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Öğe Catechol-Attached Polypeptide with Functional Groups as Electrochemical Sensing Platform for Synthetic Cannabinoids(Amer Chemical Soc, 2020) Durmus, Ceren; Aydindogan, Eda; Gumus, Zinar Pinar; Endo, Takeshi; Yamada, Shuhei; Coskunol, Hakan; Yagci, YusufHerein, we first constructed a functional surface using a catechol-attached polypeptide (CtP) for the detection of JWH-018 (N-4-hydroxypentyl metabolite). K2 antibody was then incorporated to the polymer via covalent cross-linker. Step-by-step modifications on the glassy carbon electrode surface were characterized by electrochemical measurements such as differential pulse voltammetry, cyclic voltammetry, impedance spectroscopy, and X-ray photoelectron spectroscopy. Linearity and the limit of detection for JWH-018 (N-4-hydroxypentyl metabolite) were determined as 10-500 ng/mL with an equation of y = 0.0018x + 0.136 (R-2 = 0.993) and 5.892 ng/mL, respectively. the selectivity of the biosensor was evaluated with different interfering molecules (methamphetamine, codeine, and cocaine). Finally, the biosensor was successfully used in the determination of JWH-018 (N-4-hydroxypentyl metabolite) in spiked synthetic urine samples, and a high-performance liquid chromatography (HPLC) system was used as a reference method to confirm the sample application. the results show that this biosensor platform can be applied to detect other JWH series of synthetic cannabinoids with high sensitivity and accuracy.Öğe Complex Structured Fluorescent Polythiophene Graft Copolymer as a Versatile Tool for Imaging, Targeted Delivery of Paclitaxel, and Radiotherapy(Amer Chemical Soc, 2016) Guler, Emine; Akbulut, Huseyin; Geyik, Caner; Yilmaz, Tulay; Gumus, Z. Pinar; Barlas, F. Baris; Ahan, Recep Erdem; Demirkol, Dilek Odaci; Yamada, Shuhei; Endo, Takeshi; Timur, Suna; Yagci, YusufAdvances in polymer chemistry resulted in substantial interest to utilize their diverse intrinsic advantages for biomedical research. Especially, studies on drug delivery for tumors have increased to a great extent. In this study, a novel fluorescent graft copolymer has been modified by a drug and targeting moiety and the resulting structure has been characterized by alterations in fluorescent intensity. The polythiophene based hybrid graft copolymer was synthesized by successive organic reactions and combination of in situ N-carboxy anhydride (NCA) ring opening and Suzuki coupling polymerization processes. Initially, targeted delivery of the graft copolymer was investigated by introducing a tumor specific ligand, anti-HER2/neu antibody, on the structure. The functionalized polymer was able to differentially indicate HER2-expressing A549 human lung carcinoma cells, whereas no signal was obtained for Vero, monkey kidney epithelial cells, and HeLa, human cervix adenocarcinoma cells. After integrating paclitaxel into the structure, cell viability, cell cycle progression, and radiosensitivity studies demonstrate HER2/neu targeting polymers inhibit cell proliferation. Importantly, the graft copolymer used had no cytotoxic effects to cells, as evidenced by cell viability and cell cycle analysis. This work clearly confirms that a specially designed and fabricated graft copolymer with a highly complex structure is a promising theranostic agent capable of targeting tumor cells for diagnostic and therapeutic purposes.Öğe Electrochemical deposition of polypeptides: bio-based covering materials for surface design(Royal Soc Chemistry, 2014) Akbulut, Huseyin; Yavuz, Murat; Guler, Emine; Demirkol, Dilek Odaci; Endo, Takeshi; Yamada, Shuhei; Timur, Suna; Yagci, YusufA simple and efficient approach for the electrochemical deposition of polypeptides as bio-based covering materials for surface design is described. The method involves N-carboxyanhydride (NCA) ring-opening polymerization from its precursor to form a thiophene-functionalized polypeptide macromonomer (T-Pala), followed by electropolymerization. The obtained conducting polymer, namely polythiophene-g- polyalanine (PT-Pala), was characterized and utilized as a matrix for biomolecule attachment. The biosensing applicability of PT-Pala was also investigated by using glucose oxidase (GOx) as a model enzyme to detect glucose. The designed biosensor showed a very good linearity for 0.01-1.0 mM glucose. Finally, the antimicrobial activities of newly synthesized T-Pala and PT-Pala were also evaluated by using the disc diffusion method.