Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis The Effect of Surface Modification of Biomaterials on the Cellular Interactions(Izmir Institute of Technology, 2008) Özgür, Melek; Çiftçioğlu, Muhsin; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe preparation and characterization of chitosan-hydroxyapatite composite scaffolds and protein adsorption chracteristics of these scaffolds have been investigated in this study. The effects of different chitosan/hydroxyapatite contents of the low density composites on the protein adsorption behaviour were experimentally examined.Bradford method at 595 nm and 280 nm UV protein absorption methods were used for the determination of adsorbed amount of bovine serum albumin (BSA) and human serum protein (HSP). In this study low molecular weight chitosan and hydroxyapatite have been used for the preparation of the scaffold composites by freeze drying and SEM was used for microstructural analysis. The thermal behaviour of the composites was investigated by DSC and TGA. Composite scaffolds were prepared by using different amounts of chitosan and hydroxyapatite (HA) and six different scaffolds were prepared and coded as C100H0, C80H20, C70H30, C50H50, C30H70, and C20H80. The porous low density scaffolds had 93.5-96.3% porosity with a slight increase in density with increasing HA content. The interconnected pore network was formed from 50-250 .m relatively uniform size pores with thin pore walls. The HA particles were fully embedded in the polymer matrix in the pore walls. The TGA curves have shown that the freeze dried phase seperation induced biopolymer sturucture degrates at lower temperatures faster than the original raw polymer. The adsorptions of BSA and HSP onto composites have been studied as a function of time, protein concentration and pH. Adsorption experiments were also conducted with commercial HA powder. The adsorption kinetics experiments have indicated that protein adsorption was almost completely achieved in the first 2-3 hours with relatively high uptake values of up to 45-60 mg/g and 40-60 mg/g for 595 nm Bradford and 280 nm methods. The adsorption behaviour did not fit to the commonly known Langmuir and Freundlich isotherms. This was attributed to the swelling/degradation tendency of the freeze-dried chitosan containing scaffolds. The HSP uptake of 30 and 50 wt% HA containing composites were in the 50-60 mg/g range which was higher than other composites and the raw unprocessed chitosan.Master Thesis In Vitro Evaluation of Comb-Type Poly (ethylene Glycol) - Cell Interactions and Comparison With Linear Poly (ethylene Glycol)(Izmir Institute of Technology, 2012) Toker, Tuğba; Bulmuş Zareie, Volga; Bulmuş Zareie, Esma Volga; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aim of this study is to investigate physicochemical characteristics and in vitro cell interactions of comb-type poly(ethylene glycol) (Mn= 10 700 and Mn= 20 200 g/mol, p(PEG-A) 10K and p(PEG-A) 20K, respectively) in comparison with linear poly(ethylene glycol) (Mn= 10 000 and Mn= 20 000 g/mol, PEG 10K and PEG 20K, respectively) of equivalent molecular weight. In vitro cytotoxicity, cell uptake and intracellular distribution profile of comb-type and linear polymers were investigated using human lung adenocarcinoma epithelial cells (A549). The dynamic light scattering (DLS) analysis showed that the comb-type polymers had smaller hydrodynamic diameters (Dh) (4.5±0.3 nm - 5.9±0.3 nm) than linear PEGs (5.6±0.5 nm - 7.8 ±0.2 nm) in water and phosphate buffer solution at pH 7.4. While the Dh of p(PEG-A) 10K and 20K in RPMI 1640 and RPMI 1640 containing 10% FBS ranged between 44.4±1.8 nm and 58±5.3 nm, the Dh of PEG 10K and 20K in the same media were between 54.5±4.7 nm and 63.5±2 nm. According to the AFM analysis, PEG 10K forms supramolecular linear structures whereas p(PEG-A) 10K forms spherical structures. None of the polymers caused significant cytotoxic effect on A549 cells under the conditions tested via a cell viability assay. Cell uptake studies via flow cytometry showed that the uptake of p(PEG-A) 10K by A549 cells was significantly higher than the other polymers tested. All polymers were internalized by A549 cells via an active transport mechanism. The uptake increased with increasing polymer concentrations. None of the polymers affected the cell cycle of A549 cells under the conditions tested. Both the comb-type and linear PEGs were found to localize in the lysosomes of A549 cells.