Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Kalsiyum Bazlı Çift Karbonatların Kimyasal Sentezi için Yöntem Geliştirilme(2025) Hajıyev, Gasham; Özdemir, EkremBu çalışmanın amacı, düşük sıcaklık ve basınç koşullarında kalsiyum bazlı çift karbonatların kimyasal sentez yöntemlerini geliştirmektir. Sentezlenmesi hedeflenen çift karbonatlar BaCa(CO₃)₂, CoCa(CO₃)₂, SrCa(CO₃)₂ ve MgCa(CO₃)₂'dir. Sentez için doğrudan karıştırma ve kesikli reaktör olmak üzere iki yöntem kullanılmıştır. Doğrudan karıştırma yönteminde M²⁺/Ca²⁺ oranları 0.5, 1.0 ve 2.0 olarak belirlenmiştir. Kesikli reaktörde ise 0, 3, 5 ve 10 mM Ca(OH)2 çözeltileri kullanılmıştır. Kristal yapı ve bileşimler X-ışını kırınımı (XRD), taramalı elektron mikroskobu (SEM) ve enerji saçılım spektroskopisi (EDX) ile analiz edilmiştir. İlgili mineral fazlarının doygunluk indeksi değerleri PHREEQC kullanılarak hesaplanırken, sulu türlerin dağılımını pH'ın bir fonksiyonu olarak görselleştirmek için Medusa & Hydra kullanılmıştır. Ba²⁺ ve Sr²⁺ iyonları için çift karbonatlar elde edilebilmiş, ancak Co²⁺ ve Mg²⁺ iyonları için çift karbonatlar elde edilememiştir. Kalsiyum bazlı çift karbonatların sentezinde iyonik yarıçapın belirleyici faktörlerden biri olduğu sonucuna varılmıştır. Elde edilen partiküller, endüstriyel kullanım için alternatif malzemeler açısından önem taşımaktadırMaster Thesis Effect of Ions on Particle Size and Morphology in Calcium Carbonate (caco3) Crystallization(01. Izmir Institute of Technology, 2021) Osman Adam Osman, Ahmed; Özdemir, EkremThe particle sizes of calcium carbonate (CaCO3) produced by the chemical crystallization method were reported to be almost always larger than 3 µm. Our recent studies in our lab has shown that the nano-CaCO3 particles can be obtained when calcium hydroxide (Ca(OH)2) solution was used as a stabilizer. In this study, an experimental setup was developed to crystalize CaCO3 from sodium carbonate (Na2CO3) and calcium chloride (CaCl2) solutions in a plug flow reactor (PFR) with a retention time of 9 seconds and added into a stabilizing solution. The CaCO3 particles of about 30% of vaterite and 70% of calcite were produced with a size larger than 13 µm in the PFR tubular reactor. The influence of cations and anions on the particle size and morphology were investigated. The hydroxide form of sodium (Na+), potassium (K+), calcium (Ca++), ve barium (Ba++) were used as the stabilizer solution containing cations. Totally calcite particles at sizes larger than 2 μm were produced with homogenous size distribution in the presence of Na+ and K+ ions. Nano-calcite particles were produced in solution containing Ca++ ions. A new crystalline form, Barytocalcite (BaCa(CO3)2), and whitherite (BaCO3) particles were produced in solution containing Ba++ ions. The sodium form sulfate (SO4=), nitrate (NO3-), carbonate (CO3=) and bisphosphate (HPO4=) were used as the stabilizer solution containing anions. The size and morphology of vaterite and calcite particles were seen almost the same and did not change with the particles synthesized in the PFR tubular reactor in the presence of SO4=, NO3-, and CO3= ions. A different form of particles such as monetite (CaHPO4) and hydroxyapatite (Ca5(PO4)3OH) were synthesized in the presence of HPO4= ion in the stabilizer solution. These formations clearly indicated that the CaCO3 particles synthesized in the PFR tubular reactor were dissolved and recrystallized in the stabilization solutions. It was successfully demonstrated that the synthesis of CaCO3 in nano sizes with the chemical method was achieved and devised a novel technique for the continuous production of nano-CaCO3. It was demonstrated that nano-calcite particles of about 350 nm were produced by the chemical method not previously reported in the literature.Master Thesis Increasing Doxorubicin (dox) Release From Liposomes(Izmir Institute of Technology, 2019) Hanoğlu, Berçem Dilan; Özdemir, Ekrem; Altun, Zekiye SultanCancer is the second most common cause of death in the world and its incidence is increasing day by day. Doxorubicin (DOX) is an anthracycline group drug frequently used in many cancer treatments including breast cancer. However, free DOX has many harmful side effects and need to be encapsulated into nanocarrier such as liposomes. Although liposomal DOX has many advantages over its free form, liposomal DOX has undesirable side effects such as hand and foot syndrome. In