Browsing by Author "Vieira, Adriana Isabel Ramos"
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- Cellular Mechanisms of Toxicity of Ingested NanomaterialsPublication . Vieira, Adriana Isabel Ramos; Louro, Maria Henriqueta; Silva, Maria JoãoTitanium dioxide (TiO2) nanomaterials (NMs) are used in a variety of consumer products, namely in the food sector, but their application has raised some concerns regarding their negative impacts on human health and particularly, on the gastrointestinal tract (GIT) following digestion, as this may be a major route of exposure. However, the toxicity studies currently available in the literature are contradictory and the majority do not consider the influence of human digestion in the ingested NMs safety assessment. This work aimed to understand the potential toxic effects of three TiO2 NMs (NM-102, NM-103 and NM-105) with distinct physicochemical properties, in the intestine, using human intestinal cells (Caco-2 and HT29-MTX-E12) as in vitro models. It was also intended to comprehend the impact of an in vitro simulated human digestion process on the NMs’ characteristics and to correlate these differences with the toxicity induced by digested TiO2 NMs, in comparison with undigested NMs. Regarding the cytotoxicity, both undigested and digested NM-105 led to a decrease in HT29-MTX-E12 cell viability, which was more pronounced in the digested sample, concomitantly with a decrease in its hydrodynamic size. Furthermore, digested NM-105 induced an increase in the DNA strand break level in both cell lines and in oxidative DNA damage, only in HT29-MTX-E12 cells, thus being classified as potentially genotoxic, through the comet assay. Digested NM-103 showed also an equivocal genotoxic response in Caco-2 cells. FPG-modified comet assay revealed an induction of DNA oxidative base lesions in Caco-2 and HT29-MTX-E12 exposed to undigested NM-103 and NM-102. Lastly, through the micronucleus assay, increased chromosomal damage effects were observed following treatment with some of the undigested and digested NMs. The present results reinforce the conception that NMs biological interactions are context-dependent, since their physicochemical properties can be changed after the digestion process, consequently leading to different biological effects.