Bottom-up Design of Organic Selenide Interfaces for Sensitive Electrocatalytic Detection of Peroxynitrite: A Fundamental Investigation and Application

Peroxynitrite (PON) is a potent oxidative stress species that has been linked with both oxidation and nitration reactions in biological systems. It emerged as a major cytotoxic agent that is implicated in a host of pathophysiological conditions. Reports emphasized the deleterious physiological reactivity of peroxynitrite with different cellular targets including DNA, proteins, and lipids in cell membranes. This oxidant has also been linked to cytoprotective roles under certain conditions. The balance between the deleterious reactivity and its potential cytoprotective roles of peroxynitrite depends on the dynamic concentration of this species. However, accurate determination of peroxynitrite concentration is inherently difficult particularly in biological systems. Various methods for peroxynitrite determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. While the development of electrochemical sensors for PON is currently a very active field, viable electrochemical probes for PON detection and quantification are still relatively illusive. In this work, we prepared and characterized a series of functional thin film materials based on organic diphenyl selenides on graphite electrodes and used these interfaces to compare and contrast their performance in terms of electrochemical determination of peroxynitrite. We will describe the preparation and grafting of the catalytic material based on the electrodeposition of various organic aminodiphenyl selenides on graphite electrodes. Several physicochemical methods including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the resulting modified interfaces. We will describe the performance of resulting selenide thin films as peroxynitrite sensing interfaces using voltammetry and amperometry. The grafted thin film materials show a significant enhancement in peroxynitrite oxidative current compared to controls under the same conditions. For all selenides tested, we show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted aniline selenide-based material at the oxidized state mediates the electrocatalytic oxidation of peroxynitrite. We will compare and contrast the performance of the various selenide systems and explore if the modulation of the electronic properties of the selenium catalytic center results in proportional changes in PON catalytic efficiency. Figure 1