Impediment to growth and yeast-to-hyphae transition in Candida albicans by copper oxide nanoparticles

Abstract

The effects of two prominent copper oxide nanoparticles (CuO-NP and Cu₂O-NP), with the oxidation state of Cu⁺⁺ (cupric) and Cu⁺ (cuprous), on Candida albicans were evaluated. CuO-NP and Cu₂O-NP were synthesized and characterized by XRD, FESEM, HR-TEM and Zeta potential. At sub-MIC (50 µg ml⁻¹), both cupric and cuprous oxide NPs prevented yeast-to-hyphae switching and wrinkling behaviour in C. albicans. The mechanism for the antifungal action of the two NPs differed; CuO-NP significantly elicited reactive oxygen species, whereas membrane damage was more pronounced with Cu₂O-NP. Real time PCR analysis revealed that CuO-NP suppressed the morphological switching of yeast-to-hyphae by down-regulating cph1, hst7 and ras1 and by up-regulation of the negative regulator tup1. In comparison, Cu₂O-NP resulted in down-regulation of ras1 and up-regulation of the negative regulators nrg1 and tup1. Between the two NPs, CuO exhibited increased antifungal activity due to its stable oxidation state (Cu⁺⁺) and its smaller dimensions compared with Cu₂O-NP.

Graphical Abstract

Keywords:

• Copper oxide nanoparticles
• Candida albicans
• cell membrane integrity
• ergosterol
• ROS generation

Acknowledgements

The authors gratefully acknowledge the technical assistance provided by Dr Abdul Nishad, Water and Steam Chemistry Division, Bhabha Atomic Research Centre Facilities, Kalpakkam and Mr Binaya Kumar Sahu, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

Financial assistance provided to ARP in the form of K.S. Krishnan Research Associateship (PD/9(1)2017R-IV/4286) by Board of Research in Nuclear Sciences (BRNS), DAE, Government of India