Single and combined nanotoxicity of titanium dioxide and cadmium: implications for skeletal and behavioral...

Titanium dioxide nanoparticles (TiO₂ NPs) are emerging contaminants of global concern. However, knowledge about their interactive effects with metals on developing aquatic vertebrates is still scarce. Thus, the current study investigated cartilage and bone toxicity and behavioral changes in Danio rerio (zebrafish) larvae after exposure to single and combined TiO₂ NPs (0.1 µg L^-1, 1.0 µg L^-1, and 10 µg L^-1) and Cd (10 µg L^-1) for 168 h. The results showed that environmentally relevant concentrations of single TiO₂ NPs did not cause skeletal changes in zebrafish larvae. In contrast, single Cd and combined with TiO₂ NPs induced significant skeletal changes, such as malformation of chondrocranial structures and inhibition of ossification. Despite that, single TiO₂ NPs or combined with Cd did not induce changes in the locomotor behavior of zebrafish larvae. This study demonstrated the chondrotoxicity and osteotoxicity of Cd, single, and combined with TiO₂ NPs, on zebrafish, highlighting the potential ecotoxicological impact of co-exposure to inorganic nanoparticles and metals on aquatic organisms, especially on the development of the skeletal system.