Renewal-Center for the Environmental Implications of Nanotechnology

The UK’s research team will continue to contribute to research activities in and cutting across Themes 1, 2, and 3 in collaboration with other CEINT researchers. Planned activities related to theme 1 are to examine the primary transformation pathways of a range of metal and metal oxide nanomaterials (NMs) in soil and aquatic systems and determine the characteristics, stability, and fate of the transformed NMs in laboratory (Theme 1) and mesocosm (Theme 3) experiments. An important and unique contribution of the UK team to these activities is the continued development of cutting-edge techniques for isolating and characterizing MNs and transformed MNs in complex environmental media and biological tissues using asymmetric flow field flow fractionation (AF4) coupled to a variety of in-line detectors (e.g., DLS, UV-Vis, Fluorescence, Refractive Index, ICP-MS) and combined with more traditional TEM and synchrotron based X-ray microprobe analyses. Spatially resolved laser ablation (LA) coupled with ICP-MS is also used to interrogate soil and biological samples to determine the spatial distribution of MNs and transformed MNs in various compartments. Contributions to Theme 2 will involve comparison of the bioavailability and effects of pristine and transformed MNs to a variety of ecoreceptors as measured by both ecologically relevant (growth, reproduction, behavior, mortality) as well as toxicogenomic end points. We will examine the influence of NM and transformed NM chemical composition, size, and surface properties (e.g., charge and hydrophobicity) on bioavailability to plants (Medicago truncatula and Trticum aestivum), rhizobacteria (Bacillus subtilis, Pseudomonas fluorescens, and Sinorhizobium meliloti), fungal spores (Beauveria bassiana), and the soil invertebrate, Caenorhabditis elegans. Studies will examine the role of surface chemical properties of NMs, transformed NMs, and designed and synthesized NMs (in collaboration with Core A) as well characterized analogues for transformed NMs on the partitioning and uptake of NMs to the different biological receptors as well as associated effects. These experiments will be designed to examine chronic effects over environmentally relevant concentrations of NMs. Furthermore, the UK team will lead much of the work in theme 2 on transgenerational effects. We propose to examine multigenerational changes in DNA germline mutations in response to NM exposure using the model organism C. elegans. C. elegans has a short maturation period, ranging only 3 days from egg to an adult stage, thus providing a unique opportunity to screen many generations for mutations. Short tandem repeat loci, microsatellites, will be used to detect changes in mutation frequencies before and after exposure to NMs over several generations. Microsatellite instability has been shown to be associated with DNA damage occurring in mismatch repair (MMR) genes which are responsible for accuracy of DNA replication and play an essential role in maintaining genomic stability. . In addition to screening microsatellite loci, we will also sequence regions of the well characterized MMR genes (msh-2 and msh-6 ) and methyltransferase (met-1), a gene associated with MMR pathways, to examine for any deficiency in these genes. Since mutations in the coding regions are likely to occur at much lower frequency than at microsatellite loci, the screening of these genes will be conducted every five generations. Accumulation of mutations can result in overall genomic instability which can have detrimental effects on organismal fitness in a population and may eventually lead to adverse changes on population level. Therefore, we will be also measuring changes in reproduction over multiple generations of C. elegans exposed to low concentrations of nanomaterials (pristine and aged) to establish whether changes in genomic instability are associated with changes in this important for population fitness parameter. In addition, given that met-1 is responsible for histone trimethylation (H3K36 and H3K9) during embryo development, we will screen for transgenerational changes in these methylation patterns to examine whether epigenetic changes are induced by exposure to MNs.