Antifungal Efficacy of Plasma-Activated Liquids against <i>Candida albicans</i> : A Potential Alternative for Oral Candidiasis Treatment

The increasing incidence of oral candidiasis refractory to conventional antifungal treatments, coupled with limited therapeutic alternatives, underscores an urgent need for novel interventions. Plasma-activated liquids (PALs), generated via nonthermal plasma, have shown antimicrobial promise, yet their antifungal efficacy, particularly against <i>Candida albicans</i>, remains understudied, and no investigations have addressed their use in oral candidiasis. In this study, PALs were produced using a gliding-arc plasma reactor with argon and compressed air (pure and mixed) at gas flows of 1.5 and 3.0 L/min, and an average power range of 25-60 W. Two liquid substrates, distilled water and 0.9% sodium chloride (saline) solution, were plasma-activated and characterized in terms of physicochemical parameters (pH, ORP, TDS, conductivity) and reactive oxygen and nitrogen species (RONS), including H₂O₂, NO₂ ^-, NO₃ ^-, HNO₂, and O₃, via spectrophotometry and reactive-strip analysis. The antifungal activity of PALs was assessed against <i>C. albicans</i> in both planktonic and biofilm forms. After 30 min exposure, argon-activated saline (S1) and distilled water (D1), and argon-air activated distilled water (D2), achieved ∼50% reduction in planktonic viability; only S1 and D1 maintained significant effects on 24- and 48 h biofilms. Moreover, PALs frozen at -18 °C for 24 h retained antifungal efficacy. Cytotoxicity assays using Vero cells confirmed that D1 and S1 were nontoxic over both immediate and 24 h exposures (viability >70%). In sum, argon-derived PALs based on distilled water and saline exhibited selective antifungal and antibiofilm activity against <i>C. albicans</i>, without toxicity to mammal cells, highlighting their potential as adjunctive therapies in candidiasis management. These findings support further optimization for clinical applications.