Browsing by Author "Guler, Muhammet"

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Determination of Malation, Methidathion, and Chlorpyrifos Ethyl Pesticides Using Acetylcholinesterase Biosensor Based on Nafion/Ag@rgo-nh2 Nanocomposites
(Pergamon-elsevier Science Ltd, 2017) Guler, Muhammet; Turkoglu, Vedat; Basi, Zehra
Herein, a facile electrochemical acetylcholinesterase (EC 3.1.1.7; AChE) biosensor based on nafion (NA) and Ag nanoparticles supported on amine functionalized reduced graphene oxide (rGO-NH2) was developed. The Ag@rGO-NH2 nanocomposite was characterized using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). After being optimized, the biosensor exhibited excellent electrochemical response to the oxidation of thiocholine, the hydrolysis product of acetylthiocholine chloride (ATCl) catalyzed by AChE. An apparent Michealis-Menten value of 20.5 mu M was obtained. Under optimized conductions, the biosensor detected malation, methidathion, and chlorpyrifos ethyl in the linear range from 0.0063 to 0.077 mu g/mL, from 0.012 to 0.105 mu g/mL, and from 0.021 to 0.122 mu g/mL, respectively. The detection limit (LoD) was 4.5 ng/mL for malation, 9.5 ng/mL for methidathion, and 14 ng/mL for chlorpyrifos ethyl. Also, the NA/Ag@rGO-NH2/ AChE/GCE biosensor showed god sensitivity, stability and repeatability, which provides a promising tool for the detection of organophosphate pesticides. (C) 2017 Elsevier Ltd. All rights reserved.
Development of a Functionalized SiO2 Supported Ni Nanoparticles Based Non-Enzymatic Amperometric Dopamine Sensor
(2024) Yıldırım, Yunus Emre; Guler, Muhammet
In the present work, a novel electrochemical dopamine (DA) sensor depending on Nickel (Ni) nanoparticles decorated (3-aminopropyl)triethoxysilane (APTES) modifed silica (SiO2) was fabricated. Hence, Ni@SiO2-APTES was synthesized by the conventional wet-impregnation method. The structure of the compozite was evaluated using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and X-ray diffraction (XRD). The synthesized Ni@SiO2-APTES was loaded on glassy carbon working electrode (GCE). Also, Nafion (Nf) was drop-casted on Ni@SiO2-APTES/GCE to stabilize the electrode. The fabricated Nf/Ni@SiO2-APTES/GCE working electrode was electrochemicaly evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometry. CV and EIS results indicated that Ni nanoparticles increased both the conductivity and sensitivity of the working electrode. The linear detection range for DA was found to be 0.2 – 252 µM with limit of detection (LOD) was 0.07 µM depending on S/N of 3. The sensitivity was found to be 578.26 µA mM-1 cm-2 depending on the active surface area of the modified working electrode. The sensor exhibited excellent selectivity in the electrolyte solution including ascorbic acid, glucose, fructose, sucrose, mannose, uric acid, and phenylalanine. The sensor had satisfactory repeatability and reproduciblity. It was observed that the sensor showed an electrocatalytic response of 95.33% after 28 days. According to this result, it was concluded that the sensor was extremely stable within the studied time period. The applicability of Nf/Ni@SiO2-APTES/GCE was tested using dopamine HCl injection (200 mg/5 mL).
