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 TiO2 nanoparticles (nano‐TiO2) 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‐TiO2 and found the same requirement for MN induction. Nano‐TiO2 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‐TiO2 also increased the activity of the inflammatory factor NFkB but not of AP1 in a reporter‐gene HepG2 cell line. Suspension of nano‐TiO2 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.