Fig. 4

NP effect on MMP and cell viability in 3D human neural models. a Representative images of MitoTracker® staining in 3D LUHMES and BrainSpheres after 24 and 72 h exposure to Au-SC (6 μg/mL), Au-PEG (20 μg/mL) and PLA-NP (20 μg/mL). Reduction in the Mitotracker fluorescence intensity upon treatment with NP represents the reduction in uptake of the fluorescence probe due to impaired mitochondrial membrane potential. b MMP levels in 3D LUHMES and BrainSpheres after 24 and 72 h exposures to Au-SC (0.06, 0.6 and 6 μg/mL), Au-PEG (0.2, 2, 20 μg/mL) and PLA-NP (0.2, 2 and 20 μg/mL) normalized to the untreated spheroids controls. c Percent of LDH release in 3D LUHMES and BrainSpheres models after 24 and 72 h exposures to Au-SC (6 μg/mL), Au-PEG (20 μg/mL) and PLA-NP (20 μg/mL). ‘- Control’ corresponds to LDH released from untreated spheroids. Results are expressed as mean (±SEM). Each experimental group corresponds to three independent experiments imaging at least 20 spheroids. One-way ANOVA with Bonferroni’s multiple comparisons post-test was used for analysis of statistical significance (*p < 0.05, **p < 0.01, ***p < 0.001)