Comparative in vitro cytotoxicity study of silver nanoparticle on two mammalian cell lines

In this study the cytotoxic effect of commercially available silver (Ag) nanoparticle was evaluated using human dermal and cervical cancer cell lines. Prior to the cellular studies a full particle size characterisation was carried out using Dynamic Light Scattering (DLS), Transmission Electron Microscopy and Scanning Electron Microscopy in distilled water and cell culture media. The Zeta Potential (ZP) associated with the Ag nanoparticle was also determined in order to assess its stability in the solutions and its possible interaction with the media. The DLS and ZP study have suggested interaction of Ag nanoparticles with the media, which can lead to secondary toxicity. The toxic effects of Ag nanoparticles were then evaluated using different cytotoxic endpoints namely the lysosomal activity, mitochondrial metabolism, basic cellular metabolism, cellular protein content and cellular proliferative capacity. The cytotoxic effect of Ag nanoparticle was dependant on dose, exposure time and on the cell line tested. Further investigation was carried out on HeLa and HaCaT cell lines to elucidate the mechanism of its cytotoxicity. The Ag nanoparticle was noted to induce elevated levels of oxidative stress, glutathione depletion and damage to the cell membrane as found from the adenylate kinase assay and that leads to the apoptosis. Overall, significant differences were observed between the sensitivity of the two cell lines which can be understood in terms of their natural antioxidant levels.