Rapid Screening of Aquatic Toxicity of Several Metal-Based Nanoparticles Using the Metplate™ Bioassay

Creator(s)

Lok R. Pokhrel, East Tennessee State University
Thilini Silva, East Tennessee State University
Brajesh Dubey, University of Guelph
Amro M. El Badawy, University of Cincinnati
Thabet M. Tolaymat, National Risk Management Lab
Phillip R. Scheuerman, East Tennessee State UniversityFollow

Document Type

Article

Publication Date

6-1-2012

Description

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 nTiO₂ 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 TiO₂ 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: CdCl₂ > AgNO₃ > PVP-nAg > unclean Citrate-nAg > clean Citrate-nAg > ZnSO₄ > nZnO > CdSe QDs > nTiO₂/TiO₂. 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.

Citation Information

Pokhrel, Lok R.; Silva, Thilini; Dubey, Brajesh; El Badawy, Amro M.; Tolaymat, Thabet M.; and Scheuerman, Phillip R.. 2012. Rapid Screening of Aquatic Toxicity of Several Metal-Based Nanoparticles Using the Metplate™ Bioassay. Science of The Total Environment. Vol.426(1). 414-422. https://doi.org/10.1016/j.scitotenv.2012.03.049 ISSN: 0048-9697