Biomedical Engineering Reference
In-Depth Information
20
µ
m
config. 1
Ca
2
+
0
1
5
10
20
50
100
200
500
1
5
10
20
50
nm
µ
m
Figure 7.5
A schematic comparison on the size of some
magnetic micro-/nanoparticles and a human cell.
with, for example, carboxylic acid functionality are around 250 nm in diameter.
However, a number of reports on preparing functionalized magnetic nanoparticles
<
150 nm are widely available [35].
We should note that an ion channel is only around a few nanometers wide;
large magnetic nanoparticles may cause complications. For example, since these
particles usually have many functional groups, several ion channels attached to one
large particle can occur. On the other hand, small particles, with a small magnetic
core, may not generate enough pulling force to stimulate the ion channels. As a
result, small particles with a high magnetization would be ideal in this application.
This can be achieved by either increasing the iron oxide content or using a core
material with a higher specific magnetization value, for example, metallic iron or
ferrites (MFeO
4
,whereM
=
Co, Ni, Mn). Research on these areas has already
begun [36].
There is a common misunderstanding on the magnetization properties of these
magnetic nanoparticles. The magnetization of any magnetic materials depends on
the nature of the materials and the volume of particle domain size. As a result,
the magnetization value of a single nanoparticle is usually lower than that of
its bulk counterpart [37]. However, most of the common commercial magnetic
particles (150 nm to 4
m) are made of aggregates of small superparamagnetic
nanoparticles (10-20 nm). The overall size of these particles may only have a small
effect on the overall magnetization value if the iron oxide content remains the
same.
µ
