BIOTRIBOCORROSION: IN VITRO NEUROTOXICITY OF TITANIUM NANOPARTICLES.

Titanium (Ti) is one of the most frequently used metallic biomaterials in the biomedical field. It develops a passivating layer of titanium dioxide (TiO2). As a result of biotribocorrosion, TiO2 nanoparticles can be released from the surface into the biological milieu. It is known that NPs derived from transition metals can pass through the hematoencephalic barrier and cause damage, altering the integrity of the brain. In previous studies evaluating different sized TiO2 NPs (5, 10 or 150 nm) in a murine model we found the smallest NPs (5nm) to show the highest concentration in the brain. Although TiO2 NPs are thought to have low toxicity, little is known about their neurotoxic effects. Objective: To evaluate the effect of 5nm TiO2 NPs on a human neuroblastoma cell line (SH-SY5Y) as an in vitro model of neurotoxicity. Methods: The cells were grown in Ham’s-F12: EMEM? (1:1) with 10% BFS, 1% BTA, and seeded on plates with 24 wells (160.000 cells/well). The cultures were divided into two groups: Control Group (CG) and 5nm-TiO2 Group (exposed to 5nm TiO2 particles). The following concentrations were used: 5, 10, 50 o 100 µg/ml for 24 h. Generation of superoxide anion (O2-) was assessed by NBT reduction test, apoptosis was evaluated by active caspase-3 expression, and senescence was determined by ?–galactosidase activity. Results: The 5nm TiO2 NPs induced O2- generation and apoptosis in a dose dependent manner (p<0.001). O2- generation increased up to 5-fold compared to GC (C: 4.45±1.03, 5ug/ml: 11.38±2.66, 10ug/ml: 17.5±2.5, 50ug/ml: 29.1±2.7, 100ug/ml: 44.6±2.9). A significant 4-10-fold increase in apoptosis was also observed compared to controls. Exposure to 5nm TiO2 NPs induced apoptosis in the SH-SY5Y cell line, possibly due to an imbalance in O2- generation. No differences in cellular senescence were observed at the studied concentrations. Conclusion: Even at very low concentrations, 5nm TiO2 NPs had a neurotoxic effect on human neuroblastoma cells, triggering apoptosis as the main mechanism of cell death.