Mechanistic aspects of photoinactivation of Candida albicans by exogenous porphyrins

Sarit Oriel, Yeshayahu Nitzan

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The mechanism of photoinactivation of Candida albicans by 3.5 μm uncharged, cationic or anionic porphyrins under blue light (407-420 nm) was found to be dependent on the uptake of porphyrins into yeast cells, and was also dependent on the presence or absence of proteins in the photosensitization medium. In a very protein-rich medium, a decrease in viability was observed only with the uncharged porphyrin. Photoinactivation by uncharged or cationic porphyrins in a protein-poorer medium resulted in total eradication, whereas no significant decrease was observed with the anionic porphyrin. Phototreatment in PBS resulted in eradication with all three porphyrins. X-ray microanalysis after phototreatment by the uncharged or cationic porphyrins in the protein-poor medium exhibited ion loss, indicating cell-membrane damage. Transmission electron microscopy indicated cellular and chromosomal damage. No ion loss or cell damage was observed in this medium with the anionic porphyrin. The efficiency of photoeradication of C. albicans is dependent on porphyrin uptake, which might lead (upon illumination) to processes that facilitate the formation of reactive oxygen species that damage the cells. Uptake of charged porphyrins is dependent on protein quantity and quality in the photosensitization microenvironment. This fact must be taken into account when using charged photosensitizers. The mechanism of photoinactivation of Candida albicans by uncharged, cationic or anionic porphyrins under blue light, was found to be dependent on the uptake of the porphyrins into yeast cells, and was also dependent on the protein's quantity and quality in the photosensitization medium. Only phototreatment in phosphate buffered saline resulted in eradication with all three porphyrins. X-ray microanalysis demonstrated that only with the uncharged or cationic porphyrins in a protein-poor medium exhibited ion loss, indicating cell-membrane damage. Transmission electron microscopy indicated cellular and chromosomal damage. Only taken up porphyrins might lead (upon illumination) to processes that facilitate the formation of reactive oxygen species that will damage and inactivate the yeast cells.

Original languageEnglish
Pages (from-to)604-612
Number of pages9
JournalPhotochemistry and Photobiology
Volume88
Issue number3
DOIs
StatePublished - May 2012

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