Interactions between cerium dioxide nanoparticles and arsenite change their biological fate in the gastrointestinal tract of mice

The large-scale production of engineered nanoparticles (ENPs), such as cerium dioxide nanoparticles (CeO₂ NPs), raises concerns towards their impact on human health. The co-existence of ENPs and heavy metals in the natural environment is particularly worrisome because people are ingesting them. In this study, the behaviors of CeO₂ NPs and arsenite (As(iii)) during the digestive process were first investigated using an in vitro gastrointestinal tract (GIT) model, and then studied in a mouse model via oral co-exposure. The results suggest that CeO₂ NPs of both 10 nm and 30 nm in diameter strongly adsorbed As(iii) during the digestive process, resulting in the decreased bioaccessibility of As in the GIT fluids. Corresponding to the decreased As bioaccessibility obtained from the in vitro GIT model, exposure to a 10 nm CeO₂ NP—As(iii) mixture led to a decrease in As(iii) bioaccumulation in organs. However, exposure to a 30 nm CeO₂ NP—As(iii) mixture increased the relative bioavailability of Ce and As in mice. Interestingly, toxicity enhancement was observed in the 30 nm CeO₂ NP—As(iii) mixture exposure group, probably due to the redox reaction between Ce(iv) and As(iii) taking place on the NP surface, affecting the As(iii) metabolism in the liver. Our findings showed the first step in elucidating the effect of two types of pollutants increasingly found in our environment, ENPs and heavy metals, on mammalian health.