Involvement of both Type I and Type II mechanisms in Gram-positive and Gram-negative bacteria photosensitization by a meso-substituted cationic porphyrin - EHESP - École des hautes études en santé publique Access content directly
Journal Articles Solar Energy Year : 2008

Involvement of both Type I and Type II mechanisms in Gram-positive and Gram-negative bacteria photosensitization by a meso-substituted cationic porphyrin

Abstract

A meso-substituted cationic porphyrin (TMPyP) showed a photocytotoxicity against Gram-positive and Gram-negative bacteria. In order to determine the mechanism involved in the phototoxicity of this photosensitizer, electron paramagnetic resonance (EPR) experiments with 2,2,6,6-tetramethyl-4-piperidone (TEMP), a specific probe for singlet oxygen, and the spin-trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were carried out with illuminated TMPyP. An EPR signal characteristic of TEMP-singlet oxygen (TEMPO) adduct formation was observed, which could be ascribed to singlet oxygen (1O2) generated by TMPyP photosensitization. The signal for the DMPO spin adduct of superoxide anion (DMPO-OOH) was observed in DMSO solution but not in aqueous conditions. However, an EPR spectrum characteristic of the DMPO-hydroxyl radical spin adduct (DMPO-OH) was observed in aqueous conditions. The obtained results testify a primary hydroxyl radical ({radical dot}OH) generation probably from superoxide anion (O2{radical dot} -) via the Fenton reaction and/or via Haber-Weiss reaction. Gram-positive and Gram-negative bacteria inactivation by TMPyP photosensitization predominantly involved Type II reactions mediated by the formation of 1O2, as demonstrated by the effect of quenchers for 1O2 and scavengers for {radical dot}OH (sodium azide, thiourea, and dimethylsulphoxide). Participation of other active oxygen species cannot however be neglected since Type I reactions also had a significant effect, particularly for Gram-negative bacteria. For Gram-negative bacteria the photoinactivation rate was lower in the presence of superoxide dismutase, a specific O2{radical dot} - scavenger, and/or catalase, an enzyme which specifically eliminates H2O2, but was unchanged for Gram-positive bacteria. The generation of 1O2, O2{radical dot} - and {radical dot}OH by TMPyP photosensitization indicated that TMPyP maintained a photodynamic activity in terms of Type I and Type II mechanisms.

Dates and versions

hal-04061016 , version 1 (06-04-2023)

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Karim Ergaieg, Martine Chevanne, Josiane Cillard, René Seux. Involvement of both Type I and Type II mechanisms in Gram-positive and Gram-negative bacteria photosensitization by a meso-substituted cationic porphyrin. Solar Energy, 2008, 82 (12), pp.1107-1117. ⟨10.1016/j.solener.2008.05.008⟩. ⟨hal-04061016⟩
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