title: The phototoxicity of phenothiazinium-based photosensitizers to bacterial membranes.
abstract: 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.
authors.affiliation: Department of Forensic and Investigative Science, Faculty of Science, University of Central Lancashire, Preston PR1 2HE, UK.
authors.forename: Saimah
authors.initials: S
authors.lastname: Hussain
authors.forename: Frederick
authors.initials: F
authors.lastname: Harris
authors.forename: David A
authors.initials: DA
authors.lastname: Phoenix
mesh_terms: D001433:Bacteriolysis; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects*; D003624:Darkness; D004926:Escherichia coli / Q000187:drug effects*; D005227:Fatty Acids / Q000032:analysis; D008027:Light; D010640:Phenothiazines / Q000737:chemistry / Q000633:toxicity*; D017319:Photosensitizing Agents / Q000737:chemistry / Q000633:toxicity*
chemical_list: D005227:Fatty Acids; D010640:Phenothiazines; D017319:Photosensitizing Agents