Effect of real food matrix on the behavior and toxicity of TiO₂ nanoparticles

The interactions between nanoparticles (NPs) and the components of the surrounding environment have been reported to affect the physical and toxicological properties of NPs. In the present study, the effects of the presence of a real food matrix (milk) on the behavior and toxicity of “nano”-sized TiO₂ (30 nm; Ti30 and 100 nm; Ti100) particles upon in vitro digestion simulation were evaluated. Before digestion, bare Ti30 and Ti100 were both in a highly aggregated state while the interaction with milk reduced the aggregate sizes, significantly. This reduction is considered to be caused by the steric effect of protein corona, mainly composed of caseins. Upon digestion, the aggregate size of Ti30 and Ti100 in a simplified simulated milk ultrafiltrate buffer (SMUB) remained nearly the same in the oral phase, while a further reduction was observed in gastric and intestinal phases. TiO₂ NPs in SMUB did not cause any difference in cell viability while the milk-interacted TiO₂ NPs had an adverse effect on cell viability. ROS generation was remarkably increased for high NP concentration which is more pronounced for Ti30. The presence of milk led to a reduction in ROS generation of TiO₂ NPs which is more pronounced for Ti30. These findings show the importance of the presence of a real food matrix on the behavior and toxicity of NPs when digested.