Uptake routes and toxicokinetics of silver nanoparticles and silver ions in the earthworm Lumbricus rubellus.
Current bioavailability models, such as the free ion activity model and biotic ligand model, explicitly consider that metal exposure will be mainly to the dissolved metal in ionic form. With the rise of nanotechnology products and the increasing release of metal-based nanoparticles (NPs) to the environment, such models may increasingly be applied to support risk assessment. It is not immediately clear, however, whether the assumption of metal ion exposure will be relevant for NPs. Using an established approach of oral gluing, a toxicokinetics study was conducted to investigate the routes of silver nanoparticles (AgNPs) and Ag(+) ion uptake in the soil-dwelling earthworm Lumbricus rubellus. The results indicated that a significant part of the Ag uptake in the earthworms is through oral/gut uptake for both Ag(+) ions and NPs. Thus, sealing the mouth reduced Ag uptake by between 40% and 75%. An X-ray analysis of the internal distribution of Ag in transverse sections confirmed the presence of increased Ag concentrations in exposed earthworm tissues. For the AgNPs but not the Ag(+) ions, high concentrations were associated with the gut wall, liver-like chloragogenous tissue, and nephridia, which suggest a pathway for AgNP uptake, detoxification, and excretion via these organs. Overall, the results indicate that Ag in the ionic and NP forms is assimilated and internally distributed in earthworms and that this uptake occurs predominantly via the gut epithelium and less so via the body wall. The importance of oral exposure questions the application of current metal bioavailability models, which implicitly consider that the dominant route of exposure is via the soil solution, for bioavailability assessment and modeling of metal-based NPs.
Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire, United Kingdom.
Maria
M
Diez-Ortiz
Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire, United Kingdom.
Elma
E
Lahive
Cardiff School of Biosciences, University of Cardiff, Cardiff, Wales, United Kingdom.
Peter
P
Kille
Cardiff School of Biosciences, University of Cardiff, Cardiff, Wales, United Kingdom.
Kate
K
Powell
Cardiff School of Biosciences, University of Cardiff, Cardiff, Wales, United Kingdom.
A John
AJ
Morgan
Department of Materials, Oxford University, Yarnton, Oxfordshire, United Kingdom.
Kerstin
K
Jurkschat
Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands.
Cornelis A M
CA
Van Gestel
Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, United Kingdom.
J Fred W
JF
Mosselmans
Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire, United Kingdom.
Claus
C
Svendsen
Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire, United Kingdom.
David J
DJ
Spurgeon
D000818:Animals; D001682:Biological Availability; D007477:Ions / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D009835:Oligochaeta / Q000187:drug effects* / Q000378:metabolism; D018570:Risk Assessment; D012834:Silver / Q000032:analysis* / Q000378:metabolism; D012989:Soil Pollutants / Q000032:analysis / Q000493:pharmacokinetics* / Q000633:toxicity; D014018:Tissue Distribution; D056928:X-Ray Absorption Spectroscopy
D007477:Ions; D012989:Soil Pollutants; D012834:Silver
Exposure route; Nanoparticles; Silver; Uptake; X-ray absorption near-edge spectroscopy