBV-P(L-D,L)LA-PGS blends allowed penetration of WJ MSCs and improved cell proliferation. To obtain the 3D myocardial graft, the WJ MSCs were seeded on the mats, which were then wrapped around macroporous tubings. The 3D construct (4 mm x 3.5 cm x 2 mm) was incubated in a bioreactor and maintained the uniform distribution of aligned cells for 2 weeks. The positive effect of nutrient flow within the 3D structure was significant. This study represents an important step towards obtaining a thick, autologous myocardial patch, with structure similar to native tissue and capability to grow, for ventricular restoration.

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Barragán, Dan Jarry. "Biodegradability in soil determination and fate of some emerging biodegradable materials for agricultural mulching." Doctoral thesis, Universitat de Lleida, 2012. http://hdl.handle.net/10803/107948.

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The purpose of this PhD thesis was to evaluate the biodegradability potential and ecotoxicological effects of several biodegradable plastics for agricultural use under controlled laboratory conditions in soil. In this study, commercial and still in experimental stage biodegradable plastic films were chosen: Mater-Bi® (corn starch), Bio-Flex® (polylactic acid), Biofilm® (cereal flour), Bioplast® (potato starch), MirelTM (polyhydroxyalcanoates) Ecovio® and Bionelle®. In addition, a sheet commercially known as MimGreen® paper was evaluated. Initially, a gravimetric and FTIR analyses were carried out to determine changes in both weight loss and molecular changes in the plastics respectively. A second experiment consisted in assessing the biodegradability of the materials by designing and building a respirometric system. This system allowed me to measure, with a higher sensitive, the biodegradation process of the materials under laboratory conditions in soil. In addition, I compared the biodegradability of these materials with the remains of a typical crop used for mulch application, tomato (Lycopersicum esculentum). Finally, the ecotoxicological effects of biodegradable films on Zea mays plants, earthworms Eisenia fetida and microbial soil activity were evaluated using the standardised regulations or existing methods. Thus, I was able to prove ecological advantages of these materials.
El propòsit d'aquesta tesi doctoral ha estat valorar el potencial de biodegradabilitat i efectes ecotòxics de diferents plàstics biodegradables per a ús agrícola sota condicions controlades al laboratori. En l'estudi es van triar set films plàstics biodegradables de diferent composició química, tant comercial com encara en fase experimental: Mater-Bi® (midó de blat de moro), Bio-Flex® (àcid polilàctic), Biofilm® (farina de cereals), Bioplast® (midó de patates), MirelTM (polihidroxialcanoatos), Ecovio® i Bionelle®, a més d'una làmina de paper (Mimgreen®). Es van realitzar dos experiments. El primer concistía en realitzar un estudi gravimètric per mesurar el grau de degradació dels plàstics mitjançant la pèrdua de pes, a més es va dur a terme un anàlisi espectroscòpic FTIR, que va permetre discernir els canvis en els entorns moleculars que faciliten o dificulten el procés de biodegradació dels materials. El segon experiment va consistir a valorar la biodegradabilitat dels materials mitjançant el disseny i construcció d'un sistema respiromètric, que va permetre mesurar amb major sensibilitat el grau de biodegradació dels materials seleccionats sota condicions de laboratori en sòl. Addicionalment es va comparar la biodegradabilitat dels materials provats amb restes d'un cultiu típic d'ús de encoixinat com és el cas del tomàquet (Lycopersicum esculentum). Finalment, es van investigar els efectes ecotòxics dels films biodegradables sobre plantes de Zea mays, cucs Eisenia fetida i l'activitat microbial del sòl, els assaigs van ser realitzats a partir de les normatives o mètodes estandarditzats vigents el que va permetre comprovar els avantatges ecològics d'aquests materials.
El propósito de la presente Tesis Doctoral ha sido valorar el potencial de biodegradabilidad y efectos ecotóxicos de diferentes plásticos biodegradables para uso agrícola bajo condiciones controladas de laboratorio en suelo. En el estudio se eligieron siete films plásticos biodegradables de diferente composición química tanto comercial como aún en fase experimental: Mater-Bi® (almidón de maíz), Bio-Flex®(ácido poliláctico), Biofilm® (harina de cereales), Bioplast® (almidón de patatas), MirelTM(polihidroxialcanoatos), Ecovio® y Bionelle®; además de una lámina para acolchado con el nombre de papel Mimgreen®. Como primer paso diferentes ensayos fueron realizados entre ellos uno gravimétrico para medir la pérdida de peso de los materiales y otro mediante análisis espectroscópico FTIR, lo que permitió discernir los cambios en los entornos moleculares que facilitan o dificultan el proceso de biodegradación de los materiales. El segundo experimento consistió en valorar la biodegradabilidad de los materiales mediante el diseño y construcción de un sistema respirométrico que permitió medir con mayor sensibilidad el grado de biodegradación de los materiales seleccionados bajo condiciones de laboratorio en suelo. Adicionalmente se comparó la biodegradabilidad de los materiales probados con restos de un cultivo típico de uso de acolchado como es el caso del tomate (Lycopersicum esculentum). Finalmente, se investigaron los efectos ecotóxicos de los films biodegradables sobre plantas de Zea mays, lombrices Eisenia fetida y la actividad microbial del suelo; los ensayos fueron realizados a partir de las normativas o métodos estandarizados vigentes lo que permitió comprobar las ventajas ecológicas de estos materiales.

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Lin, Angela Sheue-Ping. "Biodegradable implants produced using fiber coating technologies." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15927.

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Leadley, Robert Stuart. "The surface characterisation of novel biomedical materials." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259860.

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Manzanedo, Diana. "Biorubber (PGS) : evaluation of a novel biodegradable elastomer." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37687.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references (p. 49-51).
Poly(glycerol sebacate) (PGS), or biorubber, is a tough, biodegradable elastomer made from biocompatible monomers. The material was designed, synthesized and characterized in the Department of Chemical Engineering at MIT. Its main features are good mechanical properties, rubberlike elasticity and surface erosion biodegradation. PGS was proved to have similar in vitro and in vivo biocompatibility to PLGA, poly(L-lactic-co-glycolic acid), a widely used biodegradable polymer. PGS has been tested for use as nerve guide material and to fabricate artificial capillary networks for tissue engineering applications, both yielding promising results. Currently, the PGS research group continues to develop the material and to seek applications to maximize market potential and impact in the medical field, i.e. stenting (cardiovascular and non-vascular) and tissue engineering (cardiovascular and musculoskeletal). These markets were estimated at $5 billion dollars [1] and potentially over $10 billion dollars [2], respectively in the U.S. for 2004. Another promising field involves drug delivery, particularly in combination devices like drug-eluting stents. The potential non-medical applications are biodegradable rubbish bags, the absorbent material used in sanitary napkins or diapers, and even fishing lure or chewing gum.
(cont.) MIT submitted a patent application for PGS titled "Biodegradable Polymer": US2003/0118692 Al. The patent strongly presents the quality of the technology, protects methods for synthesizing the material and supports several products made from or with it; thus rendering large market potential for PGS. A patent search compares the PGS patent to intellectual property for other competing biodegradable elastomers; mainly to polymers developed by Ameer et al. in Northwestern University, using citric acid (PDC and POC) and similar to PGS in mechanical properties, elasticity and degradation mechanism. The recommended business model is to pursue development through NIH grants within MIT collaborating with Northwestern University. A joint venture for both materials can lead to founding a medical device start-up funded by SBIR grants or the Deshpande Center at MIT. After pre-clinical trials, the company may be offered for sale to larger players, i.e. Johnson & Johnson or Boston Scientific for stenting; and Genzyme, Advanced Tissue Science, or other upcoming companies focused on tissue engineering.
by Diana Manzanedo.
M.Eng.

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10

Tiasha, Tarannum R. "Biodegradable Magnesium Implants for Medical Applications." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562059856412.

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11

Casadio, Ylenia Silvia. "Biodegradable PHEMA-based biomaterials." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0173.

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[Truncated abstract] The synthetic hydrogel poly(2-hydroxyethyl methacrylate) (PHEMA) has been used as a biocompatible biomaterial in ocular devices, such as soft contact lenses, intraocular lenses and an artificial cornea. Due to its favourable properties as an already established (but non-biodegradable) biomaterial, PHEMA is an interesting candidate for use as a material for scaffolds in tissue engineering. A tenant of tissue engineering scaffolds is obtaining the appropriate porous morphology to allow for successful cellular attachment and support. PHEMA hydrogels exhibit varied morphological features, which range from non-porous (homogeneous) to macroporous (heterogeneous) and can be readily obtained by fine-tuning the polymerisation conditions. A desirable feature for matrices that are to be used as tissue supports is the ability to biodegrade in a biological environment. This thesis describes the preparation and enzymatic biodegradation behaviour of novel porous PHEMA hydrogels that have been crosslinked with biodegradable peptide-based crosslinking agents. Peptide-based crosslinking agents were designed to contain two terminal polymerisable groups flanking an internal biodegradable backbone. This backbone was specifically designed to be targeted by the proteolytic enzyme papain. The general design template allowed for the development of a synthetic methodology that was readily implemented for the production of a range of olefin-peptide conjugates. A suite of olefin-peptide conjugates of general structure I were synthesised, characterised and further tested with papain to determine their biodegradation properties. ... The second strategy for producing bioresorbable degradation fragments involved the incorporation of the highly hydrophilic comonomer, poly(ethylene glycol) PEG into the PHEMA backbone. The addition of PEG to PHEMA resulted in the formation of homogeneous hydrogels that had an improved hydrophilicity compared to their heterogeneous PHEMA counterparts. The synthetic conditions for the preparation of PHEMA and PHEMA-co-PEG hydrogels by photoinitiated polymerisation were thoroughly investigated. It was found that the pore morphology and general properties (non-porous to macroporous) of these hydrogels could be controlled by the appropriate choice of polymerisation conditions. The hydrogels were characterised by scanning electron microscopy, thermal gravimetric analysis and differential scanning calorimetry. The peptide-based crosslinking agents were successfully co-polymerised with the HEMA and PEGMA via photoinitiated polymerisation to provide a range of PHEMA and PHEMA-co-PEG hydrogels that displayed both homogeneous and heterogeneous hydrogel properties. The final crosslinked hydrogels were characterised by scanning electron microscopy and were subjected to enzymatic hydrolysis. The PHEMA-peptide conjugate hydrogels proved to be biodegradable, with degradation behaviour dependent on the hydrogel formulation and the length of the peptide-based crosslinking agent.