Öğe An immunoelectrochemical platform for the biosensing of 'Cocaine use'(Elsevier Science Sa, 2017) Sengel, Tulay Yilmaz; Guler, Emine; Gumus, Z. Pinar; Aldemir, Ebru; Coskunol, Hakan; Akbulut, Huseyin; Colak, Demet Goen; Cianga, Ioan; Yamada, Shuhei; Timur, Suna; Endo, Takeshi; Yagci, YusufIn the present work, we demonstrate a novel surface design by combination of benzoylecgonine (BE) antibody and poly-L-phenylalanine bearing electroactive macromonomer (EDOT-BTDA-PPhe). This system served as an electro-immunosensor platform for the analysis of cocaine use by detecting both BE and cocaine. To construct the immunosensor, a glassy carbon electrode was covered with EDOT-BTDA-PPhe. Subsequently, BE antibody was immobilized on the polypeptide chains. The surface modifications were confirmed by electrochemical techniques. The immunosensor was used for the electrochemical detection of BE and cocaine as evidence of drug addiction. For both analytes, linearity was obtained between 0.5-25 mu M. Finally, the proposed system was successfully employed for the analysis of synthetic biological fluids. (C) 2017 Elsevier B.V. All rights reserved.Öğe Polypeptide Functional Surface for the Aptamer Immobilization: Electrochemical Cocaine Biosensing(Amer Chemical Soc, 2016) Bozokalfa, Guliz; Akbulut, Huseyin; Demir, Bilal; Guler, Emine; Gumus, Z. Pinar; Demirkol, Dilek Odaci; Aldemir, Ebru; Yamada, Shuhei; Endo, Takeshi; Coskunol, Hakan; Timur, Suna; Yagci, YusufElectroanalytical technologies as a beneficial subject of modern analytical chemistry can play an important role for abused drug analysis which is crucial for both legal and social respects. This article reports a novel aptamer-based biosensing procedure for cocaine analysis by combining the advantages of aptamers as selective recognition elements with the well-known advantages of biosensor systems such as the possibility of miniaturization and automation, easy fabrication and modification, low cost, and sensitivity. In order to construct the aptasensor platform, first, polythiophene bearing polyalanine homopeptide side chains (PT-Pala) was electrochemically coated, onto the surface of an electrode and then cocaine aptamer was attached to the polymer via covalent conjugation chemistry. The stepwise modification of the surface was confirmed by electrochemical characterization. The designed biosensing system was applied for the detection of cocaine and its metabolite, benzoylecgonine (BE), which exhibited a linear correlation in the range from 2.5 up to 10 nM and 0.5 up to 50 mu M for cocaine and BE, respectively. In,order to expand its practical application, the proposed method was successfully tested for the analysis of synthetic biological fluids.Öğe Polypeptide with electroactive endgroups as sensing platform for the abused drug 'methamphetamine' by bioelectrochemical method(Elsevier Science Bv, 2016) Demir, Bilal; Yilmaz, Tulay; Guler, Emine; Gumus, Z. Pinar; Akbulut, Huseyin; Aldemir, Ebru; Coskunol, Hakan; Colak, Demet Goen; Cianga, Ioan; Yamada, Shuhei; Timur, Suna; Endo, Takeshi; Yagci, YusufAffinity-type sensors have emerged as outstanding platforms in the detection of diagnostic protein markers, nucleic acids and drugs. Thus, these novel platforms containing antibodies could be integrated into the monitoring systems for abused drugs. Herein, we established a novel detection platform for the analysis of a common illicit drug; methamphetamine (METH). Initially, a fluorescent-labeled polypeptide (EDOT-BTDA-Pala), derived from L-alanine N-carboxyanhydride (L-Ala-NCA) via ring-opening polymerization using 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzo[c][1,2,5]thiadiazole-5,6-diamine (EDOT-NH2-BTDA) as initiator, was