Nanopores have been shown to be a useful analytical tool for single molecule detection. They have been used to study the composition of DNA and other molecules of interest. These pores are usually α-hemolysin which is a toxin from Staphylococcus aureus or more recently nanoscale synthetic solid state pores. Now we are beginning to look at other molecules or proteins by sending them into the nanopores and measuring a characteristic partial current blockade. In this thesis we look at polyethylene glycol (PEG) as it enters and blocks current through a single alpha hemolysin pore. We report the effects of ionic strength, PEG size, and applied voltage on the depth and duration of the current blockades. We also apply autocorrelation analysis on the arrival times of PEG molecules to the pore see if we can identify if the PEG is translocating through the pore or escaping from the same side it enters. This suggests a new approach to current blockade analysis.

A colonoscopia é atualmente o padrão ouro para investigação da mucosa dos cólons, reto e íleo terminal. Para sua realização, há necessidade de uso de soluções para limpeza do cólon que, em geral, são mal toleradas pelos pacientes. Os objetivos do presente estudo foram comparar duas soluções de preparo intestinal para colonoscopia, quanto à efetividade, tolerabilidade, aceitabilidade e segurança em pacientes que se submeteriam a colonoscopia eletivamente, no Centro de Diagnóstico em Gastroenterologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Trata-se de estudo unicêntrico, prospectivo, com alocação aleatória dos pacientes. Cem pacientes pareados por sexo e idade foram randomizados em dois grupos. O grupo I recebeu bisacodil mais 1 litro de Polietilenoglicol (PEG) na véspera e 1 litro no dia do exame. O grupo II recebeu bisacodil na véspera e 1 litro de manitol 10% no dia do exame. A mesma dieta foi orientada nos dois grupos. A qualidade do preparo foi graduada através das escalas de Boston e Ottawa. A tolerabilidade e aceitabilidade foram aferidas por questionários previamente estudados. Quanto à segurança, foram ava liadas: variação de sinais vitais antes e após o preparo e complicações. Noventa e seis pacientes (96%) completaram o estudo. Não se observou diferença na qualidade do preparo entre os grupos(p = 0,059). Quanto à tolerabilidade, o grupo I (PEG) apresentou frequência significativamente menor de náusea, vômito, dor abdominal e distensão abdominal (p < 0,05). A aceitabilidade foi significativamente melhor com o grupo I (PEG) (p < 0,05). Em relação à segurança, o grupo I (PEG) apresentou-se mais seguro. No presente estudo, podemos concluir que ambos os preparos são semelhantes em eficácia (p > 0,05) e a solução de PEG apresentou melhor tolerabilidade, aceitabilidade e segurança em comparação ao preparo com manitol (p < 0,05). / Colonoscopy is currently the gold standard to examine the colon, the rectum, and the terminal ileum. To perform a colonoscopy, is necessary to use solutions to clean the colon that are generally poorly tolerated by the patients. The study aims to compare the effectiveness, tolerability, acceptability and safety of two solutions used for intestinal preparation for elective colonoscopy examination in the Diagnosis Center Of Hospital das Clinicas, Faculty of Medicine, University of São Paulo. It is a Prospective study carried out in a single center, with random allocation of the patients. One hundred patients that were paired based on sex and age were randomized into two groups. Group I received bisacodyl plus 1 liter of polyethylene glycol (PEG) the night before and 1 liter on the day of the exam. Group II received bisacodyl the night before and 1 liter of a 10% mannitol solution on the day of the exam. The patients diet was the same for both groups. The quality of the preparation was graded based on the Boston and Ottawa scales. Tolerability and acceptability were measured using previously validated questionnaires. In terms of safety, variations in vital signs before and after the preparation were recorded, as well as any complications. Ninety-six patients (96%) completed the study. No difference was observed in the quality of the preparation between the two preparation methods (p = 0,059). As for tolerability, group II (the mannitol preparation group) presented a significantly higher frequency of nausea, vomiting, abdominal pain and abdominal distension (p < 0,05). Acceptability was significantly better in group I (p < 0,05). The PEG solution was also shown to be safer than mannitol. Based on the present study, the following conclusions can be made: 1) Both methods of preparation had similar efficiencies (p > 0,05); 2) PEG method showed higher tolerability, acceptability and safety compared to the mannitol method (p < 0,05).

