Biomedical Engineering Reference
Fig. 2.10 A combination DEP/magnetic chip deforms a vesicle. The vesicle is held in place by
dielectrophoresis while a magnetic field pulls an iron oxide particle out of the vesicle
the magnetic field is turned off, the vesicle contracts back to its original shape. This
chip can be useful in single-cell rheological studies for point-of-care diagnostics.
Poration is used to release vesicle contents, as seen in Fig. 2.11 . Electroporation
involves using electric fields to destabilize the vesicle membrane and create small,
short-lived holes [ 21 ]. The holes are large enough to allow macromolecules to
enter and leave the vesicle. AC electric fields in the 1-Hz-10-kHz range induce
transmembrane voltages large enough to cause a dielectric breakdown of the
membrane, thus destabilizing it [ 21 , 22 ]. In Fig. 2.11 , a vesicle was placed in a
fluid containing fluorescein, a fluorescent molecule [ 10 , 12 ]. At time t
0 s, the
vesicle was electroporated, allowing fluorescein to enter. In a second experiment,
a vesicle was prefilled with fluorescein and submerged in water. It was similarly
electroporated, diffusing away its fluorescein and losing its fluorescence.