title: Quantification and visualization of cellular uptake of TiO2 and Ag nanoparticles: comparison of different ICP-MS techniques.
abstract: BACKGROUND
  Safety assessment of nanoparticles (NPs) requires techniques that are suitable to quantify tissue and cellular uptake of NPs. The most commonly applied techniques for this purpose are based on inductively coupled plasma mass spectrometry (ICP-MS). Here we apply and compare three different ICP-MS methods to investigate the cellular uptake of TiO2 (diameter 7 or 20 nm, respectively) and Ag (diameter 50 or 75 nm, respectively) NPs into differentiated mouse neuroblastoma cells (Neuro-2a cells). Cells were incubated with different amounts of the NPs. Thereafter they were either directly analyzed by laser ablation ICP-MS (LA-ICP-MS) or were lysed and lysates were analyzed by ICP-MS and by single particle ICP-MS (SP-ICP-MS).
  
  
  RESULTS
  All techniques confirmed that smaller particles were taken up to a higher extent when values were converted in an NP number-based dose metric. In contrast to ICP-MS and LA-ICP-MS, this measure is already directly provided through SP-ICP-MS. Analysis of NP size distribution in cell lysates by SP-ICP-MS indicates the formation of NP agglomerates inside cells. LA-ICP-MS imaging shows that some of the 75 nm Ag NPs seemed to be adsorbed onto the cell membranes and were not penetrating into the cells, while most of the 50 nm Ag NPs were internalized. LA-ICP-MS confirms high cell-to-cell variability for NP uptake.
  
  
  CONCLUSIONS
  Based on our data we propose to combine different ICP-MS techniques in order to reliably determine the average NP mass and number concentrations, NP sizes and size distribution patterns as well as cell-to-cell variations in NP uptake and intracellular localization.
authors.affiliation: Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589, Berlin, Germany.|Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: I-Lun
authors.initials: IL
authors.lastname: Hsiao
authors.affiliation: Division of Inorganic Trace Analysis, German Federal Institute for Materials Research and Testing (BAM), Berlin, Germany.
authors.forename: Frank S
authors.initials: FS
authors.lastname: Bierkandt
authors.affiliation: Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589, Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Reichardt
authors.affiliation: Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589, Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Luch
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yuh-Jeen
authors.initials: YJ
authors.lastname: Huang
authors.affiliation: Division of Inorganic Trace Analysis, German Federal Institute for Materials Research and Testing (BAM), Berlin, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Jakubowski
authors.affiliation: Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589, Berlin, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Tentschert
authors.affiliation: Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589, Berlin, Germany. andrea.haase@bfr.bund.de.
authors.forename: Andrea
authors.identifier: http://orcid.org/0000-0002-5288-7876
authors.initials: A
authors.lastname: Haase
mesh_terms: D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D053758:Nanoparticles / Q000032:analysis* / Q000633:toxicity / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012834:Silver / Q000032:analysis / Q000493:pharmacokinetics* / Q000633:toxicity; D014025:Titanium / Q000032:analysis / Q000493:pharmacokinetics* / Q000633:toxicity
chemical_list: C009495:titanium dioxide; D012834:Silver; D014025:Titanium
keywords: Cellular internalization; Laser ablation ICP-MS; Nanoparticles; Neurons; Single particle ICP-MS