Fig. 6

(Geno)toxicity assessment of silica nanoparticles exposed at equivalent doses to the 2D and 3D test systems: (a) 16 nm-SiO₂, and (b) 85 nm-SiO₂. BARS = micronucleus frequency; LINES/POINTS = cell viability. 2D cell cultures (2D) (n = 6, error bars = SD)/3D tissues (n = 2, error bars = range; except 1000 μg where n = 1) were exposed for 24 h in absence of cyt B via the 3D topical / in-medium or 2D exposure routes. Genotoxicity was assessed until cell viability decreased below 50 %. Equivalent 2D/3D doses were established by total mass dose normalisation according to the total number of cells in each culture model at time of inoculation (see Methods). (*) (**) (***) indicate statistical significance relative to control at p < 0.05, p < 0.01 and p < 0.001 respectively. Alternative dose metrics including the 3D equivalent total mass doses with area (topical exposures) and volume (in-medium exposures) unit components are provided in Table 2