Effect of media composition on bioavailability and toxicity of silver and silver nanoparticles in fish intestinal cells (RTgutGC).
To understand conditions affecting bioavailability and toxicity of citrate-coated silver nanoparticles (cit-AgNP) and dissolved silver at the luminal enterocyte interface, we exposed rainbow trout (Oncorhynchus mykiss) gut cells (RTgutGC) in media of contrasting composition: two amino acid-containing media, one of which was supplemented with proteins, as can be expected during digestion; and two protein and amino acid-free media contrasting low and high chloride content, as can be expected in the lumen of fish adapting to freshwater or seawater, respectively. Dose-response curves were generated measuring cell metabolic activity, membrane and lysosome integrity over a period of 72 hours. Then, nontoxic doses were applied and total silver accumulation, metallothionein and glutathione reductase mRNA levels were determined. The presence of proteins stabilized cit-AgNP keeping them in suspension. Conversely, in protein-free media, cit-AgNP agglomerated and settled, resulting in higher cellular accumulation of silver and toxicity. Chloride concentrations in exposure media modulated the toxicity of AgNO3but not of cit-AgNP. Moreover, while amino acid-containing media are protective against AgNO3, likely due to the formation of thiolate complexes, they are only partially protective against cit-AgNP. Viability assays indicated that lysosomes are targets of cit-AgNP, supporting the hypothesis that cit-AgNP exert toxicity intracellularly. Metallothionein, a sensor of metal bioavailability, was induced by cit-AgNP in high chloride medium but not in low chloride medium, indicating that chloride might have a role in mobilizing silver from intercellular vesicles. Overall, this study shows that AgNP bioavailability and toxicity in the intestine is linked to its luminal content.
a Eawag, Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland.|b Department of Integrative Biology , Oklahoma State University , Stillwater , OK , USA.
Matteo
M
Minghetti
a Eawag, Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland.|c School of Architecture, Civil and Environmental Engineering, EPF Lausanne , Switzerland , and.|d Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich , Switzerland.
Kristin
K
Schirmer
D000818:Animals; D001682:Biological Availability; D018929:Cell Culture Techniques; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002712:Chlorides / Q000737:chemistry; D016895:Culture Media, Serum-Free / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D005980:Glutathione Reductase / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000187:drug effects*; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D008668:Metallothionein / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012834:Silver / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
D002712:Chlorides; D016895:Culture Media, Serum-Free; D012834:Silver; D008668:Metallothionein; D005980:Glutathione Reductase
Lysosome integrity; high and low chloride; metallothinein; rainbow trout