Cytotoxicity and apoptosis induced by silver nanoparticles in human liver HepG2 cells in different dispersion media

Silver nanoparticles (Ag NPs) have been widely used in medical and healthcare products owing to their unique antibacterial activities. However, their safety for humans and the environment has not yet been established. This study evaluated the cellular proliferation and apoptosis of Ag NPs suspended in different solvents using human liver HepG2 cells. The ionization of Ag NPs in different dispersionmedia [deionized water, phosphate-buffered saline (PBS), saline and cell culture] wasmeasured using an Ag ion selective electrode. The MTT assay was used to examine the cell proliferation activities. The effects of Ag NPs on cell cycle, induction of apoptosis, production of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were analyzed using flow cytometry. The degree of Ag NPs ionization differed with dispersionmedia, with the concentrations of silver ions in deionized water being the highest in all suspensions. Ag NPs could inhibit the viability of HepG2 cells in a time-and concentration-dependentmanner. Ag NPs (40, 80 and 160 mu gml(-1)) exposure could cause cell-cycle arrest in the G2/Mphase, significantly increasing the apoptosis rate and ROS generation, and decreasing the MMP in HepG2 cellsmore sensitive to deionized water than in cell culture. These results suggested that the cellular toxicological mechanism of Ag NPs might be related to the oxidative stress of cells by the generation of ROS, leading to mitochondria injury and induction of apoptosis. It also implies that it is important to assess the physicochemical properties of NPs in the media where the biological toxicity tests are performed. Copyright (C) 2015 John Wiley & Sons, Ltd.