title: Effect of monovalent and divalent cations on the photoinactivation of bacteria with meso-substituted cationic porphyrins.
abstract: It is well established that for successful photoinactivation (PI) of gram-negative bacteria a cationic photosensitizer is required. This requirement suggests a charge-dependent interaction between the photosensitizer and the gram-negative bacterium, which may be influenced by the presence of ions in the suspending medium. The aim of the present study was to investigate the effect of cations Na+ and Ca2+ on the efficacy of the PI of the gram-negative Pseudomonas aeruginosa and the gram-positive Staphylococcus aureus. The bacteria were suspended in buffer containing either meso-tetra(N-methyl-4-pyridyl)-porphyrin or meso-mono-phenyl-tri(N-methyl-4-pyridyl)-porphyrin as photosensitizer and various concentrations of Na+ or Ca2+. The cell suspensions were exposed to a broadband light dose of 9 J/cm2. In buffer without added cations, P. aeruginosa and S. aureus were equally sensitive to PI. Addition of cations strongly decreased the sensitivity of both bacteria to PI, with the PI of P. aeruginosa being much more decreased than that of S. aureus, and Ca2+ being more effective than Na+. The decreased sensitivity was accompanied by a reduced binding of the photosensitizers to the bacteria.
authors.affiliation: Laser Center, University of Amsterdam, Amsterdam, The Netherlands. s.a.lambrechts@amc.uva.nl
authors.forename: Saskia A G
authors.initials: SA
authors.lastname: Lambrechts
authors.forename: Maurice C G
authors.initials: MC
authors.lastname: Aalders
authors.forename: Diana H
authors.initials: DH
authors.lastname: Langeveld-Klerks
authors.forename: Youssef
authors.initials: Y
authors.lastname: Khayali
authors.forename: Johan W M
authors.initials: JW
authors.lastname: Lagerberg
mesh_terms: D001667:Binding, Competitive; D002021:Buffers; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D002414:Cations, Monovalent; D008027:Light; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011166:Porphyrins / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000528:radiation effects; D012964:Sodium / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000528:radiation effects
chemical_list: D002021:Buffers; D002413:Cations, Divalent; D002414:Cations, Monovalent; D017319:Photosensitizing Agents; D011166:Porphyrins; C021096:tetra(4-N-methylpyridyl)porphine; D012964:Sodium; D002118:Calcium