Biomedical Engineering Reference
In-Depth Information
Figure 10.10
Principle of 2D protein electrophoresis. The first step is a IEF determination (charge
sorting), the second step a SDS PAGE (molecular weight sorting). In the final electrophoregram, each
spot is a single protein.
10.1.6 Cell Electrophoresis
Cells are difficult to separate with electrophoresis because, like for proteins, size
is only one part of the information. The task is usually to separate cells that have a
distinctive property from other cells. The equivalent of SDS has not been found for
cells so even a size separation does not give very good results. Besides, gels are not
well-suited for these large objects. Therefore, electrophoresis does not seem to be
the technique adapted to this problem. Dielectrophoretic measurements, described
in the next section, are more suitable [32].
10.2 Dielectrophoresis
In contrast with the previously described electrophoresis, dielectrophoresis is not
a transport technique, except in some cases that we will review in the end of this
section; it is rather a micromanipulation tool. Based on a contrast between the po-
larizabilities of the particle and the medium, it can be used on any kind of particle
charged or not.
10.2.1 Theoretical Basis
10.2.1.1 The Dielectrophoretic Force
Although the physics of dielectrophoresis (DEP) has been known and character-
ized for a long time, this effect has recently regained some interest in the biology-
