On the mechanism of Candida tropicalis biofilm reduction by the combined action of naturally-occurring anthraquinones and blue light

MARIONI, JULIANA; BRESOLÍ-OBACH, ROGER; AGUT, MONTSERRAT; COMINI, LAURA R.; CABRERA, JOSÉ L.; PARAJE, MARÍA G.; NONELL, SANTI; NÚÑEZ MONTOYA, SUSANA C.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2017 vol. 12

1932-6203

The photoprocesses involved in the photo-induced Candida tropicalis biofilm reduction by two natural anthraquinones (AQs), rubiadin(1) and rubiadin-1-methyl ether (2), were examined. Production of singlet oxygen ( O ) and of superoxide radical anion (O ) wasstudied. Although it was not possible to detect the triplet state absorption of any AQs in biofilms, observation of O phosphorescenceincubated with deuterated Phosphate Buffer Solution, indicated that this species is actually formed in biofilms. 2 was accumulated in thebiofilm to a greater extent than 1 and produced measurable amounts of O after 3h incubation in biofilms. The effect of reactiveoxygen species scavengers on the photo-induced biofilm reduction showed that Tiron (a specific O scavenger) is most effective thansodium azide (a specific O quencher). This suggests that O formed by electron transfer quenching of the AQs excited states, is themain photosensitizing mechanism involved in the photo-induced antibiofilm activity, whereas O participation seems of lesserimportance.