Chemical Engineering / Kimya Mühendisliği

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Now showing 1 - 10 of 29
  • Article
    Citation - WoS: 8
    Citation - Scopus: 11
    The Effect of Protein Bsa on the Stability of Lipophilic Drug (docetaxel)-Loaded Polymeric Micelles
    (Elsevier, 2021) Polat, Hürriyet; Çevik Eren, Merve; Polat, Mehmet
    Polymeric micelles are promising delivery vehicles for improving the efficacy of anticancer drugs and reducing their side effects. However, considering the binding ability of serum albumin, the possible interaction of micelles with the native plasma components in the bloodstream raises serious questions on micellar stability. The stability of barren or drug-loaded copolymeric micelles was investigated systematically in distilled water (DW) and simulated body fluid (SBF) solutions in the presence of a model protein. The copolymer was a Pluronic® series triblock copolymer (P-123), the drug was strongly lipophilic docetaxel (DOC) and the protein was Bovine Serum Albumin (BSA). The effect of such factors as BSA and DOC concentrations and the aging of the micellar solutions was studied. Both the barren and drug-loaded micelles were quite stable in blank DW and SBF solutions for long times up to 10 days. They lost integrity and showed no inclination to re-assemble when the BSA concentration reached a critical value, which was very close to the plasma Human Serum Albumin (HSA) concentration. The presence of DOC in the micellar cores could not prevent disintegration. The results illustrate clearly that ensuring the stability of polymeric micelles in blood plasma should be an important design factor in their use as drug carriers.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Investigating the Effects of Ultrasonic Energy on the Flotation Behavior of Pyrite and Galena Minerals
    (Oficyna Wydawnicza Politechniki Wroclawsjiej, 2020) Horasan, Ümit; Tanrıverdi, Mehmet; Çicek, Tayfun; Polat, Mehmet
    Although pyrite is one of the more abundant minerals of the earth crust, it has low economic value. When it reports to the concentrate during flotation along with the valuable minerals, it decreases the grade of the valuable minerals and leads to an increase in smelting costs. Numerous modifications have been suggested in the literature to increase the selective recovery of pyrite containing base metal-sulfide ores. The use of ultrasonic applications is one such method. In this study, the effect of the ultrasonic application on the flotation behavior of galena and pyrite mineral was investigated through systematic Hallimond Tube experiments. In the initial phase of the experiments, the optimum flotation conditions (particle size, pH, amount of air, and amount of reagent) were determined for the two minerals. Subsequent experiments were carried out under these optimums to distinguish the effect of the ultrasonic application. The influence of how the ultrasonic application was applied (i.e. before and during the conditioning stage or before the re-flotation of the concentrate) was also studied. It was observed that the ultrasonic application had a strong activating influence if it was administered before or during the conditioning stage. The effect was similar to whether the minerals were floated individually or from their mixtures. However, when it was applied to a flotation concentrate before re-flotation, it selectively displayed a depressant action for the pyrite to the extent that no depressants were needed. The results conclusively showed that the ultrasonic application could drastically improve the selectivity of the complex ores.
  • Conference Object
    Solution of the Non-Linear Poisson Boltzmann Theory for the General Case of Dissimilar Double Layers
    (2006) Polat, Mehmet
    Calculation of the surface potentials, surface charges or electrostatic pressure for interacting colloidal particles is exceedingly important in mineral processing, environmental engineering, ceramic sciences, etc. Such calculations require solving the non-linear Poisson-Boltzmann theory at each plate separation. Though approximate analytical solutions of this theory are available for simplified cases, a general, but compact analytical solution is yet to be developed. A solution with no restrictions on surface potentials or charges is developed in this paper. The expressions developed are straightforward and require as input only the surface potentials at infinite separations.
