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Fig. 1.

SSB and base damage recognized by FPG in A549, HepG2 or HT29 cells treated with Aeroxide P25 TiO2 NP for 2 h (left panel) and 24 h (right panel) at concentrations indicated. Numbers (1, 2) denote results of Tukey’s test post hoc analysis, indicating a significant difference of the means from the control when NP concentration was considered (1) or a significant difference of the means between the same NP concentration, but different treatment times (2).
SSB and base damage recognized by FPG in A549, HepG2 or HT29 cells treated with Aeroxide P25 TiO2 NP for 2 h (left panel) and 24 h (right panel) at concentrations indicated. Numbers (1, 2) denote results of Tukey’s test post hoc analysis, indicating a significant difference of the means from the control when NP concentration was considered (1) or a significant difference of the means between the same NP concentration, but different treatment times (2).

Fig. 2.

Mitochondrial activity (MTT assay) of cells treated with Aeroxide P25 TiO2 NP for 24 h and measured 72 h after treatment expressed as a percent of the control (untreated cells). The asterisk denotes a statistically significant difference from the control. Two-way ANOVA with Tukey’s HDS post hoc comparison. P < 0.05.
Mitochondrial activity (MTT assay) of cells treated with Aeroxide P25 TiO2 NP for 24 h and measured 72 h after treatment expressed as a percent of the control (untreated cells). The asterisk denotes a statistically significant difference from the control. Two-way ANOVA with Tukey’s HDS post hoc comparison. P < 0.05.

Fig. 3.

Short-term survival of cells treated with Aeroxide P25 TiO2 NP for 24 h, as measured by neutral red assay. The asterisk denotes a statistically significant difference from the control. Two-way ANOVA with Tukey’s HDS post hoc comparison. P < 0.05.
Short-term survival of cells treated with Aeroxide P25 TiO2 NP for 24 h, as measured by neutral red assay. The asterisk denotes a statistically significant difference from the control. Two-way ANOVA with Tukey’s HDS post hoc comparison. P < 0.05.

Fig. 4.

Cloning ability determination of A549, HT29 and HepG2 cells growing in the presence of Aeroxide P25 TiO2 NP.
Cloning ability determination of A549, HT29 and HepG2 cells growing in the presence of Aeroxide P25 TiO2 NP.

Fig. 5.

Generation of ROS in HepG2, A549 and HT29 cells incubated with Aeroxide P25 TiO2 NP. H2O2 in a concentration of 1 mM served as a positive control. The data provided are in the form mean ± SD. n denotes the number of experiments; n = 3. The asterisk denotes statistically significant difference from unexposed control, P < 0.05.
Generation of ROS in HepG2, A549 and HT29 cells incubated with Aeroxide P25 TiO2 NP. H2O2 in a concentration of 1 mM served as a positive control. The data provided are in the form mean ± SD. n denotes the number of experiments; n = 3. The asterisk denotes statistically significant difference from unexposed control, P < 0.05.

Frequency of micronuclei and mean number of γ-H2AX foci per nucleus after 2 h and 24 h treatment with TiO2 NP concentrations indicated, and with the effect of X-irradiation with 2 Gy shown for comparison

Micronuclei frequency
Treatment Dose Cell line/time of treatment
A549 HepG2 HT29
2 h 24 h 2 h 24 h 2 h 24 h
Control 22.9 ± 9.5 31.5 ± 2.0 34.6 ± 3.4 26.3 ± 7.8 5.9 ± 3.2 7.5 ± 1.8
X-ray 2 Gy 80.1 ± 5.2a 155.2 ± 7.7a 45.5 ±0.3a
TiO2 NP 21 nm 10 μg/mL 33.2 ± 6.9 26.8 ± 7.5 22.3 ± 8.8 27.0 ± 9.5 6.8 ± 1.0 8.5 ± 6.6
50 μg/mL 22.5 ± 9.6 25.2 ± 3.7 24.6 ± 4.5 23.0 ± 4.4 5.5 ± 0.9 7.8 ± 1.6
100 μg/mL 25.5 ± 5.8 30.0 ± 8.2 24.5 ± 12.5 23.5 ± 6.4 6.1 ± 2.8 10.0 ± 7.2
The mean number of γ-H2AX foci per nucleus
Treatment Dose Cell line/time of treatment
A549 HepG2 HT29
2 h 24 h 2 h 24 h 2 h 24 h
Control 10.8 ± 5.7 10.7 ± 3.0 23.6 ± 10.8 7.2 ± 2.1 25.5 ± 10.1 26.4 ± 10.1
X-ray 2 Gy 78.2 ± 10.2a 87.2 ± 10.0” 87.9 ± 3.4a
TiO2 NP 21 nm 10 μg/mL 11.2 ± 6.8 10.5 ± 3.1 21.1 ± 6.0 9.7 ± 4.0 25.4 ± 10.0 25.0 ± 9.4
50 μg/mL 10.3 ± 3.5 7.8 ± 1.5 19.3 ± 5.6 11.4 ± 2.7 26.6 ± 6.8 23.7 ± 8.8
100 μg/mL 10.6 ± 4.1 6.4 ± 2.5 18.3 ± 8.0 9.5 ± 3.2 28.0 ± 5.0 24.5 ± 10.5

