Biomedical Engineering Reference
In-Depth Information
7.3
Magnetic Stimulation on Cells
Recent advancement in magnetic nanoparticles allows mechanical stimulation
forces on cells to be applied through an external magnetic field. These magnetic
nanoparticles are designed to target particular receptors on the surfaces of cells, by
tagging specific active biomolecules, including antibodies, peptides, and ligands.
The idea of using magnetic device for studying cells was introduced over 80 years
ago [26, 27]. Later, Crick
et al
. exploited this idea to study the cell rheology [28]. In
the 1980s, a ''twisting'' technique was introduced by Valberg
et al
. [29-31] and this
was later used by several research groups to activate mechanosensitive ion channels
[32]. Since then, research on magnetic stimulation on cells has been intense. We
discuss the latest state of the art in this area of research in the subsequent sections
of this chapter.
7.3.1
Magnetic Nanoparticles for Cell Stimulation
Generally, magnetic nanoparticles used for cell biology are mainly iron-oxide-based
nanomaterials because of their low toxicity and high magnetization [33]. Indeed,
iron oxide micro- or nanoparticles have been clinically approved for several medical
applications including as contrast agents for MRI scans [34]. For many biological
applications, a layer of protective coating is coated on the surface of these iron oxide
particles in order to prevent unwanted corrosion and provide a surface for tethering
organic functionalities. This allows binding of biomolecules of interest such as
antibodies. Figure 7.4 illustrates the common design of magnetic nanoparticles for
cell stimulation.
7.3.1.1
Properties of Magnetic Nanoparticles
The size of a nanoparticle is critical to such an application. Figure 7.5 shows the
size relation between a cell and its receptor. The diameter of commercial magnetic
nanoparticles ranges from20 up to 600 nm. Particles with larger dimensions should
not be classified as ''nanoparticles.'' However, among these commercial particles,
the smaller particles are usually not unfunctionalized with no coating. The size of
coated particles starts from around 150 nm while the smallest magnetic particles
Magnetic core
Protective coating
Organic linker
Active molecule
Figure 7.4
A common design of a magnetic nanoparticle for biomedical applications.
