A combined toxicity study of zinc oxide nanoparticles and vitamin C in food additives

Abstract

At present, safety evaluation standards for nanofood additives are made based on the toxic effects of a single additive. Since the size, surface properties and chemical nature influence the toxicity of nanomaterials, the toxicity may have dramatically changed when nanomaterials are used as food additives in a complex system. Herein, we investigated the combined toxicity of zinc oxide nanoparticles (ZnO NPs) and vitamin C (Vc, ascorbic acid). The results showed that Vc increased the cytotoxicity significantly compared with that of the ZnO only NPs. When the cells were exposed to ZnO NPs at a concentration less than 15 mg L(-1), or to Vc at a concentration less than 300 mg L(-1), there was no significant cytotoxicity, both in the case of gastric epithelial cell line (GES-1) and neural stem cells (NSCs). However, when 15 mg L(-1) of ZnO NPs and 300 mg L(-1) of Vc were introduced to cells together, the cell viability decreased sharply indicating significant cytotoxicity. Moreover, the significant increase in toxicity was also shown in the in vivo experiments. The dose of the ZnO NPs and Vc used in the in vivo study was calculated according to the state of food and nutrition enhancer standard. After repeated oral exposure to ZnO NPs plus Vc, the injury of the liver and kidneys in mice has been indicated by the change of these indices. These findings demonstrate that the synergistic toxicity presented in a complex system is essential for the toxicological evaluation and safety assessment of nanofood.

Is nano safe in foods? Establishing the factors impacting the gastrointestinal fate and toxicity of organic and inorganic food-grade nanoparticles

“…36,45 These aggregates are typically many times larger than the individual nanoparticles, with their size and structure depending on solution conditions, which is likely to have a major effect on their GIT fate and toxicity. Feeding studies with frogs have shown that zinc oxide nanoparticles exhibit greater toxicity than a dissolved form of zinc, which was attributed to their greater capacity to induce oxidative damage in cells.…”

“…15,33,49 As a result, many biochemical functions required to maintain cell viability, such as ATP production, DNA replication, and gene expression, may be adversely affected. 33 A number of studies have reported the ability of inorganic nanoparticles to increase the generation of ROS in cells and to produce cytotoxicity, including silicon dioxide nanoparticles, 81 ZnO nanoparticles, 36,126,127 and silver nanoparticles. 15 Some inorganic nanoparticles produce toxicity by generating ions (such as Ag + from silver nanoparticles or Zn 2+ from zinc oxide nanoparticles) that interact with the normal functioning cellular components (such as proteins, nucleic acids, or lipids) required to maintain biochemical processes.…”

“…44 Interestingly, one study showed that ZnO nanoparticles were not toxic when used in isolation, but that they become toxic when mixed with ascorbic acid. 36 This suggests that it is important to measure the impact of specific food components on the toxicity of this type of nanoparticle.…”

“…Zinc oxide (ZnO) nanoparticles may be used as a source of zinc in supplements and functional foods, since this is an essential trace element needed to maintain human health and wellbeing. 36 ZnO nanoparticles may also be utilized in food packaging as antimicrobial agents to prevent contamination of foods with harmful bacteria 37 or as ultraviolet (UV) light absorbers to protect foods that are sensitive to UV light exposure. 38 In principle, nanoparticles in packaging may leach into food products and therefore be ingested as part of the human diet.…”

Zinc oxide nanoparticles induce toxic responses in human neuroblastoma SHSY5Y cells in a size-dependent manner

“…9 Wang et al 44 found that vitamin C enhanced ZnO NP-induced toxicity due to its acidity, thereby accelerating ZnO NP dissolution. Other studies have indicated that ZnO NPs can dissolve in lysosomes in an acidic environment.…”