Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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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.
Toz Kömürlerin Zenginleştirilmesinde Yağ Aglomerasyonu Yöntemi ve Yenilikler
(İstanbul Üniversitesi, 2010) Kılınç Aksay, Ece; Arslan, Vedat; Polat, Hürriyet
Kömürün üretim teknolojisindeki gelişmeler, kömür üretimi sürecinde oluşan ince boyutlu (toz) kömürün miktarını arttırmaktadır. Bu tür toz kömürlerin zenginleştirilerek değerlendirilmesi, hem madencilik maliyetini azaltmakta, hem de önemli bir çevre problemini ortadan kaldırmaktadır. Ayrıca eneıjiye olan gereksinim, her geçen gün teknolojinin ilerlemesiyle doğru orantılı olarak artmaktadır. Dolayısıyla, çevre problemi yaratan sınırlı enerji kaynaklarının, çevre dostu yöntemlerle değerlendirilmesi gerekmektedir. Yağ aglomerasyonu yöntemi, bu yöntemlerden biridir. Özellikle çok ince boyutlu kömür tanelerinin kazanılmasında flotasyona alternatif bir yöntemdir. Bu yöntem, yüksek devirli karıştırıcılar kullanılarak, kömür tanelerinin yağ tarafından ıslatılması ve birbirlerine bağlanarak iri taneler haline getirilmesi prensibine dayanır. Yağın, kömür-su sistemine verilmeden önce, su içerisinde gerek mekanik karıştırma ile gerekse çeşitli yüzey aktif reaktiflerin kullanımı ile emülsiye edilmesi (dağıtılması) veya kömür yüzeyinin yine çeşitli yüzey aktif reaktiflerle hava/yağ sever özellik kazandırılması, yöntemin başarısını hem teknik hem de ekonomik yönden arttırmaktadır. Yağ aglomerasyonu yöntemindeki bu yenilikler, günümüzde linyit gibi düşük kaliteli kömürlerin bile, bu yöntem ile başarıyla zenginleştirilebilmesine olanak sağlamaktadır. Bu makalede, yağ aglomerasyonu yönteminin temel prensipleri, yöntemi etkileyen parametreler ve farklı tip kömürler için yöntemin uygulamasına yönelik araştırmalar detaylı olarak açıklanmış, yöntem ile ilgili yenilikler tartışılmıştır.
Solunabilir Tozun Su Spreyleri Kullanılarak Bastırılmasında Son Gelişmeler
(2000) Polat, Hürriyet; Polat, Mehmet; Gürgen, Sabit
Türkiye'de görülen meslek hastalıklarının çoğunu tozun solunmasından kaynaklanan pnömokonyoz oluşturmaktadır. Bu yazının amacı, yeraltı ocaklarında işçi sağlığı açısından sakıncalı olan havada asılı tozların, su spreyleri kullanılarak bastırılması konusunda gelinen aşamayı sunmaktır. Bu amaçla, havada asılı toz ve su damlalarıyla yapılan detaylı çalışmalar ışığında, sprey suyuna katılan yüzey aktif maddelerin istenen verim artışını sağlayamama nedenleri ele alınmakta ve su spreylerinin Türkiye'deki maden ocaklarında kullanım olanakları tartışılmaktadır.
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.
Citation - WoS: 2
Reduction of Carbon Dioxide During the Synthesis of Metal Nano-Particles in Water
(Elsevier Ltd., 2003) Polat, Hürriyet; Cohen, H; Meyerstein, D; Rusonik, I.
An effort was made to synthesize "carbon-free" metal (Fe-0, Co-0, Ni-0) nano-particles via the reduction of their salts with BH4- in aqueous solutions. Surprisingly it was found that when the synthesis is carried out in the presence of CO2, e.g., in aerated solutions, the CO2 is catalytically reduced by BH(4)(-)on the surface of the metal particles. Carbon-free metals can be prepared by reduction under an inert atmosphere. Thus metal surfaces might have acted as catalysts for CO2 fixation, probably via the initial formation of carbon clusters, in the reductive atmosphere in the prebiotic era. (C) 2003 Elsevier B.V. All rights reserved.
