Caglar Ozdemir

Ege University, Ismir, İzmir, Turkey

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Publications (9)12.38 Total impact

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    ABSTRACT: An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.
    Food Analytical Methods 01/2012; · 1.97 Impact Factor
  • Food Analytical Methods 01/2012; · 1.97 Impact Factor
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    [Show abstract] [Hide abstract]
    ABSTRACT: An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.
    Food Analytical Methods 01/2012; · 1.97 Impact Factor
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    ABSTRACT: Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH2) was used as the biosensing platform for glucose analysis. Electrochemical measurements were carried out by following the consumed oxygen due to the enzymatic reaction of glucose oxidase (GOx) at −0.7 V vs Ag/AgCl. Optimisation of pH, enzyme loading, stability experiments were carried out. Effect of NP was investigated by monitoring the signal responses at different AuNP sizes and amounts. A linear relation of y = 1.597x + 0.264 (R2 = 0.993) was found for glucose concentrations between 0.002 and 5.0 mM. The analytical characteristics of the system were also evaluated for glucose determination in flow injection analysis (FIA) mode. Finally, the system was checked for glucose detection on real samples.Research highlights►Polymerisation of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine as sensor matrix. ► Modification of SNS-NH2 polymer with gold nanoparticles as sensing platform. ► Combination of AuNP with a conducting polymer and glucose oxidase for glucose sensing.
    Food Chemistry. 01/2011; 127(3):1317-1322.
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    ABSTRACT: An electrochemical biosensor with improved performance was designed through the immobilization of glucose oxidase (GOx) onto conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH 2) modified with carbon nanotubes (CNTs). For the optimization and characterization of the biosensor, pH profile, enzyme loading, reproducibility, operational stability experi-ments were carried out. It was found that the use of CNTs in a biosensing system enhanced the biosensor response. The linear relation was observed using glucose as the substrate in the range of 0.1–2.0 mM and defined by the equation; y = 8.582x + 2.945 (R 2 = 0.994, where y and x stand for concentration in mM and current signal as µA/cm 2). Finally, proposed biosensor was applied for glucose detection in real samples.
    Journal of Macromolecular Science Part A Pure and Applied Chemistry 01/2011;
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    ABSTRACT: This article deals with the use of pyranose oxidase (PyOx) and glucose oxidase (GOx) enzymes in amperometric biosensor design and their application in monitoring fermentation processes with the combination of flow injection analysis (FIA). The amperometric studies were carried out at -0.7 V by following the oxygen consumption due to the enzymatic reactions for both batch and FIA modes. Optimization studies (enzyme amounts and pH) and analytical parameters such as linearity, repeatability, effect of interference, storage, and operational stabilities have been studied. Under optimized conditions, for the PyOx-based biosensor, linear graph was obtained from 0.025 to 0.5 mM glucose in phosphate buffer (50 mM) at pH 7.0 with the equation of y = 3.358x + 0.028 and R(2) = 0.998. Linearity was found to be 0.01-1.0 mM in citrate buffer (50 mM and pH 4.0) with the equation of y = 1.539x + 0.181 and R(2) = 0.992 for the GOx biosensor. Finally, these biosensor configurations were further evaluated in a conventional flow injection system. Results from batch experiments provide a guide to design sensitive, stable, and interference-free biosensors for FIA mode. Biosensor stability, dynamic range, and repeatability were also studied in FIA conditions, and the applicability for the determination of glucose in fermentation medium could be successfully demonstrated. The FIA-combined glucose biosensor was used for the offline monitoring of yeast fermentation. The obtained results correlated well with HPLC measurements.
    Biotechnology Progress 11/2010; 27(2):530-8. · 1.85 Impact Factor
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    ABSTRACT: In situ synthesis of poly(ethylene glycol) (PEG) hydrogels containing gold nanoparticles (AuNPs) and glucose oxidase (GOx) enzyme by photo-induced electron transfer process was reported here and applied in electrochemical glucose biosensing as the model system. Newly designed bionanocomposite matrix by simple one-step fabrication offered a good contact between the active site of the enzyme and AuNPs inside the network that caused the promotion in the electron transfer properties that was evidenced by cyclic voltammetry as well as higher amperometric biosensing responses in comparing with response signals obtained from the matrix without AuNPs. As well as some parameters important in the optimization studies such as optimum pH, enzyme loading and AuNP amount, the analytical characteristics of the biosensor (AuNP/GOx) were examined by the monitoring of chronoamperometric response due to the oxygen consumption through the enzymatic reaction at -0.7 V under optimized conditions at sodium acetate buffer (50 mM, pH 4.0) and the linear graph was obtained in the range of 0.1-1.0 mM glucose. The detection limit (LOD) of the biosensor was calculated as 0.06 mM by using the signal to noise ratio of 3. Moreover, the presence of AuNPs was visualized by TEM. Finally, the biosensor was applied for glucose analysis for some beverages and obtained data were compared with HPLC as the reference method to test the possible matrix effect due to the nature of the samples.
    Bioelectrochemistry (Amsterdam, Netherlands) 10/2010; 79(2):211-7. · 2.65 Impact Factor
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    Caglar Ozdemir, Fatma Yeni, Dilek Odaci, Suna Timur
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    ABSTRACT: A novel pyranose oxidase (PyOx) biosensor based on gold nanoparticles (AuNPs)–polyaniline(PANI)/AgCl/gelatin nanocomposite has been developed for the glucose detection. PyOx was immobilized on the surface of glassy carbon electrode (GCE) via the nanocomposite matrix. The electrode surface was imaged by scanning electron microscopy (SEM). Amperometric detection of the consumed oxygen during the enzymatic reaction was monitored at −0.7 V. After optimization studies, analytical characterization of the biosensor was carried out. The linear response of the AuNPs–AgCl/PANI/gelatin modified PyOx biosensor is found to be from 0.05 to 0.75 mM glucose with the equation of y = 2.043x + 0.253; R2 = 0.993. Finally, proposed biosensor was used to analyze glucose content in real samples. Obtained data from the biosensing system was compared with a commercial enzyme assay kit based on spectrophotometric Trinder reaction as a reference method.
    Food Chemistry. 01/2010;
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    ABSTRACT: Fe3O4 magnetic nanoparticles (MNPs) were synthesized and silanized to form a core–shell (Fe3O4–SiO2) structure. Afterwards, surface modification with amino silane was carried out to produce amino groups on the MNPs for the biomolecule immobilization. In order to test the performance of amino functional MNPs as immobilization platform in biosensing applications, glucose oxidase was immobilized on the surface via glutaraldehyde. Obtained Bio-MNPs were then fixed onto the carbon paste electrode by the aid of magnetic force and used as the working electrode during the amperometric measurements at −0.7 V versus Ag/AgCl. After optimization of some parameters affecting the biosensor performance, analytical characterization was carried out. Linearity was found in the range of 0.25–2.0 mM glucose and defined by the equation of y = 8.366x + 1.819, (R 2 = 0.996). Proposed biosensor was then applied for the glucose analysis in various beverages. Finally, data were compared with a commercial enzyme assay kit based on spectrophotometric Trinder reaction as a reference method. Figure Schematic representation of the biosensing system based on core-shell modified magnetic nanoparticles
    Food Analytical Methods 5(4). · 1.97 Impact Factor