Ergun Ekinci

Electrochemical synthesis and sensor application of poly (1,4-diaminobenzene)

This paper describes a novel polymeric matrix, poly (p-phenylenediamine), as glucose oxidase entrapment media for amperometric glucose determination. The glucose sensor was constructed in a one-step procedure by anodic electropolymerization of p-phenylenediamine and concomitant incorporation of glucose oxidase at a potential of 0.7 V versus Ag/AgCl. Results show that the new glucose sensor has a linear range up to 6 mM, fast response time (less than 4 s) and high sensitivity. The specificity of the enzyme electrode for possible interfering species such as lactose, sucrose and urea was tested, and no discernible anodic signal was detected above the background current. Moreover, the effects of pH and temperature on the amperometric response were systematically investigated and the activation energy for enzymatic reaction was calculated as 41 kJ/mol. Also, the biosensor was found to be stable for more than 30 days.

Synthesis, Characterization of a New Organosoluble Polyimide and Its Application in Development of Glucose Biosensor

A new aromatic organosoluble polyimide was synthesized from the 4,4′-Diaminodiphenileethane with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) via a conventional two-stage process. This polymer showed good solubilities in N-methyl-2-pyrrolidone and m-cresol. The polyimide was characterized by FT-IR, GPC, TGA, DSC and DTA, with intrinsic viscosity and adhesive properties also being evaluated. Then, glucose oxidase (GOD) enzyme was immobilized into aromatic organosoluble polyimide by two different methods. It was demonstrated that the poly[4,4′-Diamina very promising substrate for the immobilization and stabilization of enzymes and the development of highly stable biosensors.

Poly[tris((p-aminophenoxy)phosphineoxide)-3,3′,4,4′-benzophenonetetracarboxylicdiimide] as a New Polymeric Membrane for the Fabrication of an Amperometric Glucose Sensor

Poly[tris((p-aminophenoxy)phosphineoxide)-3,3′,4,4′-benzophenonetetracarboxylicdiimide] (PAB) was used as an immobilized enzyme membrane for the fabrication of an amperometric glucose sensor. Enzyme immobilization was performed by two different methods and structural morphology of immobilized enzyme membrane was studied by SEM. The amperometric response of the sensor to hydrogen peroxide, formed as the product of the enzymatic reaction, was measured at a potential of 0.7 V in phosphate buffer solution by means of the TB technique. The influence of preparation conditions (polyimide film thickness, enzyme amount) on electrode performance was examined to obtain the optimal experimental parameters. Sensor characteristics (pH, response time, selectivity, stability) of the PAB/GOx/Pt electrode prepared under optimal conditions has been investigated. Results showed that this sensor exhibited a linear range up to 6 mM and a response time of about 60 s. with good stability. When glucose was injected into the PBS solution in the presence of fouling substances (lactose, sucrose, and urea), excellent amperometric responses were observed. Also, it was seen that the PAB/GOx-Pt electrode blocked the signal current of electroactive oxalic acid.

Electropolymerized Polytyramine Film for the Selective Determination of Uric Acid

Electropolymerized polytyramine film was proposed for determination of uric acid in the presence of ascorbic acid. The influence of electropolymerization conditions on performance of the polytyramine film was examined to obtain the optimal experimental parameters. The voltammetric results demonstrated that polytyramine film obtained at the optimized conditions allowed penetration of large amounts of uric acid while blocking the permeation of electroactive (ascorbic acid, cysteine and oxalic acid) and non-electroactive interferents (lactose, sucrose and urea) through film in PBS. Therefore, it has been claimed that the polymeric film could be used as uric acid-selective membrane over a broad range of interference.

Poly (3-aminophenol) Film as a Uric Acid-Selective Electrode

In order to prepare uric acid-selective polymeric membrane in the presence of electroactive (ascorbic acid, cysteine, oxalic acid) and nonelectroactive (lactose, sucrose and urea) substances, poly (3-aminophenol) films were prepared by means of electropolymerization on Pt electrodes. By systematically investigating the influence of polymerization conditions on sensor performance of the poly (3-aminophenol) film, the optimal parameters were determined. The voltammetric results showed that polymeric films obtained at the optimized conditions were allowed penetration of large amounts of uric acid (UA) while rejecting ascorbic acid, cysteine and oxalic acid in PBS. Therefore, it has been claimed that the polymeric films could be used as uric acid-selective membrane.

