Titanium dioxide nanoparticles translocate through differentiated Caco-2 cell monolayers, without disrupting the barrier functionality or inducing genotoxic damage

The widespread use of titanium dioxide nanoparticles (TiO(2)NPs) in commercial food products makes intestinal cells a suitable target. Accordingly, we have used the human colon adenocarcinoma Caco-2 cells to detect their potential harmful effects. Caco-2 cells can differentiate in to enterocytic-like cells, forming consistent cell monolayers and are used as a model of the intestinal barrier. Using both undifferentiated and differentiated Caco-2 cells, we have explored a set of biomarkers, aiming to evaluate undesirable effects associated to TiO2NP exposure. Results indicate non-toxic effects in exposures ranging 1-200 mu g ml(-1). Significant differences were observed in cell uptake, with a higher amount of incorporated TiO(2)NPs in undifferentiated cells, as visualized using confocal microscopy. In well-established monolayers, translocation was detected using both confocal microscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy. In spite of the observed uptake and translocation, TiO2NP exposures did not modify the integrity of the monolayer, as measured using the transepithelial electrical resistance and Lucifer yellow methods. The potential genotoxic effects in differentiated cells were evaluated in the comet assay, with and without formamidopyrimidine DNA glycosylase enzyme to detect oxidatively the damaged DNA bases. Although some changes were detected at the lower dose (10 mu g ml(-1)), no effects were observed at higher doses.