title: Porphyrin-silica microparticle conjugates as an efficient tool for the photosensitised disinfection of water contaminated by bacterial pathogens.
abstract: A tetracationic meso-substituted amphiphilic porphyrin (abbreviated as C14) was encapsulated within silica microparticles to yield a conjugate with a mean particle diameter of ca. 0.9 μm. The conjugate displayed a complete stability for at least 3 months when suspended in a neutral aqueous medium. The encapsulated C14 underwent a limited photobleaching when the conjugate was exposed to full spectrum visible light. Illumination of the silica microparticle-bound C14 by visible light resulted in the generation of singlet oxygen and induced a decrease in the survival of 4 log for a 20 min irradiation of the Gram-positive bacterium meticillin-resistant Staphylococcus aureus (MRSA) and a 30 min irradiation of the Gram-negative bacterium Escherichia coli (E. coli). Under identical experimental conditions photoexcited free C14 caused a decrease in viability of 5 log for MRSA and 6 log for E. coli. When the conjugate loaded with 12 μM C14 was added to a water sample contaminated with MRSA (10(8) cells per ml) a tight association of the bacterial cells with the silica microparticle-porphyrin system was achieved. Subsequent illumination of the conjugate with visible light (30 min, 100 mW cm(-2)) caused a 3 log reduction in the population of MRSA cells in the water sample. Importantly, the conjugate was readily recovered by filtration of the aqueous suspension and shown to maintain a high antibacterial photoactivity when introduced into a new MRSA-contaminated medium and irradiated.
authors.affiliation: Department of Biology, University of Padova, 35131 Padova, Italy. jori@bio.unipd.it.
authors.forename: Michela
authors.initials: M
authors.lastname: Magaraggia
authors.forename: Giulio
authors.initials: G
authors.lastname: Jori
authors.forename: Marina
authors.initials: M
authors.lastname: Soncin
authors.forename: Claire L
authors.initials: CL
authors.lastname: Schofield
authors.forename: David A
authors.initials: DA
authors.lastname: Russell
mesh_terms: D004203:Disinfection / Q000379:methods*; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D010316:Particle Size; D017319:Photosensitizing Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D011166:Porphyrins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D026082:Singlet Oxygen / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D026082:Singlet Oxygen; D012822:Silicon Dioxide