In vivo effect of industrial titanium dioxide nanoparticles experimentally exposed to hairless rat skin

We morphologically investigated animal skin exposed to W/O emulsion containing 10 wt % ultrafine TiO2 particles that had been characterized. After 4 h, exposed skin was investigated by light microscopy, confocal laser scanning microscopy (CLSM) and electron microscopy with energy-dispersive X-ray spectrometry (EDX). Light microscopic evaluation was also performed on the exposed skin after 24, 72 and 168 h. Light microscopy did not show any morphological and immunohistochemical changes in the skin. Electron microscopy revealed that the most TiO2 particles were localized in the interfollicular stratum disjunctum and the keratinized layer of follicular infundibulum. No TiO2 particles were detected in the viable skin, which was confirmed by EDX. Furthermore, we demonstrated a specific TiO2 affinity to the follicular opening area by light microscopy and low-vacuum scanning electron microscopy with EDX. Our study suggests that TiO2 particles neither penetrate into viable cell layers nor biologically cause any cellular changes.