8.5 Applications of Superparamagnetic Materials 169
Applications in medicine and biotechnology are, from the standpoint of economy,
the most successful ones. As already mentioned in Chapter 6 on nanofluids, the
application as a means to improve the contrast in magnetic resonance tomography
(MRT) (also called nuclear magnetic resonance imaging, NMR or MRI) [9] is very
successful; suspensions of superparamagnetic particles replace, to some extent,
gadolinium salts, which are now in use. The application of particles has an additional advantage, as it allows functionalization of the surface with proteins or
enzymes, which are characteristic of a specific organ or tumor. The contrast
improvement by superparamagnetic nanoparticles is based on the local change of
the magnetic susceptibility caused by local differences of the concentration of
these particles, which, locally, changes the magnetic field. This changes the nuclear
spin resonance frequency, which is used as a signal for imaging. In particular,
magnetic particles functionalized to attach locally, promise many advantages. For
application, the superparamagnetic particles are suspended in a suitable, waterbased liquid. The patient gets this suspension injected with a syringe. Figure 8.22
shows a comparison between an MRT image taken without contrast enhancement
and one taken with a superparamagnetic fluid for contrast enhancement.
A further example is directed to biotechnology. Often, there is the necessity to
separate cells from other objects in a suspension. This is a very timeconsuming
and expensive task as, conventionally; it is done by hand under observation in
a microscope. The idea is to use magnetic particles, which are functionalized
to attach exactly on the type of cells in question. To do this, a suspension of
these functionalized superparamagnetic particles is added to the suspension containing the cells. It is intended that the cells with the attached magnetic particles
Figure 8.22 Contrast enhancement in NMR
imaging of a metastases of a gall bladder
carcinoma using superparamagnetic γ-Fe 2 O 3
particles [10]. (a) Image recorded shortly
after the application. (b) Image contrast
improved by injecting water-suspended
superparamagnetic γ-Fe 2 O 3 particles into the
patient’s blood. The bright spots represent
the metastasis of the tumor. (Courtesy of
Tombach, B. Department of Radiology,
University Hospital Muenster, Germany,
private communication).
(a)
(b)
Applications in medicine and biotechnology are, from the standpoint of economy,
the most successful ones. As already mentioned in Chapter 6 on nanofluids, the
application as a means to improve the contrast in magnetic resonance tomography
(MRT) (also called nuclear magnetic resonance imaging, NMR or MRI) [9] is very
successful; suspensions of superparamagnetic particles replace, to some extent,
gadolinium salts, which are now in use. The application of particles has an additional advantage, as it allows functionalization of the surface with proteins or
enzymes, which are characteristic of a specific organ or tumor. The contrast
improvement by superparamagnetic nanoparticles is based on the local change of
the magnetic susceptibility caused by local differences of the concentration of
these particles, which, locally, changes the magnetic field. This changes the nuclear
spin resonance frequency, which is used as a signal for imaging. In particular,
magnetic particles functionalized to attach locally, promise many advantages. For
application, the superparamagnetic particles are suspended in a suitable, waterbased liquid. The patient gets this suspension injected with a syringe. Figure 8.22
shows a comparison between an MRT image taken without contrast enhancement
and one taken with a superparamagnetic fluid for contrast enhancement.
A further example is directed to biotechnology. Often, there is the necessity to
separate cells from other objects in a suspension. This is a very timeconsuming
and expensive task as, conventionally; it is done by hand under observation in
a microscope. The idea is to use magnetic particles, which are functionalized
to attach exactly on the type of cells in question. To do this, a suspension of
these functionalized superparamagnetic particles is added to the suspension containing the cells. It is intended that the cells with the attached magnetic particles
Figure 8.22 Contrast enhancement in NMR
imaging of a metastases of a gall bladder
carcinoma using superparamagnetic γ-Fe 2 O 3
particles [10]. (a) Image recorded shortly
after the application. (b) Image contrast
improved by injecting water-suspended
superparamagnetic γ-Fe 2 O 3 particles into the
patient’s blood. The bright spots represent
the metastasis of the tumor. (Courtesy of
Tombach, B. Department of Radiology,
University Hospital Muenster, Germany,
private communication).
(a)
(b)