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Luo, Mengdi. "Materials and microfabrication approaches for completely biodegradable wireless micromachined sensors." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53093.

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Implantable sensors have been extensively investigated to facilitate diagnosis or to provide a means to generated closed loop control of therapy by yielding in vivo measurements of physical and chemical signals. Biodegradable sensors which degrade gradually after they are no longer functionally needed exhibit great potential in acute or shorter-term medical diagnostic and sensing applications due to the advantages of (a) exclusion of the need to a secondary surgery for sensor removal, and (b) reduction of the risk of long-term infection. The objective of this research is to design and characterize microfabricated RF wireless pressure sensors that are made of completely biodegradable materials and degrade at time-controlled manner (in the order of years and months). This was achieved by means of investigation of appropriate biodegradable materials and development of appropriate fabrication processes for these non-standard (Microelectromechanical systems) MEMS materials. Four subareas of research are performed: (1) Design of sensors that operate wirelessly and are made of biodegradable materials. The structure of the wireless sensor consists a very compact and relatively simple design of passive LC resonant circuits embedded in a polymer dielectric package. To design the sensor with a particular resonant frequency range, an electromagnetic model of the sensor and a mechanical model for circular plate are developed. The geometry of the sensor is established based on the analytical and finite element simulations results. (2) Investigation of the biodegradable materials in the application of implantable biodegradable wireless sensors to achieve controllable degradation lifetimes. Commercially available and FDA approved biodegradable polymers poly(L-lactic acid) (PLLA) and a "shell-core" structure of poly(lactic-co-glycolic acid) (PLGA) and polyvinyl alcohol (PVA) are utilized as the dielectric package for slow and rapid degradation sensors, respectively. Biodegradable metallic zinc and zinc/iron couples are chosen as conductor materials. The degradation behavior of Zn and Zn/Fe-couple are investigated in vitro. (3) Development of novel fabrication processes. The process exploit the advantages of MEMS technology in fabricating miniaturized devices, while protecting vulnerable biodegradable materials from the strong and/or hazardous chemicals that are commonly used in conventional MEMS fabrication process. These new processes enable the fabrication of biocompatible and biodegradable 3-D devices with embedded, near-hermetic cavities. (4) Testing the pressure response functionality and studying the degradation behavior of the wireless biodegradable pressure sensors. Both PLLA-based and PLGA/PVA-based sensors are characterized in vitro by being immersed in 0.9% saline for prolonged time. All the sensors exhibit three stages of behavior in vitro: equilibration, functional lifetime, and performance degradation. During the functional lifetime, most sensors exhibit fully stable functionality. The PLLA-based sensors show no significant weight loss within 8 month and are expected to fully degrade after 2 years, while the PLGA/PVA-based sensors can degrade completely within 26 days.

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Córdoba, Román Laura Catalina. "Magnesium-based biodegradable materials : from surface functionalization to cellular evaluation." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066237/document.

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Les alliages de Magnésium (Mg) sont une nouvelle génération de matériaux biodégradables ayant une bonne ostéointégration et un module d'élasticité similaire à celle de l'os humain. Ces propriétés rendent ces matériaux attrayant pour produire des implants temporaires pour la réparation osseuse. Toutefois, les alliages Mg se dégradent rapidement in vivo, rendant nécessaire de contrôler leur vitesse de corrosion pour accompagner la régénération tissulaire. Parmi les approches proposées pour réduire la corrosion et la biocompatibilité des alliages Mg, les plus utilisées sont les couches de conversion et les revêtements de surface. Dans ce travail une approche synergique qui combine une réduction du taux de corrosion avec l'amélioration de la biocompatibilité des alliages Mg est proposée. De nouveaux revêtements bicouches ont été déposés sur la surface d'alliages AZ31 et ZE41 : (i) un revêtement de silane-TiO2 déposé par dip-coating et (ii) des couches supérieures de collagène de type I et/ou de chitosane. Le revêtement inférieur a été efficace pour réduire la corrosion des alliages dans un fluide corporel simulé et en milieu de culture. La culture cellulaire in vitro de fibroblastes et ostéoblastes, a révélé que le dépôt additionnel de biopolymères a amélioré la réponse biologique du revêtement de silane-TiO2. Ces résultats montrent qu'il existe un effet combiné des revêtements bicouches et de la composition des alliages sur la réponse à la corrosion et sur le comportement cellulaire. Ce travail apporte donc une nouvelle contribution à la compréhension de l'évolution de la corrosion des alliages Mg dans des environnements biologiques
Magnesium (Mg) alloys are a new generation of biodegradable materials with good osseointegration and elastic modulus similar to that of human bone. These properties make them attractive materials to produce biodegradable implants for bone repairing applications that require temporary support. However, Mg alloys degrade rapidly in the in vivo environment making necessary to control their corrosion rate to accompany the tissue healing processes. Several approaches have been proposed for reducing corrosion rate and improving biocompatibility of Mg alloys. The most used ones are conversion films and surface coatings. This project proposes a synergistic approach that combines both decreased corrosion rate and improved biocompatibility of Mg alloys: we developed novel bi-layered coatings to functionalize the surface of AZ31 and ZE41 Mg alloys for bone repair applications. First, a bottom silane-TiO2 coating was formulated and deposited on both alloys by the dip-coating technique. The silane-based coating was effective in slowing down the corrosion rate of the substrates in simulated body fluid (SBF) and in Dulbecco’s Modified Eagle’s Medium (DMEM). Secondly, top layers of type I collagen and/or chitosan were developed. Cell in vitro tests, with fibroblasts and osteoblasts, revealed that the biopolymers enhanced the biological response of the silane-TiO2 coating. Furthermore, the findings showed that there is a combined effect of the bi-layered coatings and the nature of the alloys on their final corrosion response and on the fate of the cells. In the same way, this work contributes to elucidating corrosion processes of Mg alloys in organic solutions in the long-term

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Alalwiat, Ahlam Adnan. "Mass Spectrometry Methods for the Analysis of Biodegradable Hybrid Materials." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1434894354.

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15

Wang, Liang. "Aerogels based on biodegradable polymers and clay." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/336971.

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Foam-like aerogels based on biodegradable polymers and sodium montmorillonite (Na+-MMT) clay were prepared through an environmentally friendly freeze-drying process. Both synthesized and bio-based polymers were utilized in this thesis, including polyvinyl alcohol (PVOH), carboxylmethylcellulose (CMC), xanthan gum, agar, Arabic gum and starch. The morphologies of aerogels were characterized using scanning electron microscopy. The mechanical properties investigation included compression and impact tests. Porosities and solid densities were measured using a helium pycnometer while the pore size distribution was determined by automated mercury porosimeters. Most of polymer-clay aerogels exhibited porous and layered structures that were formed via ice templating. However, high viscosity of the precursor solution may break the layered architecture by retarding the formation of ice crystals (e.g. 2.5 wt% agar aqueous solution). The structures as well as the properties of aerogels were mainly influenced by polymer/clay proportion. Polymer molecules play a role of glue linking the clay nanoparticles, improving the structural integrity and hence the mechanical performance of the aerogels. On the other hand, clay platelets serve as a physical barrier that increases the heat endurance. Recycled cellulose fibers (RCF) that were isolated from waste paper pulp were also used to prepare bio-based aerogels. Adding another biopolymer CMC into RCF aerogels, the resultant RCF-CMC composite aerogels showed different microstructures and enhanced mechanical properties. Physical blending and chemical crosslinking were used to tailor the mechanical properties of xanthan gum/clay aerogels and starch/clay aerogels, respectively. Blending agar with xanthan gum in aqueous solution, the resultant aerogels displayed a significant improvement in mechanical properties compared with those containing a single biopolymer. Moreover, they exhibited tunable microstructures and mechanical properties by changing agar/xanthan gum ratio in the aerogels. As to starch/clay aerogels, the incorporation of glutaraldehyde enhanced the structural integrity and mechanical properties of the aerogels through crosslinking reaction between glutaraldehyde and starch molecules, which was proved by Fourier-Transform infrared (FT-IR) spectroscopy analysis. The evaluation of the flammability of aerogels was conducted with a cone colorimeter while the thermal stability was obtained from the results of thermogravimetric analysis. In regard to PVOH-clay aerogel, different types of flame retardant fillers, such as aluminum trihydroxide (ALH), ammonium polyphosphate (APP), silica gel and potassium carbonate, were adopted to modify their flame retardant properties. The results showed that ALH addition enhanced the flame retardancy as well as mechanical properties. For RCF-CMC aerogels, APP and clay played a synergetic effect on the flame retardancy and thermal stability.
En esta Tesis se han preparado diversos aerogeles usando polímeros biodegradables como matriz y arcilla como refuerzo, a través de un proceso de fabricación amigable con el medio ambiente. Los polímeros empleados han sido tanto de origen natural (goma árabiga, agar-agar, goma xantana, almidón) o sintéticos como la carboximetilcelulosa (CMC) o el alcohol polivinílico. Los compuestos formados se han caracterizado a través de diferentes técnicas con el objeto de relacionar las morfologías generadas con las propiedades térmicas y mecánicas resultantes. La gran mayoría de los aerogeles polímero/arcilla exhiben una estructura porosa y laminar que se forma a raíz de la liofilización. Sin embargo, se ha apreciado que altas viscosidades en la solución precursora puede romper la arquitectura laminar al retardar el crecimiento de los cristales de hielo (ej. Solución acuosa de 2.5 % peso de agar). La estructura y las propiedades de los aerogeles están asimismo y en general influenciados por la relación polímero/arcilla. En estos sistemas, las moléculas de polímero actúan a manera de pegamento uniendo las partículas de arcilla, incrementando de esa manera notablemente la capacidad mecánica de los aerogeles. Por otro lado la arcilla actúa entre otras formas, como barrera térmica incrementando la resistencia térmica y al fuego de las espumas formadas. Dentro de este trabajo se han empleado fibras de celulosa recicladas de residuos de papel en un intento de preparar bio-aerogeles a partir de material de desecho. La unión de estas fibras con CMC permitió obtener aerogeles con propiedades mejoradas y la posibilidad de emplear estos residuos en un segundo uso. Además del mezclado físico, en algunos casos se ha realizado una reacción de entrecruzamiento para ajustar las propiedades finales, como en el caso de los aerogeles goma xantana/arcilla o almidón/arcilla. La mezcla de agar con goma xantana en solución acuosa resultó en un notable aumento de propiedades con respecto a las composiciones que contenían un único polímero, debido al cambio morfológico inducido, pasando de una estructura laminar a una de tipo panal de abeja (honeycomb). De esta forma y a través de la relación entre estos dos polímeros naturales ha sido posible balancear y definir las propiedades finales deseadas para el aerogel. En los sistemas almidón/arcilla el entrecruzamiento se ha conseguido a través de un agente externo como el glutaraldehido. Atendiendo a su posible uso final, unas de las propiedades más relevantes en los aerogeles que se ha estudiado ha sido la estabilidad térmica y la resistencia al fuego. En este sentido, se han preparado sistemas basados en Polivinilalcohol/arcilla modificados con diferentes retardantes de llama. De los diversos aditivos probados la combinación con hidróxido de aluminio ha mostrado un efecto sinérgico incrementando tanto de la resistencia a fuego como las propiedades mecánicas. En los sistemas basados en celulosa la presencia de polifosfato de amonio y arcilla ha demostrado así mismo un efecto potenciador de la estabilidad térmica y en el retardo de llama.

