Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: a review.

The electropolymerization of different azines from aqueous solutions was investigated. The structure of monomers was systematically varied changing both the nature of the second heteroatom and the substituents in the aromatic rings. Considering the electropolymerization process and the properties of the resulting polymers one can denote polyazines as a new group of electroactive polymers. The electrochemical and spectroelectrochemical investigation of polyazines was done. A hypothesis on azine polymer structure is presented.

Electropolymerized Azines: A New Group of Electroactive Polymers

This review deals with the use of pyridine-nucleotide dependent dehydrogenase enzymes in amperometric biosensor design. The electrochemistry of the nicotinamide coenzymes, their mechanism and the challenges associated with their direct oxidation on solid electrodes are discussed. In addition, a survey of the different solutions proposed in the literature for addressing these problems and some of their applications are presented.

Amperometric biosensors based on NAD(P)‐dependent dehydrogenase enzymes

The developments in the techniques of NADH catalytic oxidation relevant for incorporation in amperometric biosensors with dehydrogenase enzymes are reviewed with special emphasis in the years following 1990. The review stresses the direct electro-catalytic methods of NAD+ recycling as opposed to enzymatic regeneration of the coenzyme. These developments are viewed and evaluated from a mechanistic perspective of recycling of NADH to enzymatically active NAD+, and from the point of view of development of technologically useful reagentless dehydrogenase biosensors. An effort is made to propose a method for the standardization of evaluation of new mediating and direct coenzyme recycling schemes. A perspective is given for the requirements that have to be met for successful biosensor development incorporating dehydrogenase enzymes that open the analytical possibilities to a number of new analytes. The intrinsic limitations of the system are finally discussed and a view of the future of the field is presented.

Catalytic electrooxidation of NADH for dehydrogenase amperometric biosensors

A comparative investigation of catalytic activity of different polyazines in NADH electrooxidation is reported. The structure of azine monomers taken for electropolymerization was varied systematically changing both the second heteroatom and the substituents of aromatic rings. It was found that the monomer structure affects catalytic activity of the resulting polymer in the following way: (i) additional substitution of benzene ring by alkyl group reduced the catalytic activity, (ii) polymerized phenoxazine Brilliant Cresyl Blue was a better electrocatalyst than the corresponding phenothiazine (o-Toluidine Blue), (iii) ring substitution with only tertiary nitrogen atoms as ligands provides higher catalytic activity, (iv) higher redox potential of the polymer also provides higher catalytic activity.

Electropolymerized Azines: Part II. In a Search of the Best Electrocatalyst of NADH Oxidation

A poly(thionine)-modified basal-plane pyrolytic graphite electrode, which can be prepared by a potential-sweep electrolysis of the corresponding monomer in acetonitrile media, shows an excellent electrocatalytic activity for NADH oxidation in phosphate buffer solutions (pH 6.9), with an activation overpotential which is ca. 400 mV lower than that of the bare electrode.

Electrocatalysis of poly(thionine)-modified electrodes for oxidation of reduced nicotinamide adenine dinucleotide

Poly(thionine)-modified electrodes have been prepared using basal-plane pyrolytic graphite, glassy carbon and In-Sn oxide conducting glass as electrode substrates by an electrooxidative polymerization of thionine in both aqueous and acetonitrile media. It was found that the prepared films, the surface concentration of which can be controlled over the range of ca. 10-10-10-8mol cm-2 by appropriately choosing the electropolymerization conditions (e.g., solvent, concentration of thionine and electrolysis time), are electroactive (the formal potential is ca. 0.0V vs. Ag/AgCl at pH 7.0) and chemically stable. The modified electrodes exhibited excellent electrocatalysis for NADH oxidation in neutral aqueous solutions, with an activation overpotential which is ca. 400mV lower than that of a bare electrode. Further, the modified glassy carbon electrode was found to be promising as an amperometric detector for the flow-injection analysis of NADH, typically with a dynamic range of 5μM-1mM.

Preparation of Poly(thionine)-Modified Electrode and Its Application to an Electrochemical Detector for the Flow-Injection Analysis of NADH.

A poly(phenosafranine)-modified electrode, which can be prepared by a potential-sweep oxidative electrolysis of the corresponding monomer in both aqueous and acetonitrile media, shows excellent electrocatalytic activity for NADH oxidation in phosphate buffer solutions (pH 7), with an activation overpotential which is more than 1 V lower than that of the bare electrode.

Koichiro Tanaka

Papers

Electrocatalysis of poly(thionine)-modified electrodes for oxidation of reduced nicotinamide adenine dinucleotide

Preparation of Poly(thionine)-Modified Electrode and Its Application to an Electrochemical Detector for the Flow-Injection Analysis of NADH.

An excellent electrocatalysis of poly(phenosafranine)-modified electrode for oxidation of reduced β-nicotinamide adenine dinucleotide

Electrocatalysis of Poly(thionine)‐Modified Electrodes for Oxidation of Reduced Nicotinamide Adenine Dinucleotide.