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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, Ahmet
In 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.
Amperometric xanthine biosensors based on electrodeposition of platinum on polyvinylferrocenium coated Pt electrode
(ELSEVIER, 2011) Bas, Salih Zeld; Gulce, Handan; Yildiz, Salih
Novel xanthine biosensors were successfully fabricated by immobilizing xanthine oxidase on polyvinylferrocenium perchlorate matrix (PVF+ClO4-) and platinum electrodeposited polyvinylferrocenium perchlorate matrix. PVF+ClO4- film was coated on Pt electrode at +0.7 V vs. Ag/AgCl by electrooxidation of polyvinylferrocene (PVF). Platinum nanoparticles were deposited on PVF+ClO4- electrode by electrochemical deposition in 2.0 mM H2PtCl6 solution at -0.2 V. Xanthine oxidase was incorporated into the polymer matrix via ion exchange process by immersing modified Pt electrodes in the enzyme solution. The amperometric responses of the biosensors were measured via monitoring oxidation current of hydrogen peroxide at +0.5 V. Under the optimal conditions, the linear ranges of xanthine detection were determined as 1.73 x 10(-3)-1.74 mM for PVF+XO- and 0.43 x 10(-3)-2.84 mM for PVF+XO-/Pt. The detection limits of xanthine were 5.20 x 10(-4) mM for PVF+XO- and 1.30 x 10(-4) mM for PVF+XO-/Pt. Moreover, the effects of applied potential, electrodeposition potential, H2PtCl6 concentration, amount of electrodeposited Pt nanoparticles, thickness of polymeric film, temperature, immobilization time, xanthine and xanthine oxidase concentrations on the response currents of the biosensors were investigated in detail. The effects of interferents, the operational and storage stabilities of biosensors and the applicabilities to drug samples of the biosensors analysis were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.
ANTIOXIDANT ACTIVITY AND FATTY ACID COMPOSITION OF GINKGO BILOBA FROM TURKEY
(WILEY-BLACKWELL, 2011) Maltas, Esra; Vural, Hasibe Cingilli; Yildiz, Salih
In this study, we investigated the antioxidant capacity and total phenolic content of the extracts Ginkgo biloba from Turkey. The antioxidant activity of the methanolic and acetone extracts from G. biloba leaves was measured by various assays, including ferric reducing antioxidant power assay, cupric reducing antioxidant capacity assay and metal chelating capacity. Total phenolic content of the extracts was measured as gallic acid equivalents (GAE) by Folin-Ciocalteu reagent. The methanolic extract showed higher antioxidant activity related to high phenolic content with 76.0 +/- 5.2 mg GAE/g dry weight. Fatty acid compositions of the methanolic and acetone extracts of G. biloba were analyzed. Data suggested that G. biloba grown in Turkey may be an important source of natural antioxidant.
Biochemical and molecular analysis of soybean seed from Turkey
(ACADEMIC JOURNALS, 2011) Maltas, Esra; Dageri, Nazan; Vural, Hasibe Cingilli; Yildiz, Salih
We aimed molecular analysis of soybean by lecithin specific primer pairs LE5/LE6. Genomic DNA was extracted from soybean by CTAB method and EZ1 nucleic acid isolation system. A sensitive qualitative detection method for soybean, using the polymerase chain reaction was developed with E5/LE6 primers, produced a 195 bp product. However, the antioxidant activity of methanolic extract of soybean from Turkey by using DPPH and ABTS radical scavenging assays, showed higher antioxidant activity with 53.19 +/- 0.87% and 45.10 +/- 0.32%, respectively. Fatty acid compositions and several phenolic acids and flavonoids of soybean extract were analysed by gas and high performenace chromatography. Data showed that, the main compounds of the extract were eriodictyol, naringenin and linoleic acid.
Chemical modification kinetics of polystyrenes having various molecular weights
(ELSEVIER SCIENCE BV, 2007) Bas, Salih Zeki; Yildiz, Salih
In 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.
DISTRIBUTION OF SECONDARY METABOLITES IN BRASSICA NAPUS GENOTYPES
(WILEY-BLACKWELL, 2011) Maltas, Esra; Yildiz, Salih
Secondary metabolites (flavonoids and phenolics) in the methanolic extracts of Brassica napus genotypes, spring and winter canola were evaluated. Antioxidant activity of the extracts was evaluated by beta-carotene linoleic acid model system, scavenging ability of hydrogen peroxide (H(2)O(2)) assay and cupric reducing antioxidant capacity (CUPRAC) assay. Also, total flavonoid contents of the extracts were determined by aluminum chelating method. Results showed that naringin and eriodictyol were found to be in both species. Data showed that winter canola exihibited high antioxidant capacity with 60.6 +/- 0.4% in beta-carotene linoleic acid model system and also CUPRAC value (4.18 +/- 0.11 mM TEAC/g) and scavenging ability of H(2)O(2) (57.12 +/- 1.13%) was higher than spring canola. However, total flavonoid content of spring canola was higher than that of winter canola. Both canola species may be of importance in variety improvement, nutraceuticals, bio-pharmaceuticals and food additives as natural antioxidants.
