Graphene oxide quantum dot exposure induces abnormalities in locomotor activities and mechanisms in zebrafish (Danio...

Graphene oxide quantum dots (GOQDs) have broad applications such as bioimaging and drug delivery, among others, even expanding into the aquatic environment. However, reports on the adverse effects of GOQDs on fish development are limited. In this study, we exposed zebrafish embryos to GOQDs for 7 days after fertilization and found that GOQDs exposure at low concentrations (12.5, 25, 50 or 100 μg/L) decreased the total distance and the mean velocity of larvae movement. Additionally, the GOQDs significantly reduced the enzyme activity related to energy supply and locomotor capacity, including Ca²⁺ -ATPase in the 12.5, 25, 50 and 100 μg/L GOQDs groups and Na⁺ /K⁺ -ATPase in the 25 and 50 μg/L GOQDs groups. Moreover, GOQD exposure altered the mRNA expression of genes involved in energy supply and calcium transport. The levels of the atp2a2b, atp2a1, and cacna1sb genes were significantly downregulated in the 25, 50 and 100 μg/L GOQDs groups, and ryr3 expression was significantly reduced in the 25 and 50 μg/L GOQDs groups. The expression level of cacna1c was significantly upregulated in the 50 and 100 μg/L GOQDs groups. In summary, GOQD exposure induced a decrease in locomotor capacity in zebrafish, which may be due to the reduction of Ca²⁺ -ATPase and Na⁺ /K⁺ -ATPase activity levels, and dysregulated expression of the genes involved in energy metabolism and calcium transport. Our study provides novel insight into the effects of GOQDs on the embryonic development of fish, which will be useful for the development of environment-friendly GOQDs that reduce the potential hazard to aquatic species.