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Antimicrobial photodynamic inactivation is potentiated by the addition of selenocyanate: Possible involvement of selenocyanogen?
Author(s) -
Huang Liyi,
Xuan Weijun,
Zadlo Andrzej,
Kozinska Anna,
Sarna Tadeusz,
Hamblin Michael R.
Publication year - 2018
Publication title -
journal of biophotonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 66
eISSN - 1864-0648
pISSN - 1864-063X
DOI - 10.1002/jbio.201800029
Subject(s) - singlet oxygen , chemistry , potassium thiocyanate , antimicrobial , methylene blue , thiocyanate , antibacterial activity , sulfite , potassium cyanide , rose bengal , potassium ferricyanide , bacteria , nuclear chemistry , cyanide , photochemistry , oxygen , organic chemistry , photocatalysis , biology , genetics , catalysis
We previously showed that antimicrobial photodynamic inactivation (aPDI) of Gram‐positive and Gram‐negative bacteria mediated by the phenothiazinium dye, methylene blue (MB), was potentiated by the addition of potassium thiocyanate (10 mM). The mechanism was suggested to involve a singlet oxygen‐mediated reaction with SCN to form sulfite and cyanide and then to produce sulfur trioxide radical anion. We now report that potassium selenocyanate (concentrations up to 100 mM) can also potentiate (up to 6 logs of killing) aPDI mediated by a number of different photosensitizers (PS): MB, rose bengal and 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrin dihydrochloride (as low as 200 nM). When a mixture of selenocyanate with these PS in solution was illuminated and then bacteria were added after the light, there was up to 6 logs of killing (Gram‐negative > Gram‐positive) but the antibacterial species decayed rapidly (by 20 minutes). Our hypothesis to explain this antibacterial activity is the formation of selenocyanogen (SeCN) 2 by reaction with singlet oxygen ( 1 O 2 ) as shown by quenching of 1 O 2 by SeCN and increased photoconsumption of oxygen. The fact that lead tetraacetate reacted with SeCN (literature preparation of (SeCN) 2 ) also produced a short‐lived antibacterial species supports this hypothesis.