Effect of Titanium Dioxide Nanoparticle Exposure on the Ocular Surface: An Animal Study

Abstract Purpose To evaluate the effect of titanium dioxide (TiO2 ) nanoparticle exposure on the ocular surface. Methods Eighty eyes of 40 rabbits were used. The TiO2 -1D group (n = 20) received a single instillation of TiO2 in the right eye. The TiO2 -4D group (n = 20) received a TiO2 instillation in the right eye once a day for four days. The 40 untreated left eyes were used as controls. Ocular surface staining (n = 5 for each group) was performed with rose bengal dye, tear secretion (n = 5) was measured using the phenol red thread test, lactic dehydrogenase (LDH) activity (n = 5) and MUC5AC levels (n = 5) were measured in tears, and the area of the conjunctival goblet cells (n = 5) was measured through impression cytology and scanning electron microscopy 24 hours after the last TiO2 instillation. Results Ocular surface staining was increased but the tear secretion was not changed after TiO2 exposure. The TiO2 -1D (1.39 OD) and TiO2 -4D groups (0.58 OD) had higher median tear LDH activity than the control groups (0.57 OD and 0.29 OD, respectively). Although the median tear MUC5AC level in the TiO2 -1D group (92.7 ng/ml) was higher than that of control 1 group (37.4 ng/ml), there was no significant difference in MUC5AC levels between the TiO2 -4D and control 2 groups. Conjunctival goblet cell area decreased after TiO2 exposure. Conclusions Exposure to TiO2 nanoparticles induced ocular surface damage. Although the tear MUC5AC level increased after a single exposure, it decreased to normal levels after repeated exposures. The area of conjunctival goblet cells decreased after TiO2 exposure.