Development of Non-Enzymatic Electrochemical P-Nitrophenol Sensor Based on Carboxylated Graphene Oxide Modified Glassy Carbon Electrode
(2024) Guler, Muhammet; Hussein, Zhivan Tayeb Ali
The current work reports a new electrochemical p-nitrophenol (p-NP) sensor which depends upon the carboxyl functionalized graphene oxide (GO-COOH) modified of glassy carbon electrode (GCE). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were performed to examine the morphology of GO-COOH. The GO-COOH/GCE sensor was electrochemically characterized by means of chronoamperometry, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). A distinct cathodic peak of p-NP was seen on the GO-COOH/GCE in 0.1 M phosphate buffer solution (pH 6.5). The sensor displayed three dynamic linear ranges for p-NP under optimum conductions. The linear detection ranges were 2.0×10-7 - 2.95×10-6 M, 2.95×10-6 – 2.74×10-4 M, and 2.74×10-4 – 7.25×10-4 M with the sensitivities of 39622.1 A/Mm2, 9959.3 A/Mm2, and 6395 A/Mm2, respectively. It was found that detection limit (LOD) was 5.3×10-8 M at a signal to noise ratio of 3. The GO-COOH/GCE demonstrated satisfactory performance factors such as selectivity and repeatability. Additionally, the GO-COOH/GCE sensor was demonstrated to be utilized to electrochemically determine p-NP in a variety of water samples.
Differential Pulse Voltammetric Determination of Dopamine Using Pd Nanoparticles Deposited on (3-Aminopropyl)triethoxysilane Functionalized Ceo2 Nanoparticles
(Tubitak Scientific & Technological Research Council Turkey, 2018) Guler, Muhammet
In this study, a novel and effective electrochemical sensor for determination of dopamine (DA) was successfully developed by the modification of a glassy carbon electrode (GCE) using Pd nanoparticles deposited on (3-aminopropyl)triethoxysilane functionalized nanoceria (Pd@CeO2-APTES) and nation used as a protective membrane. The synthesized nanocomposites were evaluated using X-ray diffraction, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. Moreover, the electrochemical properties of the modified electrodes were investigated using cyclic voltammetry, electrochemical impedance voltammetry, and differential pulse voltammetry (DPV) The Nf/Pd@CeO2-APTES/GCE showed a linear range of 2.5-149.5 mu M for DA by DPV with a notable sensitivity of 3.89 mA mM(-1) cm(-2) and a low limit of detection of 0.46 mu M based on the signal-to-noise ratio of 3 (S/N = 3). In addition, the sensor exhibited satisfactory selectivity, remarkable sensitivity, repeatability, and reproducibility. The sensor protected 92.07% of its initial electrocatalytic activity toward the oxidation of dopamine after 30 days. The Nf/Pd@CeO2-APTES/GCE was used for determination of DA in serum samples. The results indicate that the sensor can be a notable device for the detection of DA in biological fluids.
Electrochemical Characterization of Vitamin B2 (Riboflavin) at Ag Nanoparticles Synthesized by Green Chemistry Dispersed on Reduced Graphene Oxide
(Elsevier Science Sa, 2023) Guler, Muhammet; Meydan, Ismet; Seckin, Hamdullah
The present study describes a novel electrochemical riboflavin (RF) sensor based on the green synthesis of silver (Ag) nanoparticles dispersed on reduced graphene oxide (rGO). The Ag nanoparticles was synthesized using Arum italicum leaf extract as reducing and stabilizing agent. The characterization of Ag nanoparticles was carried out using FT-IR, XRD, and SEM-EDX. The electrochemical studies were performed using cyclic voltammetry and differential pulse voltammetry. The Ag/rGO modified glassy carbon electrode (Ag/rGO/GCE) exhibited excellent electrochemical responses to the oxidation/reduction (redox) of RF. The sensor exhibited a linear determination range from 2 x 10-9 to 2.2 x 10-6 M with limit of detection (LOD) of 0.6 nM. The sensor had the sensitivity of 71.4 mu A mu M-1 cm-2. The sensor had satisfactory selectivity, reproducibility of 3.4 % and storage stability of 90.4 %. Also, the fabricated sensor was proved to be useful for the determination of RF in pharmaceutical samples.
