Curcumin-mediated antimicrobial photodynamic therapy prevents Candida biofilm formation in a species-dependent manner

This study aimed to systematically evaluate the antibiofilm efficacy of curcumin-mediated antimicrobial photodynamic therapy (aPDT) activated by 450 nm LED light against biofilm formation and mature biofilms of clinically relevant Candida species, with particular emphasis on preventive potential and species-dependent susceptibility; Biofilm formation and maturation were investigated in five standard Candida strains. Biofilm formation (preventive approach) and established biofilms were treated with curcumin followed by irradiation with 450 nm LED light. Biofilm biomass was quantitatively assessed using the crystal violet assay. Comparative analyses were performed to determine species-dependent responses to aPDT. Data normality was assessed using the Shapiro-Wilk test, and intergroup comparisons were performed using the Kruskal-Wallis test followed by Dunn's post hoc test when appropriate. All Candida strains demonstrated a pronounced ability to form biofilms, being classified as strong biofilm producers, except Candida dubliniensis, which exhibited moderate biofilm formation. Curcumin-mediated aPDT significantly inhibited biofilm development across all tested species (p < 0.05), achieving reductions of 86.82% for C. metapsilosis, 85.05% for C. orthopsilosis, 83.33% for C. parapsilosis, 75.34% for C. dubliniensis, and 68.19% for C. albicans. This preventive antibiofilm effect is likely associated with reactive oxygen species generation, resulting in oxidative damage to essential cellular structures and impairment of early extracellular matrix establishment. In contrast, aPDT activity against mature biofilms was significantly attenuated and highly species-dependent, with reductions ranging from 49.63% (C. parapsilosis) to 0.64% (C. dubliniensis); however, these reductions were not statistically significant (p > 0.05). Curcumin-mediated aPDT exerted a significant preventive antibiofilm effect against Candida biofilm formation but showed limited and non-significant activity against mature biofilms. These findings position curcumin-mediated aPDT as a promising strategy for preventing Candida biofilm establishment, while indicating that improved photosensitizer delivery and optimized irradiation protocols are required to enhance activity against established biofilms.