Polymeric dyes redox reactions

To increase the stability of the phenothiazine dye CMEs, investigations of the electrochemical reactions of redox proteins at polymer CMEs have been undertaken. One example of such a study is the heterogeneous redox reaction of Cyt c at an electrochemically polymerized polypyrrole-methylene blue (PPy-MB) film CME. Figure 17 shows the cyclic voltammetric response that occurs during the preparation of this CME by potential... 

Much of the work in this area has focussed on polymeric dyes which can participate in redox reactions. Early work by Manecke and Kossmehl on vinyl Malachite Green (VMG) is specially significant as it established a simple method of entry into the polymerizable triphenylmethane class of dyes. Thus the carbinol base form (ill) of VMG was synthesized by a Grignard reaction between vinyl-phenyl magnesium chloride (l) and Michler s ketone (ll). 

Oxidation of P-nicotinamide adenine dinucleotide (NADH) to NAD+ has attracted much interest from the viewpoint of its role in biosensors reactions. It has been reported that several quinone derivatives and polymerized redox dyes, such as phenoxazine and phenothiazine derivatives, possess catalytic activities for the oxidation of NADH and have been used for dehydrogenase biosensors development [1, 2]. Flavins (contain in chemical structure isoalloxazine ring) are the prosthetic groups responsible for NAD+/NADH conversion in the active sites of some dehydrogenase enzymes. Upon the electropolymerization of flavin derivatives, the effective catalysts of NAD+/NADH regeneration, which mimic the NADH-dehydrogenase activity, would be synthesized [3]. 

Moreover, novel redox-responsive polycationic hydrogels of AAf-diethylacrylamide (DEAAm) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) were successfully synthesized by cross-linking reactions via quaternary ammonium compounds with a disulfide. The ability of the polymer netwoik to enclose and release substances by reductive cleavage or oxidative formation of disulfide bonds was shown exemplarily using different dyes. The redox-responsive character was proven by oscillatory rheological measurements and different material properties of polycationic polymer discs were also investigated. Because of its polycationic structure, this polymeric system could be a promising compound for complexation of DNA-like substances. Its ability for selective release in reductive environments, like tumor tissues, could possibly be used in medical applications or in chemotherapy [162]. 

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