Objectives: To investigate the in vitro effects of purpurin on Candida albicans hyphal development and biofilm formation.
Methods: C. albicans SC 5314 biofilms were prepared in polystyrene, flat bottom 96-well microtiter plates. The cell suspension (100 µl, 107cells/ml in YNB) was transferred to the wells and incubated at 37oC, 75 rpm for 1.5 h. After the removal of loosely adherent cells by washing, fresh YNB (200 µl) was added to the wells and incubated for 24 h for biofilm formation. Thereafter, the wells were washed with PBS and purpurin (200 µl, 5µg/ml in YNB) was added and incubated at similar conditions for 24 h. The susceptibility of C. albicans biofilms to purpurin was assessed semi-quantitatively by XTT reduction assay, and the effects of purpurin on hyphal development and biofilm architecture were qualitatively assessed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).
Results: XTT assay indicated that the susceptibility of C. albicans biofilms to purpurin was dose-dependent. At 5µg/ml, biofilm viability was reduced by ~22% and by ~46% at high concentration (20µg/ml) (P \u3c 0.05). The SEM and CLSM results confirmed the inhibitory effect of purpurin on C. albicans architecture. Purpurin-treated C. albicans biofilms were scanty, and exclusively consisted of blastospores compared to its control which was relatively confluent, and rich in hyphae.
Conclusions: Purpurin inhibits hyphal development in C. albicans and disintegrates the biofilm. Its ability to inhibit these candidal virulence factors may shed light on further development of antifungal strategies against this human fungal pathogen
