Photodynamic inactivation of different Candida species and inhibition of biofilm formation induced by water-soluble porphyrins

Background: Candida spp. is the main fungal genus related to infections in humans, and its treatment has become a challenge due to the production of biofilm and its resistance/multi-resistance profile to conventional anti-fungals. Antimicrobial photodynamic therapy stands out as a treatment characterized by a broad spectrum of antimicrobial action, being able to induce oxidative stress in pathogens, and porphyrins are photosensitizers with high selectivity to pathogens. Thus, this work aimed to analyze the photoinactivation of different species of Candida by two cationic (4-H2TMeP+ and 3-H2TMeP+) and one anionic (4-H2TPSP-) porphyrins. Materials and Methods: Microdilution assays were performed to determine the MIC100, with subsequent determination of MFC100. Determination of oxidative species was done through the use of scavengers, while biofilm morphological features were investigated using the atomic force microscopy.Results: Cationic porphyrins were significantly efficient in inactivating Candida albicans and non-albicans species with 100% growth inhibition and fungicidal activity (MFC100/MIC100 <= 4.0). The cationic porphyrins were also able to interfere in Candida spp biofilm formation. The photo-oxidative mechanism activated by 3-H2TMeP+ in Candida spp. is concurrent with the production of singlet oxygen and oxygen radical species. In the AFM analysis, 3-H2TMeP+ was able to reduce yeast adhesion to the surface. Conclusions: Cationic porphyrins can photo-inactivate different species of Candida in both planktonic and biofilm-associated forms, and reduce the adhesion of these fungi to the surface.

Automated summary

Cationic porphyrins can effectively photo-inactivate different species of Candida and reduce their adhesion to the surface. These porphyrins have a broad spectrum of antimicrobial action and can inhibit the growth of Candida completely under photodynamic therapy conditions.