title: The oxidative potential of differently charged silver and gold nanoparticles on three human lung epithelial cell types.
abstract: BACKGROUND
  Nanoparticle (NPs) functionalization has been shown to affect their cellular toxicity. To study this, differently functionalized silver (Ag) and gold (Au) NPs were synthesised, characterised and tested using lung epithelial cell systems.
  
  
  METHODS
  Monodispersed Ag and Au NPs with a size range of 7 to 10 nm were coated with either sodium citrate or chitosan resulting in surface charges from -50 mV to +70 mV. NP-induced cytotoxicity and oxidative stress were determined using A549 cells, BEAS-2B cells and primary lung epithelial cells (NHBE cells). TEER measurements and immunofluorescence staining of tight junctions were performed to test the growth characteristics of the cells. Cytotoxicity was measured by means of the CellTiter-Blue ® and the lactate dehydrogenase assay and cellular and cell-free reactive oxygen species (ROS) production was measured using the DCFH-DA assay.
  
  
  RESULTS
  Different growth characteristics were shown in the three cell types used. A549 cells grew into a confluent mono-layer, BEAS-2B cells grew into a multilayer and NHBE cells did not form a confluent layer. A549 cells were least susceptible towards NPs, irrespective of the NP functionalization. Cytotoxicity in BEAS-2B cells increased when exposed to high positive charged (+65-75 mV) Au NPs. The greatest cytotoxicity was observed in NHBE cells, where both Ag and Au NPs with a charge above +40 mV induced cytotoxicity. ROS production was most prominent in A549 cells where Au NPs (+65-75 mV) induced the highest amount of ROS. In addition, cell-free ROS measurements showed a significant increase in ROS production with an increase in chitosan coating.
  
  
  CONCLUSIONS
  Chitosan functionalization of NPs, with resultant high surface charges plays an important role in NP-toxicity. Au NPs, which have been shown to be inert and often non-cytotoxic, can become toxic upon coating with certain charged molecules. Notably, these effects are dependent on the core material of the particle, the cell type used for testing and the growth characteristics of these cell culture model systems.
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. Paul.Schlinkert@sbg.ac.at.
authors.forename: Paul
authors.initials: P
authors.lastname: Schlinkert
authors.affiliation: Institute Catalá de Nanotecnologia, Barcelona, Spain. Eudald.casals@icn.cat.
authors.forename: Eudald
authors.initials: E
authors.lastname: Casals
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. Matthew.Boyles@sbg.ac.at.
authors.forename: Matthew
authors.initials: M
authors.lastname: Boyles
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. Ulrike.tischler@sbg.ac.at.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Tischler
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. Eva.hornig@med.uni-muenchen.de.
authors.forename: Eva
authors.initials: E
authors.lastname: Hornig
authors.affiliation: Institute Catalá de Nanotecnologia, Barcelona, Spain. Ngoc.tran@icn.cat.
authors.forename: Ngoc
authors.initials: N
authors.lastname: Tran
authors.affiliation: Institute for Work and Health, Lausanne, Switzerland. Jiayuan.Zhao@chuv.ch.
authors.forename: Jiayuan
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. Martin.Himly@sbg.ac.at.
authors.forename: Martin
authors.initials: M
authors.lastname: Himly
authors.affiliation: Institute for Work and Health, Lausanne, Switzerland. Michael.Riediker@hospvd.ch.|Institue for Occupational Medicine (IOM) Singapore, Downtown Core, Singapore. Michael.Riediker@hospvd.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Riediker
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. geja.oostingh@fh-salzburg.ac.at.|Biomedical Sciences, Salzburg University of Applied Sciences, Puch, Salzburg, Austria. geja.oostingh@fh-salzburg.ac.at.
authors.forename: Gertie Janneke
authors.initials: GJ
authors.lastname: Oostingh
authors.affiliation: Institute Catalá de Nanotecnologia, Barcelona, Spain. victor.puntes@icn.cat.
authors.forename: Victor
authors.initials: V
authors.lastname: Puntes
authors.affiliation: Department of Molecular Biology, Paris Lodron-University of Salzburg, Hellbrunnerstr. 34, A-5020, Salzburg, Austria. albert.duschl@sbg.ac.at.
authors.forename: Albert
authors.initials: A
authors.lastname: Duschl
mesh_terms: D001980:Bronchi / Q000166:cytology; D002460:Cell Line / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002474:Cell-Free System; D002478:Cells, Cultured; D048271:Chitosan / Q000737:chemistry; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006046:Gold / Q000494:pharmacology*; D006801:Humans; D008168:Lung / Q000166:cytology*; D053768:Metal Nanoparticles / Q000009:adverse effects / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D016877:Oxidants; D017382:Reactive Oxygen Species; D012834:Silver; D006046:Gold; D048271:Chitosan