A new amperometric cholesterol biosensor based on poly(3,4-ethylenedioxypyrrole)

Cholesterol oxidase (ChOx) was physically entrapped in poly(3,4-ethylenedioxypyrrole) (PEDOP) to construct an amperometric cholesterol biosensor. The responses of the enzyme electrodes were measured via monitoring oxidation current of H2O2 at +0.7V in the absence of a mediator. Kinetic parameters, operational and storage stabilities, pH and temperature dependencies were determined. K-m, I-max and sensitivity (I-max/K-m) were calculated as 3.4 mM, 34 mu A cm(-2) and 10 mu A mM(-1) cm(-2), respectively. The minimum detectable substrate concentration was 0.4 mM and for a period of 20 days the biosensor showed the maximum relative activity

Poly(pyrrole) versus poly(3,4-ethylenedioxythiophene): amperometric cholesterol biosensor matrices

Two conducting polymers, poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) were used as immobilization matrices for cholesterol oxidase (ChOx). The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H2O2 at +0.7 V in the absence of a mediator. Kinetic parameters, such as K (m) and I (max), operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. K (m) values are found as 7.9 and 1.3 mM for PPy and PEDOT enzyme electrodes, respectively; it can be interpreted that ChOx immobilized in PEDOT shows higher affinity towards the substrate

Immobilization of Tyrosinase in Poly(2-thiophen-3-yl-alkyl ester) Derivatives

In this study, construction of novel biosensors for the determination of phenolic compound was performed via immobilization of tyrosinase during the electrochemical synthesis of conducting block copolymers of 2-thiophen-3-yl-alkyl ester derivatives with 3,4-ethylenedioxythiophene and synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultant biosensors were characterized in terms of their maximum reaction rates, Michaelis-Menten constants (Km), temperature and pH stabilities. All the copolymer matrices represented higher reaction rates and higher Km values in comparison to both polypyrrole and PEDOT matrices and a relation between the morphology of the matrice and the kinetic parameters was observed. Biosensors maintained their activity even at temperatures as high as 80C and could be used at pHs higher than 8 with high precision. The amount of phenolics in actual samples (red wines) was investigated using electrodes, and results were compared with those found from Folin-Ciocalteau method. Hence, the present study has proven the suitability of these copolymers to be used as polymer matrices for enzyme immobilization

Entrapment of invertase in an interpenetrated polymer network of alginic acid and poly (1-vinylimidazole)

In this work, we have investigated the synthesis and characterization of a proton conductor based on alginic acid and poly (1-vinylimidazole). The polymer network was obtained by mixing alginic acid and poly (1-vinylimidazole) at various stoichiometric ratios. The polymer electrolytes were characterized by elemental analysis and FT-IR spectroscopy. Invertase was entrapped in the polymer networks during complex formation. Additionally, the maximum reaction rate and Michaelis-Menten constant were investigated for the immobilized invertase. The temperature and pH optimization, operational stability and shelf life of the polymer network were examined

The Synthesis of Complex Polymer Electrolytes Based on Alginic Acid and Poly(1-vinylimidazole) and Application in Tyrosinase Immobilization

In this study, proton conducting polymer electrolyte networks consisting of alginic acid (AA) and poly(1-vinylimidazole) (PVI) were prepared. The polymer networks were obtained by mixing AA and PVI with several stoichiometric ratios, x (with respect to monomers). Polymer networks were characterized by FT-IR spectroscopy and their compositions were investigated by elemental analysis (EA). Enzyme entrapped polymer networks (EEPN) were produced by immobilization of tyrosinase in the AA/PVI matrix during complexation. The maximum reaction rate (V-max) and Michaelis-Menten constant (K-m) were investigated for the immobilized tyrosinase. Also, the temperature and pH optimizations, operational stability and shelf life of enzyme immobilized in the polymer network were examined

