Emre Çevik

Construction of novel xanthine biosensor by using polymeric mediator/MWCNT nanocomposite layer for fish freshness detection.

A novel nanocomposite host matrix for enzyme immobilization of xanthine oxidase was developed by incorporating MWCNT in poly(GMA-co-VFc) copolymer film. In the food industry fish is a product with a very low commercial life, and a high variability as well elevated level of xanthine is an important biomarker as a sign of spoilage. The fabricated process was characterized by scanning electron microscopy (SEM), and the electrochemical behaviors of the biosensor were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The prepared enzyme electrodes exhibited maximum response at pH 7.0 and 45°C +0.35 V and reached 95% of steady-state current in about ∼ 4 s and its sensitivity was 16 mAM(-1). Linear ranges (2-28 μM, 28-46 and 46-86 μM), analytical performance and a low detection limit 0.12 μM obtained from the xanthine biosensor gives reliable results in measuring xanthine concentration in the fish meat. All the results indicating that the resulting biosensor exhibited a good response to xanthine that was related to the addition of MWCNT in the polymeric mediator film which played an important role in the biosensor performance. In addition, the biosensor exhibited high good storage stability and satisfactory anti-interference ability.

Construction of novel electrochemical immunosensor for detection of prostate specific antigen using ferrocene-PAMAM dendrimers.

In this study, an immunosensor was designed to utilize for the detection of prostate specific antigen (PSA) based on three different generations (G1, G2 and G3) of ferrocene (Fc) cored polyamidiamine dendrimers (Fc-PAMAM) gold (Au) electrode. The self-assembled monolayer principle (SAM) was used to fabricate the sensitive, selective and disposable immunosensor electrodes. In electrode fabrication cysteamine (Cys) was the first agent covalently linked on the Au electrode surface. Immobilized redox center (ferrocene) cored PAMAM dendrimers served as a layer for the further binding of biological components. The monoclonal antibody of PSA (anti-PSA) was covalently immobilized on dendrimers which were attached onto the modified Au surface (Au/Cys/Fc-PAMAMs/anti-PSA). PSA levels were quantitatively analyzed by using electrochemical differential pulse voltammetry (DPV) whose lowest detection limit was calculated as 0.001ngmL(-1). The Au/Cys/FcPAMAM/anti-PSA immunosensor showed excellent performance for PSA at the pulse amplitude; 50mV and the scan rate; 10mV/s in a wide linear concentration range of 0.01ng-100ngmL(-1). Analytical performance and specificity assays were carried out using human serum and different proteins.

Development of glucose biosensor based on reconstitution of glucose oxidase onto polymeric redox mediator coated pencil graphite electrodes

In this study, a novel glucose biosensor was fabricated by reconstitutional immobilization of glucose oxidase (GOx) onto a poly(glycidyl methacrylate-co-vinylferrocene) (poly(GMA-co-VFc)) film coated pencil graphite electrode (PGE). The amperometric current response of poly(GMA-co-VFc)-GOx to glucose is linear in the concentration range between 1 and 16mM (correlation coefficient of 0.9998) with a detection limit of 2.7μM (S/N=3). Experimental parameters were studied in detail and optimized, including the pH and temperature governing the analytical performance of the biosensor. The stability and reusability of the biosensor as well as its kinetic parameters have also been studied.

An electrochemical immunosensor for sensitive detection of Escherichia coli O157:H7 by using chitosan, MWCNT, polypyrrole with gold nanoparticles hybrid sensing platform

An electrochemical immunosensor for the common food pathogen Escherichia coli O157:H7 was developed. This novel immunosensor based on the PPy/AuNP/MWCNT/Chi hybrid bionanocomposite modified pencil graphite electrode (PGE). This hybrid bionanocomposite platform was modified with anti-E. coli O157:H7 monoclonal antibody. The prepared bionanocomposite platform and immunosensor was characterized by using cyclic voltammetry (CV). Under the optimum conditions, the results have shown the order of the preferential selectivity of the method is gram negative pathogenic species E. coli O157:H7. Concentrations of E. coli O157:H7 from 3×101 to 3×107cfu/mL could be detected. The detection limit was ∼30cfu/mL in PBS buffer. Briefly, we developed a high sensitive electrochemical immunosensor for specific detection of E. coli O157:H7 contamination with the use of sandwich assay evaluated in this study offered a reliable means of quantification of the bacteria. For the applications in food quality and safety control, our immunosensor showed reproducibility and stability.

