Effects of Cu2O nanoparticle and CuCl2 on zebrafish larvae and a liver cell-line

The extensive uses of nanomaterials have caused many concerns of their potential hazards to the aquatic environments. As partial dissolution of metal nanoparticles may occur, it is important to study the toxic effects of nanoparticles and determine the no observable effect levels (NOELs) and lowest observable effect levels (LOELs) of these materials in water by using biomarker genes’ expression in zebrafish (Danio rerio). In this study, the toxic effects of Cu2O nanoparticle (NP) on zebrafish larvae and zebrafish liver cell-line (ZFL) were evaluated by determining their 96 h LC50 values (zebrafish larvae: 242.4 ppb; ZFL: 110 ppm), which was less toxic than CuCl2 (zebrafish larvae: 85.73 ppb; ZFL: 23.04 ppm). However, zebrafish larvae are sensitive to both Cu2O NP and CuCl2. We also examined the effects of elevated Cu2O NP and CuCl2 on the expression of several copper related genes in zebrafish larvae by using real-time quantitative polymerase chain reaction. It was found that Cu2O NP and CuCl2 induced the mRNA levels of metallothionein (MT), Cu/Zn superoxide dismutase (Cu/Zn SOD), metal regulatory transcription factor 1 (MTF1) and copper transporters, ATP7A and 7B, but down-regulated the mRNA levels of glutathione sulfur transferase (GST). Interestingly, the inductions of MT, ATP7A and ATP7B in the Cu2O NP exposure groups were much higher than that of the CuCl2 exposure groups, and resulted in higher copper accumulation in the Cu2O NP exposure groups. Furthermore, as determined by using MT, ATP7A and ATP7B gene expression, the NOELs of CuCl2 and Cu2O NP were 11 ppb and 30 ppb whereas the LOELs of CuCl2 and Cu2O NP were 43 ppb and 121 ppb, respectively.