Hemolysis Caused by Titanium Dioxide Particles

Abstract

Washed human erythrocytes were incubated with titanium dioxide (TiO₂) particles at 37°C for 1 hr and hemolysis was determined by the percentage of hemoglobin released (optical density at 540 nm; OD540) from the cells. Effects of TiO₂ on OD540 were corrected and dose-response curves were analyzed by the Hill plot. Judging from the estimated dose to cause 50% hemolysis, the anatase form of micron-scale (<5000 nm) particles was 73 and 11 times more potent than the amorphous (<50 nm) and rutile (<5000 nm) forms, respectively, whereas it was 1.3 times more potent than the nano-scale (<25 nm) anatase particles. Plasma abolished the hemolysis due to anatase and rutile forms. Thus, hemolytic effects of TiO₂ can be greatly different depending on the polymorph but not on the primary size (nano- or micron-scale) of particles. TiO₂-induced hemolysis is unlikely to occur in vivo because of the presence of plasma.