Porphyrin derivatives as photosensitizers for the inactivation of Bacillus cereus endospores.
OBJECTIVE
In this study, we propose (i) to study the photodynamic inactivation (PDI) efficiency of neutral and cationic porphyrin derivatives, (ii) to characterize the kinetics of the inactivation process using Bacillus cereus as a model endospore-producing bacterium and (iii) to conclude on the applicability of porphyrin derivatives in the inactivation of bacterial endospores.


RESULTS
The study of PDI of Bacillus cereus endospores, taken as model-endospores, using porphyrin derivatives differing in the number of positive charges and in the meso-substituent groups, showed that neutral, monocationic and dicationic porphyrins are quite ineffective, in contrast with the tri- and tetra-cationic molecules. The most effective porphyrin is a tricationic porphyrin with a meso-pentafluorophenyl group. With this photosensitizer (PS), at 0.5 micromol l(-1), a reduction of 3.5 log units occurs after only 4 min of irradiation. None of the porphyrin derivatives showed toxicity in the absence of light.


CONCLUSIONS
Some porphyrin derivatives are efficient PSs for the inactivation of bacterial endospores and should be considered in further studies. Small modifications in the substituent groups, in addition to charge, significantly improve the effectiveness of the molecule as a PS for endospore inactivation.


CONCLUSIONS
Tetrapyrrolic macrocycles should be regarded as worthy to explore for the PDI of spore-producing gram-positive bacteria. The development of molecules, more selective and effective, emerges as a new objective.
Oliveira
A
A
Department of Biology & CESAM, University of Aveiro, Aveiro, Portugal.
Almeida
A
A
Carvalho
C M B
CM
Tomé
J P C
JP
Faustino
M A F
MA
Neves
M G P M S
MG
Tomé
A C
AC
Cavaleiro
J A S
JA
Cunha
A
A
D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001409:Bacillus cereus / Q000187:drug effects* / Q000254:growth & development; D002478:Cells, Cultured; D015169:Colony Count, Microbial; D008027:Light; D017319:Photosensitizing Agents / Q000737:chemistry / Q000494:pharmacology*; D011166:Porphyrins / Q000737:chemistry / Q000494:pharmacology*; D013171:Spores, Bacterial / Q000187:drug effects* / Q000254:growth & development
D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D011166:Porphyrins