The development of new charge transport materials for use in phosphorescent organic light-emitting diodes (OLEDs) remains an important area of research. In this thesis, several examples of carbazole-containing norbornene-based side-chain polymers were synthesized and studied. In addition, several examples of ambipolar transport moieties were produced by combining hole- (carbazole) and electron- (oxadiazole or triazole) transport groups and examined as both small molecules and as norbornene-based side-chain polymers. UV-visible absorption, fluorescence spectroscopy, cyclic voltammetry, and other methods were used to evaluate the properties of the charge transport materials for use as hole- and/or host layers. It was found that side-functionalization produced polymers with photophysical and electrochemical properties corresponding to the charge transport side groups attached. In addition, several crosslinkable hole-transporting materials (copolymer or small molecule-based) incorporating either benzocyclobutenes, trifluorovinyl ethers, oxetanes, or bis(styrene)s were developed. Thin-films of the crosslinkable materials were shown to be readily insolubilized by thermal treatment permitting the deposition of a subsequent layer from solution onto the crosslinked layer. OLEDs fabricated using several of these materials produced efficient devices. Overall, it was shown that side-chain functionalization can be used to afford solution-processable charge transport polymers where the properties are determined mainly by the side group attached. As such, this approach could be extended to additional examples of charge transport moieties.

Thesis (Ph.D)--Biomedical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Elliot Chaikof; Committee Member: Marc Levenston; Committee Member: Robert Nerem; Committee Member: Vincent Conticello; Committee Member: Yadong Wang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Background: Today corneal crosslinking with ultraviolet-A photoactivation of riboflavin is an established method to halt the progression of keratoconus. In some cases, when the refractive errors are large and the visual acuity is low, conventional corneal crosslinking may not be sufficient. In these cases it would be desirable with a treatment that both halts the progression and also reduces the refractive errors and improves the quality of vision. Aims:  The aims of this thesis were to determine whether mechanical compression of the cornea during corneal crosslinking for keratoconus using a sutured rigid contact lens could improve the optical and visual outcomes of the treatment, and also to find methods to evaluate the effect of different corneal crosslinking treatment regimens. Methods: In a prospective, open, randomized case-control study, 60 eyes of 43 patients with progressive keratoconus, aged 18-28 years, planned for routine corneal crosslinking, and a corresponding age- and sex-matched control group was included. The patients were randomized to conventional corneal crosslinking (CXL; n=30) or corneal crosslinking with mechanical compression of the cornea during the treatment (CRXL; n=30). Biomicroscopy, autorefractometry, best spectacle corrected visual acuity, axial length measurement, Pentacam® HR Scheimpflug photography, pachymetry, intraocular pressure measurements and corneal biomechanical assessments were performed before treatment (baseline) and at 1 month and 6 months after the treatment. One of the articles evaluated and compared the optical and visual outcomes between CXL and CRXL, while the other three articles focused on methods to evaluate treatment effects. In Paper I, the corneal light scattering was manually quantified from Scheimpflug images throughout the corneal thickness at 8 measurements points, 0.0 to 3.0 mm from the corneal centre, in patients treated with CXL. In Paper IV the corneal densitometry (light scattering) was measured with the Pentacam® HR software, in 4 circular zones around the corneal apex and at 3 different depths of the corneal stroma, in both CXL and CRXL treated corneas. Paper III quantified the biomechanical effects of CXL in vivo. Results: Corneal light scattering after CXL showed distinctive spatial and temporal profiles and Applanation Resonance Tonometry (ART) -technology demonstrated an increased corneal hysteresis 1 and 6 months after CXL. When comparing the refractive and structural results after CXL and CRXL, CRXL failed to flatten the cornea, and the treatment did not show any benefits to conventional CXL treatment, some variables even indicated an inferior effect. Accordingly, the increase in corneal densitometry was also less pronounced after CRXL. Conclusions: Analysis of corneal light scattering/densitometry shows tissue changes at the expected treatment location, and may be a relevant variable in evaluating the crosslinking effect. ART -technology is an in vivo method with the potential to assess the increased corneal hysteresis after CXL treatment. By refining the method, ARTmay become a useful tool in the future. Unfortunately, CRXL does not improve the optical and visual outcomes after corneal crosslinking. Possibly, stronger crosslinking would be necessary to stabilize the cornea in a flattened position.