The extent of apoptosis after 2 h and 24 h treatment with TiO2 NP at indicated concentrations

Treatment Dose Cell line/time of treatment
A549 HepG2 HT29
2h 24 h 2h 24 h 2h 24 h
Control Viable 99.16 ± 0.14 98.36 ± 0.16 97.63 ± 0.29 96.34 ± 0.43 98.03 ± 0.55 97.04 ± 0.69
Early apoptosis 0.54 ± 0.21 1.34 ± 0.26 2.20 ± 0.30 3.22 ± 0.29 1.80 ± 0.56 2.61 ± 0-43
Late apoptosis and necrosis 0.30 ± 0.10 0.30 ± 0.08 0.17 ± 0.15 0.44 ± 0.17 0.17 ± 0.06 0.35 ± 0.09
Staurosporine/24 hb Viable 32.48 ± 8.88a 23.70 ± 5.33a 20.20 ± 3.20a
Early apoptosis 7.98 ± 2.33a 48.20 ± 3.22a 58.03 ± 4.98a
Late apoptosis and necrosis 59.54 ± 3.99a 28.10 ± 2.56a 21.77 ± 2.37a
TiO2 NP 10 mg/mL Viable 93.07 ± 0.81a 93.30 ± 1.20a 93.20 ± 0.26a 92.93 ± 0.64a 93.13 ± 0.25a 92.50 ± 1.46a
Early apoptosis 5.10 ± 0.44a 4.70 ± 0.75a 5.03 ± 1.03 4.53 ± 0.40a 4.43 ± 0.75 4.17 ± 0.79
Late apoptosis and necrosis 1.83 ± 0.40a 2.00 ± 0.46a 1.77 ± 0.81 2.53 ± 0.26a 2.43 ± 0.50a 3.33 ± 0.81a
TiO2 NP 50 mg/mL Viable 92.10 ± 0.80a 93.93 ± 1.75a 93.97 ± 0.65a 91.13 ± 1.37a 93.17 ± 0.78a 91.83 ± 1.60a
Early apoptosis 5.97 ± 0.76a 3.83 ± 1.33a 3.97 ± 0.61 6.00 ± 1.15a 3.70 ± 0.60 5.17 ± 1.40a
Late apoptosis and necrosis 1.93 ± 0.15a 2.23 ±0.42a 2.07 ±0.15a 2.87 ± 0.35a 3.13 ±0.25a 3.00 ± 0.26a
TiO2NP 100 mg/mL Viable 93.63 ± 1.20a 91.87 ± 1.10a 93.73 ± 0.64a 90.87 ± 0.96a 92.23 ± 1.46a 90.57 ± 0.23a
Early apoptosis 3.97 ± 0.75a 5.90 ± 1.47a 4.27 ± 0.40a 6.33 ± 0.91a 4.70 ± 0.79a 6.17 ± 0.65a
Late apoptosis and necrosis 2.40 ± 0.46a 2.23 ± 0.40a 2.00 ± 0.26a 2.80 ± 0.26a 3.07 ± 0.81a 3.27 ± 0.47a

Caspase 3 activity after 2 h and 24 h treatment with TiO2 NP at indicated concentrations

Treatment Cell line/time of treatment
A549 HepG2 HT29
2 h 24 h 2 h 24 h 2 h 24 h
Control 0.12 ±0.05 0.05 ±0.01 1.02 ±0.03 1.42 ±0.02 0.26 ±0.02 0.42 ±0.03
TiO2 NP 10 mg/mL 0.10 ± 0.02 0.06 ± 0.01 0.98 ± 0.02 1.43 ± 0.09 0.31 ± 0.01 0.41 ± 0.06
TiO2 NP 50 mg/mL 0.13 ± 0.02 0.07 ± 0.01 1.08 ± 0.07 1.37 ± 0.05 0.51 ± 0.05a 0.63 ±0.05a
TiO2 NP 100 mg/mL 0.11 ± 0.01 0.07 ± 0.01 1.39 ± 0.06a 1.39 ± 0.03 0.37 ± 0.02a 0.55 ± 0.04a
Positive control: Jurkat cells treated with 1 mM staurosporine for 24 h : 39.89 ± 3.82a

Hydrodynamic diameter and zeta potential of Aeroxide P25 TiO2 NPs in water, EMEM, F12 and DMEM media

Medium Hydrodynamic diameter (nm) Polydispersity index (PDI) Zeta potential 7.4 (mV)
Water 356 ± 1 0.457 ± 0.04 –15.3 ± 0.5
EMEM 246 ± 1 0.193 ± 0.07 –25.5 ± 0.6
F12 295 ± 3 0.220 ± 0.05 –28.7 ± 2.5
DMEM 300 ± 2 0.280 ± 0.07 –27.5 ± 0.2
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Chemistry, Nuclear Chemistry, Physics, Astronomy and Astrophysics, other