title: Internalization of paramagnetic phosphatidylserine-containing liposomes by macrophages.
abstract: BACKGROUND
  Inflammation plays an important role in many pathologies, including cardiovascular diseases, neurological conditions and oncology, and is considered an important predictor for disease progression and outcome. In vivo imaging of inflammatory cells will improve diagnosis and provide a read-out for therapy efficacy. Paramagnetic phosphatidylserine (PS)-containing liposomes were developed for magnetic resonance imaging (MRI) and confocal microscopy imaging of macrophages. These nanoparticles also provide a platform to combine imaging with targeted drug delivery.
  
  
  RESULTS
  Incorporation of PS into liposomes did not affect liposomal size and morphology up to 12 mol% of PS. Liposomes containing 6 mol% of PS showed the highest uptake by murine macrophages, while only minor uptake was observed in endothelial cells. Uptake of liposomes containing 6 mol% of PS was dependent on the presence of Ca2+ and Mg2+. Furthermore, these 6 mol% PS-containing liposomes were mainly internalized into macrophages, whereas liposomes without PS only bound to the macrophage cell membrane.
  
  
  CONCLUSIONS
  Paramagnetic liposomes containing 6 mol% of PS for MR imaging of macrophages have been developed. In vitro these liposomes showed specific internalization by macrophages. Therefore, these liposomes might be suitable for in vivo visualization of macrophage content and for (visualization of) targeted drug delivery to inflammatory cells.
authors.affiliation: Department of Biomedical Engineering, Biomedical NMR, Eindhoven University of Technology, PO Box 513, Eindhoven, MB, 5600, the Netherlands.
authors.forename: Tessa
authors.initials: T
authors.lastname: Geelen
authors.forename: Sin Yuin
authors.initials: SY
authors.lastname: Yeo
authors.forename: Leonie E M
authors.initials: LE
authors.lastname: Paulis
authors.forename: Lucas W E
authors.initials: LW
authors.lastname: Starmans
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000493:pharmacokinetics*; D008264:Macrophages / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D051379:Mice; D018613:Microscopy, Confocal; D010587:Phagocytosis; D010718:Phosphatidylserines / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D002412:Cations; D008081:Liposomes; D010718:Phosphatidylserines