Bacteria have been confirmed as the main etiological factor for root canal infection as well as for root canal treatment failure. Thus the success of endodontic treatment depends on the complete elimination of bacteria and prevention of bacterial recolonization in the root canal system. The major challenge for conventional root canal disinfection strategies is the ability of bacteria to persist as biofilms within the anatomical complexities of the root canal system. In addition, the alterations in the ultrastructure of dentin tissue results in compromised structural integrity of root dentin leading to higher risk of fracture in root-filled teeth. The objectives of this study are twofold: 1) develop and test functionalized nanoparticles to eliminate biofilm bacteria and, 2) to stabilize and strengthen the dentin organic matrix by crosslinking collagen fibrils in the presence of biopolymeric nanoparticles. A bioactive polymeric nanoparticle functionalized with a photosensitizer may present as a single step treatment to achieve both the objectives. Chitosan a bioactive polymer was used owing to their inherent antibacterial and biocompatible characteristics. Chitosan micro-/nanoparticles were synthesized as well as functionalized with photosensitizer (rose bengal) for photodynamic activation. Bioactive chitosan nanoparticle functionalized with a rose bengal is expected to combine the properties of chitosan i.e., polycationic with higher affinity to bacterial cell wall and alter membrane integrity; that of a photosensitizer i.e., to generate singlet oxygen when photoactivated; and the nano-form further potentiate these specific properties. These photodynamically activable chitosan nanoparticles showed the distinct characteristics of chitosan and rose bengal. The synergistic effect of the chitosan conjugated nanoparticles was able to eliminate monospecies and multi-species bacterial biofilms with complete disruption of the biofilm structure. The singlet oxygen generated during photoactivation produced photochemical crosslinking of dentin collagen and infiltration of chitosan nanoparticles. Following crosslinking the dentin collagen showed significantly improved mechanical properties (ultimate tensile strength and toughness) and improved resistance to degradation by bacterial collagenase. In conclusion, this study presents a potential photosensitizer functionalized chitosan nanoparticles based treatment strategy to improve the success of endodontic treatment to achieve complete disinfection of the root canal system and enhanced the mechanical/ structural integrity of the root-filled teeth.

Bacteria have been confirmed as the main etiological factor for root canal infection as well as for root canal treatment failure. Thus the success of endodontic treatment depends on the complete elimination of bacteria and prevention of bacterial recolonization in the root canal system. The major challenge for conventional root canal disinfection strategies is the ability of bacteria to persist as biofilms within the anatomical complexities of the root canal system. In addition, the alterations in the ultrastructure of dentin tissue results in compromised structural integrity of root dentin leading to higher risk of fracture in root-filled teeth. The objectives of this study are twofold: 1) develop and test functionalized nanoparticles to eliminate biofilm bacteria and, 2) to stabilize and strengthen the dentin organic matrix by crosslinking collagen fibrils in the presence of biopolymeric nanoparticles. A bioactive polymeric nanoparticle functionalized with a photosensitizer may present as a single step treatment to achieve both the objectives. Chitosan a bioactive polymer was used owing to their inherent antibacterial and biocompatible characteristics. Chitosan micro-/nanoparticles were synthesized as well as functionalized with photosensitizer (rose bengal) for photodynamic activation. Bioactive chitosan nanoparticle functionalized with a rose bengal is expected to combine the properties of chitosan i.e., polycationic with higher affinity to bacterial cell wall and alter membrane integrity; that of a photosensitizer i.e., to generate singlet oxygen when photoactivated; and the nano-form further potentiate these specific properties. These photodynamically activable chitosan nanoparticles showed the distinct characteristics of chitosan and rose bengal. The synergistic effect of the chitosan conjugated nanoparticles was able to eliminate monospecies and multi-species bacterial biofilms with complete disruption of the biofilm structure. The singlet oxygen generated during photoactivation produced photochemical crosslinking of dentin collagen and infiltration of chitosan nanoparticles. Following crosslinking the dentin collagen showed significantly improved mechanical properties (ultimate tensile strength and toughness) and improved resistance to degradation by bacterial collagenase. In conclusion, this study presents a potential photosensitizer functionalized chitosan nanoparticles based treatment strategy to improve the success of endodontic treatment to achieve complete disinfection of the root canal system and enhanced the mechanical/ structural integrity of the root-filled teeth.

No description available.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references. Also available via World Wide Web.

