Cellular interactions and biological responses to titanium dioxide nanoparticles in HepG2 and BEAS‐2B cells: Role of cell culture media

We showed previously that exposure of human lung cells (BEAS‐2B) to TiO 2 nanoparticles (nano‐TiO 2 ) produced micronuclei (MN) only when the final concentration of protein in the cell‐culture medium was at least 1%. Nanoparticles localize in the liver; thus, we exposed human liver cells (HepG2) to nano‐TiO 2 and found the same requirement for MN induction. Nano‐TiO 2 also formed small agglomerates in medium containing as little as 1% protein and caused cellular interaction as measured by side scatter by flow cytometry and DNA damage (comet assay) in HepG2 cells. Nano‐TiO 2 also increased the activity of the inflammatory factor NFkB but not of AP1 in a reporter‐gene HepG2 cell line. Suspension of nano‐TiO 2 in medium containing 0.1% protein was sufficient for induction of MN by the nanoparticles in either BEAS‐2B or HepG2 cells as long the final concentration of protein in the cell‐culture medium was at least 1%. Environ. Mol. Mutagen. 55:336–342, 2014. © 2014 Wiley Periodicals, Inc.