Antimicrobial mechanisms behind photodynamic effect in the presence of hydrogen peroxide.
This study describes the use of methylene blue (MB) plus light (photodynamic inactivation, PDI) in the presence of hydrogen peroxide (H(2)O(2)) to kill Staphylococcus aureus, Escherichia coli, and Candida albicans. When H(2)O(2) was added to MB plus light there was an increased antimicrobial effect, which could be due to a change in the type of ROS generated or increased microbial uptake of MB. To clarify the mechanism, the production of ROS was investigated in the presence and absence of H(2)O(2). It was observed that ROS production was almost inhibited by the presence of H(2)O(2) when cells were not present. In addition, experiments using different sequence combinations of MB and H(2)O(2) were performed and MB optical properties inside the cell were analyzed. Spectroscopy experiments suggested that the amount of MB was higher inside the cells when H(2)O(2) was used before or simultaneously with PDI, and ROS formation inside C. albicans cells confirmed that ROS production is higher in the presence of H(2)O(2). Moreover enzymatic reduction of MB by E. coli during photosensitizer uptake to the photochemically inactive leucoMB could be reversed by the oxidative effects of hydrogen peroxide, increasing ROS formation inside the microorganism. Therefore, the combination of a photosensitizer such as MB and H(2)O(2) is an interesting approach to improve PDI efficiency.
Centro de Pesquisa e Pós-Graduação São Leopoldo Mandic, Campinas-SP, Brazil.
Aguinaldo Silva
AS
Garcez
Silvia Cristina
SC
Núñez
Mauricio S
MS
Baptista
Nasser Ali
NA
Daghastanli
Rosangela
R
Itri
Michael R
MR
Hamblin
Martha Simões
MS
Ribeiro
D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000494:pharmacology; D008027:Light; D008751:Methylene Blue / Q000737:chemistry*; D010084:Oxidation-Reduction; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects
D000890:Anti-Infective Agents; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D008751:Methylene Blue