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Sodium Nitrite Potentiates Antimicrobial Photodynamic Inactivation: Possible Involvement of Peroxynitrate.

Abstract

We have recently shown that a wide range of different inorganic salts can potentiate antimicrobial photodynamic inactivation (aPDI) and TiO2-mediated antimicrobial photocatalysis. Potentiation has been shown with azide, bromide, thiocyanate, selenocyanate, and most strongly, with iodide. Here we show that sodium nitrite can also potentiate broad-spectrum aPDI killing of Gram-positive MRSA and Gram-negative Escherichia coli bacteria. Literature reports had previously shown that two photosensitizers (PS), methylene blue (MB) and riboflavin when excited by broad-band light in the presence of nitrite could lead to tyrosine nitration. Addition of up to 100 mM nitrite gave 6 logs of extra killing in the case of Rose Bengal excited by green light against E. coli, and 2 logs of extra killing against MRSA (eradication in both cases). Comparable results were obtained for other PS (TPPS4 + blue light and MB + red light). Some bacterial killing was obtained when bacteria were added after light using a functionalized fullerene (LC15) + nitrite + blue light, and tyrosine ester amide was nitrated using both “in” and “after” modes with all four PS. The mechanism could involve formation of peroxynitrate by a reaction between superoxide radicals and nitrogen dioxide radicals; formation of the latter species was demonstrated by spin trapping with nitromethane.

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Publication details

The article was received on 09 Oct 2018, accepted on 28 Nov 2018 and first published on 04 Dec 2018


Article type: Paper
DOI: 10.1039/C8PP00452H
Citation: Photochem. Photobiol. Sci., 2018, Accepted Manuscript
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    Sodium Nitrite Potentiates Antimicrobial Photodynamic Inactivation: Possible Involvement of Peroxynitrate.

    Y. Huang, P. Rajda, G. Szewczyk, B. Bhayana, L. Y. Chiang, T. J. Sarna and M. R. Hamblin, Photochem. Photobiol. Sci., 2018, Accepted Manuscript , DOI: 10.1039/C8PP00452H

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