Peroxynitrite (PON) emerged as a major cytotoxic agent, implicated in a host of pathophysiological conditions. Peroxynitrite, the primary product of the reaction of superoxide ion and nitric oxide, and is relatively a new member of the nitroxidative array of reactive metabolites. Early reports emphasized the deleterious physiological reactivity of PON but recent investigations shed light on its concentration-dependent protective roles. Sensitive and accurate detection of PON is of great value to investigations of the critical roles of PON in health and disease. Peroxynitrite's short half-life under physiological conditions and its reactivity with many cellular targets creates a major analytical chemistry challenge. Spectroscopic and other detection methods for peroxynitrite have been proposed; however, these are more difficult to apply for real-time quantification due to their inherent complexity. The electrochemical detection of peroxynitrite is a simpler and more convenient technique. In this paper we will describe the use of polymerized hemin (iron protoporphyrin IX) and other porphyrins as a platform for amperometric measurement of peroxynitrite both in still solutions and under flow conditions. We will also present an extension of this work to the use graphene oxide functionalized with hemin as a new catalytic platform for PON oxidative detection. We show that this hybrid nanomaterial based on graphene functionalized with catalytic heme porphyrin centers acts as a good sensing surface for electrochemical detection of PON. Sensors modified with this material show a sensitivity of ~7.5 nA/mM and a detection limit of ~ 5nM. We will compare and contrast the catalytic properties of polymerized hemin and hemin on graphene systems, and shed light on the potential mechanism of detection and the improved sensitivity of the hemin/graphene system. Understanding the fundamental processes behind the catalytic performance of the two systems offers the possibility to fine-tune them and develop better platforms for sensitive PON sensors.

Peroxynitrite sensing: From polymerized hemin modified electrodes to hemin on graphene oxide as a sensing platform

246th National Meeting (2013)

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