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Werts, Kendall (Kendall Marie). "Synthesis of biodegradable hydrogel microparticles for vaccine protein delivery." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44811.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.
Includes bibliographical references (p. 21).
Soluble protein antigens used in vaccines have shown lower immune responses when compared with certain particulate forms of these same antigens. For example, it has been shown that micro- and nano-particle mediated delivery of protein antigen can use up to 100 times less protein and still produce an effective immune response [1]. In order to use this phenomenon to make vaccines more efficient, we need a biodegradable delivery particle. This thesis modifies a particle created by Jain et al., which consists of a polymer network surrounding and trapping a protein, by removing the non-degradable crosslinker used in the original particle design and replacing it with a poly (ethylene glycol) acrylate molecule attached to ovalbumin protein. When a dendritic cell degrades the particle, the ovalbumin protein will be degraded, as will the connections between the polymer network that holds the particle together [2]. The particles degraded to 56% of their original size in 3 days, while the non-degradable particle degraded to only 80% of its original size.
by Kendall Werts.
S.B.

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Leavitt, Leah A. "Biodegradable packaging for corrosion inhibition via supercriticial fluid." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6013.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on December 28, 2007) Includes bibliographical references.

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Tsui, Yuen-kee. "New biodegradable polyhydroxyacids and polyurethane scaffolds for tissue engineering." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B30595757.

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Serra, Tiziano. "Development of 3D-printed biodegradable composite scaffolds for tissue engineering applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/145684.

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The design of smart biodegradable scaffolds plays a crucial role in the regeneration of tissues and restoration of their functionality. Advances in material science and manufacturing and in the understanding on the effects of bio-chemical and bio-physical signals on cell behavior, are leading to a new generation of 3D scaffolds. Recent developments in additive manufacturing, also known as 3D-printing, open new exciting challenges in tissue/organ regeneration by means of the fabrication of complex and geometrically precise 3D structures. This thesis aimed the development and characterization of 3D scaffolds for tissue regeneration. For this, a nozzle-based rapid prototyping system was used to combine polylactic acid and a bioactive CaP glass (coded G5) to fabricate 3-D biodegradable scaffolds. Firstly, optimization of the printing conditions represents a key challenge for achieving high quality 3D-printed structures. Thus, we stress the importance of studying the outcome of the plasticizing effect of PEG on PLA-based blends used for the fabrication of 3D-printed scaffolds. Results indicated that the presence of PEG not only improves PLA processing but also leads to relevant surface, geometrical and structural changes including modulation of the degradation rate of PLA-based 3D printed scaffolds. Secondly, the obtained scaffolds were fully characterized from the physic-chemical point of view. Morphological and structural examinations showed that 3D scaffolds had completely interconnected porosity, uniform distribution of the glass particles, and a controlled and repetitive architecture. In addition, incorporation of G5 particles increased both roughness and hydrophilicity of the scaffolds. Compressive modulus was dependent on the scaffold geometry and the presence of glass. Cell study revealed that G5 glass improved mesenchymal stem cell adhesion after 4 h. Additional biological characterization in terms of the inflammatory response were also carried out. Novel studies have pointed towards a decisive role of inflammation in triggering tissue repair and regeneration, while at the same time it is accepted that an exacerbated inflammatory response may lead to rejection of an implant. Thus, understanding and having the capacity to regulate the inflammatory response elicited by 3D scaffolds aimed for tissue regeneration is crucial. In this context, cytokine secretion and cell morphology of human monocytes/macrophages in contact with biodegradable 3D-printed scaffolds (PLA, PLA/G5 and chitosan ones) with different surface properties, architecture and controlled pore geometry was reported. Results revealed that even though the material itself induced the biggest differences, scaffold geometry also affected on the secretion of cytokines. These findings strengthen the appropriateness of these 3D platforms to study modulation of macrophage responses by specific parameters (chemistry, topography, scaffold architecture). Finally, novel scaffolds composed by two phases (PLA and PLA/G5), for use in guided bone regeneration (GBR) were evaluated. Structural, morphological changes were observed during the in vitro degradation of both PLA and PLA/G5 structures. Although mechanical properties decreased, PLA/G5 scaffolds still showed higher compressive modulus than PLA ones, confirming the reinforcing effect of glass particles after immersion time. In vivo implantation was carried out subcutaneously in mice up to 30 days. Results showed that PLA scaffolds induced mononuclear cell without activating any relevant angiogenic process, while PLA/G5 induced higher presence of multinucleated giant cells and consequently stimulated the vascularization process and further tissue regeneration. The technique/materials combination used in this PhD thesis led to the fabrication of promising fully degradable, mechanically stable, bioactive and biocompatible composite scaffolds with well-defined architectures valuable for TE applications.

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Ghaffar, Ahmed Mohamed el-Hadi Abdel. "Development of a biodegradable materials based on poly(3-hydroxybutyrate) PHB." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964167999.

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Zhang, Hao. "Biodegradable microspheres for controlled drug/cell delivery and tissue engineering." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:28e1e1fd-d050-43f4-bddc-d0ec2cd49580.

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The synthetic biodegradable polymer poly(lactide-co-glycolide) (PLGA) has been widely explored as substrate biomaterials for controlled drug delivery and tissue engineering. ECM component heparin and bone mineral hydroxyapatite (HA) are attractive biomaterials which can functionalize the PLGA surface to improve cell cell response and to bring in the dual growth factor delivery, because heparin and HA both can improve cell responses and bind with various proteins. To combine the osteoconductivity of HA and the controlled drug release of PLGA microspheres, HA coated PLGA microspheres were developed by a 3 hour rapid HA precipitation on the PLGA microsphere surface. Effects of various fabrication parameters on microsphere and HA coating morphology were evaluated. This core-shell composite worked as a dual drug delivery device and demonstrated better cell cell response than PLGA microspheres without HA coating. Three different methods, including osmogen, extractable porogen and gas-foaming porogen, were evaluated to fabricate porous microspheres as injectable cell scaffolds in the tissue engineering. The gas-foaming method produced covered porous PLGA microspheres, on which a skin layer covered all the surface pores. The skin layer was hydrolysed by NaOH to control the surface porosity. The modified open porous microspheres have large continued surface areas between pores, which provided more continued areas for cell adhesion. The porous microspheres with controllable surface porosity and large surface continuity between pores could be novel injectable cell scaffolds. Heparin was immobilized on the open porous PLGA microspheres by a facile layer-by-layer assemble to combine the advantages of porous structure and the protein binding from heparin. The heparin-coated porous microspheres promoted cell adhesion, spreading, proliferation and osteogenic differentiation. Growth factor-like protein lactoferrin was immobilized on the heparin coated porous microspheres, which further enhanced MG-63 proliferation and osteogenic differentiation. The heparin-coated porous microspheres are promising multi-functional devices for controlled drug delivery and injectable cell delivery.

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Liu, Ya, and 刘亚. "Developing bioactive and biodegradable composites for bone tissue repair." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4150835X.

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Liu, Ya. "Developing bioactive and biodegradable composites for bone tissue repair." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B4150835X.

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24

Ogunsona, Emmanuel Olusegun D'Souza Nandika Anne. "Supercritical CO₂ foamed biodegradable polymer blends of polycaprolactone and Mater-Bi." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5136.

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Lovell, Nathan Gary. "The design, synthesis and properties of pressure-processable biodegradable block copolymers." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33614.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (p. 89-95).
In this thesis, biodegradable block copolyesters were specifically designed and synthesized for their susceptibility to pressure-induced mixing. These baroplastic materials are capable of being processed and molded through the application of pressure at temperatures far below those needed in traditional melt-processing of biodegradable polyesters. Pressure molding at low temperatures reduces the danger of chain degradation during processing that is ubiquitous in biodegradable plastics. The compressible regular solution model (CRS), in combination with group contribution (GC) methods and pressure-volume-temperature (PVT) data, was used to predict the phase behavior and pressure-induced miscibility of several block copolymer systems. Small-angle neutron scattering (SANS) experiments confirmed that amorphous forms of the poly([epsilon]-caprolactone-ran-5 ethylene ketal [epsilon]-caprolactone)-block-poly(lactic acid) (PmCL-b-PLA) system exhibit pressure- induced miscibility, and small angle x-ray scattering (SAXS) revealed that the position of the upper disorder-to-order temperature (UDOT) in those systems is near the values predicted by the CRS model.
(cont.) Differential scanning calorimetry measurements suggest that poly(1,5-dioxepan-2-one)-block-poly(lactic acid) (PDXO-b-PLA), which was calculated as being more miscible than PmCL-b-PLA by the CRS model, resides in a mixed state at ambient pressure and temperature. The CRS predictions were found to be more accurate with component parameters derived directly from GC than from PVT data. Pressure processing of multiple systems at low temperatures was conducted, and the mechanical properties of these biodegradable baroplastics (bbps) were measured. Crystallinity plays a complex role in baroplastic behavior that has not been fully elucidated. The strain-to-break and modulus of the bbps is good, but somewhat reduced relative to solvent-cast or melt-processed samples. The tunability of the properties of bbps, combined with their low-temperature processability, make them promising candidates for biomedical materials and environmentally friendly plastics.
by Nathan Gary Lovell.
S.M.

