An understanding of the environmental, health, and safety implications of engineered nanomaterials is fundamental to the progression of the emerging field of nanotechnology. Engineered nanomaterials are being proposed for use for applications ranging from medicine to environmental cleanup, which will ultimately lead to their release into the environment, either directly or as waste. As many pollutants reach the aquatic environment it will become increasingly important to assess the environmental implications of nanoparticle release, including their potential impact on species within aquatic ecosystems. Many regulatory organizations are struggling to identify how to assess potential environmental impacts associated with nanomaterials as they exhibit properties that are distinct from their larger counterparts. Studies to date have focused on cellular toxicity rather than whole organism studies, and have included limited types of nanomaterials in any one study leading to difficulties in creating theories about how nanomaterial properties influence the interaction with key organisms. The PI's lab has found that nanomaterial composition and surface chemistry has an influence on the responses of the aquatic crustaceans in the genus Daphnia. Questions that need to be addressed include: A) Do nanomaterials with similar surface chemistry have similar impacts on aquatic organisms or is the composition of the core of the nanomaterial more important? B) How do different nanomaterials interact with the physiology of aquatic organisms? In this experiment, Daphnia pulex will be used as a model aquatic organism to conduct experiments on the impacts of various nanomaterials from molecular and physiological responses to population level responses. General toxicity experiments, physiological and behavioral assays will be used to determine the impact of exposure to several nanomaterials of differing chemical composition. Impacts of exposure on molecular physiology will be conducted using quantitative PCR of key genes as well as microarrays for global gene expression analysis. D. pulex is a model aquatic species for ecology and toxicology and is now a recognized model species for studies of the impact of environment changes on the genome. Using this species, results from nanoparticle experiments can be compared to genomic and toxicology information that has already been developed for other compounds and will take advantage of the resources available for this species.
The objectives of this project are to determine the characteristics of nanomaterials that make them toxic to aquatic organisms, using Daphnia pulex as a model species. The ultimate goal will be to identify the ways in which nanomaterials may be developed to be less toxic to aquatic invertebrates. Specifically they will 1) determine the impact of changes in nanoparticle chemical structure and surface chemistry on the general toxicity to Daphnia pulex, 2) determine the potential sublethal impacts on reproduction, physiology, and behavior, and 3) determine the molecular effects of nanomaterials on Daphnia pulex by characterizing gene expression patterns specific to each exposure. This molecular data will provide an indication of the mechanism by which nanomaterials alter the physiology of aquatic invertebrates.
The project proposed here will take a focused approach to examine how alterations in structure and surface chemistry of one class of nanomaterials (those based on fullerene carbon structures) will affect the interaction of a particle with the aquatic ecological, toxicological and genomic model species, Daphnia pulex. Taking this approach will provide insight into how structure and surface chemistry play a role in nanomaterial-organism interactions and will provide hypotheses with which to test with other types of particles with different core structures. The ultimate product will be not only toxicological data but a tool with which to evaluate other nanomaterials. In addition the project will provide a means to train students in an interdisciplinary manner that is requisite for understanding the environmental implications of nanotechnology.
There is a growing number of commercial products that contain carbon nanomaterials (CNMs). These nanomaterials are sometimes created with coatings on their surface that are made with different chemical compounds. There is a lack of information on the chemical makeup of the nanomaterial may affect how toxic they are to organisms. The major goals of this project were to determine how nanomaterial chemistry may influence the toxicity of nanomaterials. Many chemicals are not toxic at low-level exposures but when an organism is exposed over a long period of time different impacts are seen. In this experiment we investigated the impact of nanomaterials with differing chemistry to a model organism that is important in aquatic ecosystems the daphnia. We measured the possibility of each nanomaterial causing not only death but looked at impacts on reproduction, physiology and behavior of daphnids as well. We also used modern technologies that involve examining the way genes are expressed in an organism as an indication of how the nanomaterial is affecting the daphnids and examined how nanomaterials with different chemistries cause different changes in gene expression. Intellectual Merit: Outcomes of this work include data that suggest that the surface chemistry of a nanomaterial can change the toxicity of the material dramatically. This information can be used to inform industry regarding the potential factors that may influence toxicity of particles so companies can alter the chemistry of materials to make them safer. In addition we have evaluated behavioral assays and gene expression as high-throughput cheaper and easier methods for assessing toxicity. Behavior itself appears to be a separate but relevant outcome than acute or chronic toxicity endpoints. Gene expression may ultimately provide both mechanistic information as to how nanomaterials may impact organisms and can be a predictive tool for impacts on reproduction. Broader Impacts Results from experiments have been presented in national and international scientific meetings by the PI and graduate students, in presentations to the general public, in courses taught in the School of Freshwater Sciences, and most recently in two publications as well as another in peer-review. One graduate student and two undergraduate participated in this project and were trained in nanotoxicology, genetics, genomics, toxicology and in scientific method, writing and publishing, and ethics of science through this grant. The Ph.D. student, because of the significant training received, has gone on to a postdoctoral appointment, one of the undergraduates to professional school and the other to a position in industry.