Electrochemical Detection of Malathion Pesticide Using Acetylcholinesterase Biosensor Based on Glassy Carbon Electrode Modified With Conducting Polymer Film
(Springer Heidelberg, 2016) Guler, Muhammet; Turkoglu, Vedat; Kivrak, Arif
Acetylcholinesterase (AChE) biosensor based on conducting poly([2,2;5';2 '']-terthiophene-3-carbaldehyde) (PTT) modified glassy carbon electrode (GCE) was constructed. AChE was immobilized on PTT film surface through the covalent bond between aldehyde and amino groups. The properties of PTT modified GCE were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The biosensor showed an oxidation peak at +0.83 V related to the oxidation of thiocholine, hydrolysis product of acetylthiocholine iodide (ATCI), catalyzed by AChE. The optimum current response of the biosensor was observed at pH 7.5-8.0, 40 degrees C and 120 U/cm(2) of AChE concentration. The biosensor showed a high sensitivity (183.19 mu A/mM), a linear range from 0.015 to 1.644 mM, and a good reproducibility with 1.7 % of relative standard deviation (RSD). The biosensor showed a good stability. The interference of glycin, ascorbic acid, histidine, uric acid, dopamine, and arginine on the biosensor response was studied. An important analytical response from these inteferents that overlaps the biosensor response was not observed. The inhibition rate of malathion as a model pesticide was proportional to its concentrations from 9.99 to 99.01 nM. The detection limit was 4.08 nM.
Electrochemical Determination of 4-Nitrophenol Using Functionalized Graphene Oxide/Functionalized Multi-Walled Carbon Nanotubes Hybrid Material Modified Glassy Carbon Electrode
(Elsevier, 2025) Saeed, Pasar Nizar; Guler, Muhammet
Herein, a novel carboxylated multi-walled carbon nanotubes-carboxylated graphene oxide coated glassy carbon electrode (f-MWCNTs/f-GO/GCE) was prepared for electrochemical determination of 4-nitropehenol (4-NP). The sensor was characterized using fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), raman spectroscopy, and powder x-ray diffraction (XRD). Electrochmical experiments were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. The resulting f-MWCNTs/f-GO/GCE could be performed for quick, sensitive, and selective determination of 4-NP in the presence of other electroactive compounds. 4-NP was electrochemically detected depending on the reduction of 4-NP at -0.65 V potential using amperometric method. Under the optimum condutions, the sensor showed excellent response to the determination of 4-NP with three linear detection ranges from 0.018 to 700 mu M. The sensor exhibited extremely low limit of detection (5.4 nM). Also, the fabricated sensor was used for detection of 4-NP in different water samples.
Electrochemical Dopamine Sensor Based on Gold Nanoparticles Electrodeposited on a Polymer/Reduced Graphene Oxide-Modified Glassy Carbon Electrode
(Taylor & Francis inc, 2022) Guler, Muhammet; Kavak, Emrah; Kivrak, Arif
A novel electrochemical dopamine (DA) sensor based on Au nanoparticles (AuNPs) electrochemically loaded on poly([2,2 ';5 ',2 '']-terthiophene-3 '-carbaldehyde)/reduced graphene oxide (poly(TTP)/rGO) improved glassy carbon electrode (GCE) was fabricated. The Au@poly(TTP)/rGO/GCE was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), amperometry, and electrochemical impedance spectroscopy (EIS). The optimized Au@poly(TTP)/rGO/GCE sensor had a wide electroactive surface area and exhibited good selectivity. The linear determination range of the sensor was from 0.02 to 232 mu M with a sensitivity of 315 mu A/mM/cm(2). The limit of detection (LOD) was estimated to be 11.5 nM using signal-to-noise (S/N) ratio of 3. Additionally, the sensor displayed excellent selectivity, satisfactory response time from 4.5 to 6 s, replicability with a relative standard deviation (RSD) of 2.31%, reproducibility with a RSD of 3.67%, and storage stability with 92.57% of its initial current response for 37 days. The Au@poly(TTP)/rGO/GCE was employed to estimate DA in injection samples.
