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Mehmet S¸ enel,Muamer Dervisevic,Emre Çevik 한국물리학회 2013 Current Applied Physics Vol.13 No.7
The biosensor was constructed for determination of glucose by using glucose oxidase enzyme immobilized on poly(thiophene-3-boronic acid) (PTBA). Boronic acid functionalized polythiophene layer was obtained by electrochemical polymerization of Thiophene (Th) and thiophene-3-boronic acid (TBA) with different monomer rations. The reconstitution of the apo-glucose oxidase (apo-GOx) on a complexed flavin adenine dinucleotide (FAD) linked to polythiophene boronic acid (PTBA) monolayer yields an electrically contacted enzyme monolayer. The GOx-reconstituted enzyme electrode exhibited excellent electrocatalytic activities toward the reduction and oxidation of hydrogen peroxide as well. The PTBA/FAD/GOx biosensor shows an excellent performance for glucose at þ0.4 V with a high sensitivity (2.14 mA/mM) and lower response time (w5 s) in a wide concentration range of 0.5e18 mM (correlation coefficient of 0.9952). Furthermore, the effects of applied potential, pH, temperature, electroactive interference, stability and reusability of the biosensors were discussed.
Potentiometric urea biosensor based on poly(glycidylmethacrylate)-grafted iron oxide nanoparticles
Emre Çevik,Mehmet S¸ enel,Abdülhadi Baykal 한국물리학회 2013 Current Applied Physics Vol.13 No.1
Urease enzyme was covalently attached on the poly(glycidylmethacrylate) (PGMA)-grafted iron oxide nanoparticles on Au electrode for the fabrication of urea biosensor. The telomere of poly(- glycidylmethacrylate) (PGMA) with a trimethoxysilyl terminal group was synthesized by telomerization of glycidylmethacrylate. Iron oxide nanoparticles were coated with telomere of poly(- glycidylmethacrylate) in order to obtain good enzyme immobilization platform. The telomere and nanoparticles were characterized by using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). The biosensor’s potentiometric response was measured as a function of urea concentration in phosphate buffer solution (10 mM, pH 7.5) and showed a linear range of 0.25e5.0 mM urea. The produced biosensor exhibited a good response time of w8 s and was stable for about two months. The basic features (optimum pH, optimum temperature, interference and storage stability) of the enzyme electrode were determined
Emre Çevik,Mehmet S¸ enel,Abdulhadi Baykal,M. Fatih Abasıyanık 한국물리학회 2013 Current Applied Physics Vol.13 No.8
An amperometric phenol biosensor was constructed by using poly(glycidylmethacrylate-co-vinyl ferrocene) grafted iron oxide nanoparticles for detection of different phenolic compounds (catechol, aminophenol, phenol, p-cresol, pyrogallol). The poly(glycidylmethacrylate-co-vinyl ferrocene) and nanoparticles were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The copolymer grafted iron oxide nanoparticles and Horseradish peroxidase (HRP) were covalently attached on gold (Au) electrode surface. The effect of pH, temperature and characteristic features such as; reusability and storage stability were studied. The electrode showed good response time within w3 s. The electrocatalytic response showed a linear dependence on the phenolic compounds concentration ranging from 0.5 to 17.0 mM.
Mehmet Şenel,Emre Çevik 한국물리학회 2012 Current Applied Physics Vol.12 No.4
Horseradish peroxidase (HRP) was immobilized into an electrochemically prepared copolymer of pyrroleePAMAM (PAMAM; polyamidoamine) dendrimers for the construction of amperometric hydrogen peroxide biosensor. First, second, and third generation amidoamineepyrrole dendrons having branched amine periphery and focal pyrrole functionality were synthesized via divergent pathway. Pyrrole dendrimers were covalently attached onto the electrode surface and polymerized by electrochemical copolymerization with pyrrole monomer. The synthesized dendrimers and copolymers have been characterized by FTIR-ATR and NMR. These copolymers have been utilized as conducting films for amperometric hydrogen peroxide sensing. The HRP retains its bioactivity after immobilization into the dendronized pyrrole-copolymers. Amperometric response was measured as a function of concentration of hydrogen peroxide, at fixed potential of +0.35 V vs. Ag/AgCl in a phosphate buffered saline (pH 7.5). The effect of pH and temperature of the medium, storage, and reusability properties were investigated. The results indicate an efficient immobilization of enzyme onto the PAMAM type dendrimer modified surface containing pyrrole monomer, which leads to high enzyme loading, and increased lifetime stability of the electrode. Horseradish peroxidase (HRP) was immobilized into an electrochemically prepared copolymer of pyrroleePAMAM (PAMAM; polyamidoamine) dendrimers for the construction of amperometric hydrogen peroxide biosensor. First, second, and third generation amidoamineepyrrole dendrons having branched amine periphery and focal pyrrole functionality were synthesized via divergent pathway. Pyrrole dendrimers were covalently attached onto the electrode surface and polymerized by electrochemical copolymerization with pyrrole monomer. The synthesized dendrimers and copolymers have been characterized by FTIR-ATR and NMR. These copolymers have been utilized as conducting films for amperometric hydrogen peroxide sensing. The HRP retains its bioactivity after immobilization into the dendronized pyrrole-copolymers. Amperometric response was measured as a function of concentration of hydrogen peroxide, at fixed potential of +0.35 V vs. Ag/AgCl in a phosphate buffered saline (pH 7.5). The effect of pH and temperature of the medium, storage, and reusability properties were investigated. The results indicate an efficient immobilization of enzyme onto the PAMAM type dendrimer modified surface containing pyrrole monomer, which leads to high enzyme loading, and increased lifetime stability of the electrode.
