Toxicity and Bioaccumulation of Surface Modified Graphene Quantum Dots in Zebrafish Embryos and Larvae

Surface modified Graphene Quantum Dots (GQDs) are an important class of carbon materials widely adopted in fields such as optoelectronics and medicine. However, current research on the potential threat of GQDs on humans and the environment is limited and often lacks comparisons of the biological accumulation and toxicity effects caused by different surface functional group modifications. Therefore, this study compared the toxicity of growth and development, and biological accumulation of amino-functionalized GQDs and carboxyl-functionalized GQDs in zebrafish. The results showed that both amino-functionalized and carboxyl-functionalized GQDs at concentrations of 0.5 mg·L⁻¹ and 5 mg·L⁻¹ significantly inhibited the spontaneous movement of zebrafish, induced pericardial edema and yolk sac edema, and stimulated approximately 50% of the zebrafish to hatch earlier. The type of material and exposure concentration had no significant effect on the zebrafish's heart rate or body length. Additionally, this study used molecular fluorescence spectroscopy to measure the biological accumulation of the two materials in zebrafish after 4 days of exposure. The results indicated that carboxyl-functionalized GQDs had higher accumulation concentration and mass percentage in zebrafish than amino-functionalized GQDs, with a total accumulation of approximately 5.6 μg. Overall, carboxyl-functionalized GQDs exhibited stronger biological accumulation and toxicity effects than amino-functionalized GQDs. This study systematically reveals the differences in biological accumulation and toxicity effects of GQDs with different surface functional groups, providing evidence and a theoretical basis for assessing the ecological risks of GQDs with various surface modifications.