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 Cu(2)O 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 CuCl(2) (zebrafish larvae: 85.73 ppb; ZFL: 23.04 ppm). However, zebrafish larvae are sensitive to both Cu(2)O NP and CuCl(2). We also examined the effects of elevated Cu(2)O NP and CuCl(2) on the expression of several copper related genes in zebrafish larvae by using real-time quantitative polymerase chain reaction. It was found that Cu(2)O NP and CuCl(2) 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 Cu(2)O NP exposure groups were much higher than that of the CuCl(2) exposure groups, and resulted in higher copper accumulation in the Cu(2)O NP exposure groups. Furthermore, as determined by using MT, ATP7A and ATP7B gene expression, the NOELs of CuCl(2) and Cu(2)O NP were 11 ppb and 30 ppb whereas the LOELs of CuCl(2) and Cu(2)O NP were 43 ppb and 121 ppb, respectively.