Methods and Measurements of Nanoparticle Accumulation and Distribution in Organisms

Given the substantial differences between nanoparticles (NPs) and typical organic and inorganic environmental contaminants, new experimental methods and analytical techniques are needed to accurately measure concentrations of NPs in ecological receptors. These measurements are important because the accumulated concentration of contaminants in organisms typically directly relate to the observed toxicological impacts. Additionally, the distribution of NPs within organisms influences which organs may be affected and what toxicological effects may be observed.

Intended Impact
Understanding the potential environmental fate of NPs has direct implications to the US economy, as potential environmental and human health impacts of NPs is one of the main factors slowing the commercialization of this technology. Reducing the uncertainty regarding the environmental fate and risks of NPs will facilitate sustainable commercialization of products utilizing NPs. The results from this project are expected to also help other government agencies such as EPA and FDA with a robust and scientifically grounded risk assessment of NPs.

Objective
The objectives of this project include the development of transferable methodologies that can be used to accurately measure accumulation and distribution of organic and inorganic NPs, and achieving a mechanistic understanding of which NP properties influence accumulation and elimination rates in different environmental matrices (aquatic, sediment, and soil).

Goals

1. Development and application of novel methods to detect carbon nanotubes, fullerenes, metal oxide, and metal NPs in ecological receptors in different environmental matrices.
2. Determination of the absorption of these nanoparticles throughout the organisms.
3. Mechanistic understanding of the factors that determine uptake and elimination of nanoparticles by various organisms.

Research Activities and Technical Approach
Carbon-14 labeled carbon nanotubes (multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs)) and fullerenes will be used to make novel measurements of these carbon NPs in ecological receptors and various environmental matrices. Aquatic organism (Daphnia magna) and earthworms will be exposed to MWCNTs with different surface coatings (positive, negative, or neutral) and their accumulation and elimination rates measured. Methods will also be developed to detect carbon nanotubes and fullerenes in organisms without the use of radioactive labeling. Absorption of NPs across the gut lining will be investigated within organisms using transmission electron microscopy (TEM), and when necessary, electron energy loss spectroscopy (EELS). To test how different NP shapes and morphologies influence NP uptake, earthworms will be exposed to Au NPs with a range of sizes, shapes (spheres and nanorods), and surface coatings (tannic acid-coated or uncoated) and uptake and elimination behaviors will be tested using ICP-MS. The influence of particle size on plant accumulation of copper oxide will also be investigated.

• Different surface coatings of MWCNTs were not found to influence uptake and elimination rate measurements in Daphnia magna or earthworms.
• Fullerenes were not found to be absorbed across the microvilli of L. variegatus using TEM.
• ICP-MS was used to assess copper accumulation of radish and ryegrass species from CuO NPs, CuO bulk particles, and copper ions