Abstract
Recent studies indicate the presence of nano-scale titanium dioxide (TiO2) as an additive in human foodstuffs, but a practical protocol to isolate and separate nano-fractions from soluble foodstuffs as a source of material remains elusive. As such, we developed a method for separating the nano and submicron fractions found in commercial-grade TiO2 (E171) and E171 extracted from soluble foodstuffs and pharmaceutical products (e.g., chewing gum, pain reliever, and allergy medicine). Primary particle analysis of commercial-grade E171 indicated that 54% of particles were nano-sized (i.e., < 100 nm). Isolation and primary particle analysis of five consumer goods intended to be ingested revealed differences in the percent of nano-sized particles from 32%‒58%. Separation and enrichment of nano- and submicron-sized particles from commercial-grade E171 and E171 isolated from foodstuffs and pharmaceuticals was accomplished using rate-zonal centrifugation. Commercial-grade E171 was separated into nano- and submicron-enriched fractions consisting of a nano:submicron fraction of approximately 0.45:1 and 3.2:1, respectively. E171 extracted from gum had nano:submicron fractions of 1.4:1 and 0.19:1 for nano- and submicron-enriched, respectively. We show a difference in particle adhesion to the cell surface, which was found to be dependent on particle size and epithelial orientation. Finally, we provide evidence that E171 particles are not immediately cytotoxic to the Caco-2 human intestinal epithelium model. These data suggest that this separation method is appropriate for studies interested in isolating the nano-sized particle fraction taken directly from consumer products, in order to study separately the effects of nano and submicron particles.
Highlights
Nanoparticles are becoming increasingly common in food and pharmaceuticals [1]
The TiO2 primary particle size was determined for commercial-grade E171 (i.e., E171 before adding to products) and E171 isolated from five water-soluble foodstuff and pharmaceutical
The major finding in the present investigation was that it was possible to separate submicron particles (>100 nm) from nanoparticles ( 100 nm) isolated directly from foodstuffs and pharmaceuticals containing polydispersed TiO2 to produce nano- and submicron-enriched fractions for characterization and toxicity testing. This was first demonstrated for commercialgrade E171 and subsequently confirmed for E171 isolated from water-soluble foodstuffs and pharmaceuticals
Summary
Nanoparticles are becoming increasingly common in food and pharmaceuticals [1]. Whether this is done intentionally or unknowingly as an artifact of commercial-grade material processing [2, 3] is unknown. These additives are mixtures of nano- and submicron-scale particles and are used in consumer goods including foodstuffs as color and texture modifiers [1], moisture controllers [4, 5], or antimicrobials [6]. We define particles with sizes above 100 nm to be submicron particles, with the understanding that this definition may change as the field advances
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