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26

Gustafsson, Jesper, and Mikael Landberg. "Production of bio-plastic materials from apple pomace : A new application for the waste material." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-21216.

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Extensive quantities of apple pomace are generated annually but disposal of this waste is still much disputed. In EU alone, 500 000 tons are produced every year. Without further treatment, the acidic character of apples with their high sugar and low protein content makes the pomace unsuitable for landfilling and animal feedstock. However, further treatment is usually not economically feasible. This study addresses this issue by introducing a new approach for the apple pomace to produce sustainable materials. The high content of sugars in apple pomace which can be reshaped and reformed at higher temperatures makes the waste material suitable for plastic production. Other components found in apple pomace are 5 % proteins and 1.5 % fats. Fibers are abundant, dietary fibers amounts for more than half (55 %) the original apple pomace weight. Phenols, sorbitol and acids can be found in minor mount, 2 % or less. The apple pomace itself is a mixture of mostly pulp and peel which corresponds to 9/10 of the total mass. Whereas seeds, seed core and stalk are the remaining 1/10. The possibilities of utilizing apple pomace to produce biofilms and 3D shapes have been investigated. The effects of introducing orange pomace, another waste material produced in extensive quantities, to apple pomace samples has also been studied. Two methods were used to produce bioplastic materials; solution casting and compression molding. Glycerol was used as a plasticizer. Apple pomace, either washed or not washed, was oven-dried and milled into a fine powder. Using compression molding, plates or cups of the two powders with different amounts of glycerol were prepared. Mixtures of apple pomace and orange pomace, with or without glycerol, were prepared in the same way. The apple pomace was also used in a film casting method to produce plastic films. Applying laser cutting to the plates and plastic films, dog-bone specimens were created whose mechanical properties were analysed using a universal testing machine. Highest values in terms of tensile strength and elongation at max was reached with bioplastics produced from solution casting where the values varied in the range 3.3 – 16 MPa and 11 – 55 % respectively. The compression molding approach resulted in tensile strength values in the range 0.94 – 5.9 MPa whereas the elongation at max was in the range 0.30 – 1.9 %. A possible application for this material could be disposable tableware which does not require high mechanical strength. It was shown that it is possible to produce 3D structures and plastic films from apple pomace. Washed apple pomace with glycerol has similar properties as not washed apple pomace without the plasticizer. Adding orange pomace to apple pomace samples increases the tensile strength at the expense of the elongation at max. The pressing conditions and powder size greatly effects the mechanical properties, where a larger powder size lower the values for the mechanical properties. This new approach paves the way for a new utilization of apple pomace to replace some petroleum-based materials and at the same time solve the disposal problem of apple pomace.

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Tsui, Yuen-kee, and 崔婉琪. "New biodegradable polyhydroxyacids and polyurethane scaffolds for tissue engineering." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B30595757.

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28

Quirk, Robin Andrew. "Surface engineering of biodegradable polymers to create materials with biological mimicking activity." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342477.

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29

Rivers, Tyrell Jermaine. "Design, synthesis, and characterization of a novel biodegradable, electrically conducting biomaterial." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035967.

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Kraus, Katharina Sofie. "An Alternative Future of Spatial Materiality." Thesis, Konstfack, Inredningsarkitektur & Möbeldesign, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-5562.

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In our practice the choice of materials is mostly driven by practical reasons, aesthetics and a given budget, and it is often applied rather at the end of the process – rarely is it the driver of any design process. What often gets forgotten is that materials can carry an immaterial layer of connotations. This means that materials are not perceived neutrally but are instead always loaded with certain meanings and values we attribute to them which in return can evoke different emotions in us. In my thesis project I explore the effect of analternative design process that uses materials as the point of departure.Through experimental explorations I have produced my own materials and investigated possibilities to use them in a spatial context. I created different scenarios to speculate about the potential these materials could have. Could they become applicable materials for interior and furniture design as well as for being a carrier of meaning?

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31

Li, Yonghui. "Biodegradable poly(lactic acid) nanocomposites: synthesis and characterization." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8543.

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Doctor of Philosophy
Department of Grain Science and Industry
X. Susan Sun
Biobased polymers derived from renewable resources are increasingly important due to acute concerns about the environmental issues and limited petroleum resources. Poly(lactic acid) (PLA) is such a polymer that has shown great potential to produce biodegradable plastics. However, low glass transition temperature (Tg), low thermal stability, slow biodegradation rate, and high cost limit its broad applications. This dissertation seeks to overcome these limitations by reinforcing PLA with inorganic nanoparticles and low-cost agricultural residues. We first synthesized PLA nanocomposites by in situ melt polycondensation of L-lactic acid and surface-hydroxylized nanoparticles (MgO nanocrystals and TiO2 nanowires) and investigated the structure-property relationships. PLA grafted nanoparticles (PLA-g-MgO, PLA-g-TiO2) were isolated from the bulk nanocomposites via repeated dispersion/centrifugation processes. The covalent grafting of PLA chains onto nanoparticle surface was confirmed by Fourier transform infrared spectroscopy and thermalgravimetric analysis (TGA). Transmission electron microscopy and differential scanning calorimetry (DSC) results also sustained the presence of the third phase. Morphological images showed uniform dispersion of nanoparticles in the PLA matrix and demonstrated a strong interfacial interaction between them. Calculation based on TGA revealed that more than 42.5% PLA was successfully grafted into PLA-g-MgO and more than 30% was grafted into PLA-g-TiO2. Those grafted PLA chains exhibited significantly increased thermal stability. The Tg of PLA-g-TiO2 was improved by 7 °C compared with that of pure PLA. We also reinforced PLA with low-value agricultural residues, including wood flour (WF), soy flour (SF), and distillers dried grains with solubles (DDGS) by thermal blending. Tensile measurements and morphological images indicated that methylene diphenyl diisocyanate (MDI) was an effective coupling agent for PLA/WF and PLA/DDGS systems. MDI compatibilized PLA/WF and PLA/DDGS composites showed comparable tensile strength and elongation at break as pure PLA, with obviously increased Young’s modulus. Increased crystallinity was observed for PLA composites with SF and DDGS. Such PLA composites have similar or superior properties compared with pure PLA, especially at a lower cost and higher biodegradation rate than pure PLA. The results from this study are promising. These novel PLA thermoplastic composites with enhanced properties have potential for many applications, such as packaging materials, textiles, appliance components, autoparts, and medical implants.

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Schwarz, Karsten. "Biodegradable polyesters from solid-state precursors basic components of a biomedical materials concept /." [S.l. : s.n.], 2001. http://www.sub.uni-hamburg.de/disse/457/Disse.pdf.

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33

Liu, Zhidan [Verfasser]. "Thermomechanically processed magnesium-silver alloys as antibacterial and biodegradable implant materials / Zhidan Liu." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1155420748/34.

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Wong, Sau-shun, and 黃守淳. "Investigation on Mg-Mn-Zn alloys as potential biodegradable materials for orthopaedic applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2015. http://hdl.handle.net/10722/208603.

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In fracture management with open reduction and internal fixation with metallic implant, secondary procedure of removal of implant is often required. Such procedure causes additional surgical risks to patients, including anaesthetic risks, wound infection, bone infection, soft tissue adhesion and joint stiffness. The procedure is also costly to the patient and society. If the fixation implant is self-resorbable, the need for secondary surgery will be completely eliminated and the social resources can be saved. Making use of the corrosion process, metals can be developed into new generation of resorbable (or biocorrodible, biodegradable) implants. An ideal bioresorbable orthopaedic implant should provide adequate mechanical support that matches the bone healing process. The implant should resorb progressively as the bone heals. Many current resorbable materials are biomechanically inferior to conventional metallic implants. Magnesium based alloys are popularly studied because of their mechanical properties and biocompatibility. Implants made of magnesium based alloy are expected to resorb in the human body with no harmful effect. The major research challenge is to identify an alloy that performs satisfactorily in the following aspects: biocompatibility, degradation rate, hydrogen gas formation (gas product from the reaction between Mg and water), and mechanical strength. In addition, there is no standard evaluation method for the biodegradable alloys. It is because the interaction between the degradable implants and the physiological environment is too complicated to mimic. The in vitro and the in vivo results often mismatch. This research involved the design and the tests of three Mg based alloys. Zinc (Zn) and manganese (Mn) were chosen as the alloying elements for corrosion resistance and mechanical enhancement. Mg-1Zn-1Mn, Mg-3Zn-1Mn, Mg-5Zn-1Mn (in wt.%) were developed and compared. The study was divided into three parts: material characterization, in vitro studies, and in vivo (animal) studies. The SEM/EDX confirmed that the surface properties of the alloys were consistent after the surface treatment. From the mechanical test, the yield strengths and the densities of the alloys were found to be close to that of the natural bones. The theoretical calculation showed that the amount of Mn determined the threshold implant mass of the test alloys. The hydrogen evolution test showed that the Mg-1Zn-1Mn was the least corrodible. The elution test showed that the Mg-1Zn-1Mn was the least cytotoxic and the cytotoxicity was affected by the pH changes brought by the alloys. The live cell imaging captured the interaction between the alloys and the cells. The subcutaneous implantation showed that the Mg-3Zn-1Mn formed the smallest gas pocket. In the six-month femoral implantation study (Mg-3Zn-1Mn excluded), the Mg-1Zn-1Mn showed the least volume loss and the steadiest degradation behaviour. It was also found to associate with better bone responses. Concluding from all the results, the Mg-1Zn-1Mn demonstrated better potential to become biodegradable orthopaedic products. This work evaluated the potentials of the new alloys and proposed some suggestions for the mismatch results. Moreover, quantitative investigation of biomechanical properties, long term degradation behaviour, and toxicity are recommended to be carried out in the future.
published_or_final_version
Orthopaedics and Traumatology
Master
Master of Philosophy

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Sitorus, Henry Binsar Hamonangan. "The study of jatropha curcas oil-based biodegradable insulation materials for power transformer." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0022/document.

