Made available in DSpace on 2014-06-12T15:51:14Z (GMT). No. of bitstreams: 2 arquivo5265_1.pdf: 13873428 bytes, checksum: 26bf6010c60d0c91b603763e90054607 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2006 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nos últimos anos, os efeitos de confinamento quântico em nanocristais semicondutores (pontos quânticos) têm atraído bastante interesse devido às suas novas propriedades ópticas e também ao grande potencial para aplicações em sistemas biológicos. Neste trabalho utilizamos pontos quânticos como marcadores fluorescentes em amostras biológicas. Adaptamos protocolos para marcação de cromossomos humanos, neurônios e glioblastomas e formas infectantes do Trypanosoma cruzi, causador da doença de Chagas. As nanopartículas de sulfeto de cádmio (CdS) foram sintetizadas em solução aquosa e passivadas com Cd(OH)2. A agregação das partículas foi evitada com íons de polifosfato. As nanopartículas de CdS/Cd(OH)2 foram funcionalizadas com poli(etileno glicol) (PEG) e glutaraldeído para verificarmos seu desempenho como marcadores biológicos. As propriedades ópticas das amostras foram estudadas por espectroscopia de absorção, excitação e emissão e a caracterização morfológica foi realizada por microscopia eletrônica de transmissão. Obtivemos imagens de fluorescência por microscopia confocal mostrando claramente a marcação fluorescente em cromossomos humanos, neurônios, glioblastomas e formas infectantes do Trypanosoma cruzi. Utilizando diferentes funcionalizantes foi possível comparar diferentes marcações para as amostras biológicas estudadas. Com isso, podemos indicar o melhor protocolo, utilizando nanopartículas de semicondutores para marcações de diferentes sistemas biológicos. Os quantum dots funcionalizados com glutaraldeído apresentou bons resultados para amostras fixadas (cromossomos), enquanto que o poli(etileno glicol) (PEG) foi essencial para marcações de amostras vivas (neurônios, glioblastomas e formas infectantes de T. cruzi)

Orientador: Edvaldo Sabadini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T13:40:57Z (GMT). No. of bitstreams: 1 Sant'AnnaJunior_Walcyr_M.pdf: 635340 bytes, checksum: 1249edac738f7933eee08fdecb6d0d7f (MD5) Previous issue date: 2001 / Resumo: Este trabalho envolve o estudo do equilíbrio de fase líquido-líquido apresentado pelo sistema poli(etileno glicol), (PEG) e hidrocarbonetos aromáticos (HA). Os diagramas de fase são do tipo UCST (upper critical solution temperature), sendo que o grau de miscibilidade é fortemente dependente da massa molar do PEG e do número de CH2 presentes na cadeia alifática das moléculas dos HA. Também são mostrados estudos realizados com os isômeros o, m, e p-xileno e n e iso-propil benzeno, permitindo, nestes casos, verificar a influência da posição do substituinte e da estrutura da cadeia alifática na miscibilidade deste sistema. Os diagramas foram obtidos a partir de medidas visuais de turbidez (ponto de névoa) para as diferentes soluções poliméricas. Neste trabalho procuramos discutir os aspectos entálpicos e entrópicos que levam à separação de fases. O modelo de Flory-Huggins para soluções poliméricas foi utilizado para determinar os parâmetros de interação PEG- HA / Abstract: This work is concerned with the liquid-liquid phase equilibrium shown by a system composed of poly(ethylene glycol) [PEG] and aromatic hydrocarbons [AH]. The diagrams were obtained by cloud point titration. Studies were carried out using o, m, p-xylene isomers and normal and iso-propyl benzene isomers, in order to verify the influence of the substituent position and of the aliphatic chain structure on the miscibility of the system. The phase diagrams obtained are of the UCST (upper critical solution temperature) class. The miscibility is strongly dependent on PEG molar weight and on the number of CH2 units of the aliphatic chain. The Flory-Huggins model for polymeric solutions was employed to determine the PEG-AH interaction parameters. The enthalpic and entropic contribution which lead to phase separation are discussed / Mestrado / Físico-Química / Mestre em Química

