Reactive oxygen/nitrogen species (ROS/RNS) have great impact on cellular response to stress, cell proliferation, cell death, cancer, aging or male infertility. Also, in the food industry and for consumers it is very important to monitor quality and freshness of raw meat. Different factors are a sign of meat alteration (e.g. discoloration, rancidity) [1]. One pathway of alteration is the scavenging activity of myoglobin towards RNS (such as peroxynitrite, PON). This paper presents the development of an electrochemical PON sensor using cobalt phthalocyanine (CoPc) as simple, cost effective, highly thermally stable, biomimetic catalyst and the application of this screen-printed carbon electrode (SPCE) based sensor to meat extract samples, using flow injection analysis (FIA). The reduction of peroxynitrite, mediated by CoPc, occurs at a very low potential (≈ 0.1 V vs. Ag/AgCl pseudoreference), as for higher potentials, the mechanism of mediation changes, and the oxidation of PON is observed. The surface of the modified electrode was characterized using SEM, FTIR, Raman and Cyclic Voltametry. Peroxynitrite synthesized solutions were characterized using UV-Vis and ATR-FTIR, and compared to DFT models of relevant molecules/interfering species. The interaction of PON with myoglobin was studied using both UV-Vis and cronoamperometry (0.1 V). Calibration was performed: I_red (nA) = 6.313·C_PON (µM) + 17.469; (R² = 0.9938). The calculated LOD was 2.37 µM and the linear range was 3-180 µM. The performance of the electrode was further improved using the reduction of the CoPc film, at -0.3 V, during 60s. This helped us monitor and quantify how much PON was decomposed, when meat extracts were spiked with PON, in a highly selective, good sensitive and reproducible way.

References

1. Exner, M; Herold, S; Kinetic and mechanistic studies of the peroxynitrite-mediated oxidation of oxymyoglobin and oxyhemoglobin. Chemical research in toxicology. 2000;13(4):287-93.