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Ce travail porte sur la caractérisation physico-chimique de l'huile de Jatropha Curcas et sa capacité à remplacer l'huile minérale dans les transformateurs de puissance. Ce produit présente plusieurs avantages sur les autres huiles végétales comme l'huile de palme ou l'huile de colza, qui recommandent sa production et son utilisation. En effet, la plante de Jatropha Curcas peut être cultivée sur des sols pauvres à faibles précipitations, évitant ainsi d'utiliser des sols plus fertiles pour sa culture permettant ainsi aux petits exploitants de réserver leurs terres aux cultures de base. Cette plante peut pousser facilement dans des zones où les niveaux de précipitations annuelles sont nettement inférieures à celles requises par d'autres espèces telles que le colza, le tournesol, le soja, le maïs, le palmier à huile et d'autres. Elle peut être cultivée sur tous les types de sol en Indonésie, même sur des terres arides, dans de nombreuses régions de l'Indonésie orientale, inexploitées en raison des difficultés à planter d'autres cultures. En outre, l'huile de Jatropha Curcas est un produit non alimentaire. En faisant subir à l’huile de Jatropha Curcas brute une estérification à base alcaline avec de l'hydroxyde de potassium (KOH), on obtient de l’huile de méthylester de Jatropha Curcas (JMEO) dont la viscosité et l’acidité sont acceptables pour les équipements à haute tension en particulier pour les transformateurs de puissance. Les propriétés physico-chimiques et électriques de JMEO ont été mesurées ainsi que celles de l'huile minérale (MO) pour la comparaison. Pour les propriétés physico-chimiques, il s’agit de la densité relative, la teneur en eau, la viscosité, l'acidité, l'indice d'iode, la corrosivité, le point d'éclair, le point d'écoulement, la couleur, l'examen visuel, et la teneur en ester méthylique. Quant aux propriétés électriques, elles concernent la rigidité diélectrique sous différentes formes de tension (alternative, continu et choc de foudre), les phénomènes de pré-claquage et de claquage sous choc de foudre, les décharges glissantes sur les surfaces de carton comprimé, immergé dans JMEO et MO. Les résultats obtenus montrent que les tensions de claquage moyennes en continu et en choc de foudre des huiles JMEO et MO sont très proches ; la tension de claquage moyenne de JMEO est même plus élevée que celle de l'huile minérale (de type naphténique). La mesure des tensions de claquage des mélanges d'huiles «80% JMEO + 20% MO» et «50% JMEO et 50% MO» montrent que la tension de claquage du mélange «80% JMEO + 20% MO» est toujours supérieure à celle de l'huile minérale sous tensions alternative et continue. Cela indique que le mélange d'huile minérale et de JMEO avec un rapport de 20:80 ne dégrade pas ses performances. Le mélange d'huiles peut se produire lors du remplacement de l'huile minérale par JMEO dans les transformateurs installés et en exploitation. L'analyse des caractéristiques des streamers (la forme, le temps d'arrêt, le courant associé et la charge électrique) se développant dans les huiles JMEO et MO sous tension impulsionnelle de foudre, montre une grande similitude. Aussi, la longueur finale (Lf) et la densité des branches des décharges surfaciques se propageant sur le carton comprimé immergé dans l'huile de Jatropha Curcas de méthylester (JMEO) et de l'huile minérale (MO), sous tensions de choc de foudre positif et négatif (1,2/50 μs), pour deux configurations d'électrodes divergentes (électrode pointe haute tension perpendiculaire et tangente au carton, respectivement), sont fortement influencées par l'épaisseur du carton comprimé. Pour une épaisseur donnée, Lf augmente avec la tension et décroît lorsque l'épaisseur augmente. Lf est plus long lorsque la pointe est positive que lorsque la pointe est négative. Pour une tension et une épaisseur du carton comprimé donnée, les valeurs de Lf dans l’huile minérale et l’huile JMEO sont très proches. [...]
This work is aimed at the investigation of the physicochemical characterization of Jatropha Curcas seeds oil and its capacity to be an alternative option to replace mineral oil in power transformers. This product presents several advantages that recommend both its production and usage over those of other vegetable oils as crude palm oil and rapeseeds oil. Indeed, it may be grown on marginal or degraded soils avoiding thus the need to utilize those more fertile soils currently being used by smallholders to grow their staple crops; and it will readily grow in areas where annual rainfall levels are significantly lower than those required by other species such as palm oil, rape-seeds oil, sunflower oil, soybeans oil, corn oil and others. For instance, these plants can grow on all soil types in Indonesia, even on barren soil. The barren soil types can be found in many parts of eastern Indonesia that remain untapped because of the difficulty planted with other crops. Moreover, jatropha curcas oil is nonfood crops. Jatropha Curcas oil was processed by alkali base catalyzed esterification process using potassium hydroxide (KOH) to produce Jatropha Curcas methyl ester oil (JMEO) has a viscosity and a acidity that are acceptable for high voltage equipment especially in power transformer. The physicochemical and electrical properties of JMEO were measured as well as those of mineral oil (MO) for comparison. The physicochemical properties cover relative density, water content, viscosity, acidity, iodine number, corrosivity, flash point, pour point, color, visual examination, and methyl ester content. Meanwhile the electrical properties cover dielectric strength under AC, DC and lightning impulse voltages, pre-breakdown / streamers under lightning impulse voltage, creeping discharge over pressboard immersed in JMEO and MO. The obtained results show that the average DC and lightning impulse breakdown voltages of JMEO and MO are too close, even the average AC breakdown voltage of JMEO are higher than that of mineral oil (napthenic type). The measurement of breakdown voltages of two oil mixtures namely “80% JMEO + 20% MO” and “50% JMEO and 50% MO” shows that the breakdown voltage of the first mixture (i.e., “80%JMEO+20%MO”) is always higher than that of mineral oil under both AC and DC voltages. This indicates that mixing 20:80 mineral oil to JMEO ratio does not degrade its performance. The mixing of oils can occur when replacing mineral oil by JMEO in installed transformers. The analysis of the streamers characteristics (namely; shape, stopping length, associated current and electrical charge) developing in JMEO and MO under lightning impulse voltages, shows that these are too close (similar). It is also shown that the stopping (final) length Lf and the density of branches of creeping discharges propagating over pressboard immersed in Jatropha Curcas methyl ester oil (JMEO) and mineral oil (MO), under positive and negative lightning impulse voltages (1.2/50 μs), using two divergent electrode configurations (electrode point perpendicular and tangential to pressboard), are significantly influenced by the thickness of pressboard. For a given thickness, Lf increases with the voltage and decreases when the thickness increases. Lf is longer when the point is positive than with a negative point. For a given voltage and thickness of pressboard, the values of Lf in mineral oil and JMEO are very close. It appears from this work that JMEO could constitute a potential substitute for mineral oil for electrical insulation and especially in high voltage power transformers

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da, Silva Soares Joao Filipe. "Constitutive modeling for biodegradable polymers for application in endovascular stents." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85939.

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Percutaneous transluminal balloon angioplasty followed by drug-eluting stent implantation has been of great benefit in coronary applications, whereas in peripheral applications, success rates remain low. Analysis of healing patterns in successful deployments shows that six months after implantation the artery has reorganized itself to accommodate the increase in caliber and there is no purpose for the stent to remain, potentially provoking inflammation and foreign body reaction. Thus, a fully biodegradable polymeric stent that fulfills the mission and steps away is of great benefit. Biodegradable polymers have a widespread usage in the biomedical field, such as sutures, scaffolds and implants. Degradation refers to bond scission process that breaks polymeric chains down to oligomers and monomers. Extensive degradation leads to erosion, which is the process of mass loss from the polymer bulk. The prevailing mechanism of biodegradation of aliphatic polyesters (the main class of biodegradable polymers used in biomedical applications) is random scission by passive hydrolysis and results in molecular weight reduction and softening. In order to understand the applicability and efficacy of biodegradable polymers, a two pronged approach involving experiments and theory is necessary. A constitutive model involving degradation and its impact on mechanical properties was developed through an extension of a material which response depends on the history of the motion and on a scalar parameter reflecting the local extent of degradation and depreciates the mechanical properties. A rate equation describing the chain scission process confers characteristics of stress relaxation, creep and hysteresis to the material, arising due to the entropy-producing nature of degradation and markedly different from their viscoelastic counterparts. Several initial and boundary value problems such as inflation and extension of cylinders were solved and the impacts of the constitutive model analyzed. In vitro degradation of poly(L-lactic acid) fibers under tensile load was performed and degradation and reduction in mechanical properties was dependent on the mechanical environment. Mechanical testing of degraded fibers allowed the proper choice of constitutive model and its evolution. Analysis of real stent geometries was made possible with the constitutive model integration into finite element setting and stent deformation patterns in response to pressurization changed dramatically as degradation proceeded.

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Krikorian, Vahik. "Bio-nanocomposites fabrication and characterization of layered silicate nanocomposites based on biocompatible/biodegradable polymers / by Vahik Krikorian." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file , 11.06 Mb, 148 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3187609.

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Levato, Riccardo. "Injectable biodegradable carriers for the delivery of therapeutic agents and tissue engineering." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/285661.

