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Assessing the Implications of Modified Nanomaterials in Bioassay Testing
Citation:
KENNEDY, A. J., S. A. DIAMOND, J. GOSS, J. STEVENS, J. GUNTER, AND M. HULL. Assessing the Implications of Modified Nanomaterials in Bioassay Testing. Presented at SETAC Annual Meeting, Tampa, FL, November 16 - 20, 2008.
Impact/Purpose:
Nanotechnology is an emerging field that will produce hundreds of new and novel substances that will require regulatory toxicity testing. The international scientific community is focused on determining how such testing will be conducted. This report will describe some of the issues associated with how nanomaterials are prepared for toxicity assays, and contributes to our understanding of nanomaterials toxicity in general.
Description:
As nanotechnology advances to product development, filling environmental health and safety knowledge gaps is critical. Nanotoxicology is over-generalized, provided the permutations of nanomaterial variants created by the classes of nanomaterials (carbonaceous, metals, quantum dots) in combination with morphological (spheres, threads) and surface chemistry (functional groups, coatings, surfactants) alterations. These differences will likely influence material toxicology. Surface modifications may be induced intentionally or incidentally and can enhance or counteract van der Waals attractions (electrostatic or steric stabilization); this knowledge is applied by researchers for applications requiring stabile colloids. Preparation methods to spike nanoparticles into environmental media may create toxicological artifacts. In this study, fullerenes (C60) and multi-walled nanotubes (MWNT) were prepared by different methods. Fullerenes were stirred for three months and allowed to settle for 24-h. This aggregate suspension was tested as (1) stirred-only (~600 nm effective diameter (ED), (2) after probe sonication (~600 nm ED) and (3) after probe sonication in natural organic matter (NOM) (~300 nm ED). Concentration decreased from 60 mg/L in all preparations but was most pronounced in the stirred, followed by sonicated C60 and C60 in NOM after 48-h (2, 4 and 14 mg/L respectively). Toxicity to Ceriodaphnia dubia was similar for the stirred and sonicated aggregates (LC50 = 15 (12 - 19) and 8 (4 16) mg/L, respectively), but lower for the smaller NOM stabilized aggregates (80% survival). Preparations of MWNTs included consideration to chemicals (e.g., acids, solvents) used for functionalization and differing dispersion (stirring, sonication in presence of NOM). In water exposures, 96-h C. dubia survival was higher in the sonicated relative to the stirred MWNTs but the greatest toxicity was observed for MWNTs functionalized by octylamine (0% survival). Sediment exposures of amphipods suggest sonication may increase toxicity. These results clarify the need for standardized preparation methods for bioassays. This abstract does not necessarily reflect USEPA policy.