title: High relaxivities and strong vascular signal enhancement for NaGdF4 nanoparticles designed for dual MR/optical imaging.
abstract: Near-infrared (NIR)-to-NIR upconverting NaY(Gd)F4 :Tm(3+) ,Yb(3+) paramagnetic nanoparticles (NPs) are efficiently detected by NIR imaging techniques. As they contain Gd(3+) ions, they also provide efficient "positive" contrast in magnetic resonance imaging (MRI). Water-dispersible small (≈25 nm, "S-") and ultrasmall (<5 nm diam., "US-") NaY(Gd)F4 :Tm(3+) ,Yb(3+) NPs are synthesized by thermal decomposition and capped with citrate. The surface of citrate-coated US-NPs shows sodium depletion and high Gd elemental ratios, as confirmed by a comparative X-ray photoelectron spectroscopy (XPS)/neutron absorption analysis study. US-NaGd0.745 F4 :Tm0.005 ,Yb0.25 NPs have hydrodynamic diameters close to that measured by TEM, with the lowest relaxometric ratios (r2 /r1 = 1.18) reported for NaGdF4 nanoparticle suspensions (r1 = 3.37 mM(-1) s(-1) at 1.4 T and 37 °C). Strong relaxivity peaks in the range of 20 (0.47 T) - 300 MHz (7.05 T) are revealed in nuclear magnetic resonance dispersion profiles, with high r2 /r1 ratios at increasing field strengths for S-NPs. This indicates the superiority of US-NPs over S-NPs for achieving high positive contrast at clinical MRI field strengths. I.-v. injected citrate-coated US-NPs evidence long blood retention times (>90 min) in mice. Biodistribution studies (48 h, 8 d) show elimination through the reticuloendothelial and urinary systems, similarly to other citrate-capped US-NP systems. In summary, upconverting NaY(Gd)F4 :Tm(3+) ,Yb(3+) nanoparticles have promising luminescent, relaxometric and blood-retention properties for dual MRI/optical imaging.
authors.affiliation: Department of Chemistry and Biochemistry and Centre for NanoScience Research, Concordia University, Montréal, Québec, H4B 1R6, Canada.
authors.forename: Rafik
authors.initials: R
authors.lastname: Naccache
authors.forename: Pascale
authors.initials: P
authors.lastname: Chevallier
authors.forename: Jean
authors.initials: J
authors.lastname: Lagueux
authors.forename: Yves
authors.initials: Y
authors.lastname: Gossuin
authors.forename: Sophie
authors.initials: S
authors.lastname: Laurent
authors.forename: Luce
authors.initials: L
authors.lastname: Vander Elst
authors.forename: Cornelia
authors.initials: C
authors.lastname: Chilian
authors.forename: John A
authors.initials: JA
authors.lastname: Capobianco
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Fortin
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000473:pathology*; D003287:Contrast Media; D005459:Fluorides; D005682:Gadolinium; D008279:Magnetic Resonance Imaging; D051379:Mice; D053758:Nanoparticles / Q000648:ultrastructure; D061848:Optical Imaging; D056951:Photoelectron Spectroscopy; D012815:Signal Processing, Computer-Assisted; D013535:Suspensions; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D013535:Suspensions; D005682:Gadolinium; D005459:Fluorides
keywords: magnetic resonance imaging; neutron activation analysis; relaxometry of paramagnetic contrast agents; sodium gadolinium fluoride; upconverting nanoparticles