Enhancing antimicrobial photodynamic therapy with phenothiazinium dyes and sodium dodecyl sulfate against Candida albicans at various growth stages

• Published in: Photodiagnosis and photodynamic therapy 2023-06, Vol.42, p.103628-103628, Article 103628
• Main Authors: Machado, Gabriela Benedito, Monteiro, Carolina Montovam, Gonçalves, José Marcelo Lacerda Alves, Pavani, Christiane
• Format: Article
• Language: English
• Subjects: Antifungal Agents - pharmacology; Antimicrobial photodynamic therapy; Biofilm; Biofilms; Candida albicans; Coloring Agents - pharmacology; Methylene Blue - pharmacology; PDT; Photochemotherapy - methods; Photosensitizing Agents - pharmacology; Sodium dodecyl sulfate; Sodium Dodecyl Sulfate - pharmacology
• ISSN: 1572-1000; 1873-1597
• DOI: 10.1016/j.pdpdt.2023.103628

•Antimicrobial action of phenothiazinium dyes increases when associated with sodium dodecyl sulfate.•Antimicrobial effect of PDT is greater at the adhesion stage of biofilm growth.•PDT with phenothiazinium and surfactant can inactivate biofilm in dispersion via two serial usages. The eradication of C. albicans is difficult due to the organization of the yeast in biofilms. Photodynamic therapy (PDT) has been proposed as an alternative to antifungals. Phenothiazinium dyes, e.g. methylene blue (MB), have been proposed as photosensitizing agents (PS), and their association with sodium dodecyl sulfate (SDS) has recently been shown to improve the effectiveness of PDT in planktonic culture. In this sense, the objective of this work was to evaluate the effect of PDT with phenothiazinium dyes associated to SDS in biofilms at the different stages of growth. Experiments were carried out to evaluate the effects of PDT on biofilm formation and on established biofilms of C. albicans ATCC 10231. Samples were exposed to PS 50 mg/L (MB, Azure A – AA, Azure B - AB and dimethyl methylene blue - DMMB) dissolved in water or 0.25% SDS, for 5 min in the dark. After irradiation at 660 nm, 37.3mW/cm2 for 27 min, 60.4J/cm2 colony forming units count assay (CFU/mL) was performed. One or two irradiations were applied. Statistical methods were used to assess effectiveness. PSs showed low toxicity in the dark. An application of PDT irradiation was not able to reduce the CFU/mL both in mature biofilms (24h) and in biofilms in the dispersion phase (48h), only in the adherence phase did PDT prevent the formation of biofilms. With two successive applications of PDT irradiation in the dispersion phase, PDT with MB, AA, and DMMB completely inactivated C. albicans. The similar was not observed with mature biofilms. Different stages of biofilm growth respond differently to PDT, with the greatest inhibitory effect found in the adhesion stage. Mature and dispersed biofilms are less susceptible to PDT. The use of two successive applications of PDT with PSs associated with SDS may be a useful approach to inactivate C. albicans biofilms.