Peroxynitrite (PON) is a reactive oxygen-nitrogen metabolite that has been linked with both oxidation and nitration reactions in biological systems. PON is a major cytotoxic agent that is implicated in a host of pathophysiological conditions. It is the primary product of the reaction of superoxide anion-radical and nitric oxide radical under oxidative stress, inflammatory reactions, and other related conditions. Some literature reports highlight the deleterious physiological reactivity of PON with different cellular targets including DNA, proteins, and lipids in cell membranes. On the other hand, other reports identify counterintuitive cytoprotective roles of this species under certain conditions. The balance of deleterious reactivity versus potential cytoprotective roles of PON is apparently driven by its dynamic concentration.

Accurate determination of PON concentration is inherently difficult due to its high reactivity and the low target concentration range that is relevant to biological systems. Various methods for PON determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. In this regard, viable electrochemical probes for PON detection, including catalytic interfaces for PON detection, are still lacking, and work in this area is still in its early stages.

In this work, we prepared an interface grafted with a selenium-based compound for sensitive electrochemical determination of PON. First, we describe the preparation and grafting of 4,4' diaminodiphenyl selenide on graphite and indium-tin oxide electrodes. We characterized the modified interfaces using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). We will present and discuss these findings as well as results on the performance of the selenide-based grafted electrodes as peroxynitrite sensing interfaces using voltammetry and dose-response amperometry. The modified electrodes showed a significant enhancement in peroxynitrite oxidative current compared to controls. We will show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted selenide compound at the oxidized state mediates the oxidation of peroxynitrite at the electrode surface. To the best of our knowledge, this is the first time a selenium-based compound electrochemically grafted at an electrode surface is used for catalytic detection and quantification of peroxynitrite.