Fungicidal and antibiofilm activities of gold nanoparticles on Candida tropicalis

Aim: To investigate the antifungal activity of two different functionalized gold nanoparticles (AuNP), those stabilized with cetyltrimethylammonium bromide and those conjugated with cysteine, and their effects on the architecture of Candida tropicalis biofilms. Materials & methods: Biofilms were studied by crystal violet binding assay and scanning electron microscopy. We investigated the effects of AuNPs on reactive oxygen species, reactive nitrogen intermediates, and enzymatic and nonenzymatic antioxidant defenses. Results/Conclusion: The fungicidal activity and cellular stress of both AuNPs affected biofilm growth through accumulation of reactive oxygen species and reactive nitrogen intermediates. However, cetyltrimethylammonium bromide-stabilized AuNPs revealed a higher redox imbalance. We correlated, for the first time, AuNP effects with the redox imbalance and alterations in the architecture of C. tropicalis biofilms. Plain language summary: Biofilms are at least 100-1000-times more resistant to the effects of antimicrobial agents compared with planktonic cells, and nanoparticles have emerged to provide new approaches to improve the safety and efficacy of antimicrobial therapy. The aim of this work was to investigate the antifungal activity with two different functionalized gold nanoparticles. A significant reduction of Candida tropicalis biofilms with alterations in surface topography and architecture was observed, and the oxidative and nitrosative stress affected the biofilms. To the best of our knowledge, this is the first study that attempts to correlate the antibiofilm effects of gold nanoparticles on the redox imbalance against biofilms. These compounds could be an alternative to fungal biofilms infections treatments, applied specifically in biological and medical fields. Tweetable abstract: We investigated the antifungal activity with two different functionalized gold nanoparticles. A significant reduction of Candida tropicalis biofilms with alterations in surface topography and architecture was observed. Oxidative and nitrosative stress affected the mature biofilms.