  • Book Part
    Citation - Scopus: 6
    Recent Advances in Chitosan-Based Systems for Delivery of Anticancer Drugs
    (Springer, 2020) Polat, Mehmet; Polat, Hürriyet
    Problems in transporting drug molecules to tumor sites in required dose or constitution lead to low efficacy and significant side effects. Shielding the drug molecules in micelles, liposomes, or nanoparticles is a major line of investigation to improve chemotherapeutic treatment. Though compatibility for proper envelopment of the drug and timely release at the tumor site are required of such a carrier, protecting its own physicochemical and morphological integrity during transport is another precondition. Because of its superior polymerization capability, biocompatibility, pH dependence, and charging characteristics, chitosan has been in the forefront of potential drug carriers. Numerous synthesis routes for chitosan-based nanocarriers have been suggested to the extent that a search of the literature published since 2000 with the keywords “novel + nano + chitosan” in the title results in 527 articles, indicating the bewildering quality and quantity of the new information. This review was carried out not only to peruse this large amount of work on chitosan-based anticancer drug delivery but also to extract manageable patterns from numerous synthesis routes. The main conclusion is that the synthesis methods suggested in literature can be combined into two main routes, and the degree of hydrophobicity of the drug determines which route should be followed. © Springer Nature Singapore Pte Ltd. 2019.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 15
    Analysis of Dilution Induced Disintegration of Micellar Drug Carriers in the Presence of Inter and Intra Micellar Species
    (Elsevier, 2020) Polat, Hürriyet; Kutluay, Gülistan; Polat, Mehmet
    Micelles of self-assembling polymeric surfactant molecules are promising nanoscopic carriers for lipophilic and toxic drugs, genes, and imaging molecules. Though it is a must for successful transport, ensuring micelle integrity is a challenge during intravenous injection where micelles must endure abrupt dilutional effects and encounters with native molecules. Therefore, direct observational evidence of how micelles behave during dilution is valuable in manipulating the designs of these carriers for a succesful drug delivery. Morphology and stability of the barren and a drug-loaded (lipophilic probucol) micelles of a polymeric surfactant (Pluronic® P123) were monitored during systematic re-dilution in distilled water and simulated body fluid in the presence of a model protein (bovine serum albumin). It was observed through surface tension, dynamic light scattering, laser velocimetry, transmission scanning and transmission electron microscopy, and atomic force microscopy analyses that the micelles disintegrated to various degrees in all cases upon dilution. The results indicate that dilution effects must be taken into account in designing micellar drug carriers. The assistance of some other means of protection such as encapsulation should be considered for ensuring micelle integrity within the bloodstream. © 2020 Elsevier B.V.
  • Article
    Citation - WoS: 16
    Citation - Scopus: 19
    Designing of Spherical Chitosan Nano-Shells With Micellar Cores for Solvation and Safeguarded Delivery of Strongly Lipophilic Drugs
    (Elsevier Ltd., 2017) Cihan, Esra; Polat, Mehmet; Polat, Hürriyet
    Chitosan is a very effective biopolymer for drug delivery purposes due to its biocompatibility, positive charge and exceptionally pH sensitive degradability behavior in an aqueous medium. Nevertheless, its inability for dissolving lipophilic drug active material and the difficulties in controlling the size and shape of the synthesized particles in nanometer range are critical drawbacks in its effective use. In this study, a synthesis procedure which addresses both issues simultaneously is presented. The procedure is based on initial dissolution of lipophilic drug molecules within the hydrophobic cores of the micelles of a bio-compatible block-copolymer by ionic gelation and subsequent formation of a chitosan shell by polymerization around the micellar structures. Well-formed, hollow and perfectly spherical chitosan particles (nano-shells) in the 30–300 nm size range could be successfully manufactured. Characterization by STEM, TEM, AFM, FTIR and DLS, DLS-LDV techniques showed clearly that the drug was successfully incorporated into the chitosan structure. It was demonstrated that the particles enveloped the micelle(s) of a Pluronic copolymer (P-123) whose hydrophobic cores contained a strongly hydrophobic drug Probucol. The chitosan nano-shells are expected to act as an agent protecting the integrity of the drug-loaded micelles in the body fluid while providing a pH sensitive release medium. The drug uptake by the chitosan particles was very high. A very sharp increase in the amount of the drug released with a slight change in the acidity of the medium was an indication of the potential of the manufactured chitosan nano-shells as pH sensitive, target specific delivery vehicles for drug release.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 15
    Ancillary Effects of Surfactants on Filtration of Low Molecular Weight Contaminants Through Cellulose Nitrate Membrane Filters
    (Elsevier Ltd., 2016) Olcay, Aybike Nil; Polat, Mehmet; Polat, Hürriyet