Orientador: Maria Helena Andrade Santana / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-11T22:25:32Z (GMT). No. of bitstreams: 1 Oliveira_LucianaLimade_M.pdf: 17691359 bytes, checksum: 5472876c66ca62d739abfabe1813f0a0 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho, lipossomas compostos de lecitina de ovo comercial e do tensoativo octaoxietilenoglicol-8-lauril éster (PEG-8L) foram preparados, caracterizados e estudados quanto aos aspectos de incorporação do PEG-8L, sua transição de formas, elasticidade e reologia em membranas de nanoporos. Lipossomas convencionais (sem o PEG-8L) foram usados como controle. A cafeína concentrada, extraída de sementes de guaraná, foi incorporada com eficiência de 11,0%; 41,9% e 39,9%, para os lipossomas convencionais e elásticos com 25% e 40% de PEG-8L, respectivamente. A cinética de incorporação do PEG-8L nos lipossomas, sua reologia e transição de formas foram caracterizadas através de medidas de diâmetro médio, distribuição de tamanhos, teor de fosfato, morfologia, e tensão superficial das dispersões. A reologia foi estudada em membranas de nanoporos, sintéticas e constituída de pele de orelha de porco dermatomizada. O diâmetro médio e distribuição de tamanhos foram monitorados ao longo de 24 horas para avaliação da estabilidade dos lipossomas. Os resultados mostraram a incorporação de PEG-8L, quantificada em 20,4% e 15,4% para as proporções molares iniciais lipídio: PEG-8L 75:25 e 60:40 respectivamente. A reologia de lipossomas elásticos através de membranas de nanoporos apresentou comportamento linear entre vazão e queda de pressão, na faixa de 10 a 18 atm, com permeabilidade efetiva dependente da concentração e deformação dos lipossomas. Um modelo reológico de membrana para lipossomas convencionais foi modificado para contemplar o escoamento de lipossomas elásticos e discutida a sua aplicação. A tensão superficial, deformação e imagens dos lipossomas contendo 40% de PEG-8L após a permeação, sugerem que a elasticidade e manutenção da sua integridade são devidos à compactação das cadeias de PEG-8L na sua superfície. Esses resultados contribuem para o entendimento dos mecanismos de permeação de lipossomas através da pele e para o desenvolvimento de formulações lipossomais para o transporte transdérmico de bioativos. / Abstract: In this work, liposomes prepared with comercial egg lecithin and octaoxyethylenelaurate-ester (PEG-8L) were characterized and studied in respect to PEG-8L incorporation, shape transitions, elasticity and rheology in nanopores membranes. Conventional liposomes (without PEG-8L) were used as control. The concentrated caffeine, extracted of guarana seeds, was incorporated with efficiency of 11,0%, 41,9% e 39,9%, for conventional and elastic liposomes with 25% and 40% of PEG-8L, respectively. The kinetic of PEG-8L incorporation in liposomes, its rheology and shape transitions were characterized through average diameter measurements, sizes distribution, phosphate concentration and surface tension of dispersions. The rheology was studied in synthetic nanoporous membranes and dermatomized ear pig skin. Average diameter and sistribution wre monitored during 24 hours for evaluation of liposomes stability. The results show PEG-8L incorporation in 20,4% and 15,4% for initial molar ratios lipid:PEG-8L 75:25 and 60:40. The rheology of elastic liposome across nanoporous membranes shows linear behavior between flow and pressure drop, in the range of 2,5 to 20 atm, with effect permeability dependent of liposome concentration and deformation. The rheological model of membranes for conventional liposomes was modified to contemplate the elastic liposome flow and to discuss its application. The surface tension, deformation and electron micrographs of elastic liposome with 40% of PEG-8L after permeation, suggested that the elasticity and its integrity maintenance were due to PEG-8L chains packing at its surface. This results contribute for knowledge of liposomes permeation mechanisms across skin and development of liposome formulation for drug transdermal transport. / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química

In pharmaceutical development cell cultures are used as in vitro models to evaluate the function of drug candidates. In such research it is vital to have models that resemble the in vivo environment to get reliable results. In 3D models with hydrogels ECM like scaffolds are supporting the cells in a more in vivo like environment than flat 2D cultures. In this project PEG-peptide based hydrogels with cell binding RGD incorporated on one PEG-peptide type has been evaluated for culturing of HepG2 cells. Structure and viscoelastic properties were evaluated with techniques like circular dichroism spectroscopy, dynamic light scattering and rheology. Sterilisation impact was also evaluated for PEG-peptides. For cell culturing, observations in light microscope and evaluation with Live/Dead assay and albumin assay were performed. A few companies were interviewed regarding 3D culturing and interest in mechanically tuneable hydrogels. The HepG2 cells grows and forms spherical clusters in the 3D environment with hydrogels, percentage of RGD seems to not impact cell adhesion, growth or albumin secretion. UV irradiation was the most suitable sterilisation method for gel components. The most rigid gel combination formed had storage modulus of around 230 Pa. Mechanically tuneable hydrogels is interesting for the industry. The PEG-peptide based gels are suitable tor growing cells but too soft to closely resemble the in vivo rigidity of hepatocytes.

