Low-potential stable NADH detection at carbon-nanotube-modified glassy carbon electrodes

A sensor designed to determine the amount and concentration of analyte in a sample having a volume of less than about 1 μL. The sensor has a working electrode coated with a non-leachable redox mediator. The redox mediator acts as an electron transfer agent between the analyte and the electrode. In addition, a second electron transfer agent, such as an enzyme, can be added to facilitate the electrooxidation or electroreduction of the analyte. The redox mediator is typically a redox compound bound to a polymer. The preferred redox mediators are air-oxidizable. The amount of analyte can be determined by coulometry. One particular coulometric technique includes the measurement of the current between the working electrode and a counter or reference electrode at two or more times. The charge passed by this current to or from the analyte is correlated with the amount of analyte in the sample. Other electrochemical detection methods, such as amperometric, voltammetric, and potentiometric techniques, can also be used. The invention can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is provided as a second electron transfer agent.

Small volume in vitro analyte sensor

Electrochemical sensors based on conducting polymer—polypyrrole

Catechols are found in nature taking part in a remarkably broad scope of biochemical processes and functions. Though not exclusively, such versatility may be traced back to several properties uniquely found together in the o-dihydroxyaryl chemical function; namely, its ability to establish reversible equilibria at moderate redox potentials and pHs and to irreversibly cross-link through complex oxidation mechanisms; its excellent chelating properties, greatly exemplified by, but by no means exclusive, to the binding of Fe(3+); and the diverse modes of interaction of the vicinal hydroxyl groups with all kinds of surfaces of remarkably different chemical and physical nature. Thanks to this diversity, catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds. Such versatility has allowed catechols to participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of some transition metal ions. As a result of such an astonishing range of functionalities, catechol-based systems have in recent years been subject to intense research, aimed at mimicking these natural systems in order to develop new functional materials and coatings. A comprehensive review of these studies is discussed in this paper.

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Catechol-Based Biomimetic Functional Materials

The high cost of nicotinamide cofactors requires that they be regeneratedin situ when used in preparative enzymatic synthesis. Numerous strategies have been tested forin situ regeneration of reduced and oxidized cofactors. Regeneration of reduced cofactors is relatively straightforward; regeneration of oxidized cofactors is more difficult. This review summarizes methods for preparation of the cofactors, factors influencing their stability and lifetime in solution, methods for theirin situ regeneration, and process considerations relevant to their use in synthesis.

Regeneration of nicotinamide cofactors for use in organic synthesis.

Catalytic oxidation of reduced nicotinamide adenine dinucleotide by graphite electrodes modified with adsorbed aromatics containing catechol functionalities

An amperometric flow system combined with a glucose oxidase−mutarotase reactor was optimized and used to determine aromatic amines and phenols using peroxidase-modified graphite electrodes. An increase in currents upon injection of the analyzed substrate was shown to be approximated by a Michaelis−Menten type dependence. The detection limit was calculated as 3 times the noise, and the sensitivity was calculated as Imax/ . Commercially available horseradish peroxidase was compared with tobacco anionic and peanut cationic peroxidases for determination of aromatic amines and phenols. Detection limits of 10 nM for determination of o-aminophenol and o- and p-phenylenediamine achieved with a tobacco peroxidase-modified electrode give a promise for further improvements in sensitivities and detection limits of biosensors.

Bioelectrochemical monitoring of phenols and aromatic amines in flow injection using novel plant peroxidases.

The response currents obtained for tyrosinase-modified Teflon/graphite, carbon paste, and solid graphite electrodes in the presence of catechol are analyzed primarily using rotating disk electrode experiments The rate-limiting steps, such as the electrochemical reduction of o-quinones and the enzymatic reduction of oxygen as well as the enzymatic oxidation of catechol, are theoretically considered and experimentally demonstrated for the different electrode configurations

Rate-limiting steps of tyrosinase-modified electrodes for the detection of catechol.

Electrodes for the electrochemical regeneration of the co-enzymes NADH, NADPH or analogs thereof. The electrode surface has been modified by adsorbing thereto a condensed aromatic ring system comprising at least three, preferably four or more, condensed aromatic rings. A method of preparing the electrodes is also described, in which a condensed aromatic ring system is adsorbed to the surface of carbon or a graphitic material. Finally, there is described the use of said electrodes for the electrochemical regeneration of co-enzyme in biochemical, microbiological or biochemical processes as the anode in biochemical fuel cells or for analysis in systems utilizing co-enzyme-dependent enzyme.

Electrode for the electrochemical regeneration of co-enzyme,a method of making said electrode,and the use thereof

This paper describes a fully automated on-line system for the unattended monitoring of bioprocesses. Removal of solids and macromolecules from fermentation broth is achieved with a tangential flow filtration unit (Waters Filter/Acquisition Module). The obtained filtrate is transported in a flow system to a cleanup step, based on solid-phase extraction, followed by introduction into a column liquid chromatographic system. Carbohydrates are then detected by refractive index and ethanol content usings laboratory-made selective amperometric alcohol biosensor

L. Gorton

Papers

Catalytic oxidation of reduced nicotinamide adenine dinucleotide by graphite electrodes modified with adsorbed aromatics containing catechol functionalities

Bioelectrochemical monitoring of phenols and aromatic amines in flow injection using novel plant peroxidases.

Rate-limiting steps of tyrosinase-modified electrodes for the detection of catechol.

Electrode for the electrochemical regeneration of co-enzyme,a method of making said electrode,and the use thereof

On-line fermentation process monitoring of carbohydrates and ethanol using tangential-flow filtration and column liquid chromatography