La part des technologies membranaires en tant que technique de séparation a rapidement augmenté au cours de ces dernières années grâce à leur large gamme d'applications. Le marché en pleine expansion nécessite des matériaux polymères avancés qui montrent une résistance accrue vis-à-vis du gonflement et de la plastification en séparation de gaz (GS) ou vis-à-vis de solvants forts et des conditions de pH extrême en nanofiltration en milieu organique (SRNF). Aujourd'hui, la réticulation apparait comme une technologie prometteuse pour répondre à ces nouveaux besoins. La réticulation chimique est l'une des techniques les plus couramment utilisées et est basée sur une réaction chimique entre un polymère (par exemple un polyimide) et un réticulant (par exemple une diamine ou un diol). Cependant pour des polymères, tels que les polysulfones (PSU), qui ne contiennent pas de groupes fonctionnels chimiquement réactifs dans leur squelette, cette technique n'est pas viable. Enfin la réticulation chimique implique plusieurs étapes de traitement et induit des flux de déchets nocifs. La recherche d'une technique de traitement rapide et verte généralement applicable est donc d'une première importance. Deux nouvelles techniques de réticulation, que sont les traitements par rayons ultraviolets (UV) pour par faisceaux d'électrons (EB), ont donc été explorées dans cette thèse afin d'obtenir des membranes stables chimiquement et thermiquement, ce qui est intéressant pour les applications SRNF. Des membranes asymétriques, composées d'un réseau polymère semi-interpénétrant (SIPN), ont été préparées par séparation de phase induite par un solvant (NIPS). Le PSU a été choisi comme polymère grâce à ses caractéristiques intrinsèques suivantes : propriétés thermiques et mécaniques importante, photosensibilité et absence de groupes réactifs. Les membranes réticulées à structure SIPN ont été obtenues par traitement UV et EB. Ces techniques possèdent plusieurs avantages par rapport à la réticulation chimique : une réduction de la production de déchets, des besoins énergétiques plus faibles et des temps de traitement rapides. Dans une première partie, nous avons étudié l'influence de la fonctionnalité du réticulant, de l'énergie du rayonnement et du rapport polymère / réticulant sur l'efficacité de la réticulation par EB. Des agents de réticulation à base d'acrylate ont été utilisés. Les membranes obtenues ont été caractérisées par des expériences en ATR-FTIR, SEM et de filtration, ainsi que des essais de stabilité contre des solvants forts. Le meilleur type de réticulant et sa concentration optimale sous une dose d'EB optimale ont ensuite été sélectionnés pour les études suivantes. Dans la seconde partie, nous avons exploré les effets du rapport solvant / co-solvant et du temps d'évaporation avant la précipitation des membranes en PSU réticulées par la suite soit par UV et soit par EB; le tétrahydrofurane (THF) ou le 1,4-dioxane (DIO) étant utilisés comme solvant. Dans les deux cas, les morphologies membranaires différent en fonction des paramètres étudiés de l'inversion de phase. L'augmentation du temps d'évaporation réduit la formation de macrovides et permet l'apparition de structures spongieuses. Les flux de solvant sont généralement restés trop faible pour que les membranes soient vraiment utiles en SRNF. Un post-traitement a été effectué pour augmenter le flux en immergeant les membranes réticulées dans du dimethylformamide (DMF) pendant 48 h. Les membranes résultantes ont des perméances plus élevées et des taux de rejets plus faibles. / The importance of membrane technology as a separation technique has increased rapidly over the past decades thanks to its broad range of applications. The expanding market brings along the requirement of advanced polymeric materials, which show resistance towards swelling and plasticization in gas separation (GS) and towards harsh solvents and extreme pH conditions in solvent resistant nanofiltration (SRNF). At this stage, cross-linking has emerged as a promising technology to overcome these issues. Chemical cross- linking is one of the most commonly used techniques and is based on a chemical reaction between a polymer (e.g. polyimide) and a cross-linker (e.g. diamine or diol). However, for polymers which do not contain chemically reactive groups in their backbone, such as polysulfones (PSU), this technique is not feasible. Additionally, chemical cross-linking involves several processing steps and causes harmful waste streams, triggering the quest for a generally applicable, fast and green curing technique. Two new curing techniques, namely ultraviolet (UV) and electron beam (EB) curing, were explored in this thesis, in order to obtain chemically and thermally stable membranes, hence being attractive for SRNF applications. Asymmetric membranes, composed of a semi-interpenetrating polymer network (SIPN), were prepared via non-solvent induced phase separation (NIPS). PSU was chosen as polymer because of its robust thermal and mechanical properties, photosensitivity and lack of reactive groups. Cross-linked membranes with SIPN structure were obtained via UV and EB-curing. In the first part, the influence of cross-linker functionality, radiation energy dose and polymer/crosslinker ratio on the EB-curing efficiency was investigated. Acrylate-based cross-linkers were