Credit: © 2007 ACS

Titanium dioxide is a common ingredient found in many cosmetic products such as sunscreens because it acts as a filtering system by absorbing ultraviolet light. During this process, however, TiO2 generates reactive oxygen species (ROS) that are known to damage cells and DNA, leading to some concerns about its use in this capacity.

Researchers at the Polish Academy of Sciences and École Polytechnique Fédérale de Lausanne in Switzerland now report that TiO2-induced ROS can alter the stiffness of human skin cells. Małgorzata Lekka and colleagues1 incubated human skin cells with TiO2 nanoparticles and subjected them to different intensities of ultraviolet light. After a period of exposure, the cell stiffness was measured using an atomic force microscope. At a low TiO2 concentration (4 mg mL-1) and under low-intensity ultraviolet light, ROS were generated and the skin cells experienced a 30–75% drop in stiffness after 1 minute of exposure.

When the skin cells were additionally incubated with an antioxidant, such as β-carotene, their stiffness did not alter. It is suggested that ROS production, which is thought to damage cellular structures like the cytoskeleton and lead to the dramatic loss in cell elasticity, is inhibited by the antioxidant.