Comparison of the fungicidal efficacy of photodynamic therapy with methylene blue, silver nanoparticle, and their conjugation on oral Candida isolates using cell viability assay

This study aimed to evaluate the effect of common photodynamic therapy and photodynamic therapy by the silver nanoparticle, methylene blue, and their combination on biofilm and plankton cells of standard oral Candida isolates using cell viability assay.

In this in vitro study, biofilm and plankton cells of Candida species(i.e. C .albicans and C. parapsilosis) and plankton cells of Candida glabrata were treated with methylene blue, silver nanoparticle, and their combination once alone and then with the irradiation of total dose of 1.92 J/cm² for 60 sec. The minimum inhibitory concentration and antifungal activity of each approach were evaluated using the XTT assay.

After photodynamic therapy, methylene blue showed antifungal effect only on Candida albicans, while the antifungal effect of silver nanoparticles was increased on all Candida species. On the other hand, photodynamic therapy with the combination of methylene blue and silver nanoparticles did not have any effect on C. albicans. However, it reduced the minimum inhibitory concentration value of C. parapsilosis, and the most antifungal effect was observed on C. glabrata.

Photodynamic therapy with photosensitizers can serve as a treatment modality in Candida infections of the oral cavity. Antifungal effect of photodynamic therapy was strain- and photosensitizer-dependent.