Photodynamic Effects of Novel XF Porphyrin Derivatives on Prokaryotic and Eukaryotic Cells

Abstract

The worldwide rise in the rates of antibiotic resistance of bacteria underlines the need for alternative antibacterial agents. A promising approach to the killing of gram-positive antibiotic-resistant bacteria of the skin uses light in combination with a photosensitizer to induce a phototoxic reaction. Different concentrations (0 to 100 M) of porphyrin-based photosensitizers (CTP1, XF70, and XF73) and different incubation times (5 min, 1 h, and 4 h) were used to determine phototoxicity against two methicillin-resistant Staphylococcus aureus strains, one methicillin-sensitive S. aureus strain, one methicillin-resistant Staphylococcus epidermidis strain, one Escherichia coli strain, and human keratinocytes and fibroblasts. Incubation with 0.005 M XF70 or XF73, followed by illumination, yielded a 3-log 10 (>99.9%) decrease in the viable cell numbers of all staphylococcal strains, indicating that the XF drugs have high degrees of potency against gram-positive bacteria and also that the activities of these novel drugs are independent of the antibiotic resistance pattern of the staphylococci examined. CTP1 was less potent against the staphylococci under the same conditions. At 0.005 M, XF70 and XF73 demonstrated no toxicity toward fibroblasts or keratinocytes. No inactivation of E. coli was detected at this concentration. XF73 was confirmed to act via a reactive oxygen species from the results of studies with sodium azide (a quencher of singlet oxygen), which reduced the killing of both eukaryotic and prokaryotic cells. When a quencher of superoxide anion and the hydroxyl radical was used, cell killing was not inhibited. These results demonstrate that the porphyrin-based photosensitizers had concentration-dependent differences in their efficacies of killing of methicillin-resistant staphylococcal strains via reactive oxygen species without harming eukaryotic cells at the same concentrations.

A comparative in vitro photoinactivation study of clinical isolates of multidrug-resistant pathogens

“…There have been several previous literature reports comparing the PDI of MRSA with that of S. aureus. Maisch et al 15 used XF porphyrins as antimicrobial PSs and found identical killing of MRSA (and methicillin-resistant S. epidermidis to that found with the wild-type strains). Wainwright et al 16 found that PDI with phenothiazinium dyes killed MRSA somewhat less efficiently than wild-type S. aureus strains.…”

The role of singlet oxygen and oxygen concentration in photodynamic inactivation of bacteria

“…One promising technique is the photodynamic inactivation of bacteria, in which the generation of singlet oxygen plays a major role (28,29). To enhance this approach, we investigated the generation and decay of singlet oxygen in bacteria.…”

Inativação fotodinâmica de microrganismos

“…Apesar do considerável progresso que tem sido obtido nos tratamentos de infecções, é preocupante o crescente número de bactérias patogênicas resistentes a antibióticos no mundo todo 16 , o que, segundo Hamblin e Hasan 7 , pode levar ao fim de um extenso período que inclui os últimos 50 anos, chamado de "era do antibiótico". As bactérias multiplicam-se muito rapidamente e uma mutação que ajude um único micróbio a sobreviver na presença de um antibiótico rapidamente se tornará predominante na população microbiana.…”

“…Com relação à eficiência da inativação bacteriana, é conhecido que bactérias Gram-positivas (+) são geralmente mais susceptíveis à PDI e as espécies Gram-negativas (-) são significantemente resistentes a muitos fotossensibilizadores comumente usados em TFD de tumores 16 .…”