Anti-Candida albicans biofilm effect of novel heterocyclic compounds.

Objectives: The aims of this study were to develop new anti-biofilm drugs, examine their activity against Candida albicans biofilm and investigate their structure-activity relationship and mechanism of action.

Methods: A series of thiazolidinedione and succinimide derivatives were synthesized and their ability to inhibit C. albicans biofilm formation and destroy pre-formed biofilm was tested. The biofilms' structure, metabolic activity and viability were determined by XTT assay and propidium iodide and SYTO 9 live/dead stains combined with confocal microscopic analysis. The effect of the most active compounds on cell morphology, sterol distribution and cell wall morphology and composition was then determined by specific fluorescent stains and transmission electron microscopy.

Results: Most of the compounds were active at sub-MICs. Elongation of the aliphatic side chain resulted in reduced anti-biofilm activity and the sulphur atom contributed to biofilm killing, indicating a structure-activity relationship. The compounds differed in their effects on biofilm viability, yeast-to-hyphal form transition, hyphal morphology, cell wall morphology and composition, and sterol distribution. The most effective anti-biofilm compounds were the thiazolidinedione S8H and the succinimide NA8.

Conclusions: We developed novel anti-biofilm agents that both inhibited and destroyed C. albicans biofilm. With some further development, these agents might be suitable for therapeutic purposes.