title: Magnetic targeting of nanometric magnetic fluid loaded liposomes to specific brain intravascular areas: a dynamic imaging study in mice.
abstract: OBJECTIVE
  To prospectively determine, by using dynamic imaging, whether a magnet placed over a specific area of the mouse brain could target systemically administered rhodamine-labeled magnetic fluid-loaded liposomes (MFLs) to that brain region.
  
  
  METHODS
  Experiments were performed with a French Ministry of Agriculture permit and regional ethics committee authorization. In seven anesthetized C57BL/6 mice, a closed cranial window was implanted above the left parieto-occipital cortex. A laser-scanning confocal fluorescence microscope (LSCFM) was used to track the intravenously injected rhodamine-labeled MFLs within this cortical area, through the cranial window. The MFLs were video monitored for 2 minutes every 15 minutes for 1 hour after injection. A magnet was placed on the cranial window implanted in four mice, while no magnet was placed in three (control) mice. After dynamic in vivo imaging, static in vivo imaging was performed with a different LSCFM. Ex vivo fluorescence histologic analysis was then performed. Paired Student t testing was used to compare the cerebral blood flow and two-dimensional flow values before and 1 hour after MFL injection. For image analysis, intergroup comparisons were performed by using an independent t test.
  
  
  RESULTS
  In vivo video monitoring through the window revealed that the rhodamine-labeled MFLs accumulated in the mouse brain microvasculature exposed to the magnet-first within superficial brain venules and then within intracerebral venules-with no significant change in blood flow (P > .05). MFLs accumulated neither in the arterioles of the mice with a magnet nor in the arterioles of the control mice. Static in vivo imaging findings confirmed the microvascular localization of the rhodamine-labeled MFLs, and histologic findings specified their accumulation on the side of the magnet only.
  
  
  CONCLUSIONS
  Real-time in vivo imaging of rhodamine-labeled MFLs in the mouse brain cortex revealed that these nanosystems can be magnetically targeted, through microvessels, to selected brain areas.
authors.affiliation: Laboratoire Matière et Systèmes Complexes, CNRS UMR 7057, Université Paris 7-Denis Diderot, 140, rue de Lourmel, 75015 Paris, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Rivière
authors.forename: Marie-Sophie
authors.initials: MS
authors.lastname: Martina
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tomita
authors.forename: Claire
authors.initials: C
authors.lastname: Wilhelm
authors.forename: Alexy
authors.initials: A
authors.lastname: Tran Dinh
authors.forename: Christine
authors.initials: C
authors.lastname: Ménager
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Pinard
authors.forename: Sylviane
authors.initials: S
authors.lastname: Lesieur
authors.forename: Florence
authors.initials: F
authors.lastname: Gazeau
authors.forename: Jacques
authors.initials: J
authors.lastname: Seylaz
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008081:Liposomes; D008280:Magnetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D053758:Nanoparticles; D011446:Prospective Studies; D011897:Random Allocation; D012235:Rhodamines / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D005456:Fluorescent Dyes; D008081:Liposomes; D012235:Rhodamines