Antifungal Effects of Non-Thermal Atmospheric Pressure Plasma In Vitro and Ex Vivo

Background: Non-thermal atmospheric pressure plasma (NTAP) generates reactive oxygen species, reactive nitrogen species, and ultraviolet radiation, which can inactivate microorganisms. Onychomycosis treatment is challenging, and its prognosis is poor owing to mixed infections and dermatophytosis. Although NTAP has shown in vitro antifungal effects against dermatophytes and yeast, its efficacy against non-dermatophyte molds (NDMs) and in clinical or nail model studies remains poorly understood. Objective: We evaluated the effects of NTAP on fungi, including NDMs, and infected nail plates. Methods: For the in vitro experiments, Trichophyton rubrum, Candida albicans, Aspergillus fumigatus, and Fusarium oxysporum strains were exposed to NTAP. After NTAP exposure (2,4 and 6 minutes), growth curve, cell viability, and biofilm biomass were assessed by absorbance wavelength of 600 nm, XTT assay, and crystal violet staining, respectively. For the ex vivo experiments, infected nail plates were analyzed using a scanning electron microscope. Results: T. rubrum and C. albicans showed greater growth inhibition with increasing NTAP exposure time, whereas A. fumigatus showed enhanced growth after 6 minutes exposure. Many fungal elements within the subungual hyperkeratosis of the ex vivo specimen were all damaged following NTAP exposure. Conclusion: NTAP has antifungal effects on dermatophytes, yeast, and NDMs. We suggest that the intensity and time of NTAP application should be adjusted according to each strain and can be more effective when NTAP directly reaches the hyphae on the nail bed or subungual hyperkeratosis.