Yongshen ChenGeorgia Institute of Technology, Civil and Environmental Engineering
The unique properties of engineered nanoparticles (NPs) have not only led to the rapidly increasing applications in various industries and commercial products, but also caused environmental concerns due to the inevitable release of NPs and their unpredictable biological/ecological impacts. This talk gives an overview of our research from the following aspects: Our research initially focuses on understanding the aggregation of NPs and describing this process quantitatively, as the aggregation greatly influences the transport, fate, bioavailability and toxicity of NPs. Particularly, with CeO2 chosen as a model NP owing to its broad industrial applications, we systematically investigate the aggregation kinetics of NPs through assessment of the effect of solution chemistries (e.g., ionic strength and natural organic matter) and modeling approaches. Although most NPs are subject to slow or fast aggregation in aqueous media, there are always “real” nanosized particles existing in environmental systems, which may have unique effects at the local interface between NPs and biological systems and exert different toxicity mechanisms compared with the aggregates. To explore the biological effects of “real” NPs, we have developed systematic experimental approaches based on atomic force microscopy (AFM) to assess the effect of unaggregated NPs on single cells or DNA molecules at the local scale. In particular, we image and quantitatively characterize the adhesive, biomechanical (hardness and elasticity), and surface electrical properties of E. coli cells with and without exposure to hematite NPs. We also examine the binding of NPs onto DNA molecules, which subsequently lead to the conformational change of DNA and interfere with DNA replication processes. Another focus of our research is on the ion release behavior of certain NPs, which may be linked to their fate, transport, and even biological impacts. We have developed models to describe the ion release kinetics of NPs in aqueous environments, allowing researchers to better understand and predict the nanotoxicity of NPs. We also observe the contribution of released ions to the toxicity of NPs. Besides ion release, oxidative stress induced by reactive oxygen species (ROS) is one of the most important toxicity mechanisms of NPs. We investigate the ROS generation mechanisms of metal and metal oxide NPs. The contribution of ROS to the toxicity of NPs is validated using acute toxicity tests on E. coli cells. Overall, our research provides a comprehensive understanding of nanotoxicity by exploring the aggregation, single NPs effect, ion release and ROS production of NPs, which sheds light on the safe use of NPs.
Hosted by Brian Chaplin