this thesis, it was aimed to develop a more effective liposomal DOX delivery and release systems. Liposomes were prepared with alkaline solutions containing tris, sodium carbonate, ammonium chloride, and ammonium sulfate. DOX loading into liposomes and the percentage of release from liposomes were examined. A loading efficiency of about 80% was achieved, while the release was found to be below 13% at room temperature. The release of DOX was found to be enhanced from liposomes in the presence of ammonia (NH3), whose content was dependent on pH. Temperature was also found an important parameter and enhances DOX release at higher temperatures than the phase transition temperature of the lipid. A two-component liposomal system was proposed where ammonia (NH3) would be released from one liposome and enhance the DOX release from other liposomes. It was found that temperature, pH, and ammonia (NH3) concentration affected DOX release from liposomes. As a result, DOX was successfully loaded into liposomes and ready to study their effect on breast cancer cells.Master Thesis Design and Preparation of Alkali Liposomes for Drug Delivery(Izmir Institute of Technology, 2019) Güven, Hatice; Özdemir, Ekrem; Altun, Zekiye SultanCancer is one of the deadliest diseases among other illnesses as an uncontrolled cell division. Liposomal technology has commonly been used in cancer therapy. Chemotherapeutical drugs, genetic materials, different imaging agents can be carried with liposomes. They are preferred by several important characteristics that selective passive targeting of tumors, increased stability and therapeutic index (reducing toxicity) via encapsulation and increased circulation life times with size adjustments. One of the indicator in cell cycle is intracellular pH. The aim of this study is to produce PEGylated alkali liposomes to provide cellular uptake in cancer cells and prevent cell division by changing of intracellular pH. Combination of liposomal technology and alkaline therapy in cancer cells may lead to the development of therapeutic strategies without using any drug to overcome chemoresistance and cell proliferation. For this purpose, alkali liposomes containing sodium carbonate (Na2CO3) solution were prepared and tested their effects on 4T1 breast cancer cell lines in vitro. The cell viabilities were evaluated using trypan blue and WST-1 methods. Pictures were taken for cancer cells to differentiate live and dead cells under different alkali liposome conditions for 5 days. It was found that cell medium containing alkali liposomes up to 3% didn’t affect cell growth. However, cell medium containing alkali liposomes greater than 7% significantly affected the 4T1 breast cancer cell growth and decreased the cell viability to about 40%. It was concluded that PEGylated alkali liposomes were prepared different concentrations to decrease or stop cell division of 4T1 breast cancer cell lines in vitro.Master Thesis Influence of Ca2+ Ions on Freshly Precipitated Caco3 Particles(Izmir Institute of Technology, 2019) Majekodunmi, Olukayode Titus; Özdemir, EkremThe objective of this study was to develop a method to synthesize CaCO3 nanoparticles from a chemical precipitation reaction under ambient and high supersaturation conditions. Equimolar CaCl2 and Na2CO3 solutions were reacted in a tubular reactor at a constant rate. The particles growth inhibition was attempted by dispersing the reaction mixture in a continuously stirred Ca(OH)2 solution. This procedure separated the nucleation phase from the growth inhibition process, and was conducted without pH and composition control. The possibility of impeding the CaCO3 particles overgrowth was explored at different precipitants and Ca(OH)2 concentrations. Their effects on the particles morphology, colloidal stability and specific surface area were studied. Although rapidlysettling particles were produced at precipitants concentration of 100 mM, colloidally stable CaCO3 nanoparticles were obtained at concentrations ≤75 mM. Additive Ca2+ ions, provided by the Ca(OH)2 solutions, inhibited the crystals growth by adsorbing irreversibly on the growth sites. The synthesized particles were as much as 95% smaller than those obtained when pure H2O was used instead. Ca2+ ions concentration and amount of precipitated particles were observed to be important factors for monodispersity and high growth inhibition. Monodisperse and stable