Chemical Engineering / Kimya Mühendisliği
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Article Citation - WoS: 5Citation - Scopus: 5Evaluation of Liposomal and Microbubbles Mediated Delivery of Doxorubicin in Two-Dimensional (2d) and Three-Dimensional (3d) Models for Breast Cancer(Galenos Publishing House, 2021) Aydın,M.; Özdemir,E.; Altun,Z.; Kılıç,S.; Aktaş,S.Objective: Liposomal cancer treatment strategies are useful in removing the side effects that were the main concern in recent years. In this study, we prepared microbubble (MBs) conjugated with DOX-loaded liposomes (DOX-loaded MBs) and investigated their effectiveness in in vitro breast cancer cells in two dimensions (2D) and three dimensions (3D). Materials and Methods: With this aim, breast cancer cells with different features (4T1, MDA-MB231, MCF-7) were growth in 2D and 3D dimensions. The cytotoxic and cell death effects under different conditions, durations and doses were evaluated with WST-1, trypan-blue, colony counts. Apoptotic effects were investigated with flow cytometric Annexin-V-PI and immunohistochemical (Ki-67, caspase 3, 8, 9) methods. Results: After free DOX and LipoDOX were applied, the proliferation index of three cell lines reduced. Intrinsic and extrinsic apoptotic pathways were activated in both 2D and 3D models. However, this effect was observed at lower levels in the 3D model due to the difficulty of diffusion of DOX into the spheroids. Additionally, the suitability of the 3D model for breast cancer cells was supported by formation of ductus-like structures and spheroids. Cell deaths were not observed significantly with the DOX-loaded microbubbles due to rising of MBs to the surface and not reaching spheroids held in matrigel of 3D model. Conclusion: DOX and LipoDOX showed anti-proliferative and apoptosis-inducing effects in breast cancer cells. However, these effects indicated variability depending on the cell lines and 2D or 3D model types. ©Copyright 2021 by the the Turkish Federation of Breast Diseases Societies.Article Citation - WoS: 23Citation - Scopus: 29Dynamic Nature of Supercritical Co2 Adsorption on Coals(Springer Verlag, 2017) Özdemir, EkremAdsorption on non-rigid solids was shown to be a dynamic process. Excess adsorption and desorption isotherms of CO2 on eight Argonne Premium coal samples were measured at 55 °C and pressures up to 14 MPa by manometric method. The excess adsorption isotherms of CO2 on powdered coals showed almost Langmuir-like to rectilinear shape behavior at low pressures up to 9 MPa, and it increased noticeably at pressures higher than 9 MPa. There was a significant hysteresis between the excess adsorption and desorption isotherms for each rank of coals, which was related to the volumetric uncertainties occurring during the adsorption isotherm measurements. The parameters related to the adsorption capacity and micro porous characteristics of the coal were obtained at different pressure ranges by fitting the experimental data to the modified Dubinin-Astakhov (D-A) equation at the increasingly larger pressure ranges, using only the first 4 data points of the excess adsorption isotherm initially, and progressively using additional data points for the subsequent values. It was shown that the curve fit parameters vary with pressure, and therefore, concluded that the adsorption on non-rigid solids such as CO2 on coal is indeed a dynamic process. It was suggested that new adsorption isotherm equations need to be developed considering the dynamic nature of the adsorption on solid adsorbents.Article Citation - WoS: 23Citation - Scopus: 31Nano-Caco3 Synthesis by Jet Flow(Elsevier Ltd., 2017) Ülkeryıldız, Eda; Kılıç, Sevgi; Özdemir, EkremA new methodology was introduced to produce hollow nano calcite particles in homogenous size distribution without aggregation. The design consisted of a jet flow system in which the crystallization region was separated from the stabilization region. The newly produced nano CaCO3 particles of about 140 nm were removed from the crystallization region as quickly as possible into the stabilization region before aggregation or crystal growth. In the stages of crystallization, the particles started to dissolve from their edges which opened-up the pores inside the particles. At the late stages of crystallization, the open pores closed. These particles were stable in Ca(OH)2 solution and no aggregation was detected. Different particles with different morphologies can be produced by adjusting the stages in the crystallization.Article Citation - WoS: 48Citation - Scopus: 52Stability of Caco3 in Ca(oh)2 Solution(Elsevier Ltd., 2016) Kılıç, Sevgi; Toprak, Görkem; Özdemir, EkremThe effect of calcium hydroxide (Ca(OH)2) on the stability of calcium carbonate (CaCO3) particles was