Biomedical Engineering Reference
In-Depth Information
MNP
Applied
magnetic
force
K
+
Antibody-tagged
magnetic nanoparticle
MNP
MNP
Antibody targeting
potassium ion channels
Cytoplasm
Ion channel activated
by magnetic dragging
Figure 7.7
The mechanism of an antibody-tagged magnetic
nanoparticles targeting and activating the ion channel recep-
tor on the cell membrane.
specific direction. Such a pull force causes tension on the cell membrane and hence
activation of the ion channels. In order to control the force of stimulation, several
factors need to be considered: (i) the strength of the applied magnetic field; (ii) the
magnetic susceptibility of the particles; (iii) the number of particles attached; and
(iv) the location of the particles bound on the cell. Magnetic pulling systems with
pulling in both vertical [40, 41] and horizontal [43] directions have already been
reported.
In addition to stimulation, such magnetic pulling systems have also been
used to study the biomechanical property of cells [44-46]. However, these
studies are limited by the fact that particles are bound to specific receptors
(Figure 7.7). It is difficult to apply the force to the whole cell using magnetic
pulling.
7.3.2.2
Magnetic Twisting
Magnetic pulling, vertical or horizontal, provides a mechanism to apply forces in
one dimension. Wang and coworkers have developed a magnetic twisting tech-
nique,MTC,tostimulatethecellswitha''two-dimensional''force(seeFigure7.8).
In this system, a twisting force was applied by rotating the magnetic particles
bound on the surface of cells and the mechanical properties of the cytoskeleton of
the cells were studied [32, 47, 48]. Compared with magnetic pulling, this technique
provides a highly localized torque to the specific receptors but avoids deformation
of the cell membrane. Similar to magnetic pulling, these magnetic particles were
tagged with ligands or antibody molecules to target the receptors on the cell