No description available.

Thesis (M.Ch.E.)--University of Delaware, 2006. / Principal faculty advisor: Eric M. Furst, Dept. of Chemical Engineering. Includes bibliographical references.

Because engineered tissue constructs are inherently limited by their lack of microvascularization, which is essential to provide oxygen for cell survival, this thesis presents rationally designed materials and cell culture techniques capable of supporting functional tubule formation and stabilization. Combining a synthetic scaffold material with cells and their cell-secreted signals instigated tubule formation throughout the scaffold. Poly(ethylene glycol) (PEG) based hydrogels, biocompatible polymers which resist protein adsorption and subsequent nonspecific cellular adhesion, were modified to induce desired cell characteristics. Human umbilical vein endothelial cells were used as a reproducible and readily available cell type. Several tubule-stabilization signals, including platelet derived growth factor-BB (PDGF-BB) and ephrinA1, were covalently immobilized via conjugation to PEG to enable prolonged bioactive signaling and controlled local delivery. All hydrogels were further tested in a mouse cornea micropocket angiogenesis assay, a naturally avascular tissue for easy imaging in a reproducible and quantifiable assay. Hydrogels containing soluble growth factors induced vessel formation in the hydrogel, and the resulting vessel morphology was modulated using different growth factor concentrations. Immobilized PDGF-BB led to tubule formation in two dimensions, three dimensions, and in the mouse cornea while immobilized ephrinA1 stimulated secretion of extracellular matrix proteins laminin and collagen IV to stabilize the newly formed tubules. Finally, a co-culture of endothelial and pericyte cells encapsulated into hydrogels formed tubules that anastomosed to the host vasculature and contained red blood cells. PEG-based hydrogels represent a promising technique to induce microvascular formation in engineered constructs, leading to stable and functional vessel formation using covalently immobilized growth factors and encapsulated cells. These materials can be used for replacement of damaged or diseased tissues as the current supply of cadaveric donations cannot meet the demand of tissues for the 110,000 people awaiting an organ in the US.

In recent years, biodegradable polymeric systems have gained importance for design of surgical devices, artificial organs, drug delivery systems with different routes of administration, carriers of immobilized enzymes and cells, biosensors, ocular inserts, and materials for orthopedic applications. Polysaccharide-based polymers represent a major class of biomaterials, which includes agarose, alginate, dextran, and chitosan. Chitosan has found many biomedical applications, including tissue engineering, owing to its biocompatibility, low toxicity, and degradation in the body, which has opened up avenues for modulating drug release in vivo in the treatment of various diseases. These chitosan-based delivery systems range from microparticles to nanoparticles and from gels to films. In this study, chitosan (CH) and chitosan-polyethylene glycol (CH-PEG) microspheres with different compositions were prepared by oil/water emulsion method and crosslinked with gluteraldehyde. Some microspheres were loaded with a model chemotherapeutic drug, methotrexate (MTX). SEM, particle size and in vitro release analysis were performed. In vitro drug release studies showed that the release of MTX from CH-PEG microspheres was faster compared to CH microspheres. In the second part, CH-PEG microspheres were conjugated with a monoclonal antibody which is immunoglobulin G (IgG). The cytotoxicity efficiencies of entrapped drug were determined by using MCF-7 and MCF-7/MDA-MB breast cancer cell lines. In the third part, CHF-PEG films with the same compositions as in microspheres were prepared by solvent casting method. IR, DSC, mechanical and surface analysis were performed. The mechanical properties of films were improved by the presence of proper amount of PEG but higher amounts of PEG caused the deteriotion in the properties.

