Online supplementary information
Journal: Applied Physics Letters
Title: Mesoporous Silica Nanoparticles Encapsulating Gd2O3 as a Highly Efficient
Magnetic Resonance Imaging Contrast Agent
Authors: Shuang Li, Huan liu, Li Li, Ning-Qi Luo, Ri-Hui Cao, Di-Hu Chen,
Yuan-Zhi Shao
1：The procedures of simulation and experiment of silica Gd2O3@MCM-41
The molecular dynamics simulations were performed using Materials Studio.
The MCM-41 unit cell containing 4499 atoms was constructed by carving out
cylindrical pores in an amorphous silica matrix. The pore diameter and wall thickness
are approximately 2.88 and 0.97 nm, respectively. The unit cell was optimized
geometrically and equilibrated at 300 K by NVT to obtain the minimum energy
configuration. Each Gd2O3 cluster is about 1 nm in size and contains 14 gadolinium
and 21 oxygen atoms. The Gd2O3 clusters were assembled into the mesopores of the
equilibrated MCM-41 unit. Finally, the assembly structure unit was relaxed by
annealing to avoid metastability. Nine different units were constructed in which the
numbers of Gd2O3 clusters assembled range from zero to eight. Both the small-angle
X-ray diffraction (XRD) pattern and water adsorption of various assembly models
were simulated and compared with their experimental counterparts.
The typical one-step synthesis process of Gd2O3@MCM-41 nanoparticles is
described as follows. 0.2 g of cetyltrimethylammonium bromide (C16TAB) was
dissolved in 100 g of distilled water. 2 ml 25 % NH3.H2O was added to the vigorously
stirred solution at room temperature consequently, followed by 4.49 mmol of
tetraethoxysilane (TEOS). After stirring for 15 minutes, 0.27 mmol of GdCl3.6H2O
was added to the solution. After another 1 hour stirring, the fine particle precipitate
was centrifuged and dried in freezer dryer for 15h thereafter. The samples were
calcined at 500 oC for 5 hours to remove the templates, then the Gd2O3@MCM-41
nanoparticles were obtained with a 5.7 at.% Gd doping.
S1
The size and morphology of the samples were investigated using a JEOL JEM-2010
(HR) transmission electron microscope (TEM) and a LEO-1530VP (Germany)
scanning electron microscope (SEM). The compositions of the samples were
determined using energy dispersive X-ray spectroscopy (EDS). In order to test the
mesoporous structure, the small angle X-ray diffraction pattern (XRD) was acquired
on a Bruker D8 Advance diffractometer using Cu-Kα radiation at 35 KV, 35 mA,
between 1.2°~8.0°. The nitrogen adsorption-desorption isotherms were measured with
a Quantachrome Autosorb-iQ system, and the pore size distribution curve was
determined from the adsorption branch of the isotherm. The water adsorption of
different Gd doped nanoparticles was measured at the room temperature with
saturation pressure.
The 0.2 ml contrast agent solution with a concentration of 2.2096 mg/ml
Gd2O3@MCM-41 nanoparticles was injected into the nude mice through the tail vein.
The specimens for in vitro observation were prepared. The distribution of
nanoparticles injected in mice was observed through TEM. The in vivo T1-weighted
images of the mice with nasopharyngeal carcinoma (NPC) xenografted CNE-2 tumors
were obtained with a Signa Excite 1.5 T MRI scanner (General Electric, USA), using
a 2D gradient-echo at each time point for each mouse with a 3 mm slice thickness, no
interslice gap, a TR/TE of 400/13 ms, a field of view (FOV) of 8 mm×8 mm, a matrix
of 256×160, and a number of excitations (NEX) of 2.
2: The analyses of pore size and wall thickness
Figure S1 displays the N2 adsorption-desorption isotherm of synthetical
Gd2O3@MCM-41. The BET (Brunauer-Emmett-Teller) surface area and total pore
volume are 911.84m2/g and 0.63cc/g, respectively.
Figure S2 presents the pore size distribution, which was evaluated from the
adsorption branch of nitrogen isotherm by using the DFT (Density Functional Theory)
method. The average pore diameter is 2.94nm.
S2
Figure S1. The N2 adsorption-desorption isotherm of synthetical Gd2O3@MCM-41.
Figure S2. The pore size distribution evaluated from the adsorption branch of nitrogen
isotherm by using the DFT method.
S3
The X-ray diffraction patterns of simulated models assembled with various
Gd2O3 cluster amounts are plotted in figure S3. The addition of Gd causes a negligible
influence on the (10) peak of hexagonal array of mesopores at 2θ=2.65. According to
the patterns, the pore size, the space and wall-thickness between pores are calculated
as 2.88nm, 3.85nm and 0.97nm, respectively.
Figure S4 shows the measured XRD patterns of as-prepared samples with
different Gd doping. The (10) peak of hexagonal array of mesopores of the sample
(Gd doping 5.7%) located at 2θ=2.64, and the pore size, the space and wall-thickness
between pores are calculated as 2.94nm, 3.86nm and 0.92nm, respectively. In table S1
listed are the structure parameters of current Gd2O3@MCM-41 and that of MCM-41
silica thin films reported by Gibaud et al.1
Figure S3. The X-ray diffraction patterns of simulated models assembled with various
Gd2O3 cluster amounts.
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Figure S4. The measured XRD patterns of as-prepared samples with different Gd
doping.
Table S1. Structure parameters of Gd2O3@MCM-41
Name
Gd2O3@MCM-41
Pore diameter(nm)
Wall thickness(nm)
Model
2.88
0.97
Sample
2.94
0.92
3.50
0.80
Silica thin filmsa
a
Reference 1
3：The influence of different Gd doping on the microstructure of MCM-41 silica
Per figure S3 and S4 above, both simulated and measured X-ray diffraction
patterns, main diffraction peak (10), of MCM-41 silica are affected slightly by Gd
doping, indicating that the hexagonal array of mesopores of MCM-41 remains intact.
S5
Reference
1
A Gibaud, A Baptiste, D. A Doshi, C. J Brinker, L Yang, and B Ocko, Europhys.
Lett. 63, 833 (2003).
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