Comparative study of ZnO and TiO₂nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells

Abstract

Despite human gastrointestinal exposure to nanoparticles (NPs), data on NPs toxicity in intestinal cells are quite scanty. In this study we evaluated the toxicity induced by zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs on Caco-2 cells. Only ZnO NPs produced significant cytotoxicity, evaluated by two different assays. The presence of foetal calf serum in culture medium significantly reduced ZnO NPs toxicity as well as ion leakage and NP-cell interaction. The two NPs increased the intracellular amount of reactive oxygen species (ROS) after 6 h treatment. However, only ZnO NPs increased ROS and induced IL-8 release both after 6 and 24 h. Experimental data indicate a main role of chemical composition and solubility in ZnO NPs toxicity. Moreover our results suggest a key role of oxidative stress in ZnO NPs cytotoxicity induction related both to ion leakage and to cell interaction with NPs in serum-free medium.

Minimal Intestinal Epithelial Cell Toxicity in Response to Short- and Long-Term Food-Relevant Inorganic Nanoparticle Exposure

“…47 TiO2 at concentrations of 1-20 µg/cm 2 had no effect on Caco-2 cell viability in the presence or absence of serum. 40 TiO2 at loadings of 0.1-100 mg/L did not influence Caco-2 cell viability, as measured by MTT assay. 41 TiO2 at loading levels of 1-mixtures, similar to the NP examined in the present study, did not induce toxicity (by LDH assay) to Caco-2 cells at loading levels of 20 µg/cm 2 , but toxicity was observed at 80 µg/cm 2 .…”

“…Infrared spectrum ( Figure 3B) shows that upon suspension in serum, characteristic protein bands 31 are observed on the ZnO. It has been proposed that the presence of serum proteins will inhibit dissolution of ZnO, 40 however it is unlikely that serum can stabilize against dissolution in the highly acidic pepsin solution.…”

“…In serum-containing media, the particles appear aggregated as compared to the primary particle size (Figure 1), indicating that the asobtained particles were aggregated, consistent with previous reports. 40,41 Titania becomes positively charged and the silica particles are almost neutral in the "stomach" fluid (pepsin, pH 2.0). In the case of silica, the neutrality of the particles results in formation of large aggregates (~ 3 µm radii).…”

Zinc oxide nanoparticles exhibit cytotoxicity and genotoxicity through oxidative stress responses in human lung fibroblasts and <em>Drosophila melanogaster</em>

“…Several in vitro studies have demonstrated the undesirable toxic effects of ZnO NPs, such as the induction of oxidative stress, autophagic cell death, inflammatory responses, cellular damage and genotoxicity. [9][10][11][12][13] The toxicity of ZnO NPs has been shown to be attributed to the dissolution of Zn to free Zn 2+ ions and the generation of free radicals from the surface of ZnO, resulting in cellular ionic and metabolic imbalance that is associated with a defect in ionic homeostasis and an inhibition of ion transport. 9,12,14,15 In vitro toxicity studies revealed that generation of reactive oxygen species (ROS), followed by ROS-induced oxidative stress, is the mechanism leading to the ZnO NP-mediated toxicity.…”

“…In addition to the phase (amorphous, anatase, etc) and contact area between a single nanoparticle (NP) and a single cell, smaller and rod shaped nano ZnO (in comparison to spherical shape) is reported to be more toxic. [15][16][17] The surface charge of NPs is also an important factor in considering the toxicity, as the positively charged NPs were shown to possess a higher toxicity, 9 and differential surface charge is attributed to the cellular uptake and intracellular localization. 18 The toxic effects of in vivo exposure have been reported in vertebrates such as rodent 6 and zebra fish, 19,20 as well as the invertebrate the fruit fly Drosophila melanogaster.…”