Aplicação de porfirinas tetra-catiônicas para fotoinativação de Candida albicans no tratamento de onicomicose

Abstract

Onychomycosis is one of the most prevalent fungal infections among nail disorders. Dermatophyte fungi are the main causative agents, but yeasts of the Candida genus are emerging pathogens associated with these infections. Species of the Candida genus are natural constituents of the human microbiota, but behave as opportunistic pathogens in the presence of homeostatic changes in the body, causing infections. In addition, these fungi are capable of forming biofilms, producing an extracellular polymeric matrix that strongly adheres to the solid surface, providing protection to the microbial population. The usual treatments for onychomycosis are restricted to the use of oral and topical antifungal agents. However, the long period of treatment and the undesirable effects make it difficult to adhere to therapy, which can make the disease recurrent. In this context, the photoinactivation of microorganisms is an alternative therapy, which uses an activated photosensitive compound (photosensitizer), capable of producing reactive species, inducing cell death. Meso-tetra-substituted porphyrins are reported to be good photosensitizers due to their effectiveness in photoinactivation. The objective of this study was to evaluate, for the first time, the antifungal and antibiofilm potential of the application of tetracationic porphyrins in the photoinactivation of C. albicans, aiming at the treatment of onychomycosis. The minimum inhibitory and fungicidal concentration of the porphyrins 3PtTPyP and 4PtTPyp and 3H2TPyP and 4H2TPyP was evaluated and the results demonstrated greater efficacy of the porphyrin 3PtTPyP against the isolates tested under irradiation, being the compound of choice for the next tests. The cell viability curve showed that there was inhibition of C. albicans ATCC 14053 in 60 minutes and of C. albicans ATCC SC5314 in just 30 minutes of exposure to light. The possible photooxidation mechanism was mixed with production of hydroperoxyl radical species and singlet oxygen. The association assay between porphyrin and conventional antifungals showed indifferent activity. C. albicans biofilms were formed in vitro and in an ex vivo nail model and after treatment with 3PtTPyP, the different concentrations tested were able to significantly destroy the biofilm when compared to the positive control. Aomic force microscopy showed the damage caused to cell morphology, structure and adhesion after photosensitizer treatment. The cytotoxicity tests did not show any toxic potential to keratinocyte and fibroblast cells, with the concentrations tested being safe for use in PDT. This study revealed that PDT using porphyrins containing peripheral Pt(II) complexes may be a promising candidate as an alternative treatment against onychomycosis fungal infections.