Photodynamic inactivation of Candida albicans biofilm: Influence of the radiant energy and photosensitizer charge.

Background: The aim of this study is to investigate the photoinactivation of C. albicans biofilm on acrylic resin discs (the standard material for dental prosthesis) using the photosensitizers Methylene Blue and a Protoporphyrin IX.
Methods: Eighteen thermally activated Methyl Methacrylate Polymers were used for the biofilm growth of Candida albicans ATCC 10231. Two photosensitizers were tested: methylene blue (50μM) and protoporphyrin IX (10μM). Two custom-made LEDs emitting at 660nm and 630nm with approximately 800mW each were used for the irradiation, with duration ranging from 2 to 10min.
Results: This study demonstrates that MB decreased the aPDT CFUs by approximately two orders of magnitude, but the protoporphyrin was ineffective.
Conclusion: The aPDT with MB significantly reduces (but does not sterilize) the amount of CFU after 10min of irradiation, and it is not dose-dependent. The lack of effect of the protoporphyrin is likely because the negative charges of the proteoglycans present in the extracellular matrix repel the negative charges of the PS, thus preventing its diffusion in the cells.
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