employed. The obtained membranes were characterized with ATR-FTIR, SEM and filtration experiments, together with stability testing against harsh solvents. The best type of cross-linker and its optimum concentration under optimum EB-dose were then selected for further studies. In the second part, the effects of solvent/co-solvent ratio and the evaporation time before precipitation of UV and EB-cured PSU SRNF-membranes were explored, using tetrahydrofuran (THF) or 1,4-dioxane (DIO) as co-solvent. Both UV and EB-cured PSU membrane morphologies differed as function of the studied phase inversion parameters. Increasing evaporation time reduced macrovoid formation with appearance of spongy structures. The flux generally remained too low for membranes to become really useful in SRNF. A post treatment was performed to increase the flux by immersing UV-cured PSU-based membranes in dimethylformamide (DMF) for 48 h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates as stable supports in the preparation of thin film composite membranes. In a third part, the mechanical characteristics, the effect of casting thickness and the surface properties of the membranes cross-linked by both irradiation methods were further studied. Additionally, the swelling behavior of UV-cured thin PSU films as function of different curing parameters (i.e. radiation dose and cross-linker functionality) was analyzed with ellipsometry. In conclusion, solvent stable asymmetric PSU membranes were developed by two simple, environmentally friendly and highly effective methods. The performance and enhanced chemical resistance of the cured membranes show high potential for implementing both cross-linking procedures in adequate industrial applications after further optimization.

Submitted by Luciane Willcox (luwillcox@gmail.com) on 2016-09-12T17:18:24Z No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) / Approved for entry into archive by Luciane Willcox (luwillcox@gmail.com) on 2016-09-12T18:02:31Z (GMT) No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) / Made available in DSpace on 2016-09-12T18:02:31Z (GMT). No. of bitstreams: 1 Tese_Doutorado_ICC.pdf: 40560568 bytes, checksum: 1e1c7efcf21605b84ddacb307516a772 (MD5) Previous issue date: 2016-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Programa de Apoio à Pesquisa Estratégica em Saúde (Papes) da Fiocruz, Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Microsoft Research. / Instituto Carlos Chagas, Fiocruz-PR, Curitiba, PR, Brasil / O estudo de estruturas e interações proteicas é uma importante área de pesquisa para se entender as funções das proteínas. No entanto, essa é também uma das áreas de grandes desafios experimentais, devido à inerente complexidade atômica de proteínas e peptídeos. Os métodos de elucidação estrutural de alta resolução (e.g. difração de raios-X e RMN) são hoje os considerados “padrões-ouro” para esses tipos de estudos. No entanto, uma grande parte das proteínas e seus respectivos complexos não são passíveis de serem resolvidos por esses métodos, motivando o desenvolvimento de novas técnicas para a caracterização estrutural de proteínas e seus complexos. Neste sentido, a espectrometria de massas acoplada à técnica de crosslinking (XL-MS) é uma grande promessa, devido às suas características intrínsecas, tais como alta sensibilidade e ampla aplicabilidade. Neste trabalho, desenvolveu-se um software com aplicações pioneiras, denominado SIM-XL, capaz de identificar peptídeos covalentemente ligados e analisados por espectrometria de massas, a fim de caracterizar estruturas de proteínas, bem como de complexos proteínas-proteínas e proteína-peptídeo. Esse software faz uso de técnicas de reconhecimento de padrões para resolver um gargalo na modelagem proteica e interação proteína-proteína. Portanto, o algoritmo aqui apresentado, traz benefícios imediatos nas áreas de biologia e biotecnologia e indiretamente, em diversas outras áreas, como por exemplo, no desenvolvimento de novos fármacos. / The study of protein structures and interactions is an important area of development for understanding the function of proteins. However, this is also an area of great experimental challenge, due to the inherent atomic complexity of proteins and peptides. The methods of structural elucidation of high-resolution (e.g. X-ray diffraction and NMR) are currently considered the “gold standard” for these types of studies. However, many proteins are not amendable to being solved by these methods; thus motivating the development of new techniques for structural characterization of proteins and their complexes. In this regard, mass spectrometry coupled by crosslinking technique (XL-MS) poses as a promise to overcome these limitations as it provides a high sensitivity and wide applicability. Here we present SIM-XL, a software pioneer in many ways, capable of identifying cross-linked peptides analyzed by mass spectrometry and thus ultimately aiding in structural characterization and in determining protein-protein interactions. Our software uses pattern recognition strategies to address a bottleneck in protein modeling and protein-protein interaction. As such, various fields related to biology and biotechnology suffer an immediate benefit from this work, and other areas, say, the development of new drugs, are indirectly benefited as well.

