Transformation of Nano-Size Titanium Dioxide Particles in the Gastrointestinal Tract and Its Role in the Transfer of Nanoparticles through the Intestinal Barrier.

In this work, the size transformation of the TiO nanofraction from pharmaceutical grade E171 powder was studied during its transit through the gastrointestinal tract (GIT). It was shown that pharmaceutical-grade TiO powder contained about 0.68% (/) of particles smaller than 240 nm in diameter. In the observed GIT transit process the TiO nanoparticles were agglomerated up to 150-200 nm in simulated salivary fluid, with gradual agglomerate enlargement up to 300-600 nm and more than 1 micron in simulated gastric fluid. In the intestinal fluid the reverse process occurred, involving a decrease of agglomerates accompanied by the formation of a small fraction with ~50 nm average size. This fraction can be further involved in the histohematic transport process. The acidity degree (pH) and mineral composition of solutions, as well as the transit speed along the gastrointestinal tract, influence the nature of the particle transformation significantly. The rapid passing between the gastrointestinal tract sections creates conditions for a decrease in part of the TiO particles, up to 100 nm, and may be associated with the violation of the structural and functional integrity of the intestinal mucus layer.