investigated with respect to the surface potential and particle size. Both CaCO3 and Ca(OH)2 were dissolved in ultrapure water at concentrations up to 100 mM. The solubility limits were about 18 mM for Ca(OH)2 and about 0.13 mM for CaCO3 at 23 °C in water. Dissolution of commercial CaCO3 in 10 mM of Ca(OH)2 solution and dissolution of Ca(OH)2 in 10 mM of CaCO3 slurry were also studied at similar conditions. Conductivity, pH, zeta potential, and average particle sizes were measured for each solution. The morphological characteristics of the particles were analyzed by the SEM images. It was found that the zeta potential of CaCO3 particles was greater than + 30 mV when they were placed in the Ca(OH)2 solution compared to a zeta potential value of - 10 mV in water. It was concluded that the Ca(OH)2 solution is a stabilizer for the CaCO3 particles.Article Citation - WoS: 21Citation - Scopus: 22Role of Ph on Co2 Sequestration in Coal Seams(Elsevier Ltd., 2016) Özdemir, EkremThe effect of acidic or basic pre-treatment on the adsorption capacity of CO2 on coals was investigated. Argonne Premium Pocahontas No. 3, Upper Freeport, Pittsburgh No. 8, Lewiston-Stockton, Blind Canyon, Illinois No. 6, Wyodak, and Beulah-Zap coals were washed in weak solutions of H2SO4 and NaOH to the pH values of 10, 7, and 2, after an initial washing in acidic water. Attempts to treat the Wyodak and Beulah-Zap coals were unsuccessful because the base treatment after the initial acid treatment resulted in a suspension which could be separated neither via filtration through a 45 μm filter nor centrifugation. Equilibration took several days in some cases, although the as-received coal had been ground to 150 μm. Acid washing preferentially removed Ca (calcite) and Mg. Aluminosilicate clays were not notably removed. Iron was removed in significant amounts only after base treatment, possibly after it was converted to hematite. The adsorption capacity of CO2 on the acid treated coals was higher than both the base treated and untreated coals. The difference in adsorption capacities for acid and base treated coals was related to the pore sizes and mineral matter removal from the coals, where the calculated average pore size was higher for acid treated coals than for the base treated coals. It is concluded that the pH decrease due to CO2 dissolution in cleat water is favored in coal seam sequestration, which resulted in an increase in storage capacity of coals.Article Citation - WoS: 20Citation - Scopus: 23Rice-Like Hollow Nano-Caco3 Synthesis(Elsevier Ltd., 2016) Ülkeryıldız, Eda; Kılıç, Sevgi; Özdemir, EkremWe have shown that Ca(OH)2 solution is a natural stabilizer for CaCO3 particles. We designed a CO2 bubbling crystallization reactor to produce nano-CaCO3 particles in homogenous size distribution without aggregation. In the experimental set-up, the crystallization region was separated from the stabilization region. The produced nanoparticles were removed from the crystallization region into the stabilization region before aggregation or crystal growth. It was shown that rice-like hollow nano-CaCO3 particles in about 250 nm in size were produced with almost monodispersed size distribution. The particles started to dissolve through their edges as CO2 bubbles were injected, which opened-up the pores inside the particles. At the late stages of crystallization, the open pores were closed as a result of dissolution-recrystallization of the newly synthesized CaCO3 particles. These particles were stable in Ca(OH)2 solution and no aggregation was detected. The present methodology can be used in drug encapsulation into inorganic CaCO3 particles for cancer treatment with some modifications.Article Citation - WoS: 14Citation - Scopus: 15Effect of Carbonic Anhydrase on Caco3 Crystallization in Alkaline Solution(American Chemical Society, 2016) Molva, Murat; Kılıç, Sevgi; Özdemir, EkremThe effect of bovine carbonic anhydrase (CA) on calcium carbonate (CaCO3) crystallization was investigated. A new method was developed to estimate the biocatalytic activity of CA in alkaline solution. The CA was immobilized within polyurethane (PU) foam, and compared its biocatalytic activity with the free-CA and bare-PU foam. A minireactor was created in a calcium hydroxide (Ca(OH)2) solution in order to control the CO2 transfer rate, and reproducible results were obtained. It was found that the free-CA lost its activity in less than 6 min at pH 12.5 in alkaline Ca(OH)2 solution. The CaCO3 crystallization rates for the immobilized-CA were found to be a U-shape, relatively lower at lower immobilized-CA amounts compared to those for the free-CA and bare-PU foam and higher when the amount of immobilized-CA increased. It was concluded that a higher immobilized-CA amount is required