Relaxivity enhancement of aquated Tris(β-diketonate)gadolinium(III) chelates by confinement within ultrashort single-walled carbon nanotubes

• Published in: Contrast media and molecular imaging Vol. 9; no. 6; p. 409
• Main Authors: Law, Justin J, Guven, Adem, Wilson, Lon J
• Format: Journal Article
• Language: English
• Published: England 01.11.2014
• Subjects: Chelating Agents - chemistry; Contrast Media - chemistry; Gadolinium - chemistry; Humans; Magnetic Resonance Imaging - methods; Microscopy, Electron, Transmission; Multimodal Imaging; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Water - chemistry; carbon nanotube; relaxivity; MRI; contrast agent; gadolinium
• ISSN: 1555-4317
• DOI: 10.1002/cmmi.1603

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.