Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Investigation of Shell Microstructure of Microbubbles for Diagnostic Ultrasound(Izmir Institute of Technology, 2013) Köse, Derya; Kılıç Özdemir, Sevgi; Kılıç Özdemir, Sevgi; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study we reported the effect of shear stress, protein adhesion, temperature, secondary interactions and gas core on microbubble stability which are the main reasons of microbubble dissolution in body. Air filled DSPC/PEG40St microbubbles were examined under shear stress. Increasing PEG40St molar ratio increased the resistivity microbubbles against shear stress. To investigate effect of emulsifier type, microbubbles were produced by mixing DSPC with DSPE-PEG1000, DSPE-PEG2000 and PEG40St at 5:5 molar ratio and PEG40St microbubbles were more stable since it provide better curvature to microbubble shell due to its shape. Shear stress experiments were also performed at different temperatures. With increasing temperature microbubbles became less stable since van der Waals interactions between shell components decreased. When microbubbles were filled with perfluorocarbon, since its solubility is lower and more hydrophobic than air, the stability of microbubbles against shear stress increased. Protein adhesion to microbubble shell was investigated by Langmuir Blodgett (LB) and Surface Plasmon Resonance techniques. Both techniques showed that, as the PEG40St molar ratio and packing density increased, protein adhesion decreased. Secondary interactions between shell components were examined via LB technique and visualized via Brewster Angle Microscopy. As third component to DSPC/PEG40St mixture, StGly, StNH2, DSPS, DSTAP was added and ternary mixtures were generally miscible. Since StGly and StNH2 has single tail, they cannot provide curvature in bubble surface. DSPS and DSTAP mixtures may be recommended drug delivery.Master Thesis Preparation and Characterization of Microbubbles for Ultrasoundimaging(Izmir Institute of Technology, 2012) Sağdıç, Emine Aysu; Kılıçç Özdemir, Sevgi; 01. Izmir Institute of TechnologyUltrasound is widely used in clinical settings for diagnosis of diseases. However, the image quality in some cases is not at desirable level because most of the tissues have similar acoustic properties to many tumors. Microbubbles administired to the systemic circulation during imaging are known to increase the quality, creating contrast with respect to the surrounding tissues. Unfortunately, current formulations of microbubbles composed of phospholipid (mainly PC) and emulsifier have been found to be unstable for ultrasound imaging. In this study, it was aimed to engineer the shell structure of microbubbles to develop more stable, targetable microbubbles and investigate their adhesion characteristics to breast cancer cells as a model system. Our results indicated that increasing content of PEG40 St in the formulation resulted in microbubbles with higher yield and stability, being optimum at 50 mole %. Incorporation of lipopolymers as emulsifier instead of PEG40St in the formulation influenced stability adversely. Addition of a phospholipid capable of secondary interactions to the formulation had improved stability and size of the microbbubles, depending on the content and type of head group of the phospholipid. Usage of less water-soluble gas in the core of new microbubbles did not have further effect on the stability, as observed with the microbubbles of the current formulation. This result may suggest that the new microbubbles’ shell is densely packed such that gas diffusion is enormously minimized/inhibited. Moreover, selected formulations developed in this study provided much more adhesion than the current formulation to the cell of interest.Master Thesis Design and Characterization of Shell Structure of Microbubbles Used in Ultrasound Imaging(Izmir Institute of Technology, 2012) Bölükçü, Elif Şeniz; Kılıç Özdemir, Sevgi; Kılıç Özdemir, Sevgi; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe main goal of the study is to redesign the microbubble (MB) shell structure and investigate the interactions between the shell components in the mixed monolayers treated as a model for MBs’ shell in order to improve the stability. To examine effects of emulsifier type (DSPC/PEG40 St, DSPC/DSPE-PEGn) and additional components (DSPC/PEG40 St/DSPG, DSPC/PEG40 St/DSPA, DSPC/PEG40 St/DSPE) on stability, molecular interactions and morphological properties, mixtures having various compositions were investigated by Langmuir Blodgett (LB) method and Atomic Force Microscope (AFM) and Brewster Angle Microscope (BAM). For DSPC/PEG40 St monolayers thermodynamically analysis indicated that the attractive forces between the components in the monolayer of 30% PEG40 St were very strong. It was observed that addition of large amount of peg-grafted phospholipids (lipopolymer) increased the attractive forces between molecules in DSPC/DSPE-PEG1000 and DSPC/DSPE-PEG350 monolayers unlike DSPC/DSPE-PEG2000 monolayers. Additionally, the use of different phospholipid as an additional component such as DSPG, DSPE and DSPA in DSPC/PEG40 St mixture signified that intermolecular forces were influenced by the monolayers’ compositions and polar headgroups differences. It was noticed that among the ternary mixtures consisting 70% DSPC, DSPC/PEG40 St/DSPE monolayers exhibited stronger molecular interaction than DSPC/PEG40 St/DSPG and DSPC/PEG40 St/DSPA monolayers while DSPC/PEG40 St/DSPA mixtures showed stronger interaction for mixtures composed of 50% PEG40 St. However, phase separations detected at some regions for these monolayers by BAM and AFM may affect the stability negatively. Therefore, thermodynamically analysis, BAM and AFM results should be evaluated together to assess potential MBs’ shell structures.