<i>In Vitro</i> Antifungal Activity of Gallic Acid-Coated Gold Nanorods against <i>Candida albicans</i>

Candida albicans is an opportunistic yeast that frequently affects the mucosal surfaces and the skin, causing candidiasis with high recurrence rates associated with increased antifungal resistance. In this context, metallic nanoparticles stand out as a potential antifungal agent for the treatment of superficial Candida infections. Here, we explored an emerging field of nanobiotechnology targeted to the metallic nanoparticle production using green synthesis methods. Our goal was to investigate the antifungal activity of gold nanorods─a rod-shaped gold nanostructure─synthesized via a green chemistry approach using gallic acid (GA) as both a reducing and capping agent (GA-AuNR). GA-AuNR exhibited fungicidal effects against C. albicans at concentrations at least 100 times lower than those required for GA. Furthermore, GA-AuNR significantly reduced C. albicans filamentation and biofilm viability. GA-AuNR treatment increased the reactive oxygen species (ROS) production, leading to enhanced lipid peroxidation and decreased ergosterol levels in fungal cells. Transmission electron microscopy (TEM) revealed cell wall thickening and membrane retraction in the treated cells. Moreover, GA-AuNR exposure reduced the expression of key virulence factor genes, including BCR1, EFG1, BGR1, and SAP9. Importantly, in vivo toxicity assessment using Galleria mellonella larvae demonstrated full survival at concentrations up to 24.60 μg/mL. In conclusion, GA-AuNR showed potent antifungal activity and no in vivo toxicity, indicating their potential as a promising therapeutic agent for the treatment of C. albicans infections.