Fungicidal photodynamic effect of a twofold positively charged porphyrin against Candida albicans planktonic cells and biofilms

摘要

Background: Antimicrobial photodynamic therapy is an interesting alternative for the treatment of superficial mucocutaneous mycoses. In immunodeficient patients, these infections are frequently recurrent and resistant to the most commonly used antifungal medications. Candida albicans biofilms frequently cause such infections that can even evolve to deep-seated mycoses. Materials & methods: The efficiency of a photodynamic therapy was investigated against C. albicans using a twofold positively charged porphyrin (XF-73) in comparison with the well-known fourfold positively charged porphyrin (5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine, tetra-p-tosylate salt). Results: After incubation with 0.5 μM of XF-73 for 15 min and irradiation with blue light (12.1 J/cm2), the viability of C. albicans planktonic cells decreased by over 6 log10. For biofilm cells, a longer incubation time (4 h) with 1 μM of XF-73 and a light dose of 48.2 J/cm2 was necessary to achieve over 5 log10 cell killing. Cell killing was mediated by singlet oxygen that was directly detected via its luminescence at 1270 nm in XF-73-incubated C. albicans biofilms for the first time. Antimicrobial photodynamic therapy yielded better results for XF-73 compared with 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine, tetra-p-tosylate salt when using the same conditions. Conclusion: This study provides evidence that XF-73 is a highly efficient photosensitizer to kill C. albicans and it would be worthwhile to test this photosensitizer in clinical studies for both prophylaxis and treatment of infections caused by this microorganism, preventing the spread of C. albicans throughout the bloodstream.