Mehmet Şenel,Cevdet Nergiz 한국물리학회 2012 Current Applied Physics Vol.12 No.4
A glucose biosensor is fabricated with immobilization of glucose oxidase (GOx) on poly(pyrrole propylic acid)/Au nanocomposite by covalent attachment. Poly(pyrrole propylic acid) (PPyAA)/Au nanocomposite was prepared by chemical oxidation of pyrrole propylic acid monomer by using chloroauric acid (HAuCl4)as an oxidizing agent. The obtained nanocomposites were used to fabricate highly sensitive amperometric glucose biosensor which exhibited a high and reproducible sensitivity of 0.42 mA/mM, response time w2 s, linear dynamic range from 1 to 18 mM, correlation coefficient of R2= 0.9981, and limit of detection (LOD), based on S/N ratio (S/N = 3) of 0.05 mM. A value of 1.83 mM for the apparent Michaelis eMenten constant Kapp m was obtained. The high sensitivity, wider linear range, good reproducibility and stability make this biosensor a promising candidate for portable amperometric glucose biosensor.
Mahmut Can Şenel,Mevlüt Gürbüz 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
In the present study, boron carbide and graphene-reinforced aluminum hybrid composites with various boron carbide (1,3, 6, 9, 12, 15, 30 wt%) and graphene nanoplatelets (GNPs) content (0.15, 0.30, 0.45 wt%) were produced by the powdermetallurgy method. The method consists of mixing, ultrasonic dispersing, mixing, fltering, drying, pressing, and sinteringprocesses. The apparent density, compressive strength, and Vickers hardness of the fabricated composites were determined bydensity meter, universal test machine, and micro Vickers hardness measurement device, respectively. The phase and microstructural analysis of the fabricated composites were analyzed using an X-ray difraction device and scanning electron microscope, respectively. The maximum apparent density (2.54±0.005 g/cm3), the highest Vickers hardness (109.8±1.5 HV),the best compressive strength (244±5 MPa), and minimum porosity (4.0%) were obtained at Al-30%B4C-0.15%GNPscomposite. The enhancement in Vickers hardness and compressive strength of Al-30%B4C-0.15%GNPs composite wasdetected as +293% and +190% compared with pure aluminum. In conclusion, it was detected that the mechanical strengthof Al-30B4C-GNPs composites improved up to 0.15 wt%GNPs content. After 0.15 wt%graphene content, the mechanicalstrength of Al-30B4C-GNPs composites decreased due to the agglomerated graphene nanoparticles.
İbrahim Bozgeyik,Mehmet Şenel,Emre Çevik,M. Fatih Abasıyanık 한국물리학회 2011 Current Applied Physics Vol.11 No.4
An amperometric biosensor has been developed for the measurement of urea. To construct the proposed biosensor urease enzyme was immobilized onto poly(N-glycidylpyrrole-co-pyrrole) conducting film by direct covalent attachment. The biosensor surface was characterized by FTIR spectroscopy and atomic force microscopy (AFM). The response studies were carried out as a function of urea concentration with amperometric measurements. The biosensor showed a linear current response to the urea concentration ranging from 0.1 to 0.7 mM. The urea biosensor exhibited a sensitivity of 4.5 μA/mM with a response time of 4 s. The factors influencing on the performance of the resulting biosensor were also studied in detail.
Emre Çevik,Mehmet Şenel,M. Fatih Abasıyanık 한국물리학회 2010 Current Applied Physics Vol.10 No.5
A galactose biosensor was developed by immobilizing galactose oxidase (GAox) on poly (glycidyl methacrylate-co-vinylferrocene) (poly (GMA-co-VFc)) film. The enzyme was immobilized via amine group onto polymeric mediator. The biosensor was characterized by the specific activity of the immobilized galactose oxidase, the apparent Michaelis constant , and the stability expressed by time and a number of the performed analysis. The optimized galactose biosensor exhibited a linear response range from 2 to 20 M and detection limit of 0.1 mM toward galactose. The response time of the biosensor was 5 s. The effects of the pH and the temperature of the immobilized galactose oxidase electrode were also studied.
Kökoğlu Emel Oğuz,Kızıltepe Melih,Şaş Senem,Eldemir Yasemin Özden,Ünal Tuba Dilay Kökenek,Şenel Abdurrahman Soner 소화기인터벤션의학회 2023 International journal of gastrointestinal interven Vol.12 No.2
Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition involving the development of mass lesions of the affected organ, which can mimic many malignant disorders. IgG4-related autoimmune pancreatitis (AIP) is a common presentation form of IgG4-RD. Patients presenting with multiple mass lesions in the pancreas undergo aggressive surgeries with the misdiagnosis of pancreatic adenocarcinoma. A patient applied to the health center with back and stomach pain. She had two mass lesions involving the pancreatic head and tail; tumor markers were not significantly elevated. The patient underwent total pancreatoduodenectomy, total gastrectomy, and total splenectomy due to misdiagnosed pancreatic adenocarcinoma and developed severe morbidities afterward. She was diagnosed with IgG4-related AIP after surgery. On performing clini-cal suspicion the necessary diagnostic procedures for exclusion will protect patients from unnecessary surgeries that may lead to severe morbidities.