No description available.

Warren Buffet started an investment partnership of $100 in 1956 and has gone on to accumulate a personal net worth of over $60 billion. He started primarily as a value investor, and gradually changed over time to a strategy which uses the PEG ratio as its main tool. Peter Lynch, one of the most successful fund managers in history and had a compound annual growth rate of 29% for 13 years, was the man to first introduce the world to the PEG ratio. With such prominence, however, widespread use of previously successful strategies tend to render them ineffective due to everyone using them, and today the PEG ratio’s effectiveness as a valuation tool remains a topical debate between market commentators.This study sets out to determine if the PEG ratio adds value using JSE Main Board data from 2002 to 2012. Returns from five portfolios constructed directly from share quintiles based on PEG ratio magnitude are compared to returns of a portfolio constructed from the optimum quintile of value shares. The PEG ratio portfolio returns are examined based on 3 rebalancing period strategies, and on relative performance between the quintiles within each strategy.It is found that a 24 monthly rebalancing strategy provides superior returns to that of 3 or 12 monthly rebalancing for PEG quintiles of selected stocks. Furthermore, the lowest PEG ratio quintile in this strategy outperforms the value portfolio by a compound annual growth rate of 4.3%. The second lowest PEG ratio quintile portfolio performs slightly better to ensure that 40% of stocks selected based on the PEG ratio produced sustained superior returns to the optimum quintile value portfolio. / Dissertation (MBA)--University of Pretoria, 2012. / Gordon Institute of Business Science (GIBS) / unrestricted

För att förhindra transfusionsreaktioner utförs antikroppsidentifieringar vid misstanke om att en patient bildat förvärvade antikroppar. Förvärvade antikroppar bildas efter att en individ blivit immuniserad, genom en tidigare transfusion eller vid graviditet.Rh-systemet är ett av de kliniskt viktigaste blodgruppssystemen man tar hänsyn till vid transfusion. De viktigaste blodgrupperna inom detta system är D, c, C, e och E. Den metod som främst används vid antikroppsidentifieringar är indirekt antiglobulintest (IAT), men ibland behöver denna kompletteras med ytterligare metoder, såsom papain-gelteknik eller polyetylenglykol-IAT (PEG-IAT). Papain verkar genom att spjälka bort sialinsyrainnehållande grupper på erytrocytens yta medan PEG är en vattenlöslig polymer som konkurrerar bort vattenmolekyler. Detta gör att Z-potentialen minskar och chansen för antigen-antikroppsreaktion ökar. Syftet med studien var att studera detektionen av erytrocytantikroppar inom Rh-systemet med PEG-IAT. För att undersöka metodens prestanda jämfördes PEG-IAT med resultat från antikroppsidentifieringar som utfördes med IAT och papain-gelteknik.  Under studien genomfördes antikroppsidentifieringar på 34 avidentifierade plasmaprover med metoderna IAT, papain-gelteknik och PEG-IAT. Detta resulterade i att antikropparna D, c, C, e, E detekterades som förväntat för de flesta proverna.  PEG-IAT hittade även ytterligare antikroppar i två av proverna. Vid en jämförelse mellan de olika metoderna detekterade PEG-IAT flest antikroppar följt av IAT och papain-gelteknik. Det finns även en signifikant skillnad i reaktionsstyrka mellan de olika metoderna för en testerytrocyt som är heterozygot för samtliga testade antigen i Rh-systemet.  Slutsatsen med studien är att PEG-IAT visar lovande resultat men behöver testas mot fler kliniskt viktiga antikroppar innan det kan implementeras i verksamheten.