Synthesis, characterization of poly(4, 4’-diaminophenylethanepyromellitimide) and its use as immobilized enzyme polyimide membrane

A novel polyimide prepared from pyromellitic dianhydride (PMDA) and 1,2-bis(4-aminophenyl)ethane was characterized by Fourier transform infrared spectrometer and gel permeation chromatography. Thermal properties of the poly(4,4’-diaminophenylethane-pyromellitimide) (PDP) were evaluated by differential scanning calorimetry, differential thermal analysis and thermogravimetry. The PDP exhibited high decomposition temperature Td (°C), good thermal stability and good adhesive properties. Moreover, that the possibility of whether the chemically-prepared polyimide film could be used as a membrane for immobilization of glucose oxidase (GOx) was investigated. The amperometric response of the PDP/GOx/Pt electrode to hydrogen peroxide, formed as the product of enzymatic reaction, was measured at a potential of 700 mV (vs. SCE) in phosphate buffer solution by means of the TB technique. The amperometric glucose sensor was very high R-value (0.9995). The structure of the GOx micelles contained in polyimide membrane was observed by scanning electron microscopy. From the amperometric responses, it was also demonstrated that PDP film could be used as a solid-state immobilized enzyme polyimide membrane for biosensor design because of its strong adherence to electrode surface and chemical stability.

IMMOBILIZATION OF GLUCOSE OXIDASE IN SILICA SOL-GEL FILM FOR APPLICATION TO BIOSENSOR AND AMPEROMETRIC DETERMINATION OF GLUCOSE

In this study, an electrochemical biosensor was developed by using a sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The sol-gel coating solution was prepared by using GLYMO, TEOS, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. The amperometric responses of the resulting enzymatic electrode to glucose were rapid. It was observed that the amperometric response of the enzymatic electrode was linear for glucose concentrations in the range from 2 to18 mM with 50 s response time. LOD and LOQ for the enzymatic electrode were calculated to be 0.055 mM and 0.184 mM, respectively. It was determined that the developed biosensor had an acceptable reproducibility. The selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. The stability of the biosensor was investigated, and it was found that the sensor response decreased by 59% of its initial response over a period of 30 days of storage in dry conditions at 4 oC.

Synthesis, characterization of pyridine-based polyimides and their use as glucose oxidase immobilization media

Abstract A novel diamine monomer, containing 2,6-diaminopyridine, bis-pdimethylaminophenyl- 2,6-pyridine (S26DAP), was prepared from 4- (dimethylamino)benzaldehyde and 2,6-diaminopyridine. The monomer was characterized by FT-IR, NMR and elemental analyzer. The monomer was then utilized to prepare polyimides with dianhydrides such as pyromellitic dianhydride (PMDA), 3,3’,4,4’-benzophenonetetracarboxylic dianhyride (BPDA), 4,4’- oxydiphthalic anhydride (ODPA) and 3,3’,4,4’-biphenyltetracarboxylic dianhydride (BTDA) by the one-step method; synthesis of polyimides, followed by thermal imidization. The polyimides were characterized by FT-IR, GPC with intrinsic viscosity and adhesive properties also being evaluated. The polyimides exhibited high Tg (°C) (186-209 °C), good thermal stability and good adhesive properties. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.05-1.32 dL/g, the solubility in dipolar aprotic solvents of the polyimides were much better than that of the aromatic polyimides. Furthermore, chemically synthesized polyimides were used for immobilization of glucose oxidase (GOx). The amperometric responses of the prepared GOx-polyimide-coated electrodes to glucose were examined at a potential of 0.7 V in PBS solution by means of TB technique. The results show that polyimide (S26DAP-PI-4) can be used for immobilization of glucose oxidase.

DNA base sensor characteristics of polymeric-nanocomposite electrode

ABSTRACT The electrochemical synthesis of polyaniline films was carried out by potential sweep method in sulfuric acid solution at the glassy carbon electrode. The electrocatalytic behavior to DNA bases (adenine and guanine), uric acid, and dopamine of polyaniline nanocomposite sensor modified with nano-gold particles was investigated by DPV technique. By systematically examining the effects of the possible parameters affecting the electrocatalytic performance of the relevant sensor, the optimal value for the each parameter was determined. The detailed electrocatalytic studies of the optimized sensor revealed that this sensor could be used as DNA base sensor for guanine in the presence of adenine, dopamine, and uric acid. Moreover, the performance of the relevant sensor in thermally denatured fish sperm DNA was quite satisfactory. GRAPHICAL ABSTRACT