SNNI's Proactive Approach to Healthier and Safer Nanomaterials

In the next five years, the market for nanoenabled products is expected to top a trillion dollars. Nanomaterials may allow us to harness and store energy with increased efficiency, diagnose and treat illnesses and provide us with answers to many of the important challenges we face as a global society. Yet, despite the many promises upon which nanoscience may deliver, our understanding of these materials and the means to control their structures/properties remain tenuous¹.

Our ability to synthesize well-defined (size, shape, composition) nanomaterials, to tailor their surface chemistry appropriately and to remove impurities² continues to be an issue. Full characterization of these materials remains challenging as the tools we need are often not available³. Lack of access to well-defined materials has confounded our ability to accurately assess their properties, thus the question arises: Are those interesting electronic properties the result of quantum confinement or because we didn't purify our materials? In addition, despite the growing number of publications on toxicity of various nanomaterials, without characterization data, it is difficult to correlate the health impacts, toxicity and safety of nanomaterials with the underlying physical properties of the materials.

Given these significant challenges, a critical area of research is the development of efficient nanomanufacturing approaches that increase both the safety and usefulness of nanomaterials. Merging the principles of green chemistry with nanoscience is a key approach that meets these challenges and allows responsible development of sustainable nanotechnologies.

The Safer Nanomaterials and Nanomanufacturing Initiative (SNNI), founded in 2005, grew out of a merger of green chemistry and nanoscience a decade ago with the goal of developing more efficient nanomanufacturing processes that lead to greener and safer nanomaterials. SNNI represents a partnership between the Oregon Nanoscience and Microtechnologies Institute (ONAMI) and the Air Force Research Laboratory, and brings together over 30 top researchers (chemists, biologists, materials scientists, physicists and engineers) to ensure that nanoscience matures in a sustainable, responsible fashion.

SNNI researchers have access to a vast array of shared-user facilities and labs across ONAMI at Oregon State University, the University of Oregon, Portland State University and the Pacific Northwest National Laboratory. These facilities provide advanced measurement and fabrication services that allow industrial and academic SNNI researchers to meet the initiatives goals.

A number of approaches pioneered within SNNI are beginning to offer us a greater understanding of the health and safety implications of nanomaterials. One example is an interdisciplinary collaboration between chemists at the University of Oregon and biologists at Oregon State University that brings together precision nanoparticle synthesis with detailed investigation of their biological impacts.

Researchers in the Hutchison group at the University of Oregon have developed greener approaches for the synthesis of diverse libraries of well-characterized, functionalized nanoparticles. By adopting the principles of green chemistry, they have been able to significantly increase yields, assert full control over the core diameter of the nanoparticles and, using ligand exchange methods, tailor surface functionalization. The Hutchison group further showed that the purity of nanoparticles can be tuned using diafiltration². Through the combination of these approaches, the effects of core diameter, surface chemistry and purity on the toxicological properties of gold nanoparticles can be studied in a comprehensive fashion.

SNNI researchers at Oregon State University have developed a rapid throughput, in vivo system for delineating the effects of nanomaterials on vertebrate development using embryonic zebrafish. Embryonic zebrafish are an ideal platform due to their rapid development, access to large sample sizes and because of their molecular, cellular and physiological homology with higher vertebrates.

This exquisitely sensitive platform allows for the evaluation of nanomaterial interactions and resulting responses at the behavioral, morphological, cellular and genetic levels. Using this system, we found that core size, surface functionalization and purity influenced the biological responses of nanoparticles⁴. Functionalized nanoparticles with charged head groups produced more adverse responses than those with neutral ligands. In addition to size and surface chemistry, it was also found that increased impurity levels impacted biological responses.

While these data are interesting on their own, the capabilities they provide are even more so. Because we can establish these complex relationships between size, chemistry and toxicity, we can begin to develop design rules for nanoparticles to ensure that we take advantage of the interesting electronic and optical properties these nanoparticles provide, while minimizing the potential risks of these materials¹. Even more exciting is the fact that this approach can be applied to virtually any class of nanomaterials, and we have been able to study other types of metal nanoparticles, metal oxide nanoparticles as well as fullerenes.

Adopting a proactive, interdisciplinary and collaborative approach will be critical for realizing the promise of nanotechnology while minimizing potential health and environmental risks. While nanomaterials tend to be highly complex, this complexity offers amazingly tunable properties. By taking advantage of innovative approaches to nanoscale characterization and correlating this with toxicity data, we can develop powerful structure activity relationships and nanomaterials design rules. With these rules, we can begin harnessing the promise of nanomaterials in a responsible fashion for a nanoenabled future.

References

1. Hutchison, J. E. (2008) Greener Nanoscience: A Proactive Approach to Advancing Applications and Reducing Implications of Nanotechnology, ACS Nano 2, 395-402.
2. Sweeney, S. F., Woehrle, G. H., and Hutchison, J. E. (2006) Rapid Purification and Size Separation of Gold Nanoparticles via Diafiltration, Journal of the American Chemical Society 128, 3190-3197.
3. Richman, E. K., and Hutchison, J. E. (2009) The Nanomaterial Characterization Bottleneck, ACS Nano 3, 2441-2446.
4. Harper, S., Usenko, C., Hutchison, J. E., Maddux, B. L. S., and Tanguay, R. L. (2008) In vivo biodistribution and toxicity depends on nanomaterial composition, size, surface functionalisation and route of exposure, Journal of Experimental Nanoscience 3, 195 - 206.