Cytotoxicity and Antioxidant Defences in Euplotes aediculatus Exposed to Single and Binary Mixtures of Heavy Metals and Nanoparticles

The aim of this study was to analyse the cytotoxicity of heavy metals (HMs) and nanoparticles (NPs) on populations of the ciliated protist Euplotes aediculatus. We used ecotoxicological tests, antioxidant assays, and the MixTOX tool in Microsoft^® Excel to evaluate the toxic effect of HMs and NPs in single and binary mixtures on E. aediculatus and to detect the type of interaction between them. Based on our results, the order of toxicity was Cu > Cd >> Zn (1 h and 24 h) for HMs and ZnO > CuO >> TiO₂ >> SiO₂ (1 h) and CuO > ZnO >> TiO₂ >> SiO₂ (24 h) for NPs. The interaction between metals in binary mixtures was predominantly synergistic at low doses and antagonistic at high doses. The type of interaction depende on the metals present and their respective concentrations. Furthermore, both HMs and NPs were shown to trigger effective antioxidant responses in E. aediculatus. Our research highlights the importance of considering the combined effects of HMs and NP exposure and their potency in risk assessment.