Development of an Amperometric Hydrogen Peroxide Biosensor based on the Immobilization of Horseradish Peroxidase onto Nickel Ferrite Nanoparticle-Chitosan Composite

Nickel ferrite (NiFe2O4) nanoparticles have been dispersed in chitosan solution in order to fabricate nanocomposite films. Horseradish peroxidase (HRP) has been immobilized onto this chitosan-NiFe2O4 nanocomposite film via physical adsorption. The size of the NiFe2O4 nanoparticles has been estimated using X-ray diffraction pattern and scanning electron microscopy (SEM) to be 40±9 nm. The chitosan-NiFe2O4 nanocomposite film and HRP/chitosan-NiFe2O4 bioelectrode have been characterized using SEM technique. The HRP/chitosan-NiFe2O4 nanocomposite bioelectrode has a response time of 4 s, linearity as 0.3 to 12mM of H2O2, sensitivity as 22 nA/mM. The effects of pH and the temperature of the immobilized HRP electrode have also been studied.

Electrochemical sensing platforms based on the different carbon derivative incorporated interface.

their effects on the properties of these biosensors. Biosensors were prepared by Horseradish peroxidase (HRP) immobilization on the composite electrodes composed of carbon black, carbon nanofiber (CNF), extended graphite, multiwalled carbon nanotube (MWCNT), reduced graphene oxide (REGO) and poly(glycidyl methacrylateco-vinylferrocene) (P(GMA-co-VFc)) as mediator, covalent linker, and host matrix for carbon derivatives. The modified pencil graphite electrode (PGE) was used for the detection of hydrogen peroxide and to follow electrochemical behavior of different carbon derivatives which were recorded. The electrochemical characterization was investigated by cyclic voltammetry and electrochemical impedance spectroscopy methods. Amperometric measurements showed that the REGO and MWCNT modified electrodes have excellent performance in comparison with other carbon derivatives studied.

Novel impedimetric dopamine biosensor based on boronic acid functional polythiophene modified electrodes

In this study we report a new, simple and first impedimetric biosensor based on 3-Thienyl boronic acid for dopamine detection. Biosensor electrode preparation is 1min long by simple electro-polymerization of 3-Thienyl boronic acid and copolymer Thiophene P(TBA0.50Th0.50). Strong interaction between dopamine and thin layer of boronic acid has provided bio-sensing electrode high selectivity and stability, linear range of 7.8 to 125μM, and detection limit of 0.3μM. Characterization and optimization studies were conducted using electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV). In order to test reliability of proposed biosensor real sample application study has been conducted using non-diluted human urine and it has been found that biosensor selectivity and recovery is excellent. As well P(TBA0.50Th0.50) based electrode and dopamine interaction has been proven by single frequency impedance measurements. Biosensors acquired good reproducibility, stability, selectivity and very low interference.

Construction of ferrocene modified conducting polymer based amperometric urea biosensor

Herein, an electrochemical urea sensing bio-electrode is reported that has been constructed by firstly electropolymerizing 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline monomer (SNS-Aniline) on Pencil Graphite Electrode (PGE), then modifying the polymer coated electrode surface with di-amino-Ferrocene (DAFc) as the mediator, and lastly Urease enzyme through glutaraldehyde crosslinking. The effect of pH, temperature, polymer thickness, and applied potential on the electrode current response was investigated besides performing storage and operational stability experiments with the interference studies. The resulting urea biosensors amperometric response was linear in the range of 0.1-8.5mM with the sensitivity of 0.54μA/mM, detection limit of 12μM, and short response time of 2s. The designed bio-electrode was tested with real human blood and urine samples where it showed excellent analytical performance with insignificant interference.

Electrochemical Glucose Biosensors: Whole Cell Microbial and Enzymatic Determination Based on 10-(4H-Dithieno[3,2-b:2′,3′-d]Pyrrol-4-yl)Decan-1-Amine Interfaced Glassy Carbon Electrodes

Abstract The fabrication of amperometric biosensors based on whole cell Gluconobacter oxydans DSMZ 2343 (G. oxydans) and glucose oxidase (GOx) was performed for the detection of glucose. Glassy carbon electrodes (GCE) were coated with a 10-(4H-dithiyeno [3,2-b:2’,3’-d]pyroll-4-il)decan-1-amine (DTP-alkyl-NH2) polymer using an electropolymerization method and the formed interface was used to connect the bacteria and the enzyme to the electrode. The transfer of electrons from enzyme to electrode was successfully demonstrated by the biocatalytic activity and unique morphology of the conducting polymer. Characterization of the biosensors was assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analyses. The detection limits of the enzyme and microbial based biosensors for glucose were 0.022 and 0.081 mM, respectively. The broad linear dynamic ranges of the GOx and G. oxydans biosensors were observed to be 0.045–50.0 and 0.19–50.0 mM, respectively. The analytical performances of biosensors were compared according to the following figures of merit: detection limits, limits of quantification, pH and current response time. In addition, to demonstrate the applicability of the biosensors, real-time measurements and recovery studies were evaluated.