Biomedical Engineering Reference
In-Depth Information
inserting MNPs in lipid, Magnetoliposomes can carry the drugs to reach the tumor
under the guidance of the magnetic field in vitro. Since the magnetic particles in
Magnetoliposomes have special absorption rate on the electromagnetic wave, they
can strongly absorb the energy to improve temperature in the alternating magnetic
field, and this inhibit tumor growth, or even make the tumor disappeared.
2.2.3
Magnetic Glass-Ceramic Nanoparticles
MGC nanoparticles are produced by mixing iron oxide particles and glass ceramics.
This kind of material can satisfy the need of tumor hyperthermia, especially for
deep tumors. The coercivities of ferromagnetic glasses are much higher than that of
magnetic fluids. One reason is because glasses have larger internal stresses which
hinder the magnetic moment rotation. In addition, another reason is the magnetic
grains are separated by glasses and wollastonites without magnetism.
According to elements species, the MNPS can be classified into the following
categories.
2.2.4
Iron Oxide Particles and Other Ferrous Metals
In magnetic hyperthermia, the majority is focused on Fe
3
O
4
and gFe
2
O
3
. Many
researchers have studied their toxicity and biocompatibility. Feasibility in animal
experiments has also been proven and stepped into clinical trials (Johannsen
et al.
2007a
).
SPM iron oxide nanoparticles, possess magnetic moment of 300-400 emu/cm
3
generally. Varanda et al have synthesized Fe
3
O
4
-coated Fe
55
Pt
45
nanoparticles in a
core/shell structure with high magnetization close to the a - Fe (1,000 emu/cm
3
)
and low coercivity (~60 Oe). In addition, the nanoparticles present a slightly oxide
layer on surface favoring their functionalization as shown by the realized dextran
molecules coating (Varanda et al.
2008
).
Other ferrous metals and their alloy used in magnetic hyperthermia include
MeFe
2
O
3
(Me is Co, Mn, Ni and so on), NiCoFe, FeCo and NiFe metals.
Iron oxides are relatively safe and can regularly be excreted, while nickel and
cobalt magnetic materials have certain degrees of physiological toxicity. Their
saturation magnetization gradually increased by the order but stability decreased,
which is determined by their Gibbs free energy.
MnZn ferrites have high permeability and low magnetic losses at high frequencies
and the properties are largely dependent on their microstructure. La
3+
can change the
orientations of crystal growth of nano-MnZn ferrites, then decrease the saturation
magnetization of La
3+
doped sample and even show SPM property (Gu et al.
2004
).
Silica-coated lanthanum-strontium manganite particles with La
0.76
Sr
0.24
MnO
3+d
stoichiometric formula, due to its Curie temperature at ~40°C, has been established as
a potential candidate for self-regulated power-absorbing and temperature-controlling
materials in tumor hyperthermia treatments (Uskokovic et al.
2006
).
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