Gold nanorods non-functionalised and associated with gallic acid exhibit activity against non- <i>albicans Candida</i> species

Strategies focusing on natural compounds and nanotechnology have been explored to overcome the limitations of conventional therapies in managing <i>Candida</i> infections. In this context, metal nanoparticles, both non-functionalised and combined with gallic acid, may offer a promising alternative. This study investigated the effects of gold nanoparticles non-functionalised (AuNp) and associated with gallic acid (AuNpGA) against planktonic cells and biofilms of <i>Nakaseomyces glabratus</i>, <i>Pichia kudriavzevii</i>, <i>Candida parapsilosis</i>, and <i>Candida tropicalis</i>. Both AuNp and AuNpGA inhibited the growth of all strains at 1.56 µg/mL and exhibited fungicidal effects at concentrations ranging from 1.56 to 3.12 µg/mL. The time-kill curve revealed that AuNpGA and AuNp completely inhibited the viability of all strains in planktonic cultures at 8 and 24 h, respectively, exhibiting greater antifungal activity compared to fluconazole. Treatment with AuNp increased ROS production against <i>N. glabratus</i> and <i>P. kudriavzevii.</i> Oxidative stress was enhanced against all strains after treatment with AuNpGA, and exposure to this compound reduced ergosterol levels of <i>P. kudriavzevii</i> and <i>C. parapsilosis.</i> Furthermore, AuNpGA and AuNp significantly decreased the viability of all <i>Candida</i> biofilms at 7.8 and 15.6 µg/mL, respectively. In summary, both gold nanoparticles exhibited activity against planktonic cells and biofilms, suggesting their potential as agents for treating <i>Candida</i> infections.