Toxicological mechanisms of gold nanoclusters in zebrafish embryos

Gold nanoclusters (AuNCs), known for their distinctive structural and optical properties and widely used in nanobiotechnology, raise environmental and organismal concerns due to their ultrasmall size despite their biocompatibility. This study investigated glutathione conjugated AuNCs (GSH-AuNCs) for their toxicity and biodistribution in zebrafish embryos, an experimental organism that is frequently employed in the fields of environmental toxicology and nanosafety research. The structural and optical characterizations demonstrated the successful GSH-AuNCs synthesis using hydrothermal method. In vitro, GSH-AuNCs exhibited minimal cytotoxicity in the Vero cell line, even until 40 μg/mL concentrations. Zebrafish embryos showed no significant adverse effects or developmental delays when exposed to GSH-AuNCs at concentrations until 6 μg/mL, though significant decreases in survival and hatching rates were observed at higher concentrations (6-20 μg/mL). Accumulation of GSH-AuNC in zebrafish larvae was confirmed by fluorescence microscopy, suggesting their uptake and potential biological interactions. Increased oxidative stress enzymes activities are related to higher GSH-AuNCs concentrations (1, 2 and 3 μg/mL). This research offers significant understanding of toxicity and biodistribution of GSH-AuNCs in zebrafish embryos, contributing to the responsible development of nanotechnology for biomedical and environmental applications.