title: Size of submicrometric and nanometric particles affect cellular uptake and biological activity of macrophages in vitro.
abstract: BACKGROUND
  Micrometric and nanometric particles are increasingly used in different fields and may exhibit variable toxicity levels depending on their physicochemical characteristics. The aim of this study was to determine the impact of the size parameter on cellular uptake and biological activity, working with well-characterized fluorescent particles. We focused our attention on macrophages, the main target cells of the respiratory system responsible for the phagocytosis of the particles.
  
  
  METHODS
  FITC fluorescent silica particles of variable submicronic sizes (850, 500, 250 and 150 nm) but with similar surface coating (COOH) were tailored and physico-chemically characterized. These particles were then incubated with the RAW 264.7 macrophage cell line. After microscopic observations (SEM, TEM, confocal), a quantitative evaluation of the uptake was carried out. Fluorescence detected after a quenching with trypan blue allows us to distinguish and quantify entirely engulfed fluorescent particles from those just adhering to the cell membrane. Finally, these data were compared to the in vitro toxicity assessed in terms of cell damage, inflammation and oxidative stress (evaluated by LDH release, TNF-α and ROS production respectively).
  
  
  CONCLUSIONS
  Particles were well characterized (fluorescence, size distribution, zeta potential, agglomeration and surface groups) and easily visualized after cellular uptake using confocal and electron microscopy. The number of internalized particles was precisely evaluated. Size was found to be an important parameter regarding particles uptake and in vitro toxicity but this latter strongly depends on the particles doses employed.
authors.affiliation: LINA, Laboratoire Interdisciplinaire d'étude des Nanoparticules Aérosolisées, EA 4624, Saint-Etienne, France. leclerc@emse.fr
authors.forename: L
authors.initials: L
authors.lastname: Leclerc
authors.forename: W
authors.initials: W
authors.lastname: Rima
authors.forename: D
authors.initials: D
authors.lastname: Boudard
authors.forename: J
authors.initials: J
authors.lastname: Pourchez
authors.forename: V
authors.initials: V
authors.lastname: Forest
authors.forename: V
authors.initials: V
authors.lastname: Bin
authors.forename: P
authors.initials: P
authors.lastname: Mowat
authors.forename: P
authors.initials: P
authors.lastname: Perriat
authors.forename: O
authors.initials: O
authors.lastname: Tillement
authors.forename: P
authors.initials: P
authors.lastname: Grosseau
authors.forename: D
authors.initials: D
authors.lastname: Bernache-Assollant
authors.forename: M
authors.initials: M
authors.lastname: Cottier
mesh_terms: D000818:Animals; D002460:Cell Line; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry / Q000378:metabolism; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D012822:Silicon Dioxide; D007770:L-Lactate Dehydrogenase; D016650:Fluorescein-5-isothiocyanate