Osmotic pressure induced toxicity by aggregation of citrate-coated silver nanoparticles inside HepG2 cells

The effects of 10nm citrate-coated silver nanoparticles (AgNPs) to hepatocellular carcinoma (HepG2) cells were investigated to elucidate toxicity mechanisms. Cell viability, oxidative stress, protein expression, and cell morphology were assessed to determine the toxicity of AgNPs at various dose levels. 10nm citrate-coated AgNPs were found to be toxic to HepG2 cells at a dose of > 1.0 ppm and their LD50 was determined to be 3.0 ppm. Oxidative stress levels in the cells were found to increase with the dose of AgNPs and HepG2 cells can withstand high level of reactive oxygen species before cell death. The expressions of heat shock proteins and tubulin proteins were most significantly affected by the presence of AgNPs of 5.0 ppm. The AgNPs were observed to penetrate the cells treated with a dose of 5.0 ppm by transmission electron microscopy. Furthermore, the agglomeration of AgNPs in HepG2 cells was found and generated osmotic pressure that is likely another pathway to be responsible for the toxicity of AgNPs.