Electrochemical Sensing of Hydrogen Peroxide Using Pd@ag Bimetallic Nanoparticles Decorated Functionalized Reduced Graphene Oxide
(Pergamon-elsevier Science Ltd, 2018) Guler, Muhammet; Turkoglu, Vedat; Bulut, Ahmet; Zahmakiran, Mehmet
In this study, an excellent sensitive, selective, and stable electrochemical sensor was fabricated for the determination of hydrogen peroxide (H2O2) using nafion (Nf) and Pd@Ag bimetallic nanoparticles supported on (3-aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO-NH2) modified glassy carbon (GC) electrode. The synthesized nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometer (XRD), and High-resolution transmission electron microscopy (HRTEM). The electrochemical properties of the nanocomposites were investigated by means of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Under optimized conditions, the electrochemical detection of H2O2 was carried out using amperometric method as well as CV. The linear range for H2O2 determination was 0.002-19.500 mM with a detection limit of 0.7 mu A and sensitivity of 1307.46 mu A mM(-1) cm(-2) due to the strong synergistic effect between Pd and Ag nanoparticles. The fabricated sensor was used for the determination of H2O2 in milk samples. The obtained results showed that the novel Nf/Pd@Ag/rGO-NH2/GC sensor can be used for the determination of H2O2 in real samples. (C) 2018 Elsevier Ltd. All rights reserved.
Electrochemical Sensing of Hydrogen Peroxide Using Pd@ag Bimetallic Nanoparticles Decorated Functionalized Reduced Graphene Oxide (Vol 263, Pg 118, 2018)
(Pergamon-elsevier Science Ltd, 2018) Guler, Muhammet; Turkoglu, Vedat; Bulut, Ahmet; Zahmakiran, Mehmet
Fabrication of Glucose Bioelectrochemical Sensor Based on Au@pd Core-Shell Supported by Carboxylated Graphene Oxide
(Academic Press inc Elsevier Science, 2023) Guler, Muhammet; Zengin, Adem; Alay, Murat
The study presents a novel electrochemical glucose biosensor based on glucose oxidase (GOx) immobilized on Au@Pd core-shell nanoparticles supported on carboxylated graphene oxide (cGO). The immobilization of GOx was achieved by cross-linking the chitosan biopolymer (CS) including Au@Pd/cGO and glutaraldehyde (GA) on a glassy carbon electrode. The analytical performance of GCE/Au@Pd/cGO-CS/GA/GOx was investigated using amperometry. The biosensor had fast response time (5.2 +/- 0.9 s), a satisfactory linear determination range between 2.0 x 10(-5) and 4.2 x 10(-3) M, and limit of detection of 10.4 mu M. The apparent Michaelis-Menten constant (K-app) was calculated as 3.04 mM. The fabricated biosensor also exhibited good repeatability, reproducibility, and storage stability. No interfering signals from dopamine, uric acid, ascorbic acid, paracetamol, folic acid, mannose, sucrose, and fructose were observed. The large electroactive surface area of carboxylated graphene oxide is a promising candidate for sensor preparation.
Fabrication of Non-Enzymatic Glucose Sensor Dependent Upon Au Nanoparticles Deposited on Carboxylated Graphene Oxide
(Elsevier Science Sa, 2020) Dilmac, Yusuf; Guler, Muhammet
In this article, Au nanoparticles (AuNPs) were deposited on carboxylated graphene oxide (GO-COOH) for the electrochemical oxidation and enzyme-free voltammetric and amperometric determination of glucose. The GO-COOAu modified glassy carbon electrode (GCE) exhibited good sensitivity and stability toward glucose electro-oxidation in alkaline media. The surface morphology of the as-prepared nanocomposite was investigated by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The electrochemical characterization of theworking electrodes was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. The GO-COOAu/GCE sensor provided excellent electro-catalytic performance for glucose oxidation with a linear range from 0.02 to 4.48 mM (R-2 = 0.9919) at +0.35 V, a low limit of detection (LOD) of 6 mu M, and a high sensitivity of 20.218 mu A mM(-1) cm(-2). The GO-COOAu nanocompositemodified working electrode with high sensitivity, repeatability, reproducibility, and quantification of glucose in human serumsamples made it a promising material for the development of non-enzymatic sensors.
