CEIN: Predictive Toxicology Assessment and Safe Implementation of Nanotechnology in the Environment

CEIN IRG 1 ENM-2 Abstract Mark C. Hersam, Northwestern University Processing and Characterization of Single-Walled and Multi-Walled Carbon Nanotubes Carbon nanotubes exhibit unique physical, chemical and electrical properties that make them an attractive material for use in industry, medical diagnostics, and drug delivery. However, enthusiasm for their use has been tempered by relevant concerns regarding their toxicity. The high ratio of length to diameter (aspect ratio) of single and multi-walled carbon nanotubes has led some investigators to compare these particles with asbestos fibers, which are also characterized by a large aspect ratio but with a much larger mean diameter. The failure of resident macrophages to clear and eliminate these needle-like structures has been suggested to activate pro-inflammatory pathways in these cells that induce lung fibrosis and increase the susceptibility to pulmonary malignancies. Van der Waals interactions between individual nanotubes in air or in aqueous solutions cause them to form large aggregates, which can be more than one hundred microns in diameter, and it is the administration of these aggregates that has been associated with lung toxicity in rodents. While accidental industrial exposure to these large aggregates is certainly relevant, effective dispersal of carbon nanotubes at the nanoscale is required for them to exhibit many of their desirable physical properties. In preliminary work [1], we found single-walled carbon nanotubes that were highly dispersed using the biocompatible block copolymer Pluronic F108NF yielded exceeding low levels of pulmonary toxicity. While these previous studies suggested methods for the safe handling and processing of carbon nanotubes, the precise biological mechanisms for their reduced toxicity when well dispersed with Pluronic block copolymers remains an open question. This project will systematically explore these mechanisms by performing a thorough exploration of the interaction between carbon nanotubes and biological systems as a function of several materials parameters including the level of dispersion, dispersant identity/concentration, and carbon nanotube structure (e.g., diameter, length, single-walled versus multi-walled, etc.). Specific carbon nanotube types include: