The magnetic, relaxometric, and optical properties of gadolinium-catalyzed single walled carbon nanotubes

Abstract

We report the magnetic behavior, relaxometry, phantom magnetic resonance imaging (MRI), and near-infrared (NIR) photoluminescence spectroscopy of gadolinium (Gd) catalyzed single-walled carbon nanotubes (Gd-SWCNTs). Gd-SWCNTs are paramagnetic with an effective magnetic moment of 7.29 l B . Gd-SWCNT solutions show high r 1 and r 2 relaxivities at very low (0.01 MHz) to clinically relevant (61 MHz) magnetic fields (). Analysis of nuclear magnetic resonance dispersion profiles using Solomon, Bloembergen, and Morgan equations suggests that multiple structural and dynamic parameters such as rotational correlation time s R , rate of water exchange s M , and the number of fast-exchanging water molecules within the inner sphere q may be responsible for the increase in r 1 and r 2 relaxivity. The T 1 weighted MRI signal intensity (gradient echo sequence; repetition time (TR) ¼ 66 ms, echo time (TE) ¼ 3 ms, flop angle ¼ 108 ) of Gd-SWCNT phantom solution is 14 times greater than the Gd-based clinical MRI contrast agent Magnevist. Additionally, these nanotubes exhibit near infrared fluorescence with distinct E 11 transitions of several semiconducting SWCNTs. Taken together, these results demonstrate that Gd-SWCNTs have potential as a novel, highly efficacious, multimodal MRI-NIR optical imaging contrast agent. V C 2013 American Institute of Physics. [http://dx

Toward single‐walled carbon nanotube–gadolinium complex as advanced MRI contrast agents: Pharmacodynamics and global genomic response in small animals

“…Our synthesis method uses lanthanide nanoparticles (average size ∼1.8 nm) as catalysts to grow SWCNTs (hereafter referred as Gd‐SWCNTs; average diameter 2.05 nm, length 500 nm to 1.5 µm)17 with the lanthanide nanoparticles embedded into and located at one end of the SWCNT 18. The Gd‐SWCNTs are paramagnetic, and at clinically relevant 1.5 T magnetic field, show r 1 relaxivity (an important measure of efficacy) values of 126 mM −1 S −1 ; 25‐fold greater than the current, clinically used Gd 3+ ‐based CA Magnevist (4.5 mM −1 S −1 ) 19. Recent in vitro studies have also identified nontoxic dosages of water‐solubilized Gd‐SWCNTs that do not affect cellular anatomy or function 20.…”

“…We have recently synthesized, using a “bottom‐up” chemical approach, a novel Gd‐SWCNT complex that shows potential as a multimodal MR‐optical imaging nanoprobe 17–19. Our synthesis method uses lanthanide nanoparticles (average size ∼1.8 nm) as catalysts to grow SWCNTs (hereafter referred as Gd‐SWCNTs; average diameter 2.05 nm, length 500 nm to 1.5 µm)17 with the lanthanide nanoparticles embedded into and located at one end of the SWCNT 18.…”

Covalent Functionalization of Multi‐walled Carbon Nanotubes with a Gadolinium Chelate for Efficient T1‐Weighted Magnetic Resonance Imaging

“…In this regards both external coupling to or internal loading of CNTs with iron oxide nanoparticles may partially modify their fate in vivo, as the organism must degrade inorganic nanoparticles in addition to carbon materials, which are both slow processes. [ 22 ] Alternative strategies such as nanoscale confi nement of large quantities of Gd within ultra-short SWCNTs through sidewall defects or at the opened ends (so called gadonanotubes), [ 23 ] synthesis of SWCNT-Gd oxide complexes by use of Gd 2 O 3 catalytic nanoparticles [ 24 ] or non-covalent adsorption of Gd 3+ chelates onto MWCNT surface [ 25 ] have been shown to produce agents with very high r 1 relaxivity (relaxation enhancement per millimolar concentration of agent). However, noncovalent approaches have the disadvantages of saturating the loading capacity of CNTs or strongly reducing the possibility of further functionalization.…”

“…C) EDX spectrum confi rms the presence of Gd on CNTs internalized by liver Kupffer cells. 24 h. An aliquot of the suspension was centrifuged. The supernatant was titrated with xylenol orange to assess the amount of free Gd.…”

Functionalized carbon nanotube theranostic agents for microwave diagnostic imaging and thermal therapy of tumors

“…Many recent studies show that carbon nanotube (CNT) aqueous dispersions have promising applications in diagnostic imaging and thermal therapy due to their unique electromagnetic properties over a broad range of frequencies [4] - [9]. Particularly, at microwave frequencies, it has been shown that pristine CNT dispersions can enhance the dielectric properties of the host environment both in vitro [10], [11] and in vivo [12].…”