Immobilizing cholesterol oxidase in chitosan-alginic acid network

Proton conducting biopolymer networks have potential use for bio-sensors. The cost-effective, non-hazardous and environmentally safe biopolymer, such as chitosan, is an attractive feature for bio-sensors. Cholesterol oxidase was immobilized in conducting network via complexation of chitosan with alginic acid. A method for the preparation of the complex along with characterization by elemental analysis, FTIR spectroscopy, TGA and DSC were reported. The proton conductivity chitosan-alginic acid network was studied via impedance spectroscopy under humidified condition. The complex polymer electrolyte with x = 1 exhibited maximum proton conductivity of 1.4 x 10(-3) S/cm at RT, RH similar to 50%. The potential use of this network in enzyme immobilization was studied by manufacturing cholesterol oxidase entrapped polymer networks. Additionally, the maximum reaction rate (V-max) and Michaelis-Menten constant (K-m) were investigated for the immobilized cholesterol oxidase. Also, temperature and pH optimization studies were performed, and operational stability and shelf life of the polymer network were examined. (C) 2009 Published by Elsevier Lt

Use of a thiophene-based conducting polymer in microbial biosensing

Immobilization of whole viable Pseudomonas fluorescens cells was achieved on a graphite electrode modified with a thiophene-based conducting polymer. Microbial electrodes were constructed by the entrapment of bacterial cells on conducting copolymer matrix using a dialysis membrane. The biosensor was characterized using glucose as the substrate. As well as analytical characterization, effects of electropolymerization time, pH and temperature on the sensor response were examined. Finally, operational stability was also tested

Immobilization of Invertase in Copolymer of 2,5-Di(thiophen-2-yl)-1-p-Tolyl-1H-Pyrrole with Pyrrole

Immobilization of invertase in conducting copolymer matrix of 2,5-di(thiophen-2-yl)-1-p-tolyl-1H-pyrrole with pyrrole (poly(DDTP-co-Py)) was achieved via electrochemical polymerization. Kinetic parameters, Michaelis-Menten constant, Km and the maximum reaction rate, Vmax were investigated. Operational stability and temperature optimization of the enzyme electrodes were also examined. Immobilized invertase reveals maximum activity at 50 degrees C and; pH 8 and pH 4 for two copolymer matrices. Although the same two monomers are utilized for the copolymer synthesis, the way the copolymer is produced results in quite different responses in terms of enzyme activity, optimum pH and kinetic parameters. Excellent operational stability of the enzyme electrodes enables their repetitive use in the determination of invert sugar

L-Dopa synthesis using tyrosinase immobilized on magnetic beads

Magnetic beads were prepared via Suspension polymerization of glycidyl methacrylate (GMA) and methyl methacrylate (MMA) in the presence of ferric ions. Following polymerization, thermal co-precipitation of the Fe(III) ions in the beads with Fe(II) ions under alkaline condition resulted in encapsulation of Fe3O4 nano-crystals within the polymer matrix. The magnetic beads were activated with glutaraldehyde, and tyrosinase enzyme was covalently immobilized on the support via reaction of amino groups under mild conditions. The immobilized enzyme was used for the synthesis of L-Dopa (1-3,4-dihydroxy phenylalanine) which is a precursor of dopamine. The immobilized enzyme was characterized by temperature, pH, operational and storage stability experiments. Kinetic parameters, maximum velocity of the enzyme (V-max) and Michaelis-Menten constant (K-m) values were determined as 1.05 U/mg protein and 1.0 mM for 50-75 mu m and 2.00 U/mg protein and 4.0 mM for 75-150 mu m beads fractions. respectively. Efficiency factor and catalytic efficiency were found to be 1.39 and 0.91 for 75-150 mu m beads and 0.73 and 0.75 for 50-75 mu m beads fractions, respectively. The catalytic efficiency of the soluble tyrosinase was 0.37. The amounts of immobilized protein were on the 50-75 mu m and 75-150 mu m fractions were 2.7 and 2.8 mg protein/g magnetic beads, respectively

The Synthesis of Complex Polymer Electrolytes Based on Alginic Acid and Poly(1-vinylimidazole) and Application in Tyrosinase Immobilization

In this study, proton conducting polymer electrolyte networks consisting of alginic acid (AA) and poly(1-vinylimidazole) (PVI) were prepared. The polymer networks were obtained by mixing AA and PVI with several stoichiometric ratios, x (with respect to monomers). Polymer networks were characterized by FT-IR spectroscopy and their compositions were investigated by elemental analysis (EA). Enzyme entrapped polymer networks (EEPN) were produced by immobilization of tyrosinase in the AA/PVI matrix during complexation. The maximum reaction rate (V-max) and Michaelis-Menten constant (K-m) were investigated for the immobilized tyrosinase. Also, the temperature and pH optimizations, operational stability and shelf life of enzyme immobilized in the polymer network were examined