Abstract The polymer electrolytes (ion conducting polymers) consist of macromolecules (usually in the form of polyethereal units) that are doped with alkali mental salts. The polymer electrolytes are being used in Li-polymer buttery. It is suggested that conductivity in these systems takes place through two distinct events. The first is associated with the charge migration of ions between coordination sites in the host material, and the second is that the conductivity is generally observed to rise with increasing flexibility of the polymer chains. Rayleigh-Brillouin scattering spectra of molecular liquids will provide mechanical relaxation information in the frequency range from 10^8 to 10^11 Hz. We have carried out the Brillouin scattering study of PEG400/LiCl mixtures to probe its elastic properties. The change in the flexibility of polymer chains at different temperatures, the fraction of free ion, and their interactions with polymer all effect the Brillouin spectrum and the present work suggests the usefulness of this technique as an useful tool to probe the various interactions in polymer electrolytes.

Traumatic neuronal injury inevitably causes plasmalemmal damage, and sometimes leads to axonal severance. For any eukaryotic cell to survive following traumatic injury, the plasmalemma must be repaired (sealed). Plasmalemmal sealing occurs via a Ca²⁺-dependent accumulation of vesicles or other membranous structures that form a plug at the damage site. Using uniquely identified and damaged rat hippocampal B104 cells that extend neurites with axonal properties, or rat sciatic nerves, plasmalemmal sealing is assessed by exclusion of an extracellular dye from each damaged B104 cell, or sciatic nerves ex vivo. B104 cells with neurites transected nearer (<50 [micrometres]) to the soma seal at a lower frequency and slower rate compared to cells with neurites transected farther (>50 [micrometres]) from the soma. Sealing in B104 cells is enhanced by 1) increased [cAMP], 2) increased PKA activity, 3) increased Epac activity, 4) H₂O₂ and 5) Poly-ethylene glycol (PEG). Sealing is decreased by 1) PKA inhibition, 2), Botulinum toxins A, B, E, 3) Tetanus toxin 4), NEM, 5) Brefeldin A, 6) nPKC inhibition, 7) DTT, 8) Melatonin and 9) Methylene Blue. Substances (NEM, Bref A, PKI, db-cAMP, PEG) that affect plasmalemmal sealing in B104 cells in vitro have similar effects on plasmalemmal sealing in rat sciatic nerves ex vivo. Based on data from co-application of enhancers and inhibitors of sealing, I propose a plasmalemmal sealing model having four partly redundant, parallel pathways mediated by 1) PKA, 2) Epac, 3) cytosolic oxidation and 4) nPKCs. The identification and confirmation of these pathways may provide novel clinical targets for repairing and/or recovery from traumatic injury. The fusogenic compound PEG rapidly repairs axonal continuity of severed axons, potentially by rejoining severed proximal and distal axons. PEG-fusion is influenced by plasmalemmal sealing, since unsealed axons are easier to PEG fuse. I demonstrate that PEG restores morphological continuity, and improves behavioral recovery following crush-severance to sciatic nerves in rats in vivo. Co-application of Mel or MB prior to PEG application further improves PEG fusion (as measured by electrophysiology) and behavioral recovery following crush-severance in vivo. These PEG data may provide novel clinical techniques for rapidly repairing axonal severance. / text