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.
Citation - WoS: 5
Citation - Scopus: 5
Tannery Wastewater Sediments Produced by Clinoptiolite/Polyacrylamide-aided Flocculation as a Clay Additive in Brick Making
(Springer Verlag, 2017) Köseoğlu, Kemal; Cengizler, H.; İsrail, L. İ.; Polat, Hürriyet
Toxic tannery wastewater(s) (TWW) pose(s) a great risk to the environment. This study explores the potential of mitigating the harmful effects of TWW through sedimentation using clinoptiolite in the presence of various anionic, cationic and non-ionic flocculants with different molecular weights and charge densities followed by encapsulation in a brick structure for stability. Compressive strength (CS), size reduction after firing (SRAF), water absorption (WA) and colouring parameters of bricks were determined. X-Ray diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) analyses were conducted on brick bodies. Kinetic leaching experiments were conducted for possible heavy metal release from the bricks. Bricks containing 10 wt% leather waste and 5 wt% clinoptiolite sintered at 800 °C instead of 920 °C possessed similar properties to the standard brick (SB).
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.
Citation - WoS: 140
Citation - Scopus: 171
Physicochemical Characterization of Chitosan Extracted From Metapenaeus Stebbingi Shells
(Elsevier Ltd., 2011) Küçükgülmez, Aygül; Çelik, Mehmet; Yanar, Yasemen; Şen, Didem; Polat, Hürriyet; Kadak, Ali Eslem
In this study, chitosan was extracted from Metapenaeus stebbingi shells. In order to determine physicochemical characteristics of the extracted chitosan, the yield, moisture and ash contents, degree of deacetylation, molecular weight, water and fat binding capacities, apparent viscosity and colour properties were measured using a variety of techniques including Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. In addition, the physicochemical characteristics of the chitosan extracted from M. stebbingi shells were compared to commercial chitosan. The degree of deacetylation was calculated by the titration method and elemental analysis. The molecular weight was determined by viscosimetric methods. The results of the study indicate that shrimp shells are a rich source of chitosan as 17.48% of the shell's dry weight is consisted of this material. Extracted chitosan exhibited a lower molecular weight, higher degree of deacetylation, higher viscosity and higher water and fat binding capacities compared to the commercial chitosan.
Citation - WoS: 21
Citation - Scopus: 23
Adsorption of Methylene Blue From Aqueous Solution on High Lime Fly Ash: Kinetic, Equilibrium, and Thermodynamic Studies
(Taylor and Francis Ltd., 2012) Keleşoğlu, Serkan; Kes, Mürşide; Sütçü, Leman; Polat, Hürriyet
Kinetic, equilibrium, and thermodynamic studies were performed for the batch adsorption of methylene blue (MB) on the high lime fly ash as a low cost adsorbent material. The studied operating variables were adsorbent amount, contact time, dye concentration, and temperature. The kinetic data were analyzed using the pseudo-first order and pseudo-second order kinetic models and the adsorption kinetic was followed well by the pseudo-second order kinetic model. The equilibrium data were fitted with the Freundlich, Langmuir, and Dubinin Radushkevich (D-R) isotherms and the equilibrium data were found to be well represented by the Freundlich and D-R isotherms. Based on these two isotherms MB is taken by chemical ion exchange and active sites on the high lime fly ash have different affinities to MB molecules. Various thermodynamic parameters such as enthalpy of adsorption (ΔH°), free energy change (ΔG°), and entropy change (ΔS°) were investigated. The positive value of ΔH° and negative value of ΔG° indicate that the adsorption is endothermic and spontaneous. The positive value of ΔS° shows the increased randomness at the solid-liquid interface during the adsorption. A single-stage batch adsorber was also designed based on the Freundlich isotherm for the removal of MB by the high lime fly ash. © 2012 Copyright Taylor and Francis Group, LLC.

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