Biomedical Engineering Reference
In-Depth Information
Monodispersed ternary Mn
0.5
Zn
0.5
Fe
2
O
4
ferrite nanoparticles synthesized using
thermal decomposition of metal acetylacetonate in the presence of a high temperature
boiling point solvent and fatty acids are SPM at room temperature, and therefore
can be applied in hyperthermia (Parekh et al.
2006
).
The SPM gadonanotubes also show promise for targeted magnetic hyperthermia
(Sithararnan and Wilson
2006
). Furthermore, non-spherical particles such as the
gadonanotubes are yet to be tested as hyperthermia agents. And it is possible that
their unique rod-shaped geometry may augment performance through non-axial
Brownian relaxation.
2.2.5
Iron-Gold Nanoparticles
MNPs (Fe,Fe
3
O
4,
g - Fe
2
O
3
) can be coated by another inert shell, such as SiO
2
(Pereira et al.
2010
), gold (Ravel et al.
2002
; Tamer et al.
2010
), Ag (Choi et al.
2010
; Ding et al.
2010
), polymer (De La Cruz-Montoya and Rinaldi
2010
) and their
hybrids (Zhou et al.
2010
). SPM iron-gold (Fe@Au) nanoparticles use gold as the
shell on the surface of the core. Gold is diamagnetic, and the presence of a gold
coating inhibits oxidation and allows the particles to be stable. Besides, the gold
produces no toxicity for human body. Therefore this kind of core/shell structure can
be used in tumor hyperthermia. Their SPM behavior has been confirmed by mag-
netic measurements at various temperatures (4.2-280K) and by Mössbauer spectra
measurements. Fe and metallic Au in Fe@Au nanoparticles exist as composite
nanoparticles, not as separate particles. The Au-coated particles exhibit a surface
plasma resonance peak that red-shifts from 520 to 680 nm. The gold-coat protects
the magnetic core against oxidation, without drastic reduction of the magnetic
properties. The obtained hyperfine parameters also confirmed the absence of iron
oxides (Fe
3
O
4
, Fe
2
O
3
) (Zelenakova et al.
2008
; Ban et al.
2005
; Jafari et al.
2010
).
2.2.6
Carbon Encapsulated Iron
Metallic iron, due to higher saturation magnetization (Huber
2005
) in comparison
to iron oxides, could act better if oxidization in ambient or biological conditions is
avoided (Klingeler et al.
2008
). Recently, scientists have found a promising way
to overcome this problem, which is to coat the iron with a carbon shell by insertion
of the material inside of CNTs. Various studies have shown that, independent of
the synthesis technique, the carbon encapsulated iron is efficiently protected by the
surrounding shells and its magnetic properties are retained (Klingeler et al.
2008
).
In addition, carbon shells may act as multi-functional containers which can be filled
with different materials. Additional material such as a nanothermometer in Fe-CNT
would increase the potential of CNT as hyperthermia agents. Attaching functional
elements to the outer shell of CNT increase their biocompatibility (Klingeler et al.
2008
). Recent studies of cytotoxic effects of Fe-CNT on cells indicated no significant
toxicity of Fe-CNT prepared by the same synthesis route (Klingeler et al.
2008
).
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