World Journal of Engineering
PREPARATION OF Fe3O4/CaP CORE-SHELL NANOPARTICLES EXHIBITING GOOD
MAGNETISM AND BIOAPPLICATION
Teng Yu, Cai Qing, Fang Zhou, Li Keyu and Yang Xiaoping
Key Laboratory of carbon fiber and functional polymers, Ministry of Education,
Beijing University of Chemical Technology, Beijing 100029, China e-mail：yangxp@mail.buct.edu.cn
Introduction
Magnetic nanoparticles have been widely used in recent
years as new functional carriers especially in the biomedical
field due to their good magnetism. In addition, they have
the specialty that no residual magnetism retains after the
magnetic field is removed [1]. However, magnetic
nanoparticles exhibit some drawbacks such as poor
stablility, large aggregation and toxicity in practical
applications [2]. In order to solve these problems, they are
always surface modified. CaP compounds like
hydroxyapatite (HA) have similar compositions to bone
minerals and good biocompatibility which can participate in
treating bone defects [3], and it has been well established
that osteoblasts grow better on HA-coated metals than on
metals alone [4]. In this study, Fe3O4/CaP core-shell
nanoparticles, which could be used in controlling cell
development and bone repair engineering, were prepared.
The CaP compounds coated Fe3O4 nanoparticles were found
higher biocompatibility and more easily uptaken by
osteoblasts than pure Fe3O4 nanoparticles. The cells labeled
with Fe3O4/CaP core-shell nanoparticles are expected to be
constructed into a multilayered cell sheet with the aid of
magnetic force [5]. By changing the magnetic field intensity,
different density of cell sheet could be obtained.
Characterizations
The surface morphologies of Fe3O4 and Fe3O4/CaP were
observed using a scanning electron microscope (SEM, zeiss
supera 55, Germany). High Resolution Transmission
electron microscopy (HR-TEM, JEM-3010, Japan)
observation was performed. The crystalline phases of the
products were identified and compared with X-ray
diffraction (XRD, UItimaIII, Japan). Cell density was
measured by ELISA Reader (Bio-RAD, Model 680, Japan).
The uptake of nanoparticles by MC3T3-E1 cells was
detected by ICP analysis.
Results and Discussion
The morphology and magnetism of Fe3O4 nanoparticles
were shown in Fig.1a and b. From typical HR-TEM, the
sphere Fe3O4 nanoparticles can be clearly seen having an
average size of 30 nm. The lattice fringe pitch of 0.48 nm
corresponds well with the d-spacing of [111] reflections for
Fe3O4. The saturation magnetization of Fe3O4 nanoparticles
was as much as 76.0emu/g.
Experimental
Materials
FeCl2·H2O (1.789g, Fuchen Chemical Reagent Work,
Tianjin) and Polyethylene glycol (PEG, Mw=20000, 1.5g,
Xilong Chemical Industry Co.,Ltd) was dissolved in 30ml
deionized (DI) water and stirred. NH4OH (25%), H2O2
(30%) were of analytical grade and supplied by Beijing
Chemical Reagent Co., Ltd, and were both diluted before
use. 17 ml of NH4OH (2.5%) was added into the above
obtained solution slowly, followed by 3 ml H2O2 of (3%).
The mixture was stored in water bath at 60℃ for 1h. The
products were then redispersed into 140 ml of DI water and
sodium citrate (7g, Beijing Chemical Reagent Co., Ltd) was
added. After being treated 12h, the surface characterized
products (0.05g) was retrieved and immersed in 1L of five
times simulated body fluid (5-SBF) with slightly stirring at
37 °C, and samples were taken at time points of 3, 6, 12 and
24hr. Cytotoxicity and cell uptake of Fe3O4 and Fe3O4/CaP
core-shell nanoparticles was evaluated by co-culturing and
measuring MC3T3-E1 cell densities in different periods.
Fig.1 Typical HR-TEM images (a) and Saturation
magnetization curve (b) of Fe3O4 nanoparticles.
