Antibiofilm efficacy of 1,064-nm neodymium-doped yttrium aluminum garnet laser on Trichophyton rubrum and Candida albicans: in vitro study.

Fungal biofilms are the most important virulence factors of onychomycosis. However, traditional antifungal therapies lack antibiofilm efficacy. Although neodymium-doped yttrium aluminum garnet (Nd:YAG) laser is one of the most common laser therapies used for onychomycosis, its usage is restricted to aesthetic endpoints. Therefore, this study aimed to assess the antibiofilm activity of Nd:YAG against Trichophyton rubrum (NCCP 22456) and Candida albicans (NCCP 32703) biofilms. Biofilms were subjected to Nd:YAG (fluence 200 mJ/cm2, pulse duration, 0.1 ms; spot size, 1.5 mm; frequency, 30 Hz) for cumulative time periods (0, 10, 20, and 60 s). Biofilm biomass, cell viability, and metabolic activity were assessed using crystal violet staining, colony counting, and tetrazolium salt (2,3-bis [2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide; XTT) assay, respectively. Biofilm ultrastructure was assessed using scanning electron microscopy (SEM). Biofilm biomass significantly decreased after 10 s of laser irradiation in T. rubrum and C. albicans (P < 0.01), reaching maximum reductions of 77.1% and 58.1% after 60 s, respectively. Colony counts decreased by 66.0% for T. rubrum and 82.2% (0.75 log) for C. albicans; however, these reductions remained below 1 log (<90%), indicating limited viability inhibition. Metabolic activity significantly decreased after 10 s in both strains (P < 0.01), reaching a 45.1% reduction in T. rubrum and 72.5% in C. albicans after 60 s. SEM imaging showed damaged hyphae and extracellular matrix in T. rubrum, and shrunken and broken spores in C. albicans. Overall, Nd:YAG effectively inhibited biofilm biomass, metabolic activity, and structural integrity but had a limited effect on reducing biofilm viability.IMPORTANCEThis study assessed the effects of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation on Trichophyton rubrum and Candida albicans biofilms, including changes in biomass, viability, metabolic activity, and structure. Regarding T. rubrum, no previous in vitro study has comprehensively reported on these specific parameters following Nd:YAG exposure. Existing in vitro studies on T. rubrum have only assessed the "fungicidal" efficacy of the Nd:YAG laser; the most common method has been measuring the difference in "colony diameter" between irradiated and non-irradiated colonies, followed by scanning electron microscopy (SEM) imaging of damaged hyphae. For C. albicans, only one study has examined biofilm viability and ultrastructural changes after Nd:YAG irradiation. Therefore, in accordance with recent recommendations for biofilm research, we conducted a thorough assessment of the laser's antibiofilm activity. The antibiofilm efficacy of the Nd:YAG laser alone was suboptimal, supporting its potential use as an adjunctive therapy rather than a standalone treatment.