Fig. 2. Toxicity assessment of striped and unstructured AuNPs in U937 cells. (A) WST-8 proliferation assay upon treatment with increasing amount of AuNPs. Ctrl represents the negative control; values are mean ± SD. Positive controls (not shown) were treated with 0.01% of TritonX100, displaying a strong viability decrease (ca. 80–90%) with respect to the untreated cells. (B) ROS quantification, via DCFH-DA assay, after cellular treatment with AuNPs; values are mean ± SD. Positive controls (not shown) were treated with a free radical generator (100 μM H₂O₂), exhibiting a ROS increase of ca. 190–220% with respect to the untreated control cells. (C) Evaluation of caspase 3 activity. Values are mean ± SD. Results were analyzed by Two-way ANOVA and values compared to the control by the Bonferroni post-hoc test. Differences between treated samples and controls (n = 8) were considered statistically significant for ***P < 0.001, **P < 0.01, *P < 0.05, and non-significant for P > 0.05.