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The design of smart biomaterial devices plays a key role to improve the way conventional therapies are being delivered, and to promote the development of new approaches for advanced therapies, such as regenerative medicine and targeted drug release. Injectable biodegradable materials, such as those consisting of suspensions of polymeric particles, are highly versatile devices that can be delivered through minimally-invasive injections. The physic-chemical properties of the particles can be engineered to obtain smart scaffolds for tissue engineering, carriers for drug release and cell therapy. The aim of this Thesis is to develop a novel class of biodegradable and injectable particulate carriers based on polylactic acid (PLA), that are capable to trigger and guide specific responses from the cells and the biological milieu. First, a novel route to fabricate PLA-based microcarriers (MCs) was set and characterized. The production method involved green, non-harmful chemicals and it is easy to scale-up. Such technique allowed tuning MC size and size distribution in the range suitable for drug and cell delivery applications. The favorable regulatory status of the materials and reagents may also be beneficial for the translation of the MCs from bench to bedside. The principles guiding the fabrication procedure can inspire techniques to generate nanocarriers for controlled drug delivery. Recent studies point out the importance of drug-loaded and submicron-sized materials in the treatment of severe clinical conditions, such as persistent biofilm infections. These nanoparticles (NPs) can be endowed with smart functionalities to enhance drug delivery within the biofilm matrix. In this way, NPs encapsulating the antibiotic ciprofloxacin were produced and functionalized with DNase I. The NPs improved the antimicrobial activity of the encapsulated drug and promoted biofilm eradication, targeting and degrading directly the biofilm matrix. On the other hand, larger particles such as MC, display a high surface area for cell expansion. MCs can also deliver cells with therapeutic potential as ¿living drugs¿, ideally in a spatio-temporal controlled fashion. This is especially important, as, in standard cell therapies, direct injection of cells is accompanied by massive cell mortality that renders the treatment ineffective. PLA MCs suitable for Mesenchymal Stromal Cells (MSCs) homing have been produced and modified with different functionalization approaches. The physic-chemical properties of the MCs and bioactive coatings modulated cell adhesion, proliferation, and migratory potential in response to chemokines that regulate MSC tissue localization, like SDF-1a. The results highlight the importance of carriers design to control cell delivery, and provide important guidelines to instruct a new generation of efficient biomaterial carriers. Another exciting application of injectable, cell-laden MCs is to use them as building blocks to fabricate living tissues in vitro. Combining MC technology and bioprinting is an appealing strategy to generate tissues grafts with controlled architectures. The suspension of injectable PLA cell-laden MCs within gelatin-based hydrogels formed an extrudable, composite bioink. MCs acted as mechanical reinforcement for soft gels and as means for cell expansion to encapsulate high cell payload. MSCs were shown to form MC-MSCs aggregates, with enhanced cell-to-cell contact on surface functionalized PLA MCs, and differentiated towards the osteogenic lineage. This result suggests potential applications of MC-MSCs laden bioinks for bone tissue engineering, and the composite bioink is proposed as component to build multimaterial, 3D-printed osteochondral graft models. Taken together, the injectable devices developed in the Thesis constitute promising and highly versatile biomaterial platforms for biomedical applications, and can be employed in a wide array of tissue engineering, and cell and drug delivery strategies.
El diseño de dispositivos basados en biomateriales inteligentes, juega un papel fundamental a la hora de mejorar las terapias convencionales, así como en el desarrollo de nuevas estrategias para la medicina regenerativa y la liberación controlada de fármacos. Materiales inyectables biodegradables, tales como las suspensiones de partículas poliméricas, constituyen dispositivos versátiles, que se pueden suministrar por medio de inyecciones mínimamente invasivas. Las propiedades físico-químicas de las partículas pueden ser modificadas para obtener andamios inteligentes para la ingeniería de tejidos, transportadores para liberación de fármacos y cultivo y terapia celular. El objetivo de esta Tesis es el desarrollo de una nueva clase de partículas transportadoras inyectables y biodegradables, basadas en ácido poliláctico (PLA), que sean capaces de desencadenar y guiar respuestas específicas por parte de las células y del entorno biológico. Primero, se ha creado y caracterizado una nueva ruta para fabricar microstransportadores (MCs) basados en PLA. Este método de producción utiliza reactivos verdes y no-tóxicos, y es sencillo de adaptar para la fabricación a gran escala. Esta técnica permite controlar parámetros fundamentales en las MCs, tales como su tamaño y dispersión, que pueden ser controlados dentro de los rangos adecuados para aplicaciones de liberación de fármacos y células. El hecho que los materiales y reactivos utilizados están bien aceptados por las agencias reguladoras, puede favorecer el traslado de las partículas fabricadas desde la investigación hasta la práctica clínica. Los principios de este método pueden adaptarse a otras técnicas de fabricación para generar nanotransportadores (nanopartículas, NPs) de fármacos. Estudio recientes subrayan la importancia de biomateriales submicrométricos cargados con compuestos bioactivos en el tratamiento de enfermedades, tal como las infecciones provocadas por biofilms. Estas NPs pueden ser modificadas con funcionalidades inteligentes, para mejorar la distribución del fármaco en la matriz del biofilm. De esta manera, se han producido NPs que encapsulan el antibiótico ciprofloxacino, modificadas superficialmente con DNasa I. Estos transportadores tienen como diana la matriz que compone el biofilm y pueden degradarla, incrementando la actividad antibacteriana del ciprofloxacino y promoviendo la erradicación de los biofilms. Por otra banda, las partículas más grandes, como las MCs, poseen una superficie adecuada para la expansión celular. Las MCs se pueden usar para transportar “drogas vivas”, es decir células con potencial terapéutico, posiblemente controlando su distribución espacial y su cinética de liberación. Esto es de particular importancia, porque la ineficiencia de muchas terapias celulares actuales se debe a la gran cantidad de células que no sobreviven una vez inyectadas in vivo. Se han producido MCs de PLA modificadas por diferentes estrategias de funcionalización y aptas para suportar en su superficie células madres mesenquimales (MSCs). La biofuncionalización y las propiedades físico-químicas de las MCs juegan un papel fundamental en la adhesión y proliferación célular, así como la capacidad de las MSCs de migrar en respuesta a estímulos quimiotácticos, que regulan su localización en los tejidos, tal como el SDF-1α. Los resultados subrayan la importancia del diseño de las MCs para controlar la liberación de las células, y a la vez aportan información para desarrollar una nueva y más eficiente generación de transportadores de células. Otra aplicación prometedora de las MCs inyectables es su uso como bloques de construcción para fabricar tejidos vivos in vitro. La combinación de la tecnología de las MCs con la bioimpresión 3D constituye una estrategia atractiva para obtener injertos de tejidos multimateriales con arquitectura controlada. Se han obtenido biotintas compuestas y capaces de ser extruidas mezclando materiales basados en hidrogeles de gelatina con las MCs de PLA cargadas con células. Las MCs actúan de refuerzo mecánico para el hidrogel y como vehículo para la expansión celular (por ejemplo, en un bioreactor “spinner flask”) para encapsular elevadas cantidades de células. Las MSCs forman agregados células-particulas, una vez sembradas en las superficies de las MCs, y estos complejos, ricos en contactos célula-célula, se demostraron capaces de suportar la diferenciación osteogénica de las MSCs. Este resultado sugiere potenciales aplicaciones de las biotintas cargadas de agregados de MCs y MSCs para la ingeniería del tejido óseo. Esta biotinta ha sido también utilizada como componiente para generar un modelo de injerto osteocondral, por medio de una técnica de impresión 3D. El conjunto de dispositivos inyectables desarrollados en esta Tesis constituyen una plataforma muy versátil y prometedora para aplicaciones biomédicas, en particular en estrategias de ingeniería de tejidos, y liberación de células y fármacos

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Ogunsona, Emmanuel Olusegun. "Supercritical CO2 foamed biodegradable polymer blends of polycaprolactone and Mater-Bi." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5136/.

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Supercritical CO2 foam processing of biopolymers represents a green processing route to environmentally friendly media and packaging foams. Mater-Bi, a multiconstituent biopolymer of polyester, starch and vegetable oils has shown much promise for biodegradation. The polymer, however, is not foamable with CO2 so blended with another polymer which is. Polycaprolactone is a biopolymer with potential of 4000% change in volume with CO2. Thus we investigate blends of Mater-Bi (MB) and polycaprolactone (PCL) foamed in supercritical CO2 using the batch process. Characterization of the foamed and unfoamed samples were done using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Micrographs of the samples from the SEM revealed that the cell size of the foams reduced and increased with increase in MB concentration and increase in the foaming temperature respectively. Mechanical tests; tensile, compression, shear and impact were performed on the foamed samples. It was noted that between the 20-25% wt. MB, there was an improvement in the mechanical properties. This suggests that at these compositions, there is a high interaction between PCL and MB at the molecular level compared to other compositions. The results indicate that green processing of polymer blends is viable.

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Sagar, Ambuj Daya. "Modification and characterization of starches and starch-based blends for use as environmentally biodegradable thermoplastics." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11648.

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Shah, Mohammadi Maziar. "Silicon, iron and titanium doped calcium phosphate-based glass reinforced biodegradable polyester composites as bone analogous materials." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107830.

