The photodynamic action of rose bengal on Trypanosoma cruzi

In the presence of light and oxygen, rose bengal causes oxidative damage to Trypanosoma cruzi. The production of lipid hydroperoxides was demonstrated by thin-layer chromatography, and severe ultrastructural alterations compatible with an increased permeability of the cells, which led to gradual osmotic swelling and ultimately to lysis, were observed by electron microscopy. As a result of this treatment, the infectivity of T. cruzi trypomastigotes in mice was abolished. In addition, under anaerobic conditions, rose bengal was found to undergo a one-electron reduction in intact T. cruzi epimastigotes to produce a carbon-centered free radical as demonstrated by electron spin resonance spectroscopy. The formation of this radical was also enhanced by light.