Fig.2 shows the SEM images and particle distribution of
Fe3O4/CaP nanoparticles. The morphology of the particles
remained sphere. As the 5-SBF soaking time prolonged, the
size of the composite particles increased from 30nm to
250nm on average. In addition, EDX spectrum result
exhibited CaP is a main composition of the product besides
besides Fe3O4.
In order to further identify the crystal type of the CaP at the
surface of Fe3O4, XRD was employed (Fig.3a). There were
main peaks of Fe3O4 at 2θ = 30.1°, 35.4°, 43.0°, 57.0° and
62.4° but no distinct peaks appeared for the calcium
phosphate except for a weak wide peak at 2θ = 31.8°,
indicating the poor crystallinity of CaP depositions. The
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World Journal of Engineering
saturation magnetization of Fe3O4/CaP nanoparticles
dropped greatly comparing with pure Fe3O4 nanoparticles
(Fig.3b) because CaP surrounded the Fe3O4 cores which
would weaken the magnetism. Besides, as the
biomineralization time increased, Ms of composite particles
was lower.
reason is unclear. It might be related to the higher uptake
ability of Fe3O4/CaP nanoparticles than pure Fe3O4 by
osteoblasts owing to the increased affinity of CaP
component to cells (Fig. 4b).
Fig.4 Cytotoxicities of Fe3O4 and Fe3O4/CaP nanoparticles
with concentration of 100μg/ml after 1, 3 and 5 days
of culture (a), Amount of iron up taken by
MC3T3-E1 cells after 2, 4 and 24 h incubation with
Fe3O4 and
Fe3O4/CaP
nanoparticles
with
concentration of 100μg/ml (b).
Conclusion
Fe3O4/CaP magnetic nanoparticles were synthesized by
hydrothermal and biomineralization methods. The pure
Fe3O4 nanoparticles had an average size of 30nm and high
magnetism. With the deposition of CaP compounds on
surface, the particle size increased, while the magnetism
dropped greatly. But with increased biocompatibility and
affinity to cells, the Fe3O4/CaP core-shell nanoparticles
were more easily uptaken by osteoblasts than pure Fe3O4
nanoparticles. These primary results indicate that
Fe3O4/CaP core-shell nanoparticles have potential use in
bone defects repairing and further studies are going on. .
Fig.2 SEM images and particle distribution of Fe3O4/CaP
nanoparticles obtained at different biominerlization
time: (a) 3h, (b) 6h, (c) 12h, (d) 24h. EDX spectrum
of Fe3O4/CaP nanoparticles-3h (e).
References
1.Tsang, S. C., Yu, C. H., Gao, X. and Tam, K. Metal
nanoparticle encapsulated in oxide. J. Phys. Chem. B.,
110 (2006) 16914-16922.
2.Yang, Z. P., Gong, X. Y. and Zhang, C. J. Recyclable
Fe3O4/hydroxyapatite composite nanoparticles for
photocatalytic applications. Chem. Eng. J., 165 (2010)
117-121.
3. Nhiem, T. and Webster, T. J. Increased osteblast functions
in the presence of hydroxyapatite-coated iron oxide
nanoparticles. Acta Biomater., 7 (2011) 1298-1306.
4.Webster, T. J., Siegel, R. W. and Bizios, R. Osteoblast
adhesion on nanophase ceramics. Biomaterial. 20 (1999)
1221-1127.
5.Ito, A., Jitsunobu, H., Kawabe, Y. and Kamihira, M.
Construction of Heterotypic cell sheets by magnetic
force-based 3-D coculture of HepG2 and NIH3T3 cells. J.
Fig.3 XRD patterns (a) and saturation magnetization curve
(b) of Fe3O4/CaP nanoparticles at different
biomineralization times.
The results of cytotoxic tests showed that osteoblast
densities were similar in the presence of Fe3O4 and
Fe3O4/CaP nanoparticles at day 1 and 3, and both were
comparable with the control. However, cells cultured
associating with Fe3O4/CaP nanoparticles showed much
higher cell densities than the others at day 5 (Fig.4a). The
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World Journal of Engineering
Biosci. Bioeng., 5 (2007) 371-378.
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