Ion-exchange chromatographic analysis of peroxynitric acid

Kinetics of Bacterial Inactivation by Peroxynitric Acid in the Presence of Organic Contaminants

Low-temperature atmospheric-pressure plasma has been studied for disinfection purposes. When plasma is exposed to water, reactive oxygen and nitrogen species are generated and preserved in the water fraction (plasma-treated water [PTW]), which consequently exhibits bactericidal activity. At low temperatures, one of the bactericidal components of PTW is peroxynitric acid (PNA). Importantly, PNA can also be synthesized by chemical reaction, without exposure to plasma. In this study, we evaluated the bactericidal properties of PNA based on reaction kinetics in comparison with other disinfectants. The analysis, based on dose-dependent effects, showed that PNA exhibited about 1 and 10 times the bactericidal activity of hypochlorous acid (HOCl) and peracetic acid, respectively. In addition, we evaluated the influence of organic contaminants on the bactericidal effects of PNA and HOCl. The bactericidal potential of both disinfectants was reduced by bovine serum albumin (BSA); however, PNA showed about 30-times-higher resistance against BSA inhibition than HOCl. Analysis of the dose-dependent effects of PNA revealed that the inhibition of bactericidal effect was caused by its consumption. Further experiments using model substrates containing particular amino acid residues (Met, Cys, Lys, and Leu) suggested that the bacterial inactivation by PNA is less affected by BSA due to the low reactivity and narrow reactivity spectrum of PNA for amino acid residues. Overall, our results suggest that PNA has a great disinfection potential, especially in the presence of organic contaminants (e.g., on the surface of the human body and on medical instruments contaminated with biological fluids).IMPORTANCE A good disinfectant for the human body should have various properties, such as strong bactericidal activity, harmlessness to living tissues, and resistance against biological fluids (or other organic contaminants). Peroxynitric acid (PNA) showed a bactericidal effect that was several tens up to several hundred times higher per unit of molarity than that of sodium hypochlorite and peracetic acid, which are used as general disinfectants for medical equipment. Moreover, the high resistance of PNA to organic load was confirmed, indicating that PNA will inactivate bacteria effectively even on contaminated surfaces, such as used medical devices or the human body surface. Therefore, we propose that PNA can be used as a strong disinfectant for the human body.

Kinetics Analysis of the Reactions between Peroxynitric Acid and Amino Acids

Plasma disinfection using low-temperature atmospheric pressure plasma is widely studied in many applications, and the use of plasma-treated water (PTW) for disinfection is being developed by many researchers. Exposing plasma to water supplies and preserves reactive oxygen and nitrogen species (RONS) in the water, and this PTW exhibits bactericidal activity. In our previous study, it was revealed that peroxynitric acid (O₂NOOH, PNA) was the dominant bactericidal component in PTW. PNA can be easily synthesized without plasma treatment, and the physicochemical properties of PNA have been well-analyzed. As the application of PNA in fields related to medicine and biology has not been reported, a basic study on the behavior of PNA is required. In this study, the bactericidal activity of PNA and its reactivities with 20 naturally occurring amino acids were evaluated to understand its reaction mechanism with biomolecules. Interestingly, PNA exhibited 10^-6 times lower reactivities with amino acids when compared with hypochlorous acid and other RONS, although its bactericidal activity was 310 times higher than that of sodium hypochlorite. In addition, the reactivity of PNA with methionine was over 100 times higher than that with other amino acids, indicating that the reactions of PNA with amino acids are highly specific. No other oxidants have been reported to react selectively with only methionine. As methionine is involved in specific activities in cells, the unique reaction profile of PNA was examined in the context of biological systems.

Oxidative modification of skin lipids by cold atmospheric plasma (CAP): A standardizable approach using RP-LC/MS2 and DI-ESI/MS2

Cold atmospheric plasma (CAP) is an emerging source for the locally defined delivery of reactive species, and its clinical potential has been identified in the control of inflammatory processes, such as acute and chronic wounds, or cancerous lesions. Lipids, due to their localization and chemical structure as ideal targets for oxidative species, are relevant modifiers of physiological processes. Human forehead lipids collected on a target were treated by an argon plasma jet and immediately analyzed by direct-infusion high-resolution tandem mass spectrometry (DI-MS²) or liquid chromatography-tandem MS (RP-LC/MS²). Subsequent data analysis was performed by LipidHunter (University of Leipzig), LipidXplorer (Max Planck Institute of Molecular Cell Biology and Genetics, Dresden), and LipidSearch (Thermo Scientific). With either MS method, all major lipid classes of sebum lipids were detected. Significant differences regarding triacylglycerols (predominantly identified in RP-LC/MS²) and ceramides (predominantly identified in DI-MS²) indicate experimental- or approach-inherent distinctions. A CAP-driven oxidation of triacyclglycerols, ceramides, and cholesteryl esters was detected such as truncations and hydroperoxylations, but at a significantly lower extent than expected. Scavenging of reactive species due to naturally present antioxidants in the samples and the absence of a liquid interphase to allow reactive species deposition by the CAP will have contributed to the limited amount of oxidation products observed. In addition, limitations of the software's capability of identifying unexpected oxidized lipids potentially led to an underestimation of the CAP impact on skin lipids, indicating a need for further software development. With respect to the clinical application of CAP, the result indicates that intact skin with its sebum/epidermal lipid overlay is well protected and that moderate treatment will yield limited (if any) functional consequences in the dermal tissue.