title: Rapid screening of aquatic toxicity of several metal-based nanoparticles using the MetPLATE™ bioassay.
abstract: Current understanding of potential toxicity of engineered nanomaterials to aquatic microorganisms is limited for risk assessment and management. Here we evaluate if the MetPLATE™ test can be used as an effective and rapid screening tool to test for potential aquatic toxicity of various metal-based nanoparticles (NPs). The MetPLATE bioassay is a heavy metal sensitive test based on β-galactosidase activity in Escherichia coli. Five different types of metal-based NPs were screened for toxicity: (1) citrate coated nAg (Citrate-nanosilver), (2) polyvinylpyrrolidone coated nAg (PVP-nAg), (3) uncoated nZnO, (4) uncoated nTiO(2) and (5) 1-Octadecylamine coated CdSe Quantum Dots (CdSe QDs); and compared with their corresponding ionic salt toxicity. Citrate-nAg was further fractionated into clean Citrate-nAg, unclean Citrate-nAg and permeate using a tangential flow filtration (TFF) system to eliminate residual ions and impurities from the stock Citrate-nAg suspension and also to differentiate between ionic- versus nano-specific toxicity. Our results showed that nAg, nZnO and CdSe QDs were less toxic than their corresponding ionic salts tested, while nano- or ionic form of TiO(2) was not toxic as high as 2.5 g L(-1) to the MetPLATE™ bacteria. Although coating-dependent toxicity was noticeable between two types of Ag NPs evaluated, particle size and surface charge were not adequate to explain the observed toxicity; hence, the toxicity appeared to be material-specific. Overall, the toxicity followed the trend: CdCl(2)>AgNO(3)>PVP-nAg>unclean Citrate-nAg>clean Citrate-nAg>ZnSO(4)>nZnO>CdSe QDs>nTiO(2)/TiO(2). These results indicate that an evaluation of β-galactosidase inhibition in MetPLATE™ E. coli can be an important consideration for rapid screening of metal-based NP toxicity, and should facilitate ecological risk assessment of these emerging contaminants.
authors.affiliation: Department of Environmental Health, College of Public Health, East Tennessee State University, Johnson City, TN 37614, USA.
authors.forename: Lok R
authors.initials: LR
authors.lastname: Pokhrel
authors.forename: Thilini
authors.initials: T
authors.lastname: Silva
authors.forename: Brajesh
authors.initials: B
authors.lastname: Dubey
authors.forename: Amro M
authors.initials: AM
authors.lastname: El Badawy
authors.forename: Thabet M
authors.initials: TM
authors.lastname: Tolaymat
authors.forename: Phillip R
authors.initials: PR
authors.lastname: Scheuerman
mesh_terms: D001681:Biological Assay; D004784:Environmental Monitoring / Q000379:methods; D004926:Escherichia coli; D053768:Metal Nanoparticles / Q000633:toxicity*; D018570:Risk Assessment; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D014874:Water Pollutants, Chemical; D001616:beta-Galactosidase