employed as a glassy carbon electrode (GCE) covering host, in order to immobilize the METH selective antibody. Prior to the examination of analytical features, GCE/EDOT-BTDA-Pala/Antibody surface was successfully characterized in the way of electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and microscopic techniques (scanning electron microscopy and fluorescence microscopy). As for the analytical characterization, linearity and limit of detection (LOD) were found as 10-100 mu g/mL with an equation of y=0.0429x-0.2347, (R-2=0.996) and 13.07 mu g/mL, respectively. Moreover, sample application using artificial urine, saliva and serum samples spiked with METH (10, 25, 50 mu g/mL) were performed and LC-MS/MS system was used for further confirmation. The described platform can be adapted to monitor the other types of abused drugs by using suitably selected biorecognition elements.Öğe Surface Modification with a Catechol-Bearing Polypeptide and Sensing Applications(Amer Chemical Soc, 2018) Aydindogan, Eda; Celik, Emine Guler; Demirkol, Dilek Odaci; Yamada, Shuhei; Endo, Takeshi; Timur, Suna; Yagci, YusufA novel catechol-bearing polypeptide (CtP) was synthesized and used as a component of electrochemical biosensor involving both enzymatic activity and affinity-based sensing systems. Glucose oxidase (GOx) and anti-immunoglobulin G (Anti-IgG) were selected as model biorecognition elements for the selective analysis of glucose and IgG. Step-by-step surface modifications were followed using various techniques such as cyclic voltammetry (CV) and electrochemical impedance spectrometry (EIS) as well as X-ray photoelectron spectroscopy (XPS). Additionally, contact angles were measured in order to observe surface properties. Amperometric measurements using the GOx biosensor were performed at -0.7 V by following the oxygen consumption due to the enzymatic reaction in different glucose concentrations. Affinity-based interactions via IgG sensor were monitored using the differential pulse voltammetry (DPV) technique. As the "surface design with CtP" approach employed herein is generally applicable and easily adaptable to obtain functional matrices for biomolecule immobilization, CtP-coated surfaces can be promising platforms for the fabrication of various biobased sensing systems.Öğe Synthesis and application of a novel poly-L-phenylalanine electroactive macromonomer as matrix for the biosensing of 'Abused Drug' model(Royal Soc Chemistry, 2016) Yilmaz, Tulay; Guler, Emine; Gumus, Z. Pinar; Akbulut, Huseyin; Aldemir, Ebru; Coskunol, Hakan; Colak, Demet Goen; Cianga, Ioan; Yamada, Shuhei; Timur, Suna; Endo, Takeshi; Yagci, YusufPolypeptide-functionalized macromonomers are very fascinating candidates for the modification of various surfaces of different sizes as well as geometry, and have attracted considerable attention for biomolecule stabilization, biomedical device fabrication and bioanalytical applications. In the present work, synthesis and characterization of a novel poly-L-phenylalanine-bearing electroactive macromonomer (EDOT-BTDA-PPhe) were carried out. In the following steps, a glassy carbon electrode was covered with this material, and then cocaine aptamer was immobilized to obtain a biofunctional surface for the biosensing of ` Abused Drug' model. Aptamers attached to polypeptide side chains on the macromonomer with good orientation are induced for conformational change into three-way junction form as a result of selective binding of cocaine or its metabolite. This aptamer folding-based conformational response provides detectable signals due to formation of a compact interface which restricts electron transfer of redox probe. The stepwise modification of the surface was confirmed by electrochemical techniques. At the final step, the aptasensor was applied for the electrochemical detection of cocaine and its major metabolite, benzoylecgonine (BE), which exhibited a linear correlation between 1.0 and 10 nM and between 0.5 and 10 mu M respectively. The proposed methods were successfully employed for the analysis of synthetic biological fluids.
