Characterization and preliminary toxicity assay of nano-titanium dioxide additive in sugar-coated chewing gum

Nanotechnology shows great potential for producing food with higher quality and better taste through including new additives, improving nutrient delivery, and using better packaging. However, lack of investigations on safety issues of nanofood has resulted in public fears. How to characterize engineered nanomaterials in food and assess the toxicity and health impact of nanofood remains a big challenge. Herein, a facile and highly reliable separation method of TiO₂ particles from food products (focusing on sugar-coated chewing gum) is reported, and the first comprehensive characterization study on food nanoparticles by multiple qualitative and quantitative methods is provided. The detailed information on nanoparticles in gum includes chemical composition, morphology, size distribution, crystalline phase, particle and mass concentration, surface charge, and aggregation state. Surprisingly, the results show that the number of food products containing nano-TiO₂ (<200 nm) is much larger than known, and consumers have already often been exposed to engineered nanoparticles in daily life. Over 93% of TiO₂ in gum is nano-TiO₂, and it is unexpectedly easy to come out and be swallowed by a person who chews gum. Preliminary cytotoxicity assays show that the gum nano-TiO₂ particles are relatively safe for gastrointestinal cells within 24 h even at a concentration of 200 μg mL^-1. This comprehensive study demonstrates accurate physicochemical property, exposure, and cytotoxicity information on engineered nanoparticles in food, which is a prerequisite for the successful safety assessment of nanofood products. A facile method to separate nano-TiO₂ particles from chewing gum to achieve comprehensive characterization is reported. Over 93% of TiO₂ in gum is smaller than 200 nm, and around 95% would enter the body of a person chewing the gum. These nano-TiO₂ particles are relatively safe for gastrointestinal cells.