Acute injury of major epithelial organ systems (kidney, liver, lung, etc.) is collectively a principal cause of death worldwide. Regenerative medicine promises to meet these human health challenges by harnessing intrinsic cellular processes to repair or replace damaged tissues. Epithelial morphogenesis is a hard-wired, multicellular differentiation program that dynamically integrates microenvironmental cues to coordinate cell fate processes including adhesion, migration, proliferation, and polarization. Thus, epithelial morphogenesis is an instructive mode of tissue assembly, maintenance, and repair. Three-dimensional epithelial cell cultures in natural basement membrane (BM) extracts produce hollow, spherical cyst structures and have indicated that the BM provides the critical cell adhesion ligands to facilitate cell survival, stimulate proliferation, and promote polarization and lumen formation. However, the utility of natural BMs for detailed studies is generally limited by lot-to-lot variations, uncontrolled cell adhesive interactions, or growth factor contamination. The goal of this thesis was to engineer bioartificial extracellular matrices (ECM) that would support and modulate epithelial cyst morphogenesis. We have engineered hydrogels, based on a multi-arm maleimide-terminated poly (ethylene glycol) (PEG-4MAL), that present cell adhesive molecules and enzymatic degradation substrates and promote polarized epithelial cyst differentiation in vitro. To investigate the influence of matrix physical and biochemical signals on cyst morphogenesis, we independently varied the polymer weight percentage (wt%), the density of a cell adhesion ligand (RGD), and crosslink degradation rates of the hydrogels. Then, we evaluated functional outcomes including Madin-Darby canine kidney (MDCK II) epithelial cell survival, proliferation, cyst polarization, and lumen formation. We found that cell proliferation, but not cell survival, was sensitive to the polymer wt%, which is related to elastic modulus and crosslink density. This result defined a working range of PEG-4MAL concentration (3.5% - 4.5%) that promotes robust proliferation. Analysis of mature cysts indicated that 4.0% and 4.5% gels produced cysts resembling those typically grown in type I collagen gels while 3.5% gels produced cysts with higher incidence of inverted polarity and multiple lumens. Perturbation of matrix degradability using a slow-degrading crosslink peptide or matrix metalloproteinase inhibitors showed that the rate of matrix degradation exerts major influence on cyst growth in PEG-4MAL gels. We employed 4.0% PEG-4MAL hydrogels with RGD ligand density ranging over 0 – 2000 uM to discover that (1) lumen formation was eliminated in the absence of RGD, (2) extent of lumen formation increased with increasing RGD concentration, and (3) cyst polarity was inverted below a threshold of integrin binding to RGD. Together, these results show that the biochemical and physical properties of the matrix, particularly integrin binding and matrix degradability, effectively modulate establishment of apico-basal polarity and lumen phenotypes in MDCK II epithelial cyst structures. Furthermore, these studies validate PEG-4MAL hydrogels as a powerful culture platform to enable detailed investigation of matrix-directed modulation of epithelial morphogenesis.

A microwave assisted methodology was developed to modify Merrifield resins (1-2% cross-linked containing 1.0-3.5 mmol Cl-/g) with different nominal molecular weights PEG (200-1000). The synthesis was also carried out by conventional heating to assess the differences between the two procedures. The most efficient synthesis was achieved by using microwave and by using PEG with molecular weight 200 and MR 2% crosslinked containing 1.25 mmol Cl -/g. The structural elucidation was carried out using Fourier transform infrared (FTIR) spectroscopy and elemental analyses. Upon pyrolsis-GC/MS analysis of the PEGylated MR, the PEG showed the tendency to undergo thermal degradation by the loss of a smaller PEG fragments. This observed degradation of PEG was less prominent during microwave assisted synthesis compared to conventional heating, in addition to faster reaction rates and higher yields. As expected, the PEGylated MR showed improved swelling properties in polar solvents. The chemical reactivity of the PEGylated Merrifield resin was confirmed by the esterification with pyruvic acid and by the substitution of hydroxyl group using thionyl chloride. In addition, the PEGylated MR was converted into (1) polymer-supported acid/base or redox indicator by the attachment of a blue organic dye - 2,6-dichloroindophenol (DCIP) through a nucleophilic substitution reaction and (2) beta-cyclodextrin trap, a water insoluble inclusion-complex, by immobilization of beta-cyclodextrin through cross-linking with 1,6-hexamethylene diisocyanate reagent.