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Bone defects resulting from disease or traumatic injury is a major health care problem worldwide. Tissue engineering offers an alternative approach to repair and regenerate bone through the use of a cell-scaffold construct. The scaffold should be biodegradable, biocompatible, porous with an open pore structure, and should be able to withstand the applied forces. Phosphate-based glasses (PGs) may be used as reinforcing agents in degradable composites since their degradation can be predicted and controlled through their chemistry. This doctoral dissertation describes the development and evaluation of PGs reinforced biodegradable polyesters for intended applications in bone augmentation and regeneration. This research was divided into three main objectives: 1) Investigating the composition dependent properties of novel PG formulations by doping a sodium-free calcium phosphate-based glass with SiO2, Fe2O3, and TiO2. Accordingly, (50P2O5-40CaO- xSiO2-(10-x)Fe2O3, where x = 10, 5 and 0 mol.%) and (50P2O5-40CaO-xSiO2-(10-x)TiO2 where x = 10, 7, 5, 3 and 0 mol.%) formulations were developed and characterised. SiO2 incorporation led to increased solubility, ion release, pH reduction, as well as hydrophilicity, surface energy, and surface polarity. In contrast, doping with Fe2O3 or TiO2 resulted in more durable glasses, and improved cell attachment and viability. It was hypothesised that the presence of SiO2 in the TiO2-doped formulations could up-regulate the ionic release from the PG leading to higher alkaline phosphatase activity of MC3T3-E1 cells. 2) Incorporating Si, Fe, and Ti doped PGs as fillers, either as particulates (PGPs) or fibres (PGFs), into biodegradable polyesters (polycaprolactone (PCL) and semi-crystalline and amorphous poly(lactic acid) (PLA and PDLLA)) with the aim of developing degradable bone analogous composites. It was found that PG composition and geometry dictated the weight loss, ionic release, and mechanical properties of the composites. It was also hypothesised that a potential reaction between Si and the ester bond led to the formation of carboxylate by-products resulting in a lower molecular weight polymer, thus affecting the mechanical properties of the composites. Cytocompatibility assessment with MC3T3-E1 preosteoblasts showed that these composites were cytocompatible, and cell alignment along the PGFs was observed possibly due to their favourable ionic release properties. 3) Investigating the solid-state foaming using carbon dioxide (CO2) of PDLLA-PGP composites with up to 30 vol.% filler content. While PDLLA foams resulted in 92% porosity, the porosity of the composites ranged between 79 and 91% which decreased with PGP content. In addition, a reduction in pore size was observed with increasing PGP content; however, the pore size maintained its range of 200-500 µm in all composite foams, suitable for bone tissue engineering applications. The percentage of open pores increased significantly with PGP content (up to 78% at 30 vol.% PGP). Compressive strength and modulus of PDLLA-PGP foams showed up to approximately 3-fold increase at 30 vol.% PGP content compared to neat PDLLA foams.
Les défauts osseux découlant de maladies ou de traumatismes constituent un problème de santé majeur à l'échelle mondiale. Le génie tissulaire représente une autre option pour réparer et régénérer des os en faisant appel à l'échafaudage cellulaire. L'échafaudage ainsi produit devrait fournir un milieu adéquat pour la prolifération et la différentiation des ostéoblastes et entraîner, à terme, la formation d'os. L'échafaudage doit être biodégradable, biocompatible, poreux à structure ouverte, et doit pouvoir résister aux forces appliquées. Des verres à base de phosphate (PG) peuvent être utilisés comme agents de renforcement dans des composites biodégradables puisque leur dégradation peut être prédite et maîtrisée par l'intermédiaire de leurs propriétés chimiques. La présente thèse de doctorat décrit la mise au point et l'évaluation de polymères biodégradables renforcés avec des PG pour des applications d'augmentation et de régénération osseuses. La recherche présentée visait les trois principaux objectifs suivants : 1) l'étude des propriétés dépendantes de la composition de nouvelles formulations de PG par le dopage de verres de calcium à base de phosphate exempts de sodium (50P2O5-40CaO, en % molaire) avec du SiO2, du Fe2O3 et du TiO2. Ainsi, des formulations de (50P2O5-40CaO-xSiO2-(10-x)Fe2O3, où x = 10, 5 et 0 % mol) et (50P2O5-40CaO-xSiO2-(10-x)TiO2 où x = 10, 7, 5, 3 et 0 % mol) ont été mises au point et caractérisées. L'incorporation de SiO2 s'est traduite par une augmentation de la solubilité, de la libération d'ions, de la réduction du pH, ainsi que de l'hydrophilicité, de l'énergie de surface et de la polarité. En revanche, le dopage au Fe2O3 ou au TiO2 a donné des verres plus durables, en plus d'améliorer la fixation et la viabilité cellulaires. Il a été postulé que la présence de SiO2 dans les formulations dopées au TiO2 pourrait accroître la libération d'ions des PG, entraînant ainsi une activité de l'ALP accrue des cellules MC3T3-E1. 2) l'incorporation de PG dopés aux Si, Fe et Ti comme charges, sous forme de particules ou de fibres, dans des polyesters biodégradables (polycaprolactone (PCL) et acides polylactiques amorphes (PLA et PDLLA)) dans le but de mettre au point des composites dégradables analogues aux os. Il a été établi que la composition et la géométrie des PG déterminent la perte de poids, la libération d'ions, et les propriétés mécaniques des composites. Il a également été postulé qu'une réaction potentielle entre le Si et le lien ester entraînait la formation de sous-produits de carboxylate, ce qui se traduirait par un polymère de poids moléculaire réduit et aurait ainsi une incidence sur les propriétés mécaniques des composites. L'évaluation de la cytocompatibilité avec les préostéoblastes MC3T3-E1 a démontré que ces composites étaient cytocompatibles, et un alignement de cellules le long des PGF a été observé, qui pourrait être dû à leurs propriétés de libération d'ions favorables. 3) l'investigation du moussage en milieu solide avec du dioxyde de carbone (CO2) de composites de PDLLA-PGP contenant jusqu'à 30 % vol de charge. Alors que les mousses de PDLLA présentaient 92 % de porosité, la porosité des composites allait de 79 % à 91 %, diminuant avec la teneur en PGP. En outre, une réduction de la taille des pores a été observée avec l'augmentation de la teneur en PGP; la fourchette de dimensions des pores est toutefois demeurée la même (de 200 µm à 500 µm) pour toutes les mousses de composites, qui conviennent à des applications en génie tissulaire osseux. Le pourcentage de pores ouverts a augmenté significativement avec la teneur en PGP (jusqu'à 78 % à 30 % vol de PGP). La résistance à la compression et le module d'élasticité en compression des mousses PDLLA-PGP avaient à peu près triplé à 30 % vol de PGP par rapport à celles des mousses seulement constituées de PDLLA.

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Yu, Jiayi. "Tunable Biodegradable Polymers for Regenerative Medicine." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1524821159786707.

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Pinheiro, Ivanei Ferreira 1987. "Biocompósitos poliméricos de poli(butileno adipato-co-tereftalato) : PBAT e fibra natural de Munguba, nativa da Amazônia (Pseudobombax munguba)." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266674.

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Orientador: Ana Rita Morales
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Neste trabalho estudou-se biocompósitos poliméricos obtidos a partir de um poliéster biodegradável e fibra natural de Munguba (Pseudobombax munguba) nativa da região amazônica. Trata-se de uma fibra de grande abundância encontrada nas regiões alagadiças da floresta, para a qual não existem relatos na literatura de sua utilização em biocompósitos poliméricos. Estudou-se a influência do tamanho da fibra, da concentração, e de tratamentos químicos na superfície da fibra, sobre as propriedades finais dos biocompósitos. As fibras naturais foram moídas e classificadas por tamanho e submetidas a tratamentos químicos. A fim de avaliar as modificações promovidas pelos tratamentos empregados, as propriedades mecânicas, morfologia e propriedades de superfície foram analisadas. A análise por Espectroscopia no Infravermelho (FTIR) mostrou o aparecimento de grupos ésteres confirmando a troca de hidroxila por acetila. Os ensaios mecânicos de tração mostraram que a modificação química proporcionou aumento de 75% no módulo elástico da fibra. Pelas análises de morfologia e de ângulo de contato, foram verificadas alterações superficiais significativas da fibra de munguba, enquanto que a análise termogravimétrica (TGA) mostrou que a modificação química aumentou a estabilidade térmica em comparação com a fibra natural. Os biocompósitos foram preparados por mistura em alto cisalhamento no estado fundido, utilizando fibras naturais e quimicamente tratadas com teores de 10 e 20% variando-se o tamanho das fibras. Os resultados indicaram que o aumento na concentração de fibra foi a principal responsável pelas mudanças nas propriedades mecânicas. As análises morfológicas mostraram que os tratamentos químicos não foram eficazes em promover boa interação fibra-matriz. Modelos mecânicos foram usados para prever o módulo de elasticidade dos biocompósitos sendo que o modelo de Russell descreveu com boa adequação os sistemas estudados. Através da calorimetria exploratória diferencial (DSC) verificou-se que a adição de fibras provocou alterações na cristalinidade, diminuição na temperatura de fusão e aumento na temperatura de cristalização na matriz
Abstract: In this work it was studied polymer biocomposites made from a biodegradable polyester and natural fiber Munguba (Pseudobombax Munguba) native to the Amazon region, found in great abundance marshy areas of the forest, for which there are no literature reports of its use in polymer biocomposites. The effects of fiber size, concentration and chemical treatment on the fiber surface on the final properties of the biocomposites were studied. The natural fibers have been milled and classified by size and subjected to chemical treatment. In order to evaluate the changes promoted by employed treatment, the mechanical properties, surface properties and morphology were evaluated. Infrared Spectroscopy (FTIR) analysis showed the appearance of ester groups to hydroxyl confirming the exchange by acetyl. By the tensile strength tests showed that the chemical modification time increased by 75% the elastic modulus of the fiber. The analysis of the morphology and the contact angle, significant surface changes were observed in the Munguba fiber, whereas the thermogravimetric analysis (TGA) showed that the chemical modification increased the thermal stability in comparison to the natural fiber. The biocomposites were prepared by high shear mixing in the molten state using natural, and chemically treated fibers with levels of 10 and 20% varying the size of the fibers. The results indicated that increasing the concentration of fiber was mainly responsible for the changes in mechanical properties. The morphological analysis showed that the chemical treatments were not effective in promoting good fiber-matrix interaction. Mechanical models were used to predict the elastic modulus of the biocomposites and the model of Russell presented a good fit to the studied systems. By differential scanning calorimetry (DSC) showed that the addition of fibers caused changes in crystallinity decrease in melting temperature and crystallization temperature increase in the matrix
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

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44

Huang, Xu. "Modeling of scaffold for cleft-repairing through finite element analysis." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530273324567169.

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Kandala, Bala Subramanya Pavan Kumar. "Design, Fabrication, and Testing of Photo-chemically Etched Biodegradable Stents." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1593171197849115.

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Abdollahi, Sara. "Bioglass 45S5 transformation and molding material in the processing of biodegradable poly-DL-lactide scaffolds for bone tissue engineering." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107628.