PEGylation has been used for decades to enhance the pharmacokinetic properties of protein therapeutics. This method has been effective at increasing the serum half-life of these drugs, but the mechanism of how it does this is unclear. Chapter 1 is an introduction to the methods of PEGylation. In chapter 2 we show that the effect of PEGylation on the conformational stability of the WW domain differs based on amino acid linker and conjugation site. We show that all positions in the WW domain that were tested can be stabilized by at least one amino acid linker. The rate of proteolysis is proportional to the degree of conformational stability. Chapter 3 shows that PEG-based desolvation can increase the strength of the interaction between two salt bridge residues, though the effect of structural context is unclear. A crystal structure shows that PEG occupies the space between the PEGylation site and the salt bridge, displacing water. In Chapter 4 we discuss the effect that PEGylation has on the interaction strength of a solvent exposed hydrophobic patch. When the c Log P of the hydrophobic patch increases, PEG increases the conformational stability of the WW domain more dramatically. Chapter 5 is about the effect of PEG based desolvation on the strength of an NH-π hydrogen bond in the WW domain between Trp11 and Asn26. When Trp11 is mutated to Phe, Tyr and naphthylalanine (Nal), the melting temperatures correlate with the calculated interaction energies between the sidechain arene of the hydrogen bond acceptor and formamide. When Asn26 is PEGylated in the presence of each of these amino acids, the effect that PEG has on the conformational stability of the WW domain correlates with the melting temperature of the nonPEGylated variants, the calculated interaction energies, the arene molecular polarizability, and the arene molar volume.

Adenosine triphosphate (ATP) is the major carrier of chemical energy in cells. The diffusion of ATP in hydrogels, which have a structural resemblance to the natural extracellular matrix, is therefore of great importance to understand many biological processes. In continuation of our recent studies of ATP diffusion in poly(ethylene glycol) diacrylate (PEG-DA) hydrogels by pulsed field gradient nuclear magnetic resonance (PFG-NMR), we present precise diffusion measurements of ATP in aqueous solutions of PEG-DA polymers, which are not cross-linked to a three-dimensional network. The dependence of the ATP diffusion on the polymer volume fraction in the hydrogels, φ, was found to be consistent with the predictions of a modified obstruction model or the free volume theory in combination with the sieving behavior of the polymer chains. The present measurements of ATP diffusion in aqueous solutions of the polymers revealed that the diffusion coefficient is determined by φ only, regardless of whether the polymers are cross-linked or not. These results seem to be inconsistent with the free volume model, according to which voids are formed by a statistical redistribution of surrounding molecules, which is expected to occur more frequently in the case of not cross-linked polymers. The present results indicate that ATP diffusion takes place only in the aqueous regions of the systems, with the volume fraction of the polymers, including a solvating water layer, being blocked for the ATP molecules. The solvating water layer increases the effective volume of the polymers by 66%. This modified obstruction model is most appropriate to correctly describe the ATP diffusion in PEG-DA hydrogels.

Thesis (M. Pharm. (Pharmaceutics)) -- University of Limpopo, 2019 / Various approaches have been developed to retain dosage forms in the gastrointestinal tract. One of the commonly used approaches is the use of microspheres. Due to their intrinsic low density and small size, they are distributed throughout the gastrointestinal tract which improves drug absorption thus improving bioavailability. Ranitidine hydrochloride, an antiulcer drug is poorly absorbed from the lower gastrointestinal tract and has a short half-life of 2.5-3 hours. The aim of this study was to formulate and evaluate gastroretentive microspheres of ranitidine hydrochloride in order to extend gastric retention in the upper gastrointestinal tract, which may result in enhanced absorption and thus improved bioavailability. Pre-formulation studies were conducted to develop and validate the analytical method to identify and quantify ranitidine hydrochloride; to select the suitable polymers for further formulation development and; to determine the compatibility of the chosen polymers with ranitidine hydrochloride. The analytical method was validated and found to be sensitive, linear, precise and accurate. Preliminary formulations lead to the selection of ethyl cellulose and PEG 4000 as polymers and solvent evaporation as the method of manufacture. Compatibility studies were determined by DSC/TGA, FTIR and short-term accelerated studies and no incompatibilities were observed. Two prototype formulations of the preliminary formulations F24 and F26 were manufactured comprised of varying drug: polymer concentration. The microspheres were evaluated for morphology, particle size, flow properties, percentage yield, buoyancy and in vitro drug release. Both formulations resulted in spherical microspheres with good flow properties, high yield and buoyancy studies revealed that the microspheres would float immediately upon contact with the dissolution media and floating would continue for more than 8 hours. In vitro drug release studies revealed that polymer concentration greatly affected drug release. Dissolution kinetic studies revealed that formulation F24 and v F26 were best described by the Korsmeyer-Peppas and Higuchi kinetic models respectively. Formulation F26 was considered the best formulation, which comprised of a drug: PEG 4000 ratio of 1:2 w/w, as it yielded better in better drug encapsulation, better buoyancy results and had complete drug release.