title: Influence of polyethyleneimine graftings of multi-walled carbon nanotubes on their accumulation and elimination by and toxicity to Daphnia magna.
abstract: Modifications of carbon nanotubes (CNTs) for different applications may change their physicochemical properties such as surface charge. Assessments of the extent to which such modifications influence CNT ecotoxicity, accumulation, and elimination behaviors are needed to understand potential environmental risks these variously modified nanoparticles may pose. We have modified carbon-14 labeled multi-walled carbon nanotubes (MWNTs) with polyethyleneimine (PEI) surface coatings to increase their aqueous stability and to give them positive, negative, or neutral surface charges. Uptake and elimination behaviors of Daphnia magna exposed to PEI-coated and acid-modified MWNTs at concentrations of approximately 25 and 250 μg/L were quantified. PEI surface coatings did not appear to substantially impact nanotube accumulation or elimination rates. Although the PEI-modified nanotubes exhibited enhanced stability in aqueous solutions, they appeared to aggregate in the guts of D. magna in a manner similar to acid-treated nanotubes. The MWNTs were almost entirely eliminated by Daphnia fed algae during a 48 h elimination experiment, whereas elimination without feeding was typically minimal. Finally, PEI coatings increased MWNT toxicities, though this trend corresponded to the size of the PEI coatings, not their surface charges.
authors.affiliation: Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States. Elijah.Petersen@nist.gov
authors.forename: Elijah J
authors.initials: EJ
authors.lastname: Petersen
authors.forename: Roger A
authors.initials: RA
authors.lastname: Pinto
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Mai
authors.forename: Peter F
authors.initials: PF
authors.lastname: Landrum
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Weber
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008954:Models, Biological; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000633:toxicity; D011094:Polyethyleneimine / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity
chemical_list: D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; D011094:Polyethyleneimine