Structural Degradation at the Surface of a TiO2-Based Nanomaterial Used in Cosmetics

A number of commercialized nanomaterials incorporate TiO2 nanoparticles. Studying their structural stability in media mimicking the environment or the conditions of use is crucial in understanding their potential eco-toxicological effects. We focused here on a hydrophobic TiO2 nanoparticle-based formulation used in cosmetics: T-Lite SF. It is composed of a TiO2 core, coated with two successive protective layers of Al(OH)(3), and polydimethylsiloxane. Soon after contact with water (pH = 5, low ionic strength), the T-Lite SF becomes hydrophilic and form aggregates. During this aging, 90%wt of the total Si of the organic layer is desorbed, and the PDMS remaining at the surface is oxidized. The Al(OH)(3) layer is also affected but remains sorbed at the surface. This remaining Al-based layer still protects from the production of superoxide ions from the photoactive/phototoxic TiO2 core in our experimental conditions.