Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 10Citation - Scopus: 9Bi̇yomalzemelerden İ̇zole Edi̇len Staphylococcus Epidermidis Suşlarinin Yüzey Özelli̇kleri̇ni̇n Beli̇rlenmesi̇(Ankara Mikrobiyoloji Derneği, 2010) Sudağıdan, Mert; Erdem, İlker; Çavuşoğlu, Cengiz; Çiftçioğlu, MuhsinThe surface properties of bacteria play an important role on adhesion to the biomaterial surface. In this study, the surface properties of Staphylococcus epidermidis strains isolated from clinically used polymeric biomaterial surfaces were investigated on the basis of zeta potential, hydrophobicity and surface topography. A total of 10 S.epidermidis strains isolated from intravenous catheters (n= 5), endotracheal tubes (n= 3) and central venous catheters (n= 2) which were used in the patients of pulmonary Intensive Care Unit, Ege University Medical Faculty Hospital, were included to the study. Seven of those isolates were biofilm producers, inhabiting biofilm genes, 2 were non-biofilm producers, however, inhabiting biofilm genes, and 1 was non-biofilm producer, inhabiting no biofilm genes. Zeta potential analysis have been performed in 3 different buffers (phosphate-buffered saline, 1 mM potassium chloride and 1 mM potassium phosphate buffer) and at different pH values (pH 4.1-8.2), in order to simulate in vivo environment of the biomaterials. Hydrophobicities of the strains were examined by bacterial adhesion to hydrocarbon (BATH) test and the surface topography of biofilms and slime layers were visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. It was found that all strains have negative zeta potential values (surface charge) in all buffers and pH values. In hydrophobicity analysis, the highest value (86%) was determined for non-biofilm forming S.epidermidis strain YT-169b (endotracheal tube isolate) and the lowest hydrophobicity (2.5%) was determined for biofilm forming S.epidermidis strain YT-212 (central venous catheter isolate). Biofilm and slime layers of the strains were imaginated by AFM and SEM analysis in ?m scale. SEM analysis showed that bacteria highly adhered to rough surfaces on biomaterial surfaces and the produced slime layers covered the surface of bacteria. In conclusion, elucidating the surface properties of opportunistic pathogens in different physiologic buffers will give important clues for the production of non-adhesive materials and antibacterial surfaces for those bacteria. It was also estimated that designing the surface of the biomaterial to have negative surface charge in the body and to be as smooth as possible will hamper biofilm formation.Article Citation - Scopus: 1Synthesis of Stable Nano Calcite(Turkish Chemical Society, 2018) Kılıç, SevgiSynthesis of calcium carbonate (CaCO3) particles in the presence of a population of carbon dioxide (CO2) bubbles was investigated in the calcium hydroxide (Ca(OH)2) solution, which is a natural stabilizer for CaCO3. Possible chemical speciation reactions were presented for an inorganic synthesis of hollow nano-CaCO3 particles. In the progress of CaCO3 synthesis, some of the particles started to dissolve at their edges and turned into hollow nano-CaCO3 particles. Some of the pores closed at the end of crystallization as a result of dissolution-recrystallization mechanism. Hollow nano-CaCO3 particles with sizes of about 300 nm were synthesized with a narrow size distribution. It was concluded that the hollow nano-CaCO3 particles could be advantageous due to lower weights and higher surface areas.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: 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: 6Citation - Scopus: 7Influence of Calcination Temperature on Microstructure and Surface Charge of Membrane Top Layers Composed of Zirconia Nanoparticles(Springer Verlag, 2015) Erdem, İlker; Çiftçioğlu, MuhsinThe purpose of the research is to investigate the changes in microstructure and physicochemical characteristics, mainly surface charge (i.e. zeta potential) of zirconia membrane top layer during calcination. Zirconia is one of the most commonly preferred materials for ceramic membrane top layers due to its superior durability. The physicochemical properties of the top layer composed of submicron / nano particles is necessary not only for Donnan exclusion but also for dynamics of membrane fouling. In the present research the possibility of preparation of zirconia top layers with varying surface charge with changing calcination temperature was shown and a correlation between phase transformation and surface charge was determined.