nanoparticles were synthesized at low reactants concentration and/or precipitates volume. Vaterite phase was observed in the particles obtained when pure H2O was used as the growth-inhibiting solution. However, the presence of additive Ca2+ ions effected the crystallization of pure calcite, regardless of Ca(OH)2 or precipitants concentration, reaction mixtures retention time in the tubular reactor, volume of precipitates, and the growth-inhibiting solutions initial pH.Master Thesis Production and Characterization of Heat Insulating Panels(Izmir Institute of Technology, 2016) Yörük, Osman Giray; Özdemir, Ekrem; Özdemir, EkremHollow nano calcite particles were used as a core material in vacuum insulation panels (VIPs) and compared it with the fumed silica generally used in VIPs as the core material. Zinc-Tin-oxide (ZTO), ZnSnOx, was coated on the polyamide/polyethylene (PA/PE) polymeric films and used as the barrier material in VIPs to prohibit moisture and air transport. A fluidized bed filtration system was developed to separate the produced hollow nano particles from its slurry. ZnSnOx coating on the PA/PE polymeric films were optimized with respect to film rotation rate and oxygen content during film coating. Water permeation rate was measured as 8.32 gday-1m-2 for the commercial Aluminum-PET (Al-PET). The water permeation rate was measured as 1.15 gday-1m-2 for the 90 μm of PA/PE films coated with ZTO in 500 rpm of film rotation rate and 30 sccm Ar + 7.5 sccm O2 feed rate. It was shown that the produced ZTO coated PA/PE films had better barrier properties compared to the commercial Al-PET. The thermal conductivity was measured as 8.63 mWm-1K-1 for 3 wt% hollow nano calcite in 87 wt% of fumed silica compared to that of 9.9 mWm-1K-1 for fumed silica only. It was shown that when 3 wt% of hollow nano calcite were mixed with fumed silica as the core material, better thermal conductivity values were obtained.Master Thesis Development of Drug-Loaded Microbubbles for In-Vitro Applications in Cell Biology(Izmir Institute of Technology, 2017) Coşkun, Sema; Özdemir, Ekrem; Sultan Altun, ZekiyeDoxorubicin (DOX) is one of the drugs for cancer therapy. When DOX is used in solution, it affects not only the cancer cells but also the healthy cells. In order to eliminate possible side effects, DOX was encapsulated within liposomes and applied for the cancer therapy. Because the circulation time for liposomes is longer in the body, they accumulate in capillaries, especially at the finger tips and at the toe of the foot called the hand-and-foot syndrome. Here, we proposed to couple the liposomes containing DOX with the microbubbles as the ultrasound contrast agent and deliver the drug to the area of interest. Therefore, DOX was loaded within the liposomes and characterized for their DOX contents. The DOX containing liposomes were conjugated with microbubbles through the avidin-biotin chemistry. It was found that the loaded- DOX content within the liposomes was Langmuir-type. The loaded DOX content increased at lower DOX concentrations and leveled off at higher DOX concentrations. The Langmuir constants can be used in designing DOX loading experiments. The DOX containing liposomes were coupled with the microbubbles and found an optimum of 7.0 for the avidin/biotin mole ratio on the microbubbles. At the optimum avidin/biotin ratio, the conjugated lipo-DOX amount was 3×10-8 μg-DOX/MB. It was concluded that the DOX molecules can be loaded within the liposomes and easily conjugated with the microbubbles and employed in cancer treatments.Master Thesis Synthesis of Needle-Like and Rod-Like Nano Baco3 Particles(Izmir Institute of Technology, 2016) Kahyaoğlu, Tuğçe Nefise; Özdemir, EkremBarium carbonate (BaCO3) has been widely used in soft and heavy industries such as ferrite magnets, solid oxide fuel cells, optical glass manufacturing, coatings, and polymeric composite materials as well as ceramic and brick industries. Using BaCO3 in nano sizes will improve some of the physical properties of materials such as tensile strength, opacity, and thermal resistance. Production of BaCO3 by chemical method requires extensive crystallization times and higher temperatures. Production of BaCO3 by carbonation method usually yields particles with some agglomeration. In a study, conducted by our group funded by The Scientific and Technological Research Council (TUBITAK), a method was developed to