Titanic Inflammation In A Simulated Immune System

Titanium dioxide nanomaterials are widely used in sunblock, cosmetics, and on the surfaces of medical implants, but epidemiological studies have associated them with an assortment of health problems. Brian C. Schanen, William T. Self, and their colleagues at the University of Central Florida have built a multicell culture system that is meant to mimic the human immune system and used it to evaluate the immunogenicity of three types of titania nanoparticles (ACS Nano, DOI: 10.1021/nn900403h). At high concentrations, anatase TiO₂ crystals, rutile TiO₂ crystals, and TiO₂ nanotubes were each toxic to several types of cells. In lesser amounts, these nanoparticles prompted endothelial cells to release proinflammatory cytokines that triggered the maturation of dendritic cells, which activate CD4+ T cells that could go on to cause tissue damage. Those same materials also raise the level of reactive oxygen species, another class of molecules that stimulate inflammation. By comparison, micrometer-sized titania particles did not cause significant inflammation. Despite those results, Self says “it is too soon to warrant concern regarding nanotitania in sunscreen.”