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Applications in controlled release and delivery calls for a good understanding of molecular transport within the carrier material and the dominating release mechanisms. It is clear that a better understanding of hindered transport and diffusion of guest molecules is important when developing new porous materials, e.g., surfactant templated silica spheres, for biotechnological applications. Confocal laser scanning microscopy was used to quantify the bulk release and intraparticle transport of small charged fluorescent dyes, and fluorescently-tagged neutral dextran, from mesoporous silica spheres. The time dependent release and the concentration profiles within the spheres have been used to analyze the release mechanisms using appropriate models. While the small, non-adsorbing anionic dye is released following a simple diffusion driven process, the concentration of the cationic dye varies radially within the spheres after loading. The release of the cationic dye is controlled by diffusion after an initial period of rapid release, which could be due to a significant fraction of the cationic dye that remains permanently attached to the negatively charged walls of the mesoporous silica spheres. The diffusion of dextran and the resulting flat concentration profiles could be related to the complex structural feature of the cylindrical pores close to the surface, and a possible conformational change of the dextran with the concentration. The stability and leaching of a catalytic enzyme, lipase, immobilized in hydrophobilized mesoporous support has also been quantified. Colloidal monodisperse mesoporous silica spheres were synthesized and transmission electron microscopy showed that the inner pore structure display a radially extending pores. The mesoporous spheres were used as solid supports for a lipid membrane incorporated with a multi-subunit redox-driven proton pump, which was shown to remain functional. / Synthesis, functionalisation and controlled release of mesoporous materials

<p>This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated.</p><p>The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm^-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored.</p><p>Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding.</p> / QC20100608

Most metals and alloys in the presence of oxygen and moisture will instantaneously react and form a thin (2-5 nm) surface oxide layer. For further reaction to occur, oxygen ions and/or metal cations often diffuse through the already formed oxide layer. The corrosion resistance of a metal in aggressive environments at high temperatures depends on the properties of the surface oxide scale. Zirconium-based alloys represent the main structural materials used in water-cooled nuclear reactors. For these materials, the formation of a thin, adherent oxide scale with long-term stability in high temperature water/steam under irradiation conditions, is crucial. In this thesis, the transport of oxygen and hydrogen through Zr-based oxide scales at relevant temperatures for the nuclear industry is investigated using isotopic gas mixtures and isotope-monitoring techniques such as Gas Phase Analysis and Secondary Ion Mass Spectrometry. Porosity development in the oxide scales generates easy diffusion pathways for molecules across the oxide layer during oxidation. A considerable contribution of molecular oxygen to total oxygen transport in zirconia has been observed at temperatures up to 800°C. A novel method for evaluation of the gas diffusion, gas concentration and effective pore size of oxide scales is presented in this thesis. Effective pore sizes in the nanometer range were found for pretransition oxides on Zircaloy-2. A mechanism for densification of oxide scales by obtaining a better balance between inward oxygen and outward metal transport is suggested. Outward Zr transport can be influenced by the presence of hydrogen in the oxide and/or metal substrate. Inward oxygen transport can be promoted by oxygen dissociating elements such as Fe-containing second phase particles. The results suggest furthermore that a proper choice of the second-phase particles composition and size distribution can lead to the formation of dense oxides, which are characterized by low oxygen and hydrogen uptake rates during oxidation. Hydrogen uptake in Zr-based materials during oxidation in high temperature water/steam can generate degradation due to the formation of brittle hydrides in the metal substrate. A promising method for the suppression of hydrogen uptake has been developed and is presented in this thesis. / QC 20100629

This master thesis deals with a durability of concrete, which has become the centre of the interests of international scientific insitutes during the last years. The resistence of reinforced concrete depends on the covercrete which the aggresive liquids and gases penetrate through from the environment to reinforcement. According to the ability of the covercrete to penetrate degradative species is possible to tell the durability of concrete constructions. In experimental part we look for the actual state of covercrete, ordinary and high strength, by combination of various experiments. We can find here the test´s results of water and gas permeability and absorbability and sorption of concrete which complete the permeability tests. In final part the impact of different concrete types on durability of reinforced concrete is discussed.

<p dir="ltr">Biopharmaceuticals, such as insulin, monoclonal antibodies, growth hormones, and vaccines, have emerged as a major class of therapeutic molecules. Subcutaneous administration of biotherapeutics is a convenient drug delivery method that is less invasive, requires shorter clinic times, improves patient compliance, and reduces cost to the healthcare system compared to intravenous administration. The mass transport of a therapeutic injected into the subcutaneous tissue is dictated by physiochemical properties of the molecule such as size and electrostatic charge. The bioavailability and efficacy of the therapeutic formulation depend on efficient transport of the molecule from the injection site to lymphatic or blood vessels. The injected biotherapeutic needs to traverse complex structures of the subcutis and the extracellular matrix (ECM) before it arrives at the uptake site. In vitro transport screening platforms provide insights into the effects of tissue and therapeutic properties on macromolecular transport through biological barriers.</p><p dir="ltr">In this work, we develop an in vitro Transwell macromolecular recovery platform, an economical and high-throughput method that can be used to systematically evaluate effects of ECM components on mass transport properties of macromolecules. In Chapters 2-3, we engineer subcutaneous tissue models based on collagen type I ((Col I), the most abundant fibrillar protein in the subcutaneous ECM) and hyaluronic acid ((HA), an anionic and highly viscous polysaccharide). In Chapter 2, we optimize protocols to reproducibly fabricate Col I and combined Col I and HA (ColHA) hydrogels. In Chapter 3, we establish a workflow to characterize collagen material from different sources (animal sources, different vendors, and between batches of identical material) since inherent variabilities can occur.</p><p dir="ltr">Next, we develop and optimize a high throughput Transwell platform, and we screen the transport of macromolecules, which are representative of current therapeutics used in subcutaneous injections. We demonstrate that macromolecular transport within Col type I (Col I), blended collagen I and II (Col I/II), blended Col I and III (Col I/III), and combined Col I and HA hydrogels (ColHA) hydrogels is inversely related to the hydrodynamic radius of the diffusing macromolecules. Blending col I/II and I/III gels results in altered fibril morphologies (smaller fibrils), which decrease mass recovery rates. Increasing HA concentration within the Col I hydrogels decreases macromolecular recovery. This decrease is mainly a consequence of increased viscosity within the matrix. Recovery rates of large molecules such as immunoglobulin G (IgG), a molecule similar in size to therapeutic antibodies, were highly sensitive to HA concentration in col hydrogels. Smaller molecules, such as myoglobin and lysozyme, that are similar in size to insulin experience electrostatic effects as HA concentration increases within col gels. Recovery of macromolecules in an HA solution was a function of both electrostatic and steric interactions. The results from these studies were highly reproducible and highlighted the robustness of the optimized assay.</p><p dir="ltr">Our results thus demonstrate that the Transwell platform can be utilized for systematic evaluation of therapeutic transport as a function of molecular characteristics. The results presented can inform desirable physiochemical properties for efficient biotherapeutic transport within the subcutaneous tissue. </p><p dir="ltr">In the last main portion of the thesis, we work with elastin, another biologically derived material. In this portion, we developed an optimized method for expression and purification of elastin-like polypeptide proteins. We then present a method to chemically alter the material to introduce underwater adhesive properties to the material.</p>