Journal of Alloys and Compounds 408–412 (2006) 400–404
Study of rare earth encapsulated carbon nanomolecules
for biomedical uses
Li Qu
a
, Wenbin Cao
a
, Gengmei Xing
a
,
Jun Zhang
a
, Hui Yuan
a
, Jun Tang
a
,
Yue Cheng
a
, Bo Zhang
a
, Yuliang Zhao
a,∗
, Hao Lei
b,∗
a
Lab. for Bio-Environmental Health Sciences of Nanoscale Materials, Institute of High Energy Physics,
Chinese Academy of Sciences, Beijing 100039, China
b
State Key Lab. for Nuclear Magnetic Resonance and Atomic and Molecular Physics, Institute of Physics and Mathematics,
Chinese Academy of Sciences, Wuhan 430071, China
Received 30 July 2004; received in revised form 6 December 2004; accepted 6 December 2004
Available online 27 June 2005
Abstract
Gd@C
82
(OH)
40
has been proposed to be as a new generation of the magnetic resonance imaging (MRI) contrast agent, but water-soluble
fullerenols Gd@C
82
(OH)
n
with n > 36 can easily lead to open-caged structures of a high instability. This restricts the practical bio-uses of
Gd-metallofullerenols with a large number of hydroxyl groups. To explore how the imaging efficiency varies with decreasing hydroxyl number
in Gd@C
82
(OH)
n
of a good stability in vivo, Gd@C
82
(OH)
22
was prepared, characterized and its imaging efficiency in mice was studied.
This work aims at searching a chemical form of water-soluble Gd-metallofullerenols that satisfy both requirements of the good stability and
high imaging efficiency in vivo. The results indicate that the proton relaxivity of Gd@C
82
(OH)
22
is lower than that of Gd@C
82
(OH)
40
, but
still higher than the commercial Gd-DTPA MRI contrast agent.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Gd-metallofullerenol; Gd@C
82
(OH)
22
; Stability; MRI contrast agent; In vivo
1. Introduction
Probably, rare earth elements encapsulated metallo-
fullerenes are the most important family in the endohedral
fullerenes [1] (fullerene cage encapsulating atoms, clusters,
or small molecules), because of their potential applications.
So far, metallic elements that have been encapsulated by
fullerene cages are shown in Table 1 (the bold element sym-
bols). Among them, all of rare earth atoms encapsulated
metallofullerenes can be produced by the conventional arc
discharge method [2] similar to C
60
production. Applica-
A part of work was carried out in Beijing Synchrotron Radiation Facility.
∗
Corresponding authors. Present address: P.O. Box 918, Beijing 100049,
China. Tel.: +86 10 8823 3191; fax: +86 10 8823 3191.
E-mail addresses: zhaoyuliang@ihep.ac.cn (Y. Zhao),
leihao@wipm.ac.cn (H. Lei).
tions of these metallofullerenes are of great interest, and
they have been proposed for potential applications in many
fields including biomedical uses. More extensive applications
come from properties of a tremendous number of their deriva-
tives that can be designed according to the practical demands
and produced by chemical/physical modifications of carbon
cages.
Because of the unpaired electrons in the metallic atom
of the rare earth element, their application in magnetic
resonance imaging (MRI) is an intriguing topic. Shino-
hara et al. developed the first water-soluble gadolinium-
metallofullerenes, Gd@C
82
(OH)
40
-based MRI contrast
agent [3]. The measurement of water proton relaxivity (R
1
)
indicated that R
1
(the effect on the longitudinal relaxation
rate, 1/T
1
) was about 20 times higher than that of the commer-
cial MRI contrast agent Gd-DTPA in vitro. The MRI study
of gadolinium fullerenol in mice confirmed its significantly
0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2004.12.101