Copper Oxide Nanoparticles as Dual-Action Inhibitors of Biofilm Formation and Virulence in Candida albicans and Proteus mirabilis

Abstract

Candida albicans and Proteus mirabilis play significant roles in biofilm-related infections, primarily due to their ability to adhere to implanted medical devices and form mature biofilms. To enhance the effectiveness of medical devices and reduce the risk of infections, it is crucial to prevent both the initial adhesion of these microorganisms and the subsequent formation of biofilms on surfaces. The present study explores the antibiofilm efficacy of synthesized copper oxide nanoparticles (CuO NPs) against C. albicans and P. mirabilis, focusing on their physicochemical properties, capabilities to inhibit biofilm formation, gene expression responses, and biocompatibility with mouse embryonic kidney cell lines. The results indicate that CuO NPs possess notable antibiofilm and anti-virulent properties. Analytical techniques, including X-ray diffraction and scanning electron microscopy, confirmed that the produced CuO NPs have a crystalline structure with a cubic morphology. Importantly, CuO NPs demonstrated significant efficacy in reducing the viability of biofilm cells at relatively low concentrations—specifically, 6.25 µg/mL for P. mirabilis and 50 µg/mL for C. albicans. The scanning electron microscopy provided further evidence supporting these findings. Furthermore, CuO NPs were shown to markedly reduce the virulence of both microorganisms, for instance, urease enzyme activity in P. mirabilis and hyphal development in C. albicans decreased by 98%. Quantitative polymerase chain reaction analysis revealed a down-regulation of biofilm and virulence-associated genes in both organisms after treatment with CuO NPs. A cytotoxicity assessment indicated that CuO NPs did not significantly affect the viability of the 3T3-L1 mouse embryonic fibroblast cell line, suggesting good biocompatibility. Thus, CuO NPs emerge as a promising option for development as biocompatible antibiofilm agents to combat biofilm-related infections.