Fig. 5. Assessment of skin irritation properties of chemically reduced GOs (a) using the SkinEthic™ Skin Irritation Test^−42bis (OCED TG 439). Results represent tissue viability reductions induced by rGOs evaluated using the MTT reduction assay with respect to negative controls (RhE exposed to PBS); 5% SDS was used as the positive control. Results are the mean ± SE of three independent experiments. Statistical differences vs. negative controls: *p < 0.05; ****p < 0.0001 (one-way ANOVA and Bonferroni's post-test) and (b) the release of IL-1α from RhE exposed to chemically reduced GOs. IL-1α was measured using a specific sandwich ELISA in growth media collected from RhE after exposure to each material; 5% SDS was used as the positive control. The data, reported as pg mL⁻¹ of IL-1α released in the media, are the mean ± SE of three independent experiments. Statistical differences vs. negative controls (RhE exposed to PBS): ****p < 0.0001 (one-way ANOVA and Bonferroni's post test).