Peroxynitrite is a reactive species that emerged as a major cytotoxic agent implicated in a host of pathophysiological conditions. Reports emphasized deleterious physiological reactivity of peroxynitrite with various cell components. Accurate determination of peroxynitrite concentration is inherently difficult. Detection methods based on electrochemistry are relatively limited and the pursuit of viable electrochemical probes or catalytic materials as interfaces for efficient peroxynitrite detection is still underway. We prepared and characterized a functional thin‐film material based on an organic selenide (4,4’ diaminodiphenyl selenide) grafted on graphite electrodes and used the interface in sensitive electrochemical determination of peroxynitrite. We characterized the grafted film material on the graphite interface using various physicochemical methods. We show that peroxynitrite is electrocatalytically oxidized on the grafted selenide film. The grafted functional film material showed a significant electrocatalytic enhancement in the presence of peroxynitrite compared to controls. The selenide‐based peroxynitrite sensors show a sensitivity of 200 nA/μM and a lower limit of detection of 250 nM. To the best of our knowledge, this is the first time a grafted selenium‐based material on an electrode is used for catalytic detection and quantification of peroxynitrite.

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

Peroxynitrite is a very reactive and cytotoxic species that plays important pathophysiological roles, particularly in the brain. It is also suspected to be a factor involved in tissue damage that results from long term deep brain neural stimulation. Accurate determination of peroxynitrite concentration is inherently difficult due to its high reactivity and concentration range. Various methods for peroxynitrite determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. Currently, this field is still actively growing in the pursuit of viable electrochemical probes or catalytic materials as interfaces for efficient peroxynitrite detection. A durable and reliable electrochemical sensor would be valuable in order to monitor peroxynitrite generation near sites of electrical neurostimulation.In this work, we prepared and characterized a functional thin film material based on an organic selenide on graphite electrodes and used the interface in sensitive electrochemical determination of peroxynitrite. First, we describe the preparation and grafting of the catalytic material based on the electrodeposition of organic selenides on graphite electrodes. Next, we report on the characterization of the resulting grafted film material on graphite interface using various physicochemical methods including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). We then tested the performance of resulting aniline selenide catalytic material on modified electrodes as peroxynitrite sensing interfaces using voltammetry and dose-response amperometry. The grafted thin film material showed a significant enhancement in peroxynitrite oxidative current compared to electrodes with aniline only (i.e. materials devoid of selenium) under the same conditions. In the presentation we will show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted selenide-based organic material at the oxidized state mediates the electrocatalytic oxidation of peroxynitrite. In terms of selectivity, the electrocatalytic detection of PON on electrodes modified with the selenide compound responds better and selectively toward PON as a target analyte over other potentially interfering analytes such as nitric oxide, nitrite, and nitrate. To the best of our knowledge, this is the first time a selenium-based organic material electrochemically grafted at an electrode surface is used for catalytic detection and quantification of peroxynitrite.

The Cover Feature shows a modified electrode interface with grafted organic selenide moieties as catalytic sites for sensitive and selective electrochemical detection and quantitation of peroxynitrite. The work shows that the selenium center in the grafted organic material is crucial for peroxynitrite catalytic sensing. The electrochemical method can expand to ultramicroelectrodes for PON monitoring under physiologic settings. More information can be found in the Article by M. Bayachou et al.