Collaborative Research: Teasing apart how specific nanoparticle features relate to environmental fate and contribute to ecotoxicity

Oregon State University, Corvallis OR

Investigators

Abstract

Silver nanoparticles are extensively used for their antimicrobial properties in an increasing number of consumer and commercial products and as bacterial agents in the treatment of wastewater. Because of their high demand, over 500 tons of engineered silver nanoparticles are produced globally. While the properties of these nanoparticles are important for their antibacterial activity, some may also influence toxicity. The environmental impacts of silver nanoparticles independent of their ion leaching are challenging at best. Studies designed to evaluate the nanoparticle-specific effects of silver nanoparticles have been limited because of their propensity to undergo ionic dissolution. Furthermore, discrepancies over the relative contribution of ion to particle toxicity remain prevalent in the literature primarily due to differences in study design. Consequently, there is a great need to understand how silver nanoparticles with diverse characteristics impacts the interaction with organisms by controlling for the confounding effects of ionic contribution to toxicity as compared to particle effects. The researcher's proposed studies will contribute to the scientific understanding of how the properties of these nanoparticles play a role in biouptake, nanoparticle-biological interactions, and ecotoxicity. The research will involve the elimination of the effects of particle surface oxidation and ionic dissolution, which has complicated toxicity studies in the past. This contribution is significant because it will improve our ability to identify features of silver nanoparticles that make them eco-disruptive and predict how these features lead to adverse environmental outcomes. All data will be shared through the open-source knowledge base of Nanomaterial-Biological Interactions (NBI) globally for modeling efforts and will support the development of safety protocols, exposure guidelines, and regulations that protect human and ecosystem health. Furthermore, this research will provide design rules for the assembly of new classes of silver nanoparticles that could be commercialized without concern regarding rapid particle degradation and release into the environment. In addition, this project is designed to incorporate students from diverse backgrounds and will help build future science, technology, engineering and math (STEM) talent. The researcher's overall aim is to improve our understanding of the specific physiochemical features that dictate nanoparticle-biological interactions. First, they will design a series of lipid-coated silver nanoparticles that are differentially shielded from ion dissolution. Differentially shielded silver nanoparticles will be prepared by encapsulating silver nanoparticles of varying size and shape with a hybrid lipid-membrane to protect the surface from oxidation and ionic dissolution. Changes in the localized surface plasmon resonance (LSPR), thermal electron microscope (TEM), and (Inductively-coupled plasma mass spectrometer (ICP-MS) will be employed to monitor silver ion dissolution from the suite of nanoparticles. Second, they will identify features of lipid-coated nanoparticles that lead to particle instability. The agglomeration kinetics of the hybrid lipid-coated silver nanoparticles will be assessed using dynamic light scattering and nanoparticle tracking analysis. Third, since the goal is to ultimately relate these material features with nanoparticle-biological interactions, the researchers will determine the uptake and toxicity of the silver nanoparticle suite. Based on preliminary investigations, the hybrid lipid-coated silver nanoparticles with a robust coating should elicit minimal toxicity and a decrease in surface coverage should lead to a respective increase in toxicity. A well-established embryonic zebrafish assay will be used to identify vertebrate morbidity and mortality resulting from exposure and hyperspectral imaging (HSI) will be used to visualize nanoparticle uptake in whole animals. Finally, the researchers will assess the potential ecotoxicity of the suite using a novel nanocosm assay. Hyperspectral imaging will be used to visualize nanoparticle biodistribution among bacteria, algae, crustaceans, and fish in the small-scale freshwater assay. Collectively, the use of well-characterized silver nanoparticles tuned for ion release will allow the PIs to tease apart the relative contribution of the nanoparticle and ion to biouptake, toxicity, and potential for environmental impacts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.