The Environmental Protection Agency (EPA) recently classified carbon nanotubes (CNTs) as a new chemical substance. Consequently, CNTs are now subject to regulatory controls that require inventory control, quantification of CNT amounts, and possibly toxicity tests. However, rapidly and inexpensively quantifying the CNTs in commercially available material and assessing potential toxicity under standard conditions, are technically challenging tasks. The research proposed here exploits a rapid method for quantifying nanogram amounts of CNTs and standard protocol for assessing possible CNT toxicity. These methods will be used to develop a database correlating properties and toxicity of commercially available CNT types that will validate the wide-spread applicability of a rapid approach to quantifying CNT amounts and toxicity. Once developed, the database will facilitate launching a service business to quantify CNT amounts and toxicity for CNT manufacturers, importers, consumers, and health &safety personnel. We have developed a method that uses sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS- PAGE) for quantifying small amounts of CNTs in liquid samples. Once the weight % of CNTs in a sample is known, and a standard curve has been prepared, the method provides a label-free and inexpensive way to quantify nanogram amounts of CNTs. There are conflicting reports in the literature on the toxicity of CNTs. There are three main reasons for the poor agreement. First, many CNT preparations are contaminated with toxic metals that are catalysts used in making CNTs, such as iron, and these contaminants were not removed in many CNT toxicity studies. Second, toxicity may depend on the form of the CNTs and can vary with different types of covalent or non-covalent functionalization of the CNTs. Third, a wide variety of assays have been used to assess toxicity, including some where CNTs are now known to interfere with the assay by binding to fluorescent organic compounds that are reporters of toxicity. We have developed standard protocols to address each of these three issues. When the tasks in phase I are completed, a phase II proposal will focus on translating the technology to a service business for quantifying and measuring the toxicity of CNTs. We believe this will be a valuable service to CNT manufacturers, importers, sellers, consumers, and the health &safety medical community as the regulatory demands on CNTs continue to develop.
The use of nanomaterials is becoming more widespread. In particular, carbon nanotubes are enabling novel applications from drug delivery to implantable devices to biosensors. As the production and use of such materials grows, it will be imperative that thorough standardized characterization and evaluation of potential toxicity be established.
|Wang, Ruhung; Mikoryak, Carole; Li, Synyoung et al. (2011) Cytotoxicity screening of single-walled carbon nanotubes: detection and removal of cytotoxic contaminants from carboxylated carbon nanotubes. Mol Pharm 8:1351-61|