Cellular and tissue effects induced by Photogem® and red LED in photodynamic therapy

Abstract

In order to consider the photodynamic therapy (PDT) as a clinical treatment for candidosis, it is necessary to know its cytotoxic effect on normal cells and tissues. Therefore, this study evaluated the toxicity of PDT with Photogem® associated with red light-emitting diode (LED) on L929 and MDPC-23 cell cultures and healthy rat palatal mucosa. In the in vitro experiment, the cells (30000 cells/cm2) were seeded in 24-well plates for 48 h, incubated with Photogem® (50, 100, or 150 mg/l) and either irradiated or not with a red LED source (630 ± 3 nm; 75 or 100 J/cm2; 22 mW/cm2). Cell metabolism was evaluated by the MTT assay (ANOVA and Dunnet’s post hoc tests; p < 0.05) and cell morphology was examined by scanning electron microscopy. In the in vivo evaluation, Photogem® (500 mg/l) was applied to the palatal mucosa of Wistar rats during 30 min and exposed to red LED (630 nm) during 20 min (306 J/cm2). The palatal mucosa was photographed for macroscopic analysis at 0, 1, 3, and 7 days posttreatment and subjected to histological analysis after sacrifice of the rats. For both cell lines, there was a statistically significant decrease of the mitochondrial activity (90-97%) for all Photogem® concentrations associated with red LED regardless of the energy density. However, in the in vivo evaluation, the PDT-treated groups presented intact mucosa with normal characteristics both macroscopically and histologically. From these results, it may be concluded that the association of Photogem® and red LED caused severe toxic effects on normal cell cultures, characterized by the reduction of mitochondrial activity and morphological alterations, but did not cause damage to the rat palatal mucosa in vivo.