In Vitro Determination of 6pgd Enzyme Activity Purified From Lake Van Fish (Chalcalburnus Tarichii Pallas, 1811) Liver Exposed To Pesticides
(Springer, 2013) Guler, Muhammet; Kivanc, M. Riza; Turkoglu, Vedat; Basi, Zehra; Kivrak, Hilal
In the present study, the effect of methidathion, cypermethrin, and deltamethrin pesticides on Lake Van fish (Chalcalburnus tarichii Pallas, 1811) liver 6-phosphogluconate dehydrogenase enzyme activity was investigated due to the fact that these pesticides are extensively used to improve agricultural productivity in the Van region. 2',5'-ADP Sepharose 4B affinity chromatography was used to purify 6-phosphogluconate dehydrogenase enzyme from fish liver and SDS-PAGE technique was used to control the purity of this enzyme. The in vitro effect of methidathion, cypermethrin, and deltamethrin pesticides on the enzyme activity was investigated. The enzyme was purified 1,050-fold with specific activity of 27.04 EU/mg protein. Moreover, K-i constants of methidathion, cypermethrin, and deltamethrin were to be 3.294 +/- A 0.215, 0.718 +/- A 0.095, and 0.084 +/- A 0.009 mM respectively. The IC50 value were estimated as 9.95 x 10(-5) +/- A 0.1844 x 10(-5) mM for methidathion, 1.01 x 10(-4) +/- A 0.01413 x 10(-4) mM for cypermethrin, and 4.43 x 10(-6) +/- A 0.05653 x 10(-6) mM for deltamethrin. In conclusion, deltamethrin inhibits the enzyme activity more than methidathion and cypermethrin.
İnsan Plazma ve Eritrosit Ache’nin Çeşitli İlaçlarla İn Vitro İnhibisyonu
(2016) Guler, Muhammet; Başı, Zehra; Türkoğlu, Vedat; Kıvanç, Mehmet Rıza
Bu çalışmada; yapısal olarak farklı olan sekiz antibiyotik (sefazolin, kanamisin, gentamisin, klindamisin, ivermektin ve ampisilin) ve ağrı kesicinin (metamizol ve diklofenak) insan eritrosit ve plazma asetilkolinesteraz (AChE; EC 3.1.1.7) enzimi üzerine in vitro etkileri araştırılmıştır. Bu amaçla; farklı derişimlere sahip ilaçların neden olduğu inhibisyonu belirlemek için ilaçların $IC_{50}$ ve $K_I$ değerleri hesaplandı. Asetilkolinesteraz aktivitesi spektrofotometrik olarak Ellman yöntemiyle belirlendi. Daha sonra, ilaçlara maruz kalan enzim aktivitesi ölçüldü. AChE aktivitesine karşı ilaç derişimi ve Michealis-Menten grafikleri çizildi. Son olarak, bu grafikler yardımıyla $IC_{50}$ ve $K_I$ değerleri hesaplandı. IC50 değerleri, plazma AChE’sine diklofenak için $1.78 x10^{-8}$ M ve eritrosit AChE’sine gentamisin için 0.85 x10^{-8}$ M olduğu belirlendi. $K_I$ değerleri ise diklofenak için $1.36 x10^{-8}$ M ve gentamisin için $1.16 x10-8$ M olarak hesaplandı. Ayrıca, ivermektin, klindamisin, kanamisin, ampisilin için $IC_{50}$ ve $K_I$ değerleri elde edildi. Diklofenak, plazma AChE aktivitesi üzerine gentamisin de eritrosit AChE aktivitesi üzerine en yüksek inhibitör etkisi göstermiştir. Bulunan bu değerlerin daha önce yapılan benzer çalışmalardaki inhibisyon değerlerinden daha yüksek olduğu görülmektedir [1,2].