to accelerate the CaCO3 crystallization rates in Ca(OH)2 solution.Article Citation - WoS: 70Citation - Scopus: 80Modeling of Coal Bed Methane (cbm) Production and Co2 Sequestration in Coal Seams(Elsevier Ltd., 2009) Özdemir, EkremA mathematical model was developed to predict the coal bed methane (CBM) production and carbon dioxide (CO2) sequestration in a coal seam accounting for the coal seam properties. The model predictions showed that, for a CBM production and dewatering process, the pressure could be reduced from 15.17 MPa to 1.56 MPa and the gas saturation increased up to 50% in 30 years for a 5.4 × 105 m2 of coal formation. For the CO2 sequestration process, the model prediction showed that the CO2 injection rate was first reduced and then slightly recovered over 3 to 13 years of injection, which was also evidenced by the actual in seam data. The model predictions indicated that the sweeping of the water in front of the CO2 flood in the cleat porosity could be important on the loss of injectivity. Further model predictions suggested that the injection rate of CO2 could be about 11 × 103 m3 per day; the injected CO2 would reach the production well, which was separated from the injection well by 826 m, in about 30 years. During this period, about 160 × 106 m3 of CO2 could be stored within a 21.4 × 105 m2 of coal seam with a thickness of 3 m.Article Citation - WoS: 123Citation - Scopus: 134Effect of Moisture on Adsorption Isotherms and Adsorption Capacities of Co2 on Coals(American Chemical Society, 2009) Özdemir, Ekrem; Schroeder, KarlThe effect of moisture on the adsorption isotherms and adsorption capacities of CO 2 on Argonne Premium coals has been investigated. In some experiments a small hysteresis was observed between the adsorption and desorption isotherms. The hysteresis was absent or negligible for high-rank and as-received coals but was discernible for lower rank and dried coals. An equation that accounted for the volumetric changes when an adsorbate alters the structure of an adsorbent was employed to interpret the data. The best-fit solutions indicate that the coal volume decreases upon drying. The microscopic shrinkage estimated using helium expansion was greater than the shrinkage reported using the bed-height technique. The microscopic shrinkage was 5-10% for low-moisture medium and high-rank coals and up to 40% for low-rank coals having higher moisture contents. The CO 2 swelling of coals during adsorption isotherm measurements was estimated to be about the same as the shrinkage that occurred during the moisture loss. The adsorption capacity, isosteric heat of adsorption, average pore size, and surface area of the as-received (moist) and dried Argonne coals were estimated after accounting for the volume changes. The isosteric heat of adsorption of CO 2 was found to be between 23 and 25 kJ/mol for as-received coals and between 25 and 27 kJ/mol for dried coals, regardless of the rank. The degree of drying was shown to affect the adsorption capacity and the calculated surface area. For dried coals, the adsorption capacity showed the typical 'U-shape' dependence on rank whereas the as-received coals displayed a more linear dependence. A relationship is proposed to quantify the effect of moisture on the adsorption capacity. The mechanism of CO 2 adsorption on moist coals and the implications of the lower adsorption capacity of wet coals to coal seam sequestration of CO 2 are presented.Article Citation - WoS: 62Citation - Scopus: 67Thermal Stability of Carbonic Anhydrase Immobilized Within Polyurethane Foam(John Wiley and Sons Inc., 2010) Kanbar, Bora; Özdemir, EkremThermal stability of carbonic anhydrase (CA) immobilized within polyurethane (PU) foam was investigated. The catalytic activity of the enzyme was estimated by using p-nitrophenyl acetate (p-NPA) as the substrate in tris buffer containing 10% acetonitrile. The immobilized CA was stable during the repeatable washings and stability tests over 45 days stored in tris buffer at ambient conditions indicating that the CA was covalently attached to the polyurethane (PU) foam by crosslinking. The immobilized CA was found to be 98% stable below 50°C, whereas a drastic decrease was seen at temperatures between 50 and 60°C. The optimum temperature for the immobilized CA was found to be 45°C and it lost its activity completely at 60°C. Thermal deactivation energies for the free and immobilized CA were estimated to be 29 and 86 kcal/mol, respectively. The association of unfolded CA with the polymeric backbone chains of the PU foam was also addressed. It was concluded that the immobilized CA was highly stable at temperatures less than 50°C and could be used in biomimetic CO sequestration processes. © 2010 American Institute of Chemical Engineers