Electrochemical H2O2 Sensor Based on Graphene Oxide-Iron Oxide Nanoparticles Composite
(IEEE, 2017) Bas, Salih Zeki; Ozmen, Mustafa; Yildiz, Salih
This 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.
Extraction of genomic DNA from polysaccharide- and phenolics-rich Ginkgo biloba
(ACADEMIC JOURNALS, 2011) Maltas, Esra; Vural, Hasibe Cingilli; Yildiz, Salih
One prerequisite to reliable molecular biology work is that the genomic DNA of a sample should be of good quality. The isolation of intact, high-molecular-mass genomic DNA is essential for many molecular biology applications including long Polymerase Chain Reaction (PCR), endonuclease restriction digestion, Southern blot analysis, and genomic library construction. Many protocols are available for the extraction of DNA from plant material. DNA extraction of Ginkgo biloba is quite difficult to work on because of the high phenolic and polysaccharide content of its leaves. This study aimed to determine which protocol to use and which part of Ginkgo tree is most appropriate to extract good-quality genomic DNA. For this purpose, cetyltrimethylammonium bromide protocol and protocol of commercially available kit by EZ1 Nucleic acid isolation system have been optimized for extraction of genomic DNA from G. biloba leaves. Efficient yields of high-quality amplifiable DNA was produced rapidly with kit by EZ1 Nucleic acid isolation method. The purified DNA which has excellent spectral quality was efficiently amplified by 5 arbitrary primers (OPA11-15), and was suitable for long-fragment PCR amplification.
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, Salih
A 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.
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, Salih
In 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.
Immobilization of albumin on magnetite nanoparticles
(ELSEVIER SCIENCE BV, 2011) Maltas, Esra; Ozmen, Mustafa; Vural, Hasibe Cingilli; Yildiz, Salih; Ersoz, Mustafa
The magnetite (Fe3O4) nanoparticles were prepared by the co-precipitation of ferrous and ferric salts with NH4OH, and then modified with 3-aminopropyltriethoxysilane (APTES) by silanization reaction and subsequent reaction with glutaraldehyde (GA) to obtain functional groups on their surface. The influence of different terminated groups on protein binding was studied with bare and modified magnetite nanoparticles. Amine terminated magnetite nanoparticles were shown the highest binding ability for immobilization process compared to Fe3O4 NPs and GA bonded NPs. This binding ability was shown by using sodium dodecyl polyacrylamide gel electrophoresis technique (SDS-PAGE). Albumin attached magnetite nanoparticles were also examined by Scanning Electron Microscopy (SEM). (C) 2011 Elsevier B.V. All rights reserved.
Interaction Between Ketoconazole and Human Serum Albumin on Epoxy Modified Magnetic Nanoparticles for Drug Delivery
(AMER SCIENTIFIC PUBLISHERS, 2013) Maltas, Esra; Ozmen, Mustafa; Yildirimer, Burak; Kucukkolbasi, Semahat; Yildiz, Salih
Superparamagnetic iron oxide nanoparticles (SPIONs) were modified with [3-(2,3-epoxypropoxy)propyl] trimethoxy silane, which resulted in formation of epoxy groups on the particles surface. The epoxy functionalized SPIONs can bind to human serum albumin (HSA). The binding amount of HSA to epoxy modified SPIONs was found to be as 32.7 mu M for 1 mg epoxy modified SPIONs at 280 and 342 nm of excitation and emission wavelengths by using fluorescence spectroscopy. Interaction of ketoconazole with HSA immobilized epoxy functionalized SPIONs was studied at 300 and 390 nm of excitation and emission wavelengths, respectively. Binding mechanism of ketoconazole and HSA was identified by Stern-Volmer equation. Thermodynamic parameters (Delta H, Delta S and Delta G) were also estimated for the interaction. Therefore, the nature of the binding forces was found to be as hydrophobic interaction. Protein and drug attachments were also examined by Infrared spectroscopy (IR) and Scanning Electron Microscopy (SEM). This study show that prepared albumin-based magnetic nanoparticles carrier systems represents an attractive strategy for drug delivery.
