Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 72-74). Also available on the Internet.

Thesis (M.D.S.)--University of Hong Kong, 2005.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 36-43, 88-90, 139-140, 187, 238-241, 282-285, 323).

No description available.

Polydopamine (PDA), a unique bioinspired polymer, has been a subject of interest in fields including orthopedic biomaterials and antibacterial surfaces. Its osteogenic effects and ability to control surface traits through precise variables (e.g., pH, temperature) have led to its use as a coating in the enhancement of a wide range of materials, including metals and ceramics. In this Thesis, two studies were carried out to better understand the capability and mechanism of PDA-mediated bioactivity. In the first study, we investigated whether PDA coatings can further enhance the bioactivity of nanoporous Titanium (NPTi). While physicochemical traits were in line with literature, PDA was effective in enhancing cell proliferation, beyond NPTi, as early as 8 hours with enhancement in cell spreading and focal adhesion prevalence as early as 1 hour. No changes in adsorptive capacity were found, suggesting a serum-independent component (SIC) of the surface. The second study was focused on (1) determining how treatment parameters influence the physiochemical makeup of PDA surfaces, (2) assessing how PDA surfaces influence stem cell behavior and (3) confirming and investigating the SIC of PDA effect. Results confirm that there is indeed a SIC of PDA coatings with enhancement in cell spreading that improves with the increased size and density of PDA particles. Our findings show that the SIC works in concert with circulating sera to elicit the bioactive effects of PDA. The novel rPDA surface, obtained by adding rotation during the coating deposition, is also shown to elevate bioactivity during normal culturing, beyond classical coatings, with ongoing work suggesting enhancement in the osteogenic differentiation of hMSCs. Taken together, this work has demonstrated novel aspects underlying the potential and mechanism of action for the bioactivity of PDA, ultimately providing new evidence supporting the use of PDA as a biomedical material.

Made available in DSpace on 2014-06-11T19:32:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-23Bitstream added on 2014-06-13T20:27:52Z : No. of bitstreams: 1 capellato_p_dr_guara.pdf: 1337923 bytes, checksum: 3edc5b93305051c3258b073892d9965d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Titânio CP e a liga Ti6Al4V são amplamente empregados na fabricação de componentes para aplicações biomédicas. No entanto, estes materiais podem causar problemas de saúde em função da liberação de íons metálicos citotóxicos e reabsorção do osso adjacente devido a grande diferença entre o modulo de elasticidade do material e osso. Esses fatores têm levado ao desenvolvimento de novas ligas de titânio e também de novas técnicas de modificação de superfície. Amostras da liga experimental Ti-30Ta na forma de discos com 13 mm de diâmetro e 3 mm de espessura foram empregadas nesse estudo. O processo de anodização foi realizado sob tensão de 15V, 25V e 35V e tempos de 20 e 40 min em eletrólito formado por HF/H2SO4 com adição de dimetil sulfóxido (DMSO). A calcinação das amostras foi realizada a 530ºC durante 3 h. As superfícies foram avaliadas empregando-se MEV-FEG, EDS e a molhabilidade avaliada com ângulo de contato. Todas as condições avaliadas apresentam superfície hidrofílica. Nanotubos de Ti-30Ta foram obtidos na condição 35V-40 mim apresentado 100 nm de comprimento e 80-100 nm de diâmetro. A biocompatibilidade da liga Ti-30Ta com nanotubos foi avaliada após 24 e 72 horas de cultura celular com fibroblastos dérmicos humanos (HDF, neonatal). A adesão e proliferação celular, viabilidade, organização do citoesqueleto e morfologia celular foram investigadas por meio de imagens de microscópio de fluorescência, ensaios bioquímicos e MEV-FEG. Análise celular demonstrou aumento significativo na adesão e proliferação celular, viavilidade, alongamento e produção de matriz extracelular de fibroblastos na superfície da liga Ti-30Ta com nanotubos após 72 horas de cultura celular... / In the last years, titanium and theirs alloys have been used in dental applications due their excellent properties such as corrosion resistance and biocompatibility. However, these materials are considered bioinerts and due to your poor physiological integration that may result in fibrous encapsulation and further biomaterial rejection. Ti-30Ta alloys, for use in biomedical applications are the subject of this research. The aim is to discover optimal alloy proportions for tissue-like mechanical properties and improved biocompatibility. Of the alloys tested, 30% Ta with Ti exhibits favorable properties including a low elastic modulus, improved strain-resistance and increased elongation to failure. Recent studies have identified strong correlations between anodized metals and the production of highly biomimetic nanoscale topographies. These surfaces provide an interface of enhanced biocompatibility that exhibits a high degree of oxidation and surface energy. In this study, the mechanical substrate and topographical surface properties of anodized Ti-30Ta alloy were investigated using scanning electron microscopy (SEM), energydispersive spectroscopy (EDS) and contact angle measurement. The anodization process was performed in an electrolyte solution containing HF (48%) and H2SO4 (98%) in the volumetric ratios 1:9 with the addition of 5% dimethyl sulfóxido (DMSO) at 15V, 25V and 35V for 20 and 40 min, producing a nanotube architecture when anodized at 35V for 40 min. Human dermal fibroblasts (HDF, neonatal) were utilized to evaluate the biocompatibility of Ti-30Ta nanotubes after 24 and 72 hours of culture. Cellular adhesion, proliferation, viability, cytoskeletal organization and morphology were investigated using fluorescence microscope imaging, biochemical assay and SEM imaging respectively... (Complete abstract click eletronic access below)

Made available in DSpace on 2014-10-09T12:50:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:48Z (GMT). No. of bitstreams: 1 00879.pdf: 2651751 bytes, checksum: df2a0d74b37955445728f8c1f2aa55e9 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

Made available in DSpace on 2014-10-09T12:50:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:48Z (GMT). No. of bitstreams: 1 00879.pdf: 2651751 bytes, checksum: df2a0d74b37955445728f8c1f2aa55e9 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

M.Sc. / An annual production of approximately 46 million metric tons of polyolefins worldwide, emphasizes the industrial importance of this product and the polymerisation process. Olefins are the basic building block of the petrochemical industry and are therefore readily available and cheap. Reactivity of olefins decreases from ethylene to propylene to 1-octene and makes the study of polymerisation catalysts more complex, seeing that the activity of a catalyst differs from monomer to monomer. In this study zirconocene complexes with bridged cyclopentadienyl ligands have been prepared and investigated as , possible catalysts for the polymerisation of higher aolefins. Fulvenes have been reductively coupled and used as ligands for zirconium complexes. Steric bulk of the substituents on the ligand have been increased and changes in the polymeric products have been studied. The tacticty, endgroups and chain lengths of the polyolefins have been investigated. There is currently a considerable interest in the development of 'non-metallocene' catalysts as alternatives for the polymerisation and oligomerisation of a-olefins. Chelating diamide complexes of Group 4 metals have been the focus of much attention and these compounds have shown moderate to high reactivity. However, only a few examples of the corresponding chelating alkoxides are known. In this study, alkoxide complexes of zirconium and titanium have been prepared with Schiff bases as ligands. These complexes have been evaluated as polymerisation catalysts and the products have been studied. The titanium complexes were more active than the zirconium analogues. The narrow molecular weight distribution of the polyolefins gave evidence that these catalysts are single-sited catalysts.