Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 69Citation - Scopus: 77Novel Zein-Based Multilayer Wound Dressing Membranes With Controlled Release of Gentamicin(John Wiley and Sons Inc., 2019) Kimna, Ceren; Tamburacı, Sedef; Tıhmınlıoğlu, FundaRecently, functional multilayer scaffolds with controlled drug release ability come into prominence for wound healing applications to mimic the layered structure of skin tissue and prevent the possible infections at the defect site. In this study, controlled antibiotic releasing zein bilayer membranes were fabricated for treatment of acute skin infections. Gentamicin loaded fibers were prepared by electrospinning on the membrane surface. Membranes were characterized with scanning electron microscope, atomic force microscopy, Fourier transform infrared spectroscopy, contact angle, mechanical analysis, swelling, degradation, and water vapor permeability studies. In vitro cytotoxicity, cell attachment, and proliferation were investigated. Cell attachment on fiber layer was observed with fluorescence imaging. Fabricated fibers showed structural similarity to the skin tissue layers with a fiber diameter range of 350-425 nm and film thickness in the range of 311-361 mu m. Mechanical properties were found compatible with the skin tissue. In addition, membranes showed antimicrobial activity against Staphylococcus aureus and Escherichia coli. The sustained release was achieved with a cumulative release of 94%. Membranes did not show any cytotoxic effect. NIH/3T3 and HS2 cell lines were proliferated on each layer mimicking the multilayer skin tissue. Hence, zein-based bilayer membrane showed promising properties to be used as a potential antimicrobial wound dressing for skin tissue regeneration. (c) 2018 Wiley Periodicals, Inc.Article Citation - WoS: 1Citation - Scopus: 1The Effect of Mass Transfer Resistance and Nonuniform Initial Solvent Concentration on Permeation Through Polymer Membranes(John Wiley and Sons Inc., 2018) Zielinski, John M.; Alsoy Altınkaya, SacideA numerical simulation model has been developed which enables one to examine the effects of surface mass transfer resistance on the evaluation of permeation (P*), diffusion (D), and solubility (S) coefficients from unsteady-state mass transfer experiments as well as the transmission rate. A complementary analytical expression has been developed which validates the numerical model and facilitates the evaluation of the concentration dependence of P*, D, and S from sequential step-change experiments, under experimental conditions when the surface mass transfer resistance can be neglected.Article Citation - WoS: 27Citation - Scopus: 37Nanofibrous Gelatine Scaffolds Integrated With Nerve Growth Factor-Loaded Alginate Microspheres for Brain Tissue Engineering(John Wiley and Sons Inc., 2018) Büyüköz, Melda; Erdal, Esra; Alsoy Altınkaya, SacideNeural regeneration research is designed in part to develop strategies for therapy after nerve damage due to injury or disease. In this study, a new gelatine-based biomimetic scaffold was fabricated for brain tissue engineering applications. A technique combining thermally induced phase separation and porogen leaching was used to create interconnected macropores and nanofibrous structure. To promote tissue regeneration processes, the scaffolds were integrated with nerve growth factor (NGF)-loaded alginate microspheres. The results showed that nanofibrous matrix could only be obtained when gelatine concentration was at least 7.5% (w/v). The scaffold with a modulus value (1.2 kPa) similar to that of brain tissue (0.5–1 kPa) was obtained by optimizing the heat treatment time, macropore size and gelatine concentration. The encapsulation efficiencies of NGF into 0.1% and 1% alginate microspheres were 85% and 100%, respectively. The release rate of NGF from the microspheres was controlled by the alginate concentration and the poly(L-lysine) coating. The immobilization of the microspheres in the scaffold reduced burst release and significantly extended the release period. The nanofibrous architecture and controlled release of NGF from the microspheres induced neurite extension of PC12 cells, demonstrating that the released NGF was in an active form. The results suggest that the scaffolds prepared in this study may have potential applications in brain tissue engineering due to topologic and mechanical properties similar to brain tissue and pore structure suitable for cell growth and differentiation.Article Effects of Reactor Pressure and Inlet Temperature on N-butane/Dimethyl Ether Oxidation and the Formation Pathways of the Aromatic Species(John Wiley and Sons Inc., 2016) Bekat, Tuğçe; İnal, FikretOxidation of n-butane/dimethyl ether (DME)/O2/Ar system was studied by chemical kinetic modeling in a tubular reactor operated adiabatically and at constant pressure. Effects of the reactor pressure on the formation of various major, minor, and trace oxidation products were investigated for two different pressures (1 and 5 atm) and at six different inlet temperature values (700, 800, 900, 1100, 1300, and 1500 K). The analysis was