Yazar "Ekiz, Fulya" seçeneğine göre listele

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    Conducting polymers with benzothiadiazole and benzoselenadiazole units for biosensor applications
    (Elsevier Science Sa, 2011) Emre, Fatma Bilge; Ekiz, Fulya; Balan, Abidin; Emre, Sinan; Timur, Suna; Toppare, Levent
    Poly(4,7-di(2,3)-dihydrothienol[3,4-b][1,4]dioxin-5-yl-benzo[1,2,5]thiadiazole) (PBDT) and poly(4,7-di(2,3)-dihydrothienol[3,4-b][1,4]dioxin-5-yl-2,1,3-benzoselenadiazole) (PESeE) were electrochemically deposited on graphite electrodes and used as immobilization matrices for biosensing studies. After electrochemical deposition of the polymeric matrices, glucose oxidase (GOx) was immobilized on the modified electrodes as the model enzyme. In the biosensing studies, the decrease in oxygen level as a result of enzymatic reaction was monitored at -0.7 V vs Ag/AgCl (3.0 M KCl) and correlated with substrate concentration. The biosensor was characterized in terms of several parameters such as operational and storage stabilities, kinetic parameters (K(m) and I(max)) and surface morphologies. The biosensor was tested on real human blood serum samples. (C) 2011 Elsevier B.V. All rights reserved.
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    Electrochemical Polymerization of (2-Dodecyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3] triazole): A Novel Matrix for Biomolecule Immobilization
    (Wiley-V C H Verlag Gmbh, 2010) Ekiz, Fulya; Yuksel, Merve; Balan, Abidin; Timur, Suna; Toppare, Levent
    A recently synthesized conducting polymer [poly(2-dodecyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3] triazole (PTBT)] was tested as a platform for biomolecule immobilization. After electrochemical polymerization of the monomer (TBT) on graphite electrodes, immobilization of glucose oxidase (GOx, beta-D-glucose: oxygen-1-oxidoreductase, EC 1.1.3.4) was carried out. To improve the interactions between the enzyme and hydrophobic alkyl chain on the polymeric structure, GOx and isoleucine (Ile) amino acid were mixed in sodium phosphate buffer (pH 7.0) with a high ionic strength (250 x 10(-3) M). The solution is then casted on the polymer film, and the amino groups in the protein structure were crosslinked using glutaraldehyde (GA) as the bifunctional agent. Finally, the surface was covered with a perm-selective membrane. Consequently, cross-linked enzyme crystal (CLEC) like assembles with regular shapes were observed after immobilization. Microscopic techniques such as scanning electron microscopy (SEM) and fluorescence microscopy were used to monitor the surface morphologies of both the polymer and the bioactive layer. Electrochemical responses of the enzyme electrodes were measured by monitoring O-2 consumption in the presence of glucose at -0.7 V. The optimized biosensor showed a very good linearity between 0.05 and 2.5 x 10(-3) M with a 52 s response time and a detection limit (LOD) of 0.029 x 10(-3) M to glucose. Also, kinetic parameters, operational and storage stabilities were determined. K-m and I-max values were found as 4.6 x 10(-3) M and 2.49 mu A, respectively. It was also shown that no activity was lost during operational and storage conditions. Finally, proposed system was applied for glucose biomonitoring during fermentation in yeast culture where HPLC was used as the reference method to verify the data obtained by the proposed biosensor.
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    Functionalization of poly-SNS-anchored carboxylic acid with Lys and PAMAM: surface modifications for biomolecule immobilization/stabilization and bio-sensing applications
    (Royal Soc Chemistry, 2012) Demirci, Sema; Emre, Fatma Bilge; Ekiz, Fulya; Oguzkaya, Funda; Timur, Suna; Tanyeli, Cihangir; Toppare, Levent
    Poly(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) (SNS) acetic acid) was electrochemically deposited on graphite electrodes and functionalized with lysine (Lys) amino acid and poly(amidoamine) derivatives (PAMAM G2 and PAMAM G4) to investigate their matrix properties for biosensor applications. Glucose oxidase (GOx) was immobilized onto the modified surface as the model enzyme. X-Ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to report the surface properties of the matrices in each step of the biosensor construction. The biosensors were characterized in terms of their operational and storage stabilities and the kinetic parameters (K-m(app) and I-max). Three new glucose biosensors revealed good stability, featuring low detection limits (19.0 mu M, 3.47 mu M and 2.93 mu M for lysine-, PAMAM G2- and PAMAM G4-functionalized electrodes, respectively) and prolonged the shelf lives (4, 5, and 6 weeks for Lys-, PAMAM G2- and PAMAM G4-modified electrodes, respectively). The proposed biosensors were tested for glucose detection on real human blood serum samples.
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    Synthesis and application of poly-SNS-anchored carboxylic acid: a novel functional matrix for biomolecule conjugation
    (Royal Soc Chemistry, 2011) Ekiz, Fulya; Oguzkaya, Funda; Akin, Mehriban; Timur, Suna; Tanyeli, Cihangir; Toppare, Levent
    Here we report the synthesis of a novel conducting polymer and its properties as an immobilization platform for biosensor application. The conducting polymer has functional groups used for the formation of amide bonding with the enzyme immobilized on the polymer surface. After covalent immobilization of glucose oxidase (GOx) on the polymeric matrix, its application for glucose biosensing was investigated in detail. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to monitor the surface properties of the polymer before and after biomolecule conjugation. The optimized biosensor showed a very good linearity between 0.01 mM and 1.2 mM, a 13 s response time and a detection limit (LOD) of 0.004 mM to glucose. Also, kinetic parameters, operational and storage stabilities were determined. Apparent Michaelis constant (K-m(app)) and I-max values of 1.17 mM and 11.28 mu A, respectively, were obtained.