Interaction of donepezil with human serum albumin on amine-modified magnetic nanoparticles
(ELSEVIER SCIENCE BV, 2014) Buzoglu, Leman; Maltas, Esra; Ozmen, Mustafa; Yildiz, Salih
The interaction between the drug donepezil and human serum albumin (HSA) was examined on the surface of amine modified superparamagnetic iron oxide nanoparticles (SPIONs), which were synthesized by the coprecipitation of ferrous and ferric salts with NH4OH and then modified with [3-Aminopropyl] triethoxysilane (APTES) to obtain functional amine groups on the nanoparticles' surface. Albumin's binding capacity to APTES-modified SPIONs was estimated by fluorescence spectroscopy. After HSA was bound to the APTES modified SPIONs, donepezil was interacted with the HSA-SPIONs. The binding capacity of the drug was determined using a calibration curve equation that was drawn using fluorescence spectroscopy at 325 and 387 nm, the excitation and emission wavelengths. Thermodynamic parameters were estimated for the interaction of HSA and donepezil on amine-modified SPIONs. Binding was carried out spontaneously via electrostatic interaction. Binding was also examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SOS-PAGE), scanning electron microscopy (SEM) and zeta-potential measurements. (C) 2013 Elsevier B.V. All rights reserved,
Magnetic nanoparticles-serum proteins bioconjugates for binding of irinotecan
(ELSEVIER, 2015) Tamyurek, Ecem; Maltas, Esra; Bas, Salih Zeki; Ozmen, Mustafa; Yildiz, Salih
The 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.
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, Salih
Catechol (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.
SCREENING OF PHYTOCHEMICALS AND ANTIOXIDANT ACTIVITY OF ARUM DIOSCORIDIS SEEDS
(WILEY, 2012) Uguzlar, Huseyin; Maltas, Esra; Yildiz, Salih
The aim of this paper was to evaluate the antioxidant properties of the different extracts from Arum dioscoridis seeds (methanolic, acetone and hexane extracts) and to correlate their antioxidant potential to the composition of phenolic compounds. The scavenging ability of free radicals was measured using beta-carotenelinoleic acid model system and 2,2-diphenyl-1-picrylhydrazyl (DPPH.) analysis and the IC50 values of the extracts were also determined. The methanolic extract of A. dioscoridis seeds showed greater antioxidant activity than acetone and hexane extracts by beta-carotenelinoleic acid model system and DPPH. analysis, respectively. Qualitative and quantitative analyses of major phenolic compounds were also performed. The main antioxidant compound from the methanol extract was found to be vitexin. Other identified phenolics in all extracts that are likely to contribute to the antioxidant potential are: ferulic acid, naringin, eriodictyol and p-coumaric acid. PRACTICAL APPLICATIONS Antioxidant properties of the different extracts from Arum dioscoridis seeds (methanolic, acetone and hexane extracts) were evaluated in this study. The scavenging ability of free radicals was measured using the beta-carotenelinoleic acid model system and 2,2-diphenyl-1-picrylhydrazyl (DPPH.) analysis, and the IC50 values of the extracts were also determined. The methanolic extract of A. dioscoridis seeds showed greater antioxidant activity than acetone and hexane extracts, respectively. The main antioxidant compound from the methanol extract was found to be vitexin. Other identified phenolics such as ferulic acid, naringin, eriodictyol and p-coumaric acid in all extracts are likely to contribute to the antioxidant potential.
Synthesis and characterization of PS-b-PGMA diblock copolymer and its interaction with blood proteins and donepezil
(ELSEVIER SCIENCE BV, 2014) Buzoglu, Leman; Maltas, Esra; Ersoz, Mustafa; Yildiz, Salih
Biocompatible polystyrene-block-poly(glycidyl methacrylate) (PS-b-PGMA) diblock copolymers with different molecular weights were synthesized via atom transfer radical polymerization (ATRP), homopolymers of styrene with narrow molecular weight distribution were prepared and used macroinitiators for block copolymerization. The effect of time, temperature, solvent, and in-feed ratio on the synthesis of the polymer was examined. Human serum albumin (HSA), bovine serum albumin (BSA), globulin (Gib) and hemoglobin (Hb) which are intrinsically fluorescent blood proteins were interacted with the synthesized PS-b-PGMA diblock copolymers. A calibration curve equation was used to calculate the amount of immobilized proteins on the diblock copolymers through fluorescence spectroscopy. These occurred at wavelengths of 280 nm and 324 nm, which correspond to the excitation and emission wavelengths of tyrosine and tryptophan residues. Following the interaction of PS-b-PGMA diblock copolymer with the blood proteins, the protein was subjected to a pharmaceutical active substance, donepezil. The copolymers, homo polymers and protein-polymers along with the drug interactions were characterized using H-1 NMR, FT-IR and gel permeation chromatography (GPC), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). (C) 2014 Elsevier Ltd. All rights reserved.

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