Isolation, Characterization and Quantitation of Photoactive phases of Titanium (IV) oxide in skin-lightening products

Abstract

Titanium (IV) oxide (TiO2) is used as a physical blocker of ultraviolet (UV) radiation in many skin-care products. Absorption of TiO2 through the skin is likely to interact with viable tissues because UV radiation absorption generates toxic reactive oxygen species such as hydroxyl radicals. Studies on the acute toxicity of TiO2 nanoparticles in mammals indicate that intra-tracheal instillation, intraperitoneal injection or oral instillation of TiO2 particles to the animals evoke an inflammatory response as well as certain histopathological changes. Ultrafine particles of the anatase form of titanium (IV) oxide, which are smaller than 0.1 microns, are pathogenic. In this work eight skin-lighteners containing TiO2 from South African market were studied. The TiO2 was extracted by a fusion technique and quantified by inductively coupled plasma-optical emission spectrometry (ICP-OES). Sequential solvent extraction was employed to isolate TiO2 particles for characterization employing high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (PXRD). All samples considered in this study meet agreeable TiO2 % (m/m) levels as specified by all health regulatory bodies. Both forms of TiO2: anatase and rutile, were found to be present. Most samples contained nano-TiO2 in the particle size range of 16.23 nm to 51.47 nm that could lead to detrimental effects. The fact that the anatase form, known for its photocatalytic activity, was present, is a cause for concern.