Evaluation of toxicity and oxidative stress induced by copper oxide nanoparticles in the green alga Chlamydomonas reinhardtii

• Toxicity of CuO nanoparticles (NP) was evaluated in Chlamydomonas reinhardtii alga.
• CuO NP can cross the cell wall and be uptake into the algal cell.
• CuO NP induced growth inhibition and a significant decrease in carotenoids levels.
• Oxidative stress was induced by CuO NP by production of RS and MDA.
• Biomarkers of enzymatic antioxidants showed activity changed by CuO NP exposition.

Copper oxide nanoparticles (CuO NP) are frequently employed for their antimicrobial properties in antifouling paints. Their extensive use can contaminate aquatic ecosystems. However, the toxicological effects of this NP in the environment are poorly known. In this study, we evaluated the toxicity and oxidative stress induced by CuO NP on Chlamydomonas reinhardtii using several toxicological assays. CuO NP was found to induce growth inhibition and a significant decrease in carotenoids levels. From data on cells density after 72 h of CuO NP exposure in light, the EC50 value was calculated to be 150.45 ± 1.17 mg L−1 and the NOEC ≤ 100 mg L−1. Evaluation of esterase activity demonstrates a decrease in cell metabolism activity with the increase of CuO NP concentration. The CuO NP induced an increase of reactive species level (190 ± 0.45% at 1000 mg L−1 after 72 h of exposition, compared to control) and lipid peroxidation of cellular membranes (73 ± 2% at 1000 mg L−1 of CuO NP in 72 h of exposition, compared to control). Investigation of CuO NP uptake showed the presence of NP into C. reinhardtii cells in different sites of the cell and, biomarkers of enzymatic antioxidants showed a change of activity after CuO NP exposition. In conclusion, C. reinhardtii was shown to be sensitive to the presence of CuO NP in their environment and CuO NP treatments induced a toxic response from 0.1 mg L−1 after 72 h of treatment.