In Vitro Photoinactivation of Fusarium oxysporum Conidia with Light-Activated Ammonium Phthalocyanines

Antimicrobial photodynamic therapy (aPDT) has been explored as an innovative therapeutic approach because it can be used to inactivate a variety of microbial forms (vegetative forms and spores) without causing significant damage to host tissues, and without the development of resistance to the photosensitization process. This study assesses the photodynamic antifungal/sporicidal activity of tetra- and octasubstituted phthalocyanine (Pc) dyes with ammonium groups. Tetra- and octasubstituted zinc(II) phthalocyanines (1 and 2) were prepared and tested as photosensitizers (PSs) on Fusarium oxysporum conidia. Photoinactivation (PDI) tests were conducted with photosensitizer (PS) concentrations of 20, 40, and 60 mu M under white-light exposure at an irradiance of 135 mW center dot cm(-2), applied during 30 and 60 min (light doses of 243 and 486 J center dot cm(-2)). High PDI efficiency corresponding to the inactivation process until the detection limit was observed for both PSs. The tetrasubstituted PS was the most effective, requiring the lowest concentration and the shortest irradiation time for the complete inactivation of conidia (40 mu M, 30 min, 243 J center dot cm(-2)). Complete inactivation was also achieved with PS 2, but a longer irradiation time and a higher concentration (60 mu M, 60 min, 486 J center dot cm(-2)) were necessary. Because of the low concentrations and moderate energy doses required to inactivate resistant biological forms such as fungal conidia, these phthalocyanines can be considered potent antifungal photodynamic drugs.

Automated summary

Antimicrobial photodynamic therapy (aPDT) is an innovative therapeutic approach that can effectively inactivate microbial forms without harming host tissues or causing resistance. This study evaluates the antifungal/sporicidal activity of tetra- and octasubstituted phthalocyanine dyes with ammonium groups. Both photosensitizers tested showed high efficiency in inactivating conidia, with the tetrasubstituted dye being the most effective. These phthalocyanines have the potential to be potent antifungal drugs due to their low concentrations and moderate energy doses required for inactivation.