title: Different capacity of monocyte subsets to phagocytose iron-oxide nanoparticles.
abstract: OBJECTIVE
  To explore the capacity of human CD1⁺CD16⁺⁺ and CD14⁺⁺CD16⁻ monocytes to phagocyte iron-oxide nanoparticles in vitro.
  
  
  METHODS
  Human monocytes were labeled with four different magnetic nanoparticle preparations (Ferumoxides, SHU 555C, CLIO-680, MION-48) exhibiting distinct properties and cellular uptake was quantitatively assessed by flow cytometry, fluorescence microscopy, atomic absorption spectrometry and Magnetic Resonance Imaging (MRI). Additionally we determined whether cellular uptake of the nanoparticles resulted in phenotypic changes of cell surface markers.
  
  
  RESULTS
  Cellular uptake differed between the four nanoparticle preparations. However for each nanoparticle tested, CD14⁺⁺CD16⁻ monocytes displayed a significantly higher uptake compared to CD14⁺CD16⁺⁺ monocytes, this resulted in significantly lower T1 and T2 relaxation times of these cells. The uptake of iron-oxide nanoparticles further resulted in a remarkable shift of expression of cell surface proteins indicating that the labeling procedure affects the phenotype of CD14⁺CD16⁺⁺ and CD14⁺⁺CD16⁻ monocytes differently.
  
  
  CONCLUSIONS
  Human monocyte subsets internalize different magnetic nanoparticle preparations differently, resulting in variable loading capacities, imaging phenotypes and likely biological properties.
authors: Institut für Radiologie, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany.
authors: Marcus
authors: M
authors: Settles
authors: Martin
authors: M
authors: Etzrodt
authors: Katja
authors: K
authors: Kosanke
authors: Matthias
authors: M
authors: Schiemann
authors: Alexander
authors: A
authors: Zimmermann
authors: Reinhard
authors: R
authors: Meier
authors: Rickmer
authors: R
authors: Braren
authors: Armin
authors: A
authors: Huber
authors: Ernst J
authors: EJ
authors: Rummeny
authors: Ralph
authors: R
authors: Weissleder
authors: Filip K
authors: FK
authors: Swirski
authors: Moritz
authors: M
authors: Wildgruber
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D005290:Ferric Compounds / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008856:Microscopy, Fluorescence; D009000:Monocytes / Q000145:classification / Q000166:cytology* / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry*; D010587:Phagocytosis; D010641:Phenotype; D013054:Spectrophotometry, Atomic; D013194:Staining and Labeling
chemical_list: D015415:Biomarkers; D005290:Ferric Compounds; C000499:ferric oxide; D007501:Iron