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When bone is damaged, a scaffold can temporarily replace it in the site of injury and incite bone tissue to repair itself. A biodegradable scaffold resorbs into the body, generating non-toxic degradation products as new tissue reforms; a bioactive scaffold encourages the surrounding tissue to regenerate. In the present study, we make composite biodegradable and bioactive scaffolds using poly-DL-lactide (PDLLA), a biodegradable polymer, and incorporate Bioglass 45S5 (BG) to stimulate scaffold bioactivity. BG has an interesting trait when immersed in body fluid, a layer of hydroxycarbonate apatite, similar to the inorganic component of bone, forms on its surface. It is of utmost importance to understand the fate of BG throughout the scaffold's processing in order to assess the scaffold's bioactivity. In this study, the established different stages of BG reactivity have been verified by monitoring pH during BG dissolution experiments and by conducting an elemental analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). The composite scaffolds are synthesized by the solvent casting and particulate leaching technique and their morphology assessed by scanning electron microscopy (SEM). To understand the transformations occurred in BG during scaffold synthesis, BG as received, as well BG treated in acetone and water (the fluids involved in scaffold processing) are characterized by Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS). The results are then compared with BG extracted from scaffolds after processing. BG has been determined to start reacting during the scaffold processing. In addition, its reactivity is influenced by BG particle size. The study suggests that the presence of the polymer provides a reactive environment for BG due to pH effects.Teflon molds in scaffold fabrication are inert and biocompatibile, but their stiffness presents a challenge during de-molding. Silicone-based and polyurethane molds are attractive because they are flexible. However, there is a possibility that silicone leaches either from the material itself or the agents used to enhance their performance onto the scaffold. The second study in this thesis focuses on different types of such flexible substrates (Sil940, polyurethane, polyether, polydimethylsiloxane). The presence of Si in PDLLA films prepared on each material is inspected using XPS. Films made on all four materials are found to contain Si, indicative of the dissolution of part of the substrate in the film. However, silicon in the Si-containing catalysts used in the synthesis of polyethers is not transferred to samples, when the polyether substrate is plasma coated.
Quand l'os est endommagé, une matrice synthétique peut le substituer temporairement et encourager la reconstruction du tissu osseux. Une matrice biodégradable résorbe dans le corps, engendrant des produits de dégradation non toxique alors que de le nouveau tissu se réforme. Dans la présente étude, on fabrique un composé biodégradable et bioactifs en utilisant poly(D,L-acide lactique) (PDLLA), un polymère biodégradable, et en incorporant Bioglass 45S5 (BG) pour stimuler la bioactivité. BG est un verre à base de silice qui lors du contact avec les fluides corporels, se dissout et libère des ions de silice, phosphate, calcium et sodium. Les ions de calcium et phosphate reprécipitent et forment une couche d'hydroxycarbonate apatite sur la surface du BG, qui ressemble le composant inorganiques de l'os. Puis, la couche d'hydroxycarbonate apatite s'intègre avec le collagène fibrillaire des tissus environnants, le composant organique de l'os, pour former une matrice qui attire les ostéoblastes et stimule l'accroissement du tissu osseux. Ce composite biosynthétique est développé avec la méthode de fusion du sel et sa morphologie est déterminée avec la microscopie électronique à balayage (MEB). Pour évaluer la bioactivité de l'échafaudage, il est important de comprendre le sort du BG durant la production de la matrice. Les différents stages de la réactivité du BG ont été vérifiés en surveillant le pH durant la dissolution du BG et conduisant une analyse élémentaire par la spectrométrie d'émission optique à plasma à couplage inductif (ICP-OES). Pour comprendre les transformations du BG lors de la synthèse des matrices, le BG tel que reçu avec le BG traités dans l'acétone et l'eau (les fluides impliqués dans la procédure de la synthèse) sont caractérisées avec la spectroscopie infrarouge à transformée de Fourier (FTIR) et la spectrométrie photoélectronique X (XPS). Les résultats sont par la suite comparés aves ceux du BG extrait des matrices. Nous avons déterminées que BG réagit durant la préparation de la matrice. De plus, la réactivité du BG est influencée par la grandeur ses particules. La présence du polymère crée un milieu réactif pour le BG, ce qui est due à l'effet du pH. La moule en Teflon utilisée dans la fabrication des matrices biosynthétique est inerte et biocompatible, mais aussi rigide, ce qui peut être problématique durant l'extraction. Ceci engendre une autre investigation qui implique la recherche d'une moule malléable pour faciliter l'enlèvement de la matrice. Les moules à base de silicone et polyuréthane sont attirantes parce qu'elles sont flexibles. Pourtant, il y a une possibilité que la silicone qui fait partie du matériel ou présent dans les produits utilisées pour augmenter sa performance se retrouve sur le produit final. Une deuxième étude dans la présente thèse est donc consacrée sur différents substrats flexibles (Sil940, polyuréthane, polyéther, polydimethylsiloxane). Le XPS est utilisé pour inspecter des films de PDLLA produit sur chaque matériel. La silicone est présente dans les films préparés sur tous les quatre matériaux. Cependant, lorsque le plasma est appliqué pour recouvrir le polyéther, la silicone présente dans les catalyses utilisées pour sa fabrication n'est pas transmises sur celui-ci. Donc le polyéther traité avec le plasma est convenable pour la fabrication des matrices biosynthétiques extracellulaires.

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Joshi, Madhura A. "Growth and Characterization of Magnesium Single Crystal for Biodegradable Implant Material Application." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448275234.

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Gudima, Alexandru [Verfasser], and Julia [Akademischer Betreuer] Kzhyshkowska. "Analysis of reactions of macrophages to titanium and biodegradable coating materials / Alexandru Gudima ; Betreuer: Julia Kzhyshkowska." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177252449/34.

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Voksepp, Emmy. "Dyeing diversity : Exploring interrelations between plant dyeing techniques, design methods and biodegradable materials in textile design." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-603.

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This work explores the expressive potential of plant dyeing techniques in relation to weaving by proposing a method in regard to non-toxic containment, biodegradable materials and ethical values. Textile design and ethical values have been combined to create an “Textethical Design Method”. The personal ethical values that have been used in this project are based on a “diversity perspective”. These consist of openness in material choices that wish to expand the view of quality in relation to textile material, but also by connecting and evolving the expression through knowledge between the material selections, production and aesthetics. This project focus on finding plant dyes that are uncharacteristic for the earth tones that plant dyeing techniques often are associated with, where red cabbage was the most successful pigment. The textile techniques that will be used are plant dyeing on a multiplied layered weaved surface to investigate depth through color and three-dimensional shape. The project strives to contribute with development in design methods, sustainability and broader the field of plant dyeing techniques.

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Feng, Yuping. "Design and characterization of dense and porous Fe-based alloys for biomedical and environmental applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/460679.

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Aquesta tesi doctoral comprèn la síntesi d’aliatges basats en ferro mitjançant diversos mètodes de fabricació. Aquests aliatges s’han dissenyat amb la intenció de ser utilitzats en biomedicina o en aplicacions mediambientals. S’ha donat especial èmfasi a dissenyar una composició adequada i a estudiar la morfologia i les propietats estructurals per tal d’optimitzar tant les propietats mecàniques com les propietats magnètiques dels materials resultants. En primer lloc es va utilitzar la tècnica de fusió per arc i colada per succió amb motlle de coure per fabricar dos aliatges densos: un aliatge ferromagnètic amb composició en pes Fe-10Mn6Si1Pd i un aliatge paramagnètic amb memòria de forma amb composició en pes Fe-30Mn6Si1Pd. L’evolució de la microestructura, les propietats mecàniques i magnètiques, així com també la degradació, la citotoxicitat i la proliferació de cèl·lules en solució Hanks es van estudiar de forma sistemática en funció del temps d’immersió. Per tal de millorar la biocompatibilitat de l’aliatge Fe-10Mn6Si1Pd, aquest aliatge es va recobrir amb fosfat de calci (brushita o hidroxilapatita) mitjançant la tècnica d’electrodeposició per corrent polsant. A conseqüència de la morfologia porosa d’aquests recobriments (per exemple: en forma d’agulles, cilindres o plaques), el mòdul de Young i la duresa mesurades foren inferiors als valors obtinguts en recobriments anàlegs no porosos. Seguidament, amb l’objectiu d’incrementar la velocitat de degradació i reduir el mòdul de Young d’aquests aliatges compactes, es van fabricar aliatges porosos de Fe-30Mn6Si1Pd mitjançant un procés de premsa i sinterització de Fe, Si, Mn i Pd en pols prèviament mòlta i barrejada amb un 10, un 20 o un 40% en pes de NaCl en un molí de boles. Cal destacar, que després de submergir els aliatges porosos durant un període llarg de temps, el mòdul de Young reduït que es va mesurar en tots ells va ser d’uns 20 GPa (essent aquest valor similar al mòdul de Young de l’os humà, entre 3-27 GPa). Aquest fet afavoriria una bona compatibilitat biomecànica entre l’implant i el teixit ossi veí. Per altra banda, es van fabricar escumes de Fe i Fe-Mn de cèl·la oberta utilitzant matrius de poliuretà poroses pel mètode de rèplica. Es va observar que la resposta magnètica d’aquestes escumes, des de pràcticament no magnètica a ferrimagnètica, es podia controlar ajustant el contingut de Mn i el flux de N2. També, en el marc de propietats magnètiques, es va utilitzar la tècnica d’irradiació amb làser polsat de femtosegon per crear patrons magnètics periòdics a la superfície d'un aliatge amorf no ferromagnètic basat en Fe. Finalment, es va preparar un aliatge nanoporós ric en Fe per dissolució selectiva de cintes de Fe43.5Cu56.5 fabricades per tornejat en estat de fusió. Es va observar que els materials nanoporosos eren un excel·lent catalitzador heterogeni de la reacció de Fenton per la degradació del taronja de metil en solució aquosa.
This Thesis dissertation covers different synthetic approaches to obtain Fe-based alloys to be used for biomedical and environmental applications. Special emphasis has been placed to design a proper composition and to study the morphology and structural properties to tailor both the mechanical and magnetic properties of the resulting materials. Firstly, ferromagnetic Fe-10Mn6Si1Pd (wt.%) and shape memory, paramagnetic Fe-30Mn6Si1Pd (wt.%) compact alloys were prepared by arc-melting followed by copper mold suction casting. The evolution of microstructure, mechanical and magnetic properties, as well as the assessment of degradation, cytotoxicity and cell proliferation in Hank’s solution as a function of the immersion time were systermatically studied. With the aim to improve the biocompatibility of the Fe-10Mn6Si1Pd alloy, calcium phosphate coatings (CaP) (i.e., brushite and hydroxyapatite) were electrodeposited on the alloy by pulsed current electrodeposition. Due to porous structures resulting from needle-, rod- or plate-like morphologies, the measured Young’s modulus and hardness of these coatings were lower than those of fully-dense CaP layers with analogous compositions. Then, to increase the degradation rate and to reduce the Young’s modulus of the fully bulk alloys, porous Fe-30Mn6Si1Pd (wt.%) alloys were prepared by a simple press and sinter process from ball-milled Fe, Mn, Si and Pd powders blended with 10 wt.%, 20 wt.% and 40 wt.% NaCl. Remarkably, the reduced Young’s modulus of all the porous alloys reached values close to 20 GPa after long-term immersion, a value which is close to the Young’s modulus of human bones (3–27 GPa), hence favoring good biomechanical compatibility between an eventual implant and the neighboring bone tissue. Meanwhile, open cell Fe and Fe-Mn oxides foams were prepared by the replication method using porous polyurethane templates. The magnetic response of the foams, from virtually non-magnetic to ferrimagnetic, could be tailored by controllably adjusting the Mn content as well as the N2 flow rate. Still dealing with magnetic properties, femtosecond pulsed laser irradiation was used to create periodic magnetic patterns at the surface of a non-ferromagnetic amorphous Fe-based alloy. Finally, a nanoporous Fe-rich alloy was prepared by selective dissolution of melt-spun Fe43.5Cu56.5 ribbons. The nanoporous ribbons were found to be an excellent heterogeneous Fenton catalyst towards the degradation of methyl orange in aqueous solution.

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