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Öğe Efficient Removal of Acidic Dye Using Low-Cost Biocomposite Beads(Amer Chemical Soc, 2013) Metin, Aysegul U.; Ciftci, Hakan; Alver, ErolThe objective of this study is to prepare and characterize chitosan/zeolite biocomposite beads and utilize them as adsorbent for removal of anionic dye, Acid Black 194 (AB194). Characterization studies of biocomposite beads were carried out by using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX). The ability of chitosan/zeolite biocomposite beads as an adsorbent for the removal AB 194 from an aqueous solution has been investigated under various experimental conditions. Maximum adsorption capacity of biocomposite beads was calculated as 2140 mg/g. The increase in temperature resulted in a higher AB194 loading per unit weight of biocomposite beads. As an additional factor affecting the adsorption behavior of AB194, the effect of ionic strength was investigated, and the adsorption capacity of biocomposite beads significantly decreased. Four isotherm models were employed to elucidate the adsorption process. The most appropriate model for the equilibrium process was the Freundlich. The kinetic studies indicated that the adsorption of AB194 followed the pseudo-second-order kinetics. Thermodynamic calculations showed that the adsorption of reactive dye was a spontaneous and endothermic process. The obtained results indicate that chitosan/zeolite biocomposite beads as an adsorbent are promising for dye removal from wastewater.Öğe Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles(Springer, 2014) Ciftci, Hakan; Tamer, Ugur; Metin, Aysegul U.; Alver, Erol; Kizir, NevinThis study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 x 10(-9) mol L-1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water.Öğe Fabrication and characterization of gold-nanoparticles/chitosan film: a scaffold for L929-fibroblasts(Taylor & Francis Ltd, 2013) Turk, Mustafa; Tamer, Ugur; Alver, Erol; Ciftci, Hakan; Metin, Aysegul U.; Karahan, SiyamiThe objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929-fibroblasts. L929-fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity.Öğe Fabrication of mechanically advanced polydopamine decorated hydroxyapatite/polyvinyl alcohol bio-composite for biomedical applications: In-vitro physicochemical and biological evaluation(Elsevier, 2022) Erdem, Umit; Dogan, Deniz; Bozer, Busra M.; Turkoz, Mustafa B.; Yildirim, Gurcan; Metin, Aysegul U.In this study, polydopamine (PDA) coated hydroxyapatite (HA) reinforced polyvinyl alcohol (PVA) films were produced to be used in biomedical applications such as bone tissue regeneration. pDA is coated not only to prevent the agglomeration of HA when encountering interstitial fluids but also to strongly bind the PVA for the interaction between materials so that the mechanical performance becomes more stabilized. pDA was coated on the hydroxyapatite surface using a radical polymerization technique, and the reinforced PVA were produced with pDA-coated HA (pDA-HA/PVA) nanoparticles. Fundamental characteristic properties of pDA-HA/PVA nanocomposite films were examined by morphological/chemical (SEM-EDS), microstructural (XRD, Ft-IR, and Raman), thermodynamic (TGA and TM), mechanical performance (Vickers microhardness) and biological activity analysis (MTT, genotoxicity and antimicrobial efficacy investigations). Physicochemical analysis showed that all the samples studied exhibited homogeneous mineral distributions through the main structures. According to TGA, TMA and hardness tests, the new composite structure possessed higher mechanical properties than neat PVA. Further, pDA-HA/PVA nanocomposites exhibited high antibacterial capacities against Acinetobacter Baumannii (A.Baumannii), Staphylococcus aureus (S. aureus), and Streptococcus mutans (S.mutans). Moreover, the new nanocomposites were noted to present good biocompatibility for fibroblast (L929) cells and to support remarkably MCS cells. All in all, this comprehensive work shows that the thermo-mechanically improved pDA-HA/PVA films will increase the application fields of PVA in biomedical fields especially tooth-bone treatments for coating, filling, or occlusion purposes.Öğe Hydroxyapatite-based nanoparticles as a coating material for the dentine surface: An antibacterial and toxicological effect(ELSEVIER SCI LTD, 2020) Erdem, Umit; Dogan, Mustafa; Metin, Aysegul U.; Baglar, Serdar; Turkoz, Mustafa B.; Turk, Mustafa; Nezir, SaffetIn this study, nano sized hydroxyapatite (nHAp) and Ag(I) doped hydroxyapatite (Ag-nHAp) particles were synthesized by the precipitation method and used as a coating material for remineralization on caries-affected dentine samples. Characterization studies of both the synthesized hydroxyapatite-based particles and the coated dentine samples were performed using instrumental techniques such as SEM and FFIR, and then toxicity and antibacterial properties were also evaluated. It was observed that dentine samples were effectively coated by both nHAp and Ag center dot nHAp particles which have no toxic effects. Furthermore, the costing of nano-hydroxyapatite on dentine samples positively contributed to the viability of L929 fibroblast cells and also provided an antibacterial effect against to bacteria such as S. mutants, C. albicans and E. coli bacteria that are most frequently caused caries in the teeth. While all type of bacteria was eliminated by the nHAp coated dentine samples at 24th, Ag-nHAp coated dentine samples removed to all bacteria type at 1st.