A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3-Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide
(Wiley-v C H verlag Gmbh, 2017) Guler, Muhammet; Turkoglu, Vedat; Kivanc, Mehmet Riza
In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3-aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO-APTES) and hydrogen peroxide sensor based on rGO-APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO-APTES/GOx/GC and Nf/rGO-APTES/GC composites showed good electrocatalytical activity toward glucose and H2O2, respectively. The Nf/rGO-APTES/GC electrode exhibited a linear range of H2O2 concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 mu A mM(-1)cm(-2). The Nf/rGO-APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 mu M and sensitivity of 75.26 mu A mM(-1)cm(-2). Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.
A Novel Glucose Oxidase Biosensor Based on Poly([2,2′; 5′,2"]-Terthiophene Modified Electrode
(Elsevier Science Bv, 2015) Guler, Muhammet; Turkoglu, Vedat; Kivrak, Arif
In the study, the electrochemical behavior of glucose oxidase (GOx) immobilized on poly([2,2';5',2 '']-terthiophene-3'-carbaldehyde) (poly(TTP)) modified glassy carbon electrode (GCE) was investigated. The biosensor (poly(TTP)/GOx/GCE) showed a pair of redox peaks in 0.1 M phosphate buffer (pH 7.4) solution in the absence of oxygen the co-substrate of GOx. In here, Poly(TTP)/GOx/GCE biosensor acts as the co-substrate instead of oxygen. Upon the addition of glucose, the reduction and oxidation peak currents increased until the active site of GOx was fully saturated with glucose. The apparent m was estimated 26.13 mM from Lineweaver-Burk graph. The biosensor displayed a good stability and bioactivity. The biosensor showed a high sensitivity (56.1 nA/mM), a linear range (from 0.5 to 20.15 mM), and a good reproducibility with 3.6% of relative standard deviation. In addition, the interference currents of glycin, ascorbic acid, histidine, uric acid, dopamine, arginine, and fructose on GOx biosensor were investigated. All that substances exhibited an interference current under 10%. It was not shown a marked difference between GOx biosensor and spectrophotometric measurement of glucose in serum examples. UV-visible spectroscopy and scanning electron microscopy (SEM) experiments of the biosensor were also performed. (C) 2015 Elsevier B.V. All rights reserved.
A Novel Nonenzymatic Hydrogen Peroxide Amperometric Sensor Based on Pd@ceo2-Nh2 Nanocomposites Modified Glassy Carbon Electrode
(Elsevier Science Bv, 2018) Guler, Muhammet; Turkoglu, Vedat; Kivrak, Arif; Karahan, Fatih
Herein, (3-aminopropyl)triethoxysilane functionalized cerium (IV) oxide (CeO2-NH2) supported Pd nano particles were synthesized. The nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and High-resolution transmission electron microscopy (HRTEM). The Pd@CeO2-NH2 showed better electrocatalytic response to the reduction of H2O2 than CeO2-NH2. The fabricated sensor exhibited two linear responses to the reduction of H2O2. The first one was from 0.001 to 3.276 mM with 0.47 mu M of a limit of detection (LOD) (S/N = 3) and excellent sensitivity of 440.72 mu A mM(-1) cm(-2) and the second one was from 3.276 to 17.500 mM with the sensitivity of 852.65 mu A mM(-1) cm(-2) in the optimum conductions. Also, the sensor exhibited 91% of electrocatalytic activity toward H2O2 after having been used for 30 days and the reproducibility was also satisfactory. The sensor response to H2O2 was not affected by ascorbic acid, fructose, glycine, dopamine, arginine, mannose, glucose, uric acid, Mg+2, Ca+2, and phenylalanine at the studied potential. Also, the fabricated sensor was used to determine H2O2 in milk samples. The results show that the constructed sensor can be a promising devise for the determination of H2O2 in real samples.