Orientador: Cesar Costapinto Santana / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-29T03:19:59Z (GMT). No. of bitstreams: 1 Torres_MarcoAntonio_M.pdf: 2067792 bytes, checksum: 4a29bce462549322420c9d13dd7180eb (MD5) Previous issue date: 2001 / Resumo: biopolímero denominado quitosana vem sendo reconhecido como uma importante fonte de matrizes para adsorventes em processos de recuperação e purificação de bioprodutos, com novas aplicações em várias áreas do conhecimento como a biotecnologia. Uma importante vantagem nessa utilização é a disponibilidade da quitina na natureza, podendo ser encontrada facilmente na carapaça de crustáceos. A flexibilidade apresentada por essas matrizes se deve principalmente à compatibilidade adsorbato/adsorvente e à possibilidade de modificações estruturais de modo a atender a características diversificadas de interação química e de resistência mecânica. No presente trabalho foi realizada a caracterização reológica de soluções e géis de quitosana, com a determinação das propriedades viscosas e viscoelásticas. As soluções concentradas foram obtidas por dissolução da quitosana em solução de ácido acético e os géis foram obtidos através de modificações da quitosana com a utilização do glutaraldeído, nas concentrações de 2,5g/100ml, 3,Og/100ml e 3,5g/100ml e nas temperaturas de 10°C, 30°C e 50°C. As propriedades viscosas e viscoelásticas das amostras de quitosana foram obtidas com a utilização do reômetro Haake CV20. Esse equipamento pode ser programado para trabalhar em dois métodos de obtenção de dados experimentais. No método de cisalhamento permanente, as propriedades obtidas são representativas do comportamento viscoso das amostras, através da obtenção das seguintes variáveis: tensão de cisalhamento, taxa de cisalhamento e viscosidade de cisalhamento. No método de cisalhamento oscilatório, as propriedades determinadas são representativas do comportamento viscoelástico das amostras, através da obtenção das seguintes variáveis: módulo de rigidez, módulo de dissipação e viscosidade complexa. Foi realizada a interpretação da correlação estrutura - propriedade apresentada pela quitosana e pelos géis modificados através da reticulação com glutaraldeído. Foram atribuídos modelos específicos para o comportamento reológico das soluções e géis de quitosana. A determinação dos parâmetros nas diversas faixas estudadas permite concluir que é possível preparar e caracterizar a quitosana na forma de soluções concentradas e na forma de géis de acordo com a concentração e ° grau de reticulação das amostras analisadas / Abstract: The chitosan biopolymer has recently being appointed as an important source of matrices used as adsorbents in processes for the recovery and purification of bioproducts, with new applications in areas such as biotechnology. An important advantage is that chitin occurs naturally and is commonly found in crustacean shells. The flexibility exhibited by these matrices became from the compatibility adsorbate/adsorbent and the possibility of structural modifications to satisfy diversified characteristics of chemical interaction and mechanical strength. In this work, the rheological characterization of chitosan solutions and gels was carried out in order to investigate viscosity and viscoelasticity properties. The concentrated solutions were prepared by dissolving chitosan with acid acetic solution and the gels were prepared by adding glutaraldehyde, solutions at different concentrations of 2,5g/100ml, 3,Og/100ml and 3,5g/100ml and temperatures of 10°C, 30°C and 50°C. The viscosity and viscoelasticity properties of chitosan samples were measured with a rheometer (model Haake CV20). The equipment can be operated in two different ways in order to obtain the experimental data. The first one is the steady shear rheological measurement, where the viscosity properties are described through values for shear stress, shear rate and shear viscosity. The second is the oscillatory shear rheological measurement, where the viscoelasticity properties are described through values for storage modulus, 1055 modulus and complex viscosity. The correlation between structure and properties exhibited by chitosan samples and gels modified by crosslinking with glutaraldehyde were studied. Rheological specific models were adjusted to the experimental data in order to describe the behavior of chitosan solutions and gels. The parameter determinations allow concluding that is possible to prepare and characterize chitosan samples as concentrated solutions and gels depending only on the concentration and the degree of crosslinking of the sample studied. / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química