Poly(ethylene imine) nanocarriers do not induce mutations nor oxidative DNA damage in vitro in MutaMouse FE1 cells

Genotoxicity information on polymers used for gene delivery is scant, but of great concern, especially when developing polymeric nanocarriers as nonviral vector systems for cancer treatment. The genotoxicity of some engineered nanomaterials, e.g., metal oxides like ZnO, TiO₂, and CuO but also carbon based materials like carbon black or nanotubes, has commonly been related to oxidative stress, and subsequent inflammation. Recent studies of poly(ethylene imine) (PEI)-based polymers, important nonviral vector systems for pDNA and siRNA, might raise concerns because of their toxic effects dominated by cellular oxidative stress and inflammatory responses, similar to the mentioned effects of engineered nanoparticles. In this study, we employed a FE1-MutaMouse lung epithelial cell line based mutation assay to determine the genotoxicity of three PEI-based polymers and nanosized zinc oxide particles (NZO), all of which have previously been shown to trigger oxidative stress and inflammation. In addition, oxidative DNA damage (8-OH-dG) in FE1 cells was assessed by ELISA. The well-known carcinogen benzo[a]pyrene (B[a]P) was used as positive control. FE1 lung epithelial cells were exposed for eight sequential 72 h incubations, and reporter-gene mutation frequency or 8-OH-dG formation was determined to assess mutagenicity and oxidative DNA damage, respectively. No cytotoxic effects were detected at the exposure levels examined, which are representative of PEI concentrations normally used in in vitro transfection studies. In contrast to B[a]P, neither PEI-polymers nor NZO showed any significant mutagenic activity or oxidative DNA damage in the exposed cells, although PEI-based polymers have been shown to generate significant levels of cellular stress and inflammatory responses. We suggest that the lack of any detectable mutagenic/genotoxic activity of the PEI-based polymers studied here is a crucial step toward a safe use of such nanocarriers in clinical trials.