The effects of sedimentation, dissolution and flow rate on the cytotoxicity of Ag nanoparticles

Abstract

Nanoparticles (NPs) are being employed with increasing frequency, yet the adverse health effects associated with the prolonged exposure of humans to NPs has not been well-established. Particularly, the effects of the extrinsic (or dynamic) physicochemical properties of NPs in aqueous cell culture media (e.g., hydrodynamic size, aggregation, agglomeration, sedimentation, and dissolution of nanoparticles) on the cytotoxicities of the NPs are barely understood. In part Ι of this thesis, to investigate the effects of two important extrinsic properties of Ag NPs, namely the sedimentation and dissolution of Ag NPs, it was performed MTT cell viability tests for HeLa cells exposed to Ag NPs with varying extrinsic properties. Sedimentation of aggregated/agglomerated Ag NPs was found to contribute more significantly to the cytotoxicity of Ag NPs during early periods of exposure, whereas the cytotoxicity was more greatly enhanced later during the exposure period due to the increase in Ag+. Therefore, it is offered that any assessment of NP cytotoxicity should consider the extrinsic properties of NPs, and their time-dependent properties, because the dominant processes affecting NP cytotoxicity may change over time and lead to a misunderstanding or poor prediction of NP cytotoxicity. In part ΙΙ of this thesis, to investigate the effects of Ag NPs flow rates on the cell cycle of HeLa cells by using the μFIC based cell cycle analysis. The flow rate of Ag NPs has closely connected with DNA damage and cell death. As the flow rate increases, cells are exposed to more toxic environments, which induce more arrest in G2 phase. Shear stress of the flowing fluid and the continuous supply of Ag NPs are thought to have caused these effects of flow rates.