Öğe Immobilization of laccase onto polyethyleneimine grafted chitosan films: Effect of system parameters(Polymer Soc Korea, 2013) Metin, Aysegul U.Chitosan films were prepared via phase-inversion technique. The polyethyleneimine (PEI) was grafted onto chitosan films after activation with various agents, such as epichlorohydrin, genipin and glutaraldehyde. The PEI grafted activated chitosan films (Ch-g-PEI) were used for immobilization of laccase by adsorption. The effects of adsorption parameters on immobilization efficiency were researched. Activity and stability of immobilized laccase on Ch-g-PEI films were investigated under desired optimum conditions. Characterization studies of the supports were also performed. The effect of pH on the activity of free and immobilized laccase was carried out in the pH range 4.0-8.0, and the optimum pH was determined as 5.5. Kinetic constants of the free and immobilized laccase were calculated. The maximum activity (V (max) ) and Michealis constant (K (m) ) of immobilized laccase on the films were found to be 71.2 U/mg and 0.51 mM, respectively. Thermal stability of the enzyme increased together with immobilization on the support. Free laccase retained 39% of its original activity at 55 A degrees C for a 120 min incubation period. Immobilized laccase retained 72% of its original activity for the same period at 55 A degrees C. The free enzyme lost all of its activity during the 7 weeks storage period. Conversely, immobilized laccase lost 36% of its activity during the 7 weeks storage period.Öğe Non-enzymatic sensing of glucose using a glassy carbon electrode modified with gold nanoparticles coated with polyethyleneimine and 3-aminophenylboronic acid(Springer Wien, 2016) Ciftci, Hakan; Alver, Erol; Celik, Filiz; Metin, Aysegul U.; Tamer, UgurA non-enzymatic electrochemical method was developed for sensing glucose by using a glassy carbon electrode modified with 3-aminophenylboronic acid (APBA) immobilized on polyethyleneimine (PEI)-coated gold nanoparticles. The modified electrode was characterized by TEM, zeta potential measurements and UV-Vis spectroscopy. Its analytical performance was evaluated in pH 9 solution by potentiometry. The respective calibration plot, established at open circuit potential (vs. Ag/AgCl) covers the 0.5-50 mM glucose concentration range, which makes it suitable for blood glucose assays. The detection limit is 0.025 mM, and no interference is caused by ascorbic acid, dopamine, and uric acid. Effects of other carbohydrates such as fructose, galactose and saccharose were also investigated. The electrode was used to determine glucose in human serum samples and the results agreed well with those obtained with commercial amperometric enzymatic sensors.Öğe Synthesis and Characterization of Chitosan/Polyvinylpyrrolidone/Zeolite Composite by Solution Blending Method(Springer, 2014) Alver, Erol; Metin, Aysegul U.; Ciftci, HakanPolymer/clay composites have been studied for several decades; in the study, polymer/zeolite composite beads have been prepared by a simple solution blending method using chitosan, polyvinylpyrrolidone and zeolite particles as organic and inorganic components, respectively. Different techniques, such as SEM, FTIR spectroscopy, and thermogravimetry have been used to characterize the composite beads. Chitosan/polyvinylpyrrolidone/zeolite (CH/PVP/Z) beads are expected to have a potential as an adsorbent for wastewater treatment. To investigate its applicability, copper (II) was selected as a model compound. The results showed that the composite beads had effective loading capacity and it is a promising adsorbent for heavy metal removal.Öğe Synthesis, Physical Properties, and Application of Aminated Poly(glycidyl methacrylate)/Zeolite Composite(Wiley, 2016) Metin, Aysegul U.Poly(glycidyl methacrylate)/zeolite (PGMA/Z) composite was prepared by free radical polymerization and it was further modified to contain amino groups on its surface, by reacting to hexamethylenediamine. FTIR, TG, and SEM analyses were performed and investigated its potential as an adsorbent for removal of anionic dyes; namely, Reactive Red 120 (RR120) and Reactive Blue 4 (RB4). The effect of operational parameters was investigated. Maximum RR120 and RB4 adsorption capacities of composite were calculated as 136.5 and 189.8 mg g(-1), respectively. Isotherm, kinetic, and thermodynamic studies were also performed. It was found that the adsorption process might be heterogeneous by nature, and adsorption kinetics of reactive dyes followed the pseudo-second order. The thermodynamic calculations showed that adsorption process was spontaneous and exothermic. (C) 2015 Society of Plastics Engineers