synthesize hollow nano Calcium Carbonate (CaCO3) particles. It was aimed to apply the developed method, which is unique in its kind, to produce nano BaCO3 particles in different morphologies. Parameters such as effect of barium hydroxide (Ba(OH)2) concentration, CO2 flow rate, length in reaction chamber, and stirring rate were studied. Conductivity and pH values of the solution were monitored during crystallization. Surface morphology and crystal structure of the produced BaCO3 particles were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. It was shown that rod-like BaCO3 particles produced in nano sizes with almost homogeneous size distributions. The rod-like BaCO3 particles had a diameter from 100 to 400 nm and an aspect ratio of about from 3 to 10. The produced rod-like nano BaCO3 were all in orthorhombic phase of BaCO3 called as Witherite.Master Thesis Enztmatic Co2 Sequestration by Carbonic Anhydrase(Izmir Institute of Technology, 2008) Kanbar, Bora; Özdemir, EkremCarbonic Anhydrase (CA) was immobilized within Polyurethane (PU) Foam and characterized for CO2 sequestration purposes. The catalytic activities for the free and immobilized CA were estimated by using p-Nitrophenyl Acetate (p-NPA) as the substrate. The activities were estimated in tris buffer containing 10% Acetonitrile.Because, the p-NPA is only soluble up to 4mM in aqueous phase. Lineweaver-Burk relationship was employed to estimate the Michaelis-Menten kinetic parameters for the free and immobilized CA. The kcat, KM, and kcat/KM values for free enzyme were found to be 1.21s-1, 12.2mM, and 148.1M-1s-1, respectively. The KM value for immobilized BCA was estimated to be 9.59mM in tris buffer (50mM, pH.7.5), in the presence of 10% acetonitrile at the same conditions. The immobilized CA was stable and did not loose any activity over seven consecutive washings and activity tests. In addition, while the free CA lost its activity in 45 days stored at 4oC in fridge, the immobilized CA was stable and did not loose any activity over 45 day period. The optimum temperature for the immobilized BCA was found to be between 35oC and 45oC. No activity was observed for the immobilized CA at 60oC. Thermal deactivation energies for the free and immobilized CA were found to be 29kcal/mol and 86kcal/mol, respectively. The immobilized CA was employed in CaCO3 precipitation. It was found that the CaCO3 particles were less than 100nm and more evenly dispersed. It was concluded that the immobilized CA could be used in CO2 sequestration.Master Thesis Biocatalytic Performance of Carbonic Anhydrase Immobilized Within Polyurethane Foam in Water-Miscible Organic Solvents(Izmir Institute of Technology, 2013) Ayaz, İlyas Umur; Özdemir, EkremThe effects of water-miscible organic solvents such as acetonitrile and ethanol on the activity of free and immobilized bovine carbonic anhydrase (CA) were investigated. The CA was covalently immobilized within polyurethane (PU) foam by cross-linking. Although PU foam holds water almost 12 times of its weight, it was found that adsorption isotherm of moisture on PU foam was a Type III indicating that water and PU foam were non-interacting to each other. The activities for the free and immobilized CA were estimated using para-nitrophenyl acetate (p-NPA) as the substrate. The enzyme activities were estimated in increasing volume percents of organic solvent in Tris buffer (10-90%). p-NP, which is one of the products of the hydrolysis reaction of p-NPA, was characterized in the presence of organic solvents and it was observed that its aborptivities were decreased significantly as the organic solvent percentages were increased indicating that p-NP and the water-miscible organic solvent form a complex through mostly a hydrogen bonding. The free CA showed decreasing activity up to critical percentages of organic solvent (40-60%), and then exhibited an increasing activity. The immobilized CA showed decreasing activity in acetonitrile at percentages up to 50%, and then lost its total activity at higher acetonitrile percentages, however, the immobilized CA exhibited no activity in ethanol at percentages above 10%. Stability tests showed that the immobilized CA was dramatically inactivated in the organic solvents at percentages above 30% in shorter times. It was concluded that the water-miscible organic solvents severely perturbed the active site of the enzyme, thus denaturating the enzyme.