Food grade titanium dioxide disrupts intestinal brush border microvilli in vitro independent of sedimentation
Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25 % of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm2 cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.
KeywordsBrush border Microvilli Nanotechnology Sedimentation Titanium dioxide Toxicity
Brush border expressing 1
Inductively coupled plasma mass spectroscopy
The authors thank Mr. Xiangyu Bi for conducting ICP-MS on the TiO2 samples. We wish to thank David Lowry for his assistance in the W.M. Keck Bioimaging Facility at ASU. The authors thank Dr. Karen Sweazea for the use of Sigma Stat version 3.5 software used for multiple comparisons.
Conflict of interest
The authors declare no competing interest. Funding was provided by an NSF award (CBET 1336542) to P.W.
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