Comparison of free radical generation by pre- and post-sintered cemented carbide particles

Rapid generation of reactive oxygen species (ROS) may occur in response to cellular contact with metal particles. Generation of ROS by cobalt and/or tungsten carbide is implicated in causing hard metal lung disease (HMD) and allergic contact dermatitis (ACD). In this study, ROS generation and particle properties that influence radical generation were assessed for three sizes of tungsten, tungsten carbide, cobalt, admixture (tungsten carbide and cobalt powders), spray dryer, and post-sintered chamfer grinder powders using chemical (H(2)O(2) plus phosphate buffered saline, artificial lung surfactant, or artificial sweat) and cellular (RAW 264.7 mouse peritoneal monocytes plus artificial lung surfactant) reaction systems. For a given material, on a mass basis, hydroxyl (.OH) generation generally increased as particle size decreased; however, on a surface area basis, radical generation levels were more, but not completely, similar. Chamfer grinder powder, polycrystalline aggregates of tungsten carbide in a metallic cobalt matrix, generated the highest levels of .OH radicals (p < 0.05). Radical generation was not dependent on the masses of metals, rather, it involved surface-chemistry-mediated reactions that were limited to a biologically active fraction of the total available surface area of each material. Improved understanding of particle surface chemistry elucidated the importance of biologically active surface area in generation of ROS by particle mixtures.