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.
Departamento de Química, Universidad Nacional de Río Cuarto, Río Cuarto, Agencia Postal Nro. 3, X5804BYA Río Cuarto, Córdoba, Argentina.
Daniel A
DA
Caminos
Edgardo N
EN
Durantini
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