TY - JOUR
T1 - Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes
AU - Liu, Xinyuan
AU - Guo, Lin
AU - Morris, Daniel
AU - Kane, Agnes B.
AU - Hurt, Robert H.
N1 - Funding Information:
Financial support was provided by the NIEHS Superfund Basic Research Program P42 ES013660, EPA STAR Grant RD-83171901-0, NIEHS R01 ES016178, and NSF Nanoscale Interdisciplinary Research Team (NIRT) grant DMI0506661. Although this research was funded in part by the EPA and NIEHS, it does not necessarily reflect the views of either agency. The technical contributions of David Murray, Joseph Orchardo, William Turnbull, Charles Vaslet, Anthony McCormick and Indrek Kulaots at Brown University are gratefully acknowledged.
PY - 2008/3
Y1 - 2008/3
N2 - There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.
AB - There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.
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U2 - 10.1016/j.carbon.2007.12.018
DO - 10.1016/j.carbon.2007.12.018
M3 - Article
AN - SCOPUS:40649124725
SN - 0008-6223
VL - 46
SP - 489
EP - 500
JO - Carbon
JF - Carbon
IS - 3
ER -
