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    A benzimidazole-based conducting polymer and a PMMA-clay nanocomposite containing biosensor platform for glucose sensing
    (Elsevier Science Sa, 2015) Emre, Fatma Bilge; Kesik, Melis; Kanik, Fulya Ekiz; Akpinar, Hava Zekiye; Aslan-Gurel, Evren; Rossi, Rene M.; Toppare, Levent
    Development of materials composed of polymer-clay nanocomposites (PCN) and conducting polymers attracts great interest and preferred in various applications. Hereby, polymethylmethacrylate (PMMA) layered silicate nanocomposites were prepared by in-situ suspension polymerization by grafting PMMA with laponite using a suitable grafting agent. The properties of the as-synthesized PCN materials are characterized by differential scanning calorimetry (DSC), thermal gravimetry analysis (TGA) and gel permeation chromatography (GPC). A conducting polymer; poly(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-y1)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-y1)-2-benzyl-1H-benzo[d]imidazole) (poly(BIPE)) and a PMMA-clay nanocomposite with 2-(methacryloyloxy) ethyltrimethylammonium chloride (MTMA) modifier were examined as a platform for biomolecule deposition. Glucose oxidase (GOx, beta-D-glucose: oxygen-1-oxidoreductase, EC 1.1.3.4) was chosen as the model enzyme to prepare a scaffold for glucose sensing. Three different sensing strategies; PCN/GOx, poly(BIPE)/GOx and PCN/poly(BIPE)/GOx were analyzed and their biosensor performances were discussed. Surface morphology of the modified electrodes was characterized by scanning electron microscopy (SEM) technique. Electrochemical responses of the enzyme electrodes were monitored at -0.7 V vs. Ag reference electrode by monitoring oxygen consumption in the presence of glucose. After optimum conditions were determined, kinetic and analytical parameters; K-M(aPP), I-max, LOD and sensitivity were investigated for each sensing platform. (C) 2015 Elsevier B.V. All rights reserved.
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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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    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.