Local Generation of Reactive Oxygen Species at New Polymer-Modified Electrodes

Recently the ability of quinone compound to generate reactive oxygen species has been investigated [1]. The importance of quinone compounds in living organism was widely reported and its therapeutic effect through generation of free radicals has been studied [1-4]. In fact, the efficacy of a monolayer of quinone compound and their polymer film on electrodes to catalyze the reduction of oxygen has been evaluated [1, 2]. It has been mentioned that plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) possess also cytotoxic properties and has been exploited to produce polymer films which can be used as a controllable source of reactive oxygen species [1]. The two core functionalities of plumbagin allow to produce a redox film and at the same time to preserve the ability of the redox moiety to generate the reactive oxygen species [1]. Nevertheless, in all case the question on the nature of the formed reactive oxygen species generated is still open. In our procedure we obtained stable films of adjustable thickness by first chemically grafting a monolayer of plumbagin to an activated glassy carbon electrode followed by electropolymerization of further layers of plumbagin. These films grew to defined thickness while electropolymerization of plumbagin directly on a glassy carbon electrode led to self-inhibiting insulating films.

The obtained films showed catalytic activity of oxygen reduction. The interest was placed on the generations of hydrogen peroxide and specially superoxide radical with the final aim of design a microscopic generator for future scanning electrochemical microscopic study. The generation of hydrogen peroxide and possible generation of superoxide radical were monitored with lateral resolution by fluorescence microscopy coupled with the high speed camera and by chronoamperometric detection using biosensor based on cytochrome c.

References

[1] L. A. A. Newton, E. Cowham, D. G. Sharp, R. Leslie and J. Davis, New J. Chem. 34, 2010, 395–397.

[2] M.M. Ardakani, P.E. Karami, H.R. Zare and M. Hamzehloo, Microchim. Acta. 159, 2010, 165-173.

[3] H.Shimada, Y.Yamaoka, R. Morita, T.Mizuno, K.Gotoh, T. Higuchi, T. Shiraishi and Y.Imamura, Toxicology in Vitro 26, 2012, 252-257.

[4] V.Sivakumar, R.Prakash, M.R. Murali, H.Devaraj and S.N.Devaraj, Drug and Chemical Toxicology 28, 2005, 499-507