Relaxivity enhancement of aquated Tris(β-diketonate)gadolinium(III) chelates by confinement within ultrashort single-walled carbon nanotubes.
Ultrashort single-walled carbon nanotubes loaded with gadolinium ions (gadonanotubes) have been previously shown to exhibit extremely high T1 -weighted relaxivities (>100 mm(-1) s(-1) ). To further examine the effect of nanoconfinement on the relaxivity of gadolinium-based contrast agents for magnetic resonance imaging, a series of ultrashort single-walled carbon nanotube (US-tube) materials internally loaded with gadolinium chelates have been prepared and studied. US-tubes were loaded with Gd(acac)3  · 2H2 O, Gd(hfac)3  · 2H2 O, and Gd(thd)3 (acac = acetylacetone, hfac = hexafluoroacetylacetone, thd = tetramethylheptanedione). The longitudinal relaxivities of the prepared materials determined at 25°C in a 1.5 T field were 103 mm(-1) s(-1) for Gd(acac)3  · 2H2 O@US-tubes, 105 mm(-1) s(-1) for Gd(hfac)3  · 2H2 O@US-tubes and 26 mm(-1) s(-1) for Gd(thd)3 @US-tubes. Compared with the relaxivities obtained for the unloaded chelates (<10 mm(-1) s(-1) ) as well as accounting for the T1 reduction observed for the empty US-tubes, the boost in relaxivity for chelate-loaded US-tubes is attributed to confinement within the nanotube and depends on the number of coordinated water molecules.
Department of Chemistry, Richard E. Smalley Center for Nanoscale Science and Technology, MS-60, Rice University, PO Box 1892, Houston, TX, 77251-1892, USA.
Justin J
JJ
Law
Adem
A
Guven
Lon J
LJ
Wilson
D002614:Chelating Agents / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D046529:Microscopy, Electron, Transmission; D064847:Multimodal Imaging; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000648:ultrastructure; D014867:Water / Q000737:chemistry
D002614:Chelating Agents; D003287:Contrast Media; D037742:Nanotubes, Carbon; D014867:Water; D005682:Gadolinium
MRI; carbon nanotube; contrast agent; gadolinium; relaxivity