The increased use and incorporation of engineered nanoparticles (ENPs) in consumer products requires a robust assessment of their potential environmental implications. However, a lack of standardized methods for nanotoxicity testing has yielded an array of contradictory results that most likely stem from improper ENP characterization and use of assay methods not designed for ENPs. These assays may work appropriately for some ENPs with minimal modifications but cause artefactual results for others. Therefore, understanding the robustness of assay methods for a range of ENPs is critical. In this study, we tested a variety of ENPs including silicon (Si), polystyrene (PS), and gold (Au) with different charged coatings in a standard Caenorhabditis elegans toxicity assay and two additional assays to examine the robustness of these assays with a range of ENPs. Of all of the ENPs tested, only those with a positively charged coating had any toxic effect on growth of C. elegans using the standard toxicity assay. Most of the positively charged ENPs bind and agglomerate Escherichia coli cells, impacting the ability of nematodes to feed, and leading to a false positive toxic effect on C. elegans growth and reproduction. We then tested these ENPs in two additional assays to further investigate their potential ecotoxicity and found greatly reduced toxicity of ENPs at the concentrations tested. These results indicate the need for testing the robustness of standardized toxicity methods for use with ENPs and evaluating ENP specific artifacts that can be induced in an organism toxicity assay before test results are interpreted and used for risk assessment decision making.

Agglomeration of Escherichia coli with positively charged nanoparticles can lead to artifacts in a standard Caenorhabditis elegans toxicity assay

253rd National Meeting (2017)

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