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Öğe Amperometric biosensors based on deposition of gold and platinum nanoparticles on polyvinylferrocene modified electrode for xanthine detection(ELSEVIER, 2011) Bas, Salih Zeki; Gulce, Handan; Yildiz, Salih; Gulce, AhmetIn this study, new xanthine biosensors, XO/Au/PVF/Pt and XO/Pt/PVF/Pt, based on electroless deposition of gold(Au) and platinum(Pt) nanoparticles on polyvinylferrocene(PVF) coated Pt electrode for detection of xanthine were presented. The amperometric responses of the enzyme electrodes were measured at the constant potential, which was due to the electrooxidation of enzymatically produced H2O2. Compared with XO/PVF/Pt electrode, XO/Au/PVF/Pt and XO/Pt/PVF/Pt exhibited excellent electrocatalytic activity towards the oxidation of the analyte. Effect of Au and Pt nanoparticles was investigated by monitoring the response currents at the different deposition times and the different concentrations of KAuCl4 and PtBr2. Under the optimal conditions, the calibration curves of XO/Au/PVF/Pt and XO/Pt/PVF/Pt were obtained over the range of 2.5 x 10(-3) to 0.56 mM and 2.0 x 10(-3) to 0.66 mM, respectively. The detection limits were 7.5 x 10(-4) mM for XO/Au/PVF/Pt and 6.0 x 10(-4) mM for XO/Pt/PVF/Pt. The effects of interferents, the operational and the storage stabilities of the biosensors and the applicabilities of the proposed biosensors to the drug samples analysis were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.Öğe Chemical modification kinetics of polystyrenes having various molecular weights(ELSEVIER SCIENCE BV, 2007) Bas, Salih Zeki; Yildiz, SalihIn this study, three polystyrenes having different molecular weights have been chemically modified with maleic anhydride by using a cationic catalyst of Lewis acid type BF3O(C2H5)(2) (BF3) in chloroform. The effects of polystyrene (PS) and maleic anhydride (MA) concentrations, temperature and solvent volume on the chemical modification have been studied. IR spectra of modified polystyrene existing at the end of the chemical modification have been taken to show the presence of carboxyl group fixed to the aromatic ring of the polystyrene. Reaction rates have been calculated by determining the amount of carboxyl group using volumetric method. Some physical parameters, such as rate constants, activation energy of the reactions for chemical modification of polystyrene have also been calculated. (c) 2006 Elsevier B.V. All rights reserved.Öğe Design of a Probe Based on Poly(glycidyl methacrylate-co-vinylferrocene)-Coated Pt Electrode for Electrochemical Detection of PTEN Gene in PCR Amplified Samples from Prostate Tissues(WILEY, 2014) Bas, Salih Zeki; Maltas, Esra; Sennik, Busra; Yilmaz, Faruk; Vural, Hasibe CingilliIn this study, a new probe based on immobilization of amino linked oligonucleotide (NH2-linked DNA) on poly(glycidyl methacrylate-co-vinylferrocene)-coated Pt electrode was fabricated for the electrochemical detection of PTEN gene from human prostate tissues. The experimental parameters such as DNA immobilization time, DNA concentration, and target concentration were optimized. The selectivity of the NH2-linked DNA probe was assessed with mismatch (MM) and noncomplementary (NC) sequences. The applicability of the NH2-linked DNA probe to the PCR amplified samples correspond to PTEN gene from prostate tissues was evaluated. The immobilization of DNA on the copolymer was confirmed by FTIR, AFM, CV and DPV analysis. The PCR products were also identified by using agarose gel electrophoresis. The prepared probe indicated a linear range (10-100 g mL(-1)) with a detection limit (4.7 g mL(-1)) and a good selectivity of the NH2-linked DNA probe toward target DNA sequence. (c) 2014 Wiley Periodicals, Inc.