carried out for two different concentrations of dimethyl ether in the inlet fuel mixture (20 and 50 mol %). Higher pressure (5 atm) resulted in higher mole fractions of methane, vinylacetylene, and cyclopentadiene; and lower mole fractions of formaldehyde, acetylene, acetaldehyde, ethane, propargyl, and propane. The mole fractions of CO and CO2 were not affected considerably by the pressure change. The main formation routes of benzene were developed at two different inlet temperature values (1100 and 1300 K), and the main precursors participating in these routes were found to be propargyl, propene, and diacetylene. A skeletal mechanism was developed for the oxidation of n-butane/DME mixture from the detailed mechanism by reduction of the elementary reactions by 79%, and it was tested for accuracy by comparison with the data from the literature.Article Citation - WoS: 15Citation - Scopus: 18Preparation and Characterization of Magnesium Stearate, Cobalt Stearate, and Copper Stearate and Their Effects on Poly(vinyl Chloride) Dehydrochlorination(John Wiley and Sons Inc., 2015) Gönen, Mehmet; Egbuchunam, Theresa Obuajulu; Balköse, Devrim; İnal, Fikret; Ülkü, SemraPreparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt2), cobalt stearate (CoSt2), and copper stearate (CuSt2) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid-liquid phase transitions were observed by optical microscopy at 160oC, 159oC, and 117oC for MgSt2, CoSt2, and CuSt2, respectively. However, the melting points of MgSt2, CoSt2, and CuSt2 were determined as 115oC, 159oC, and 111oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255oC for CuSt2 and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt2. CoSt2 was effective in extending the induction time of PVC dehydrochlorination at both 140oC and 160oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt2, CoSt2, and CuSt2-containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235-244, 2015.Article Citation - WoS: 5Citation - Scopus: 5Methylene Blue Adsorption From Aqueous Solutions To Flexible Poly(vinyl Chloride) Silica Composites(John Wiley and Sons Inc., 2015) Yetgin, Senem; Ulutan, Sevgi; Balköse, DevrimMethylene blue (MB) adsorption studies were performed with poly(vinyl chloride)-(dioctyl phthalate)-silica composites, which were obtained by using plastisol-plastigel technology. The films were flexible, having elastic modulus of 1.0-1.5 GPa. Diminishing MB concentration in the aqueous phase was followed as the adsorption process advanced by using visible spectroscopy. Contributions of the individual components of the composites to adsorption were also investigated. Although the MB adsorption capacity was extensively high for silica, it was moderate for the composite, most likely owing to the occlusion of pores of silica by plasticizer to some extent. The improvement of MB adsorption capacity of the composites as the silica ratio increased was explicitly deduced from the optical microscopy photographs. The diffusion coefficients of MB through the composites were 5 × 10-13, 6 × 10-13, and 3 × 10-13 m2 s-1 with regression coefficients of 0.73, 0.89, and 0.88 for 0, 2, and 16% silica-containing composites, respectively. Because of the slow diffusion of MB in poly(vinyl chloride)-silica composites, using them as dynamic column adsorbent was not practical. However, these versatile plastics can be used as plastic labels, colored clothing, leather substitutes, antimicrobial medical devices, and laser printable surfaces.Article Citation - WoS: 35Citation - Scopus: 40Olive Leaf Extract as a Crosslinking Agent for the Preparation of Electrospun Zein Fibers(John Wiley and Sons Inc., 2015) Erdogan, I.; Demir, M.; Bayraktar, O.Incorporating active agents, reinforcing structure by crosslinking, thus changing release properties, can be listed as possible modifications in preparation methods of biopolymer fibers. This study introduces oleuropein, major component of olive leaf extract (OLE), as a natural functional crosslinker for electrospun zein fibers, owing to its antioxidant and antimicrobial properties. Incorporation of OLE causes morphological and structural changes indicated by a decrease in fiber diameter up to 27%, an increase in intensity of NH bending region due to interaction with -OH groups and observation of characteristic oleuropein bands. Extract addition also enhances thermal stability. Zein fibers without OLE is fully degraded at 600C, whereas 10% of OLE loaded zein fibers is left undegraded. Fifty percent of initial phenolic content loaded into fibers is released which indicate the effect of OLE incorporation as accumulation of oleuropein. OLE-incorporated fibers immersed in PBS are less fused than pure zein fibers, due to the crosslinking effect. © 2014 Wiley Periodicals, Inc.Article Citation - WoS: 6Citation - Scopus: 7Preparation and Characterization of Flexible Poly(vinyl Chloride) Foam Films(John Wiley and Sons Inc., 2012) Şahin, Erdem; Yaşar Mahlıçlı, Filiz; Yetgin, Senem; Balköse, DevrimIn this study, the effect of activator ZnO and heating time at 190°C on foaming, gelation, and dehydrochlorination of