Photodynamic inactivation of Escherichia coli immobilized on agar surfaces by a tricationic porphyrin.
The photodynamic activity of 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) has been studied in vitro on a typical Gram-negative bacterium Escherichia coli immobilized on agar surfaces. The results obtained for the tricationic A3B3+ porphyrin were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl)porphyrin p-tosylate (TTAP4+), which is a standard active sensitizer established to eradicate E. coli in cellular suspension. The photobleaching of these porphyrins in solution was evaluated by decay in absorbance and in fluorescence. In both cases, a higher photostability was found for A3B3+ than for TTAP4+. Photodynamic inactivation capacities of these sensitizers were analyzed in E. coli cells immobilized on agar surfaces. Small colonies were treated with different amount of sensitizer (0-14 nmol) and irradiated with visible light for 3h. The light source used was either a projector or midday sun. The A3B3+ porphyrin produced a growth delay of E. coli colonies on agar surfaces. Similar result was obtained irradiating only one isolated colony through an optical fiber. Under these conditions, A3B3+ porphyrin shows a high activity to inactivate localized bacterial cells. The higher photodynamic activity of A3B3+ was confirmed by mechanical spreading of the colonies before treatment. This procedure produces complete inactivation of E. coli cells on the agar surface. Therefore, tricationic A3B3+ porphyrin is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria growing as localized foci of infection.
Caminos
Daniel A
DA
Departamento de Química, Universidad Nacional de Río Cuarto, Río Cuarto, Agencia Postal Nro. 3, X5804BYA Río Cuarto, Córdoba, Argentina.
Durantini
Edgardo N
EN
D000362:Agar / Q000737:chemistry*; D002412:Cations / Q000737:chemistry / Q000494:pharmacology; D018914:Cells, Immobilized / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000528:radiation effects; D066298:In Vitro Techniques; D008027:Light; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D017319:Photosensitizing Agents / Q000737:chemistry / Q000494:pharmacology*; D011166:Porphyrins / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013499:Surface Properties
C512240:5,10,15,20-tetera(4-N,N,N-trimethylammoniumphenyl)porphyrin 4-tosylate; C512239:5,10,15-tris(4-(3--N,N,N-trimethylammoniumpropoxy)phenyl)-20-(4-trifluoromethylphenyl)porphyrin; D002412:Cations; D017319:Photosensitizing Agents; D011166:Porphyrins; D000362:Agar