Öğe Design of an electrochemical biosensing system for xanthine detection and a study on binding interaction of ketoconazole with xanthine oxidase(ELSEVIER SCIENCE BV, 2014) Bas, Salih Zeki; Maltas, Esra; Sennik, Busra; Yilmaz, FarukXanthine oxidase (XO) was successfully immobilized by covalent attachment on poly(glycidyl methacrylate-co-vinylferrocene) (P(GMA-co-VFc)), a redox copolymer containing pendant epoxy and ferrocene moieties, for the evaluation of both the biosensing properties and the effect of the interaction of ketoconazole (Ktc) with the immobilized XO. The binding interaction between Ktc, a drug used to treat fungal infections, and the immobilized XO on P(GMA-co-VFc) was also studied by fluorescence spectroscopy technique. The binding capacity of the drug was determined using a calibration curve equation that was drawn at excitation wavelength of 300 nm using fluorescence spectroscopy. The interaction ability was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and native-PAGE analysis. The enzyme electrode exhibited a linear range from 2.7 x 10(-3) to 0.55 mM with a sensitivity of 19.42 mu A mM(-1) cm(-2) and a detection limit of 8 x 10(-4) mM for the detection of xanthine. The activation energy (E-a) and the apparent Michaelis-Menten constant (K-mapp) values were found to be 12.30 kJ mol(-1) and 0.38 mM, respectively. (C) 2013 Elsevier B.V. All rights reserved.Öğe Electrochemical H2O2 Sensor Based on Graphene Oxide-Iron Oxide Nanoparticles Composite(IEEE, 2017) Bas, Salih Zeki; Ozmen, Mustafa; Yildiz, SalihThis study presents hydrogen peoxide determination using a new electrochemical sensor based on Fe3O4 functionalized graphene oxide (Fe3O4-APTES-GO). Fe3O4-APTES-GO was synthesized by a two-step process. First, Fe3O4 was modified by (3-aminopropyl) triethoxysilane to introduce amino groups on the surface of graphene oxide(GO). Second, APTES-Fe3O4 was reacted with the carboxylic groups of GO by an activating agent N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride to form a new material called as Fe3O4-APTES-GO. The electrocatalytic activity of Fe3O4-APTES-GO towards electrooxidation of H2O2 was described by using cyclic voltammetry technique.Öğe Glucose biosensor based on immobilization of glucose oxidase in electropolymerized poly(o-phenylenediamine) film on platinum nanoparticles-polyvinylferrocenium modified electrode(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Turkmen, Esra; Bas, Salih Zeki; Gulce, Handan; Yildiz, SalihA new biosensor based on immobilization of glucose oxidase (Gox) using enzyme solution containing o-phenylenediamine(oPD) on platinum nanoparticles (PtNPs) electrodeposited polyvinylferrocenium perchlorate matrix (PVF+ClO4-) was fabricated for the bioelectrochemical determination of glucose. Firstly, PVF+ClO4- film was electroprecipitated on Pt electrode by electrooxidation of polyvinylferrocene, and then PtNPs were electrodeposited on PVF+ClO4-/Pt. Finally, Gox was immobilized simultaneously with the electropolymerization of oPD on PtNPs/PVF+ClO4-/Pt. The biosensor showed excellent anti-interference ability to ascorbic acid and uric acid due to the permselectivity of PoPD in the structure of the proposed biosensor. The linear range of Gox-PoPD/PtNPs/PVF+ClO4-/Pt was from 0.06 mM to 9.64 mM with a sensitivity of 17.40 mu A mM(-1) cm(-2) and a detection limit of 0.018 mM. The effects of applied potential, PVF+ClO4- film thickness, oPD concentration, Gox concentration, electropolymerization time and temperature on the response current of the biosensor were investigated in detail. The electrocatalytic effect of PtNPs as well as repeatability, reproducibility and stability of the biosensor were also studied. PtNPs modified PVF+ClO4-/Pt exhibited excellent electrocatalytic activity to the electrooxidation of H2O2. In addition, the biosensor was successfully applied for the determination of glucose concentration in human blood serum samples. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Gold nanoparticle functionalized graphene oxide modified platinum electrode for hydrogen peroxide and glucose sensing(ELSEVIER, 2015) Bas, Salih ZekiThis study presents the preparation of gold nanoparticle functionalized graphene oxide (AuNPs-GO) as a new bio-compatible material for sensor applications. The electrocatalytic activity of AuNPs-GO towards electrooxidation of H2O2 was also described by using electrochemical techniques. The fabricated biosensor showed a linear range from 0.1 mM to 3.8 mM with a sensitivity of 17.68 mu A mM(-1) cm(-2) and a detection limit of 0.075 mM for the detection of glucose. (C) 2015 Elsevier B.V. All rights reserved.Öğe A gold nanoparticle functionalized multiwalled carbon nanotube-poly(o-phenylenediamine) composite film for glucose biosensing applications(ROYAL SOC CHEMISTRY, 2014) Bas, Salih ZekiA new biosensor based on immobilization of glucose oxidase on a multiwalled carbon nanotube-gold nanoparticle coated glassy carbon electrode (GCE) was fabricated for the electrochemical determination of glucose. First, a carboxylated multiwalled carbon nanotube (cMWCNT) was functionalized with 4-aminothiophenol (ATP) by a coupling agent, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and then gold nanoparticles (AuNPs) were covalently linked to the ATP-cMWCNT via the formation of a covalent Au-S bond. Finally, glucose oxidase was immobilized simultaneously by the electropolymerization of o-phenylenediamine on the AuNP-ATP-cMWCNT coated GCE. The biosensor showed a linear range from 0.05 mM to 8.85 mM with a sensitivity of 27.93 mu A mM(-1) cm(-2) and a detection limit of 0.015 mM for the detection of glucose. The biosensor was successfully applied to estimate the glucose concentration in human blood serum samples. Furthermore, the AuNP-ATP-cMWCNT was investigated for the non-enzymatic detection of hydrogen peroxide by using voltammetric and amperometric techniques, indicating a linear relationship in the range of 5 x 10(-3) to 13.10 mM.Öğe Hypoxanthine Biosensor Based on Immobilization of Xanthine Oxidase on Modified Pt Electrode and Its Application for Fish Meat(TAYLOR & FRANCIS AS, 2014) Bas, Salih Zeki; Gulce, Handan; Yildiz, SalihIn this study, hypoxanthine biosensor based on immobilization of xanthine oxidase on polyvinylferrocenium perchlorate matrix coated Pt electrode for detection of hypoxanthine was presented. The steady-state background current of the biosensor was measured at+0.5V, which was due to the electrooxidation of enzymatically produced H2O2. The biosensor exhibited a linear range from 2.15x10(-3)mM to 1.03mM (r=0.9963) with a detection limit of 6.5x10(-4)mM (S/N=3) for the detection of hypoxanthine. The storage stability of the biosensor, the effect of interference by uric acid, and the applicability to fish sample of the biosensor analysis were also evaluated.Öğe Magnetic nanoparticles-serum proteins bioconjugates for binding of irinotecan(ELSEVIER, 2015) Tamyurek, Ecem; Maltas, Esra; Bas, Salih Zeki; Ozmen, Mustafa; Yildiz, SalihThe binding of irinotecan to serum proteins (hemoglobin, globulin and human serum albumin) was studied on the surface of epoxide modified superparamagnetic iron oxide nanoparticles (GPT'S-SPIONs), which were synthesized by the coprecipitation of ferrous and ferric salts with NH4OH and then modified with [3-(2,3-epoxypropoxy)propyl] trimethoxy silane (GPTS) to obtain functional epoxide groups on the SPIONs' surface. Results were compared to find an alternative as drug carries system. Data showed that binding amount of human serum albumin (HSA), globulin (Gib) and hemoglobin (Hb) found to be as 44, 21.2 and 32.6 mu g per 20 mg of GPTS modified SPIONs, respectively. The thermal behavior of the serum protein-Ir interaction on GPTS-SPIONs was also studied by using thermo gravimetric analysis (TGA) technique and then the kinetic parameters for the thermal decomposition were determined using Horowitz-Metzger method. (C) 2014 Elsevier B.V. All rights reserved.