An in vitro assessment of panel of engineered nanomaterials using a human renal cell line: cytotoxicity, pro-inflammatory response, oxidative stress and genotoxicity

Background. It has been shown that nanomaterials (NMs) are able to translocate to secondary tissues one of the important being the kidneys. Oxidative stress has been implicated as a possible mechanism for NM toxicity, hence effects on the human renal proximal tubule epithelial cells (HK-2) treated with a panel of engineered nanomaterials (NMs) consisting of two zinc oxide particles (ZnO - coated - NM 110 and uncoated - NM 111), two multi walled carbon nano-tubes (MWCNT) (NM 400 and NM 402), one silver (NM 300) and five TiO2 NMs (NM 101, NRCWE 001, 002, 003 and 004) were evaluated. Results. We found the two ZnO NMs (24 hr LC50 – 2.5 µg/cm2) and silver NM (24 hr LC50 – 10 µg/cm2) were highly toxic to the cells. The LC50 was not attained in the presence of any of the other engineered nanomaterials (up to 80 µg/cm2). All nanomaterials significantly increased IL8 and IL6 production. Meanwhile no significant change in TNF-a or MCP-1 was detectable. Intracellular reactive oxygen species were measured utilising HE oxidation assay. The most notable increase in ROS was noted following treatment with the Ag and the two ZnO NMs. Finally, genotoxicity was measured at sub-lethal concentrations. We found a small but significant increase in DNA damage following exposure to seven of the ten NMs investigated (NM 111, NRCWE 001 and NRCWE 003 being the exception) with this increase being most visible following exposure to Ag and the positively charged TiO2. Conclusions. While the NMs could be categorised as low and highly toxic, sub-lethal effects such as cytokine production and genotoxicity were observed with some of the low toxicity materials.