    Removal of contaminants with low molecular weight (<800 Dalton) requires the use of advanced separation techniques such as ultrafiltration (UF) or micellar enhanced ultrafiltration (MEUF). However, surface active agents invariably co-exist in waste waters along with these contaminants or they may be added intentionally as part of the separation process as in the case of MEUF. Though it is quite likely that both the filter medium and the contaminants would interact with the surfactant molecules or their micelles, there is not sufficient emphasis in the literature on the concomitant aspects of such interactions.The ancillary effects created by anionic (sodium dodecyl sulfate, SDS), cationic (hexadecyltrimethyl ammonium bromide, CTAB) and non-ionic (ethoxylated octylphenol, TX-100) surfactants on the mechanism and efficiency of the filtration process were investigated in this study. Methylene blue (MB) and cellulose nitrate membrane (CNM) filters were employed as model retentate and the separation medium. A combination of surface tension, contact angle and charge measurements demonstrated that the addition of surfactants had a remarkable effect on the filtration outcome. The effect depended on both the type and concentration of the surfactant and was manifested mainly through the creation of MB-surfactant entities which acted differently than the MB alone; but more importantly, through the interactions of the surfactant molecules/micelles and the MB-surfactant pairs with the separation membrane.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 26
    Coal Fly Ash as a Potential Fixation Reagent for Radioactive Wastes
    (Elsevier Ltd., 2015) Lieberman, Roy Nir; Green, Uri; Segev, Giora; Polat, Mehmet; Mastai, Yitzhak; Cohen, Haim
    Israel produces ∼1.3 Mt/year of fly ash (FA), a byproduct of its coal-fired power plants. Due to increasing environmental regulations, these imported coals are processed to reduce the sulfur concentration (∼0.6%). These processing methods result in a material that has an enriched alkali/alkali earth component with pozzolanic and basic properties (pH > 10.5). FAs are utilized worldwide, mainly as a cement additive for the construction industry. Recently, it was demonstrated that Class F FA can act as an excellent fixation reagent for acidic wastes from the phosphate or the oil regeneration industries. In the current work the potential utilization of Class F FAs as fixation reagents for low-activity radioactive waste from the nuclear industry was examined. Aqueous solutions containing radionuclide simulants: cesium (Cs+), strontium, (Sr2+), and cerium (Ce3+, Ce4+) were used as case studies with promising results. It is suggested that the primary fixation mechanism involves the aluminate/silicate anions at the FA surface. A novel experimental fixation approach utilizing the formation of carbonates is demonstrated and a new interaction mechanism is suggested based on the electrostatic interactions of the positively charged fine precipitates with the negatively charged FA surface. © 2015 Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Determination of Electrostatic Potential Distribution by Atomic Force Microscopy (afm) on Model Silica and Alumina Surfaces in Aqueous Electrolyte Solutions
    (Elsevier Ltd., 2014) Yelken Özek, Gülnihal; Polat, Mehmet
    AFM was employed as a physicochemical probe to determine the electrostatic potential distribution quantitatively on selected ideal oxide surfaces (quartz 0 0 0 1 and sapphire 0 0 0 1) in aqueous media. The force of interaction between a silicon nitride tip and the oxide surface was measured at a given point under well-defined solution conditions. Relevant theories were used to isolate the electrostatic component from the total force of interaction which was then employed to estimate the surface potential at that point. Repeating the procedure on selected locations generated a potential map of the surface. Comparison of these potentials with those obtained from independent electrokinetic measurements confirmed the validity of the approach. © 2014 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 57
    Citation - Scopus: 69
    Leaching Behavior of Selected Trace Elements in Coal Fly Ash Samples From Yenikoy Coal-Fired Power Plants
    (Elsevier Ltd., 2012) Akar, Gül; Polat, Mehmet; Galecki, Greg; Üner, İpekoğlu
    Short-term leaching test results of alkaline fly ash from Yenikoy coal-fired power plant were reported in this paper. ASTM D-3987-85 and TCLP-1311 test methods were applied to determine leaching behavior of selected elements namely, Fe, Ca, Cu, Co, Cd, Mn, Ni, Pb Zn, and Cr (VI) at different particle size fractions and test conditions. Chemical, mineralogical and morphological characterizations of ash samples were also performed using chemical, XRD and SEM-EDS analysis methods. The results showed that CaO dominates in the Yenikoy fly ash sample which directly affects the mobility of trace elements by determining the pH of the leaching medium. Higher mobility values of Cd, Co Cu, Pb, Ni and Zn elements were observed for TCLP-1311 procedure. The concentration of these elements in leachates showed a tendency to increase by decreasing particle size. Overall results suggested that the amount of the selected elements in the final leachates of both tests was lower than the limit values of landfill regulations except Cr (VI).