title: Cytotoxic effects of nanosilver are highly dependent on the chloride concentration and the presence of organic compounds in the cell culture media.
abstract: BACKGROUND
  Nanosilver shows great promise for use in industrial, consumer or medical products because of its antimicrobial properties. However, the underlying mechanisms of the effects of silver nanoparticles on human cells are still controversial. Therefore, in the present study the influence of the chloride concentration and different serum content of culture media on the cytotoxic effects of nanosilver was systematically evaluated.
  
  
  RESULTS
  Our results show that nanosilver toxicity was strongly affected by the composition of the culture media. The chloride concentration, as well as the carbon content affected the silver agglomeration and the complex formation. But also the dissolution of nanosilver and the availability of free silver ions (Ag+) were severely affected by the compositions of the culture media. Cells, only exposed to silver particles in suspension and dissolved silver complexes, did not show any effects under all conditions. Nanosilver agglomerates and silver complexes were not very soluble. Thus, cells growing on the bottom of the culture dishes were exposed to sedimented nanosilver agglomerates and precipitated silver complexes. Locally, the concentration of silver on the cell surface was very high, much higher compared the silver concentration in the bulk solution. The cytotoxic effects of nanosilver are therefore a combination of precipitated silver complexes and organic silver compounds rather than free silver ions.
  
  
  CONCLUSIONS
  Silver coatings are used in health care products due to their bacteriostatic or antibacterial properties. The assessment of the toxicity of a certain compound is mostly done using in vitro assays. Therefore, cytotoxicity studies of nanosilver using human cell cultures have to be undertaken under well controlled and understood cultivations conditions in order to improve the compatibility of different studies. Especially when eukaryotic versus prokaryotic systems are compared for the evaluation of the use of nanosilver as antibacterial coatings for implants in order to prevent bacterial colonization.
authors.affiliation: Particles-Biology Interactions Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland. jean-pierre.kaiser@empa.ch.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Kaiser
authors.affiliation: Particles-Biology Interactions Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Roesslein
authors.affiliation: Particles-Biology Interactions Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Liliane
authors.initials: L
authors.lastname: Diener
authors.affiliation: Particles-Biology Interactions Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Adrian
authors.initials: A
authors.lastname: Wichser
authors.affiliation: Technology and Society Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Bernd
authors.initials: B
authors.lastname: Nowack
authors.affiliation: Particles-Biology Interactions Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Wick
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity; D018938:Caco-2 Cells; D018929:Cell Culture Techniques; D002470:Cell Survival; D002712:Chlorides / Q000737:chemistry*; D003470:Culture Media / Q000737:chemistry*; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D053768:Metal Nanoparticles / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000633:toxicity*; D018675:Toxicity Tests
chemical_list: D000900:Anti-Bacterial Agents; D002712:Chlorides; D003470:Culture Media; D016207:Cytokines; D017382:Reactive Oxygen Species; D012834:Silver
keywords: CaCo-2 cells; Chloride concentration; Culture conditions; Cytotoxicity; Nanosilver; Protein content