Figure 4: NF-кB response by HepG2 cells exposed to different crystalline forms of TiO2 NPs. Histogram of NF-кB response using TLR4 expression and NF-кB promoter-reporter plasmid (fold induction) by HepG2 exposed for 48 hours to different crystalline forms of TiO2 NPs (anatase form, rutile form, and mixed form, from left to right) at 10 μg/mL. White bars show the NF-кB response without the TLR4 expression vector. Black bars show the NF-кB response with the TLR4 expression vector. All values are presented as mean ± s.d. (n = 3).