Photodynamic antimicrobial chemotherapy (PACT) with methylene blue increases membrane permeability in Candida albicans

Abstract

Photodynamic antimicrobial chemotherapy (PACT) is a potential antimicrobial therapy that combines light and a photosensitizing drug, promoting a phototoxic effect on the treated cells, in general via oxidative damage. In this work we studied the effect of PACT, using methylene blue (MB), on the permeability of Candida albicans membrane. Our results demonstrated that the combination of MB and laser (684 nm) promoted a decrease in Candida growth. The inhibition was more pronounced in the presence of 0.05 mg/ml MB and with an energy density of 28 J/cm(2). The decrease in Candida growth was associated with an increase in membrane permeabilization. Thus, we suggest that a PACT mechanism using MB can be related to damage in the plasma membranes of the cells.

Susceptibility of Candida albicans to photodynamic therapy in a murine model of oral candidosis

“…42 In contrast to bacterial species, C. albicans sensitized by 100 mg/L MB was killed by visible light from a slide projector (42 mW/cm 2 ) after only 20 minutes of irradiation. 34 Giroldo et al 43 verified inhibition of C. albicans CFUs to approximately 50% in the presence of 50 mg/L MB and laser light irradiation of 28 J/cm 2 . These authors also verified that cell death promoted by this combination can be related to damage to the plasma membrane of the yeast.…”

Photoinactivation of Candida albicans using methylene blue as photosensitizer

“…The light sources used more often in PDT against Candida albicans were LED 12 and the low-intensity laser, highlighting the diode laser 6,[8][9]10,22 . In this research, diode laser of MM OPTICS (Laser DUO ® ) was used and, due to being portable and having batteries, this presents a greater advantage compared to the handling without relying on an energy source, and can be applied to patients in several environments: domestic, clinic, family health care units, or intensive care units.…”

“…The studies of Dai et al 1 , Kato et al 4 , Teichert et al 6 , Pereira et al 7 , Souza et al 8 , Queiroga et al 9 , Munin et al 10 , Silva Martins et al 17 , Giroldo et al 22 and Souza et al 23 , investigated the effects of photodynamic therapy on the viability of Candida albicans using methylene blue as a photosensitizer. The results of these studies proved the antifungal effect of this treatment modality.…”

“…The studies that evaluated PDT effect on Candida albicans used different concentrations of methylene blue, from 10 µg/mL 22 to 500 µg/mL 6 and the most used incubation time was 5 minutes [7][8][9] . Therefore, to respond to the PDT effect hypothesis on the Candida albicans cells, this study used the concentration of 150 µg/ mL and the incubation time of 5 minutes.…”

“…In the absence of light, methylene blue showed no cytotoxic effect on Candida albicans cells, corroborating with the aforementioned studies. Both the photosensitizer and the light are relatively harmless by itself, but when combined, in the presence of oxygen, cause selective destruction on the affected area 17,22 . According to Pereira & Maisch 14 and Ryskova et al 15 photosensitizing agents show no or minimal inherent toxicity and the cytotoxic effect only occurs after its illumination with specific wavelength light.…”