MTT test analysis.

U87, U87-EGFP, C3A and C3A-EGFP cells metabolic analysis was performed after 2 and 24 h of exposure to the culture medium containing nanoparticles at different concentrations: diamond 20 μg/mL (ND 20), 50 μg/mL (ND 50) and 100 μg/mL (ND 100), and graphite 20 μg/mL (NG 20), 50 μg/mL (NG 50) and 100 μg/mL (NG 100); nontreated cells were used as a control (Control). Metabolic activity of cells, expressed as I_CV, after 2 h of exposure to the culture medium with the above-mentioned different concentrations of diamond and graphite nanoparticles: U87 and U87-EGFP (A), and C3A and C3A-EGFP (B); and after 24 h of exposure to the culture medium with above-mentioned different concentrations of diamond and graphite nanoparticles: U87 and U87-EGFP (C), and C3A and C3A-EGFP (D). Data analysis was carried out by two-way ANOVA and the differences between the groups were tested by Duncan’s test. Data were averaged from three replicates (n = 3); P < 0.05. No significant interaction (nanoparticles with transduction) was observed.