poly(vinyl chloride) (PVC) plastisol was investigated. For this purpose, a PVC plastisol was prepared by mixing PVC, dioctyl phthalate (DOP), azodicarbonamide (ADC), ZnO, and the heat stabilizers calcium stearate (CaSt 2) and zinc stearate(ZnSt 2). PVC plastisol films were heated for 3, 6, 12, and 24 min periods at 190°C to see the effect of heating time on the gelation and foaming processes of the PVC foam. The time of 12 min was determined to be optimum for the completion of gelation and foaming processes without thermal degradation of PVC. No foaming was observed under the same conditions for the samples without ZnO. ZnO had a significant catalytic effect on ADC decomposition, accelerating the foaming of the films. Average porosity measurement showed a consistent increase in porosity with heating time up to 76% and the average density decreased from 1.17 to 0.29 g/cm 3 on foaming. Tensile tests showed that the tensile strength and tensile strain both increased considerably up to 0.98 MPa and 207%, respectively, with heating time and the elastic modulus was seen to gradually decrease from 4.7 to 0.7 MPa with heating time. Films without ZnO had higher tensile strength since there were no pores. PVC thermomat tests showed that ZnO lowered the stability time of plastigel film with azodicarbonamide.Article Citation - WoS: 18Citation - Scopus: 21Crystallization Kinetics and Affecting Parameters on Polycaprolactone Composites With Inorganic and Organic Additives(John Wiley and Sons Inc., 2015) Cesur, Serap; Alp, Burcu; Küçükgöksel, Yelda; Kahraman, Tansel; Balköse, DevrimThe isothermal crystallization and mechanical behavior of biodegradable polycaprolactone (PCL) composites with organic (oleic acid and glycerol monooleate) and inorganic (zinc oxide, organoclay, and hydroxy apatite) additives used alone or simultaneously were investigated. The effect of all additives on the degree of crystallinity percentage (DOC%), isothermal crystallization kinetics parameters, and mechanical test results of PCL composites was studied. The PCL composite films were prepared by solvent casting by using dichloromethane as the solvent. The films were characterized by X-ray diffraction, differential scanning calorimetry (DSC), and tensile tests. DSC of the first melting and X-ray diffraction DOC% results (for composites by solvent casting) are compatible. The values by DSC of the second melting (for composites by extrusion method) are lower. Organoclay gives the highest crystallinity among the other inorganic additives used. Small amounts of inorganic additives act as a nucleating agent and increase the crystallinity; the higher amounts decrease. The organic additives act as the plasticizer. When used alone, it lowers the crystallinity, but when used with inorganic additives, it improves the dispersion of inorganic particles in the polymer matrix. The isothermal crystallization kinetics parameters by Avrami analysis showed that crystallization was controlled by nucleation and the crystals had spherical structure. The nucleation type changed between thermal and athermal nucleation. The Pukanzky model interaction parameter B indicated that the organic additives improved the dispersion of inorganic particles in the polymer matrix. Statistically significant, eight correlations (F>6) were obtained for the crystallinity, crystallization parameters, Young's modulus, and tensile strength as a function of concentration of additives.Article Citation - WoS: 48Citation - Scopus: 58Micro-Encapsulation of Ozonated Red Pepper Seed Oil With Antimicrobial Activity and Application To Nonwoven Fabric(John Wiley and Sons Inc., 2013) Özyıldız, Figen; Karagönlü, S.; Başal, Güldemet; Uzel, Ataç; Bayraktar, OğuzIn recent years, functional fabrics possessing antimicrobial activity have drawn significant interest because antibiotic resistance is becoming widespread among pathogenic micro-organisms. The aim of this study was to produce microcapsules incorporating ozonated red pepper seed oil (ORPSO) with antimicrobial properties and apply them to nonwoven fabrics to prepare functional textiles. Red pepper seed oil (RPSO) was ozonated and micro-encapsulated via a complex coacervation method using gelatin (GE) and gum arabic (GA) as wall materials. While micro-encapsulation yield and oil loading decreased with increases in the amount of surfactant, the mean particle size increased. The antimicrobial activity of the oil was tested via the disc diffusion method. The microcapsules were also tested using the agar well method. While RPSO had no effect on the test micro-organisms, the ORPSO and microcapsules containing ORPSO were found to be active against the test micro-organisms. The microcapsules were then applied to nonwoven fabric using the padding method to produce a disposable functional textile. The microcapsule-impregnated functional fabrics provided a 5 log decrease in 1 h. It is therefore possible to functionalize nonwoven fabrics to have antimicrobial activity against antibiotic-resistant micro-organisms, using microcapsules containing ORPSO.
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