Generation of intracellular reactive oxygen species and genotoxicity effect to exposure of nanosized polyamidoamine (PAMAM) dendrimers in PLHC-1 cells in vitro

Polyamidoamine (PAMAM) dendrimers have previously been demonstrated to elicit systematically variable cyto- and eco-toxic responses, promising as the basis for structure-activity relationships governing nanotoxicological responses. In this study, increased production of intracellular reactive oxygen species (ROS), genotoxicity and apoptosis due to in vitro exposure of fish hepatocellular carcinoma cells to dendrimer generations G4, G5 and G6 is demonstrated. A PAMAM dendrimer generation dependent increase in ROS and genotoxicity was observed, consistent with our previous studies. The toxicological responses correlate well with the nanoparticle surface chemistry, specifically, the number of surface amino groups per generation. Although ROS production initially increases approximately linearly, it saturates at higher doses. Notably, normalized to the molar dose of surface amino groups, the dose-dependent ROS production for different generations overlap exactly, indicating that the response is due to these functional units. The genotoxicity response is also well correlated to the number of surface amino groups and therefore generation of PAMAM dendrimers. The observed genotoxicity, related to DNA damage, is related to the generation and dose dependent production of intracellular ROS, at low levels. At the higher ROS levels, increased DNA damage is associated with the onset of necrosis.