Developmental toxicity and cardiotoxicity of titanium carbide Ti3C2T <i>x</i> (MXene) nanosheets in zebrafish embryos

The two-dimensional nanomaterial MXene Ti3C2Tx is widely used in biomedical and water treatment research. However, the biotoxic effects and mechanisms of Ti3C2Tx in aquatic organisms remain unclear. The present study combined non-targeted metabolomics techniques and traditional toxicological methods to investigate the developmental toxicity of two sheet sizes of Ti3C2Tx-large diameter (Ti3C2Tx-LD) and Ti3C2Tx-small diameter (Ti3C2Tx-SD) to zebrafish embryos and clarify the underlying mechanisms. The results showed that the 96-hr median lethal concentrations (LC50) of Ti3C2Tx-LD and Ti3C2Tx-SD were 35.09 and 50.33 mg/L for zebrafish embryos (96 hr post fertilization), respectively, and the larger sheet size was more toxic. Both Ti3C2Tx-LD and Ti3C2Tx-SD induced concentration-related developmental abnormalities of delayed hatching, excessive reactive oxygen species (ROS) production, pericardial edema, pericardial cell apoptosis and reduced heart rate in zebrafish embryos. Metabolomics revealed that both Ti3C2Tx-LD and Ti3C2Tx-SD caused cardiac developmental toxicity in zebrafish embryos, although via different pathways of action, as Ti3C2Tx-LD mainly disrupted the glycerolipid and glycerophospholipid metabolism pathways, whereas Ti3C2Tx-SD mainly interfered with the arginine biosynthesis pathway. The results of this study highlight that Ti3C2Tx has developmental toxicity and cardiotoxicity to zebrafish embryos and should be fully evaluated for biosafety and environmental risks before mass industrial applications.