Öğe A new electrochemical sensor based on Fe3O4 functionalized graphene oxide-gold nanoparticle composite film for simultaneous determination of catechol and hydroquinone(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Erogul, Seyma; Bas, Salih Zeki; Ozmen, Mustafa; Yildiz, SalihCatechol (1,2-dihydroxybenzene) and hydroquinone (1,4-dihydroxybenzene) are two isomers of phenolic compounds which often coexist and interfere with each other during their identification in environmental samples. This study presents simultaneous determination of catechol (CC) and hydroquinone (HQ) using a new electrochemical sensor based on Fe3O4 functionalized graphene oxide-gold nanoparticle composite (AuNPs/Fe3O4-APTES-GO). CV results show well-defined oxidation peaks with anodic peaks at 0.15 V for CC and 0.05 V for HQ, and the peak-to-peak separation for CC and HQ is about 100 mV. Under the optimized conditions, the current response of AuNPs/Fe3O4-APTES-GO/GCE is linear for CC and HQ in the range of 2-145 mu M and 3-137 mu M, respectively. The detection limits for CC and HQ were found to be 0.8 mu M and 1.1 mu M, respectively. The fabricated sensor was successfully applied for the determination of CC and HQ in tap water sample with satisfactory recovery. (C) 2015 Elsevier Ltd. All rights reserved.Öğe A Novel Electrochemical Sensor Based on Metal Ion Infiltrated Block Copolymer Thin Films for Sensitive and Selective Determination of Dopamine(AMER CHEMICAL SOC, 2019) Bas, Salih Zeki; Cummins, Cian; Selkirk, Andrew; Borah, Dipu; Ozmen, Mustafa; Morris, Michael A.An electrochemical sensor using copper oxide nanodots (CuO nanodots-ITO) developed from a block copolymer template is demonstrated for sensitive and selective determination of dopamine (DA). The current signal of CuO nanodots-ITO was linear with the concentration of DA in the range between 0.12 and 56.87 mu M (R = 0.9975) with a sensitivity of 326.91 mu A mM(-1) cm(-2) and a detection limit of 0.03 mu M. Furthermore, the anti-interference ability of the present sensor to possible interfering substances including ascorbic acid, uric acid, acetaminophen, epinephrine, hydrogen peroxide, phenol, catechol, hydroquinone, and some inorganic compounds has been investigated. Our work highlights the significance of using a bottom-up nanofabrication technique to create a robust and reliable dopamine sensor that has critical importance in neurological disorders.Öğe Synthesis and Spectroscopic Studies of Novel Rhodanine Azo Dyes: An Excellent Selective Chemosensor for Naked-eye Detecting of Cu2+ Ion(SLOVENSKO KEMIJSKO DRUSTVO, 2012) Ceylan, Abdullah; Bas, Salih Zeki; Bayrakci, Mevlut; Ertul, Seref; Uysal, AhmetThis study is first report on the synthesis of novel rhodanine based azo dyes and their fluorogenic and chromogenic sensing behaviors with metal ions (Li+, Na+, K+, Rb+, Pb2+, Ni2+, Zn2+, Cu2+) by using UV-vis and fluorescence spectroscopy techniques. The results of spectroscopic experiments for rhodanine based azo dye 1a exhibited excellent selectivity for Cu2+ over the other metal ions. Furthermore, anti-bacterial studies of rhodanine azo dyes were performed towards some selected bacteria via microbroth dilution method. Obtained results showed that rhodanine ionophore 1a showed strong antibacterial activity against S. aureus.Öğe Synthesis, Characterization, and Spectroscopic Properties of a Symmetrical Schiff Base Ligand and its Bimetallic Complexes(TAYLOR & FRANCIS INC, 2011) Bayrakci, Mevlut; Ertul, Seref; Bas, Salih Zeki; Demir, IbrahimThis article presents the synthesis of new Schiff base ligand and preparation of its transition metal complexes with copper (II), nickel (II), zinc (II), and cobalt (II). Furthermore, absorption and fluorescence properties of ligand and its metal complexes are investigated. The effect of the solvents, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, methanol, 1,4-dioxane on fluorescence properties of metal complexes, are performed and obtained results are summarized. All of the structures were characterized by using spectroscopic techniques.
