Open AccessThe phototoxicity of phenothiazinium‐based photosensitizers to bacterial membranes
Author(s) -
Hussain Saimah,
Harris Frederick,
Phoenix David A.
Publication year - 2006
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.2005.00017.x
Subject(s) - phototoxicity , photosensitizer , membrane , escherichia coli , biology , biochemistry , chemistry , biophysics , photochemistry , in vitro , gene
The ability of phenothiazinium‐based photosensitizers to induce photodamage to Escherichia coli membranes is investigated. Phenothiazinium‐based photosensitizers were found to be somewhat lipophilic (log P >0.7) and to induce surface‐pressure changes (3–12 mN m −1 ) in lipid monolayers mimetic of bacterial membranes, implying that these molecules are able to penetrate biological membranes. Under dark and light conditions (3.15 J cm −1 for 30 min), phenothiazinium‐based photosensitizers were incubated with E. coli cells. These cells showed levels of dark bacteriolysis that ranged between 6% and 13%, with light conditions leading to no significant increase in these levels. Gas chromatography‐based analyses showed such incubations to produce no significant changes in the levels of C 16 and C 18 fatty acid chain saturation found in E. coli whole lipid‐extracts. It is concluded that the phenothiazinium‐based photosensitizers studied may not use E. coli membranes as their primary photodynamic target, but may inflict photodamage on cytoplasmic targets, possibly DNA.