Palladium Nanoparticles Decorated (3-Aminopropyl)triethoxysilane Functionalized Reduced Graphene Oxide for Electrochemical Determination of Glucose and Hydrogen Peroxide
(Elsevier Science Sa, 2019) Guler, Muhammet; Dilmac, Yusuf
This study presents the fabrication of a glucose biosensor based on the immobilization of glucose oxidase (GOx) on Pd nanoparticles (PdNPs) loaded (3-aminopropyl)triethoxysilane (APTES) functionalized reduced graphene oxide (rGO-APTES) and non-enzymatic H2O2 sensor based on Pd@rGO-APTES nanocomposite modified glassy carbon electrode (GCE). Also, Nafion (Nf) was used as a protective membrane for the sensor and biosensor. The electrocatalytic properties of the sensor and biosensor were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The Nf/Pd@rGO-APTES/GOx/GCE biosensor sensitively measured glucose and showed a linear range from 3 mu M to 4.57 mM with a detection limit (LOD) of 0.91 mu M. The biosensor had a sensitivity of 234.1 mu A mM(-1) cm(-2) and an acceptable selectivity for glucose. The Nf/Pd@rGO-APTES/GCE nanocomposites had an excellent electrochemical response to the reduction of H2O2. The linear range of the sensor for the detection of H2O2 concentration was from 0.7 mu M to 13.5 mM with 0.21 mu M of LOD. The sensitivity was calculated to be 1164.3 mu A mM(-1) cm(-2). In addition, the sensor and biosensor showed excellent sensitivity, selectivity, response time, linear range, LOD, repeatability, reproducibility, and storage stability when compared with reported sensors and biosensors.
Pd Nanoparticles Supported on Fe3o4 Particles Grafted With Poly(Acrylamide) Gel Brush for Simultaneous Electrochemical-Sensing of Dopamine and Paracetamol
(Wiley-v C H verlag Gmbh, 2024) Guler, Muhammet; Zengin, Adem
In the present study, a glassy carbon electrode (GCE) modified with Pd nanoparticles deposited on poly(acrylamide) gel brush-grafted magnetic particles (Pd/PAAm(GB)@Fe3O4) with core-shell structure was fabricated for simultaneous electrochemical detection of dopamine (DA) and paracetamol (PA). Electrochemical performance of Pd/PAAm(GB)@Fe3O4/GCE was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The fabricated sensor exhibited voltammetric sensing with a satisfactory linear determination range from 0.4-41 mu M for DA and from 0.5-95 mu M for PA. The limit of detection (LOD) was 0.1 mu M for DA and 0.17 mu M for PA based on signal to noise ratio of 3. The proposed sensor also had excellent reusability and selectivity, good reproducibility and stability, and satisfactory recovery in biomedical examples. It is believed that metal nanoparticles deposited on polymer gel brush composites may offer promising new horizons for sensor growth.
Properties and Some in Vitro Studies of 6-Phosphogluconate Dehydrogenase Purified From the Liver of Chalcalburnus Tarichi, the Only Fish Living in Lake Van's Highly Alkaline Water (Ph 9.8)
(Tubitak Scientific & Technological Research Council Turkey, 2015) Guler, Muhammet; Turkoglu, Vedat; Kivanc, Mehmet Riza
In this study, some enzymology parameters and some antibiotics affecting the enzyme activity of 6phosphogluconate dehydrogenase (6PGD) extracted from t the livers of fish from Lake Van (Chalcalburmas tarichi) were investigated because it is an important enzyme-producing NADPH, a reductive power, protecting the cell against the oxidative agents by producing reduced glutathione. The crude enzyme solution was obtained by using the affinity chromatography method. The native molecular weight of the enzyme is similar to 90,000 +/- 3000 Da and it is composed of two subunits with identical molecular weights of similar to 46,000 Da as exhibited on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pH and temperature for optimal conditions of 6PGD were about 8.5 and 40 degrees C, respectively, and the enzyme showed optimal activity in 40 mM ammonium sulfate solution. In addition, in vitro effects of clindamycin phosphate, streptomycin sulfate, and lincomycin antibiotics on the enzyme activity were investigated.