Fig 1: Release of IL-8 (pro-)inflammatory cytokines in 3D HepG2 liver spheroids following both acute (24 h) and longer-term (120 h) exposure to 0.2–10.0 µg/mL of (A) TiO2, (B) ZnO, (C) Ag, (D) BaSO4 and (E) CeO2 ENMs. An untreated, media only sample was used as the negative control. The positive assay control was 0.25 µg/mL of TNF-a protein (NBP2-35076-50 µg, Biotechne, UK), as indicated by the dotted line, which represents the mean positive control response for both acute (light red line) and prolonged (dark red line) exposures. Mean data of three biological replicates, analysed in triplicate (n = 9) are presented ± SEM. Significance is indicated in relation to the negative control, where * = p = 0.05