Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, BioengineeringSubject: search.filters.subject.Chitosan

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Now showing 1 - 4 of 4
  • Master Thesis
    Surface Modification of Chitosan Films/Meshes for Biomaterial Applications
    (Izmir Institute of Technology, 2019) Işıklı, Berçin; Tıhmınlıoğlu, Funda
    Modification of surface of biomaterials is a great interest for many years due to first contact of surface of materials with the biological fluids. This thesis aims to investigate surface modification effect on the chemical, surface wettability, protein adsorption as well biodegradability properties of dense chitosan (Ch) and asymmetric chitosan films (ACh). The surfaces of chitosan dense and asymmetric films were modified by ion implantation technique using carbon and carbon-nitrogen hybrid ions at a fluence of 1x1015 ions/cm2 and ion energy of 20kV. Chemical compositions of the film surfaces were analyzed by Fourier transform infrared spectroscopy (FTIR-ATR). Surface hydrophobicity measurements were conducted by static contact angle measurements. Protein adsorption on unmodified and modified surfaces on films was investigated as a function of time at various pH conditions. After ion implantation on chitosan films, both C and C-Nitrogen ion implantation, the surfaces become rougher and hydrophobic having moderate wettability (����� values in the range of 72-85°) and in good agreement with FTIR-ATR data findings. It was found pH dependence of the amount of protein adsorbed on the dense chitosan films as a function of time for both un-implanted and implanted films. BSA and fibrinogen were more adsorbed on the chitosan films at pH 5. The amount of BSA and fibrinogen protein adsorption was 0.97 and 1.33 gprotein/gfilm, respectively for 60 min incubation period. Protein adsorption enhanced for C and C+N2 ion implanted samples for BSA and fibrinogen, respectively due to the hydrophobic protein surface interaction effect. In vitro degradation results showed that ACh films degrade much faster (mass loss 57 %) than Ch films (40 %) due to the porous structure at the end of 3 weeks. However, the ion implanted Ch samples degraded much slower having mass loss of 30% and 17.7% for C+N2 and C implanted samples, respectively at the end of 3 weeks compared to un-implanted Ch films as 40 %. The results are in good agreement with water sorption and surface hydrophobicity of the implanted films. This study demonstrated that surface modification, as well as structure, changes the protein sorption, wettability and biodegradation properties of the chitosan films.
  • Master Thesis
    Chitosan-Plasmid Dna Nanoparticles: Cytotoxic and Cytostatic Effects on Human Cell Lines
    (Izmir Institute of Technology, 2015) Bor, Gizem; Şanlı Mohamed, Gülşah; Demir, Mustafa Muammer
    Although chitosan nanoparticles (CNs) became a promising tool for several biological and medical applications owing to their inherent biocompatibility and biodegrability, studies regarding their effects on cytotoxicity and cytostatic properties still remain insufficient. Therefore, in the present study, we decided to perform comprehensive analysis of the interactions between CNs – pKindling-Red-Mito (pDNA) and different cell line models derived from blood system and human solid tissues cancers. The resulting CNs-pDNA was investigated with regard to their physical-chemical properties, cellular uptake and transfection efficiency, cytotoxic and cytostatic properties. The nanoparticles showed high encapsulation efficiency and physical stability even after 2 days for various formulations. Moreover, high gene expression levels were observed already 96 h after transfection. CNs-pDNA treatment, despite the absence of oxidative stress induction, caused cell cycle arrest in G0/G1 phase and as consequence led to premature senescence, which turned out to be both, p21-dependent and p21-independent. Also, observed DNMT2 upregulation may suggest the activation of different pathways protecting from the resulting CNs-mediated stress. In conclusion, treatment of different cell lines with CNs-pDNA showed that their biocompatibility was limited and effects were cell type-dependent.
  • Master Thesis
    The Effect of Surface Modification of Biomaterials on the Cellular Interactions
    (Izmir Institute of Technology, 2008) Özgür, Melek; Çiftçioğlu, Muhsin
    The 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
    Production and Isolation of Fungal Chitosan by Submerged Fermentation
    (Izmir Institute of Technology, 2003) Alper, Seda; Harsa, Hayriye Şebnem
    Chitosan is the N-deacetylated derivative of chitin which is the supporting material of crustaceans and insects. Chitosan together with chitin are recommended as suitable functional materials because of their excellent biocompatibility, biodegradability, non-toxicity and adsorption properties and can be used in agriculture, biotechnology and food industry. Although chitosan is produced by chemical deacetylation of chitin molecule, it is also a natural component of cell walls of fungi belonging to Zygomycetes and can be produced by extraction from fungus cell walls. Fungi are thus the promising alternative sources of chitosan. Fungi can be manipulated to give chitosan of more consistent and desired physico-chemical properties compared to chitosan obtained from crustacean sources. In this study, Absidia spp, Aspergillus niger, Rhizopus arrhizus, Cunnighamella elegans, and Mucor rouxii were examined for biomass growth. At first, all five species were grown on synthetic medium at 28 C, 180 rpm in shake-flask incubator. Mucorrouxii which gave the maximum biomass concentration was also grown on molasses. The maximum biomass concentration of Mucor rouxii was found to be higher than that of synthetic medium. The best growth conditions obtained were 4% sucrose, 0.2% yeast extract, 1% peptone and 106 spores in 40 ml. The mycelia harvested at late exponential phase was treated with alkali to remove proteins and chitosan was extracted from cell wall by using acetic acid. The yield of extractable chitosan obtained from cell wall of Mucor rouxii was 2500 mg / l and it is almost 20 % of biomass and approximately 35 % of alkali insoluble fraction.