Magnetic particles with immobilized lectins can be used for the isolation of
polysaccharides or structure containing sugar moities. This technique has been
used for the isolation of various microbial cells from culture media [24].
Immunomagnetic particles – magnetic particles bearing immobilized specific
antibodies against the target structures – can be used for the selective isolation
of specific cells such as prokaryotic and eukaryotic [25, 26].
Magnetic modifications of standard immunoassays can be successfully used
for the determination of microbial cells [26], parasites [27], and viruses [28].
Cells to which magnetic carriers are attached can be removed from the system
simply by using an external magnetic field, or can also be targeted to the desired
place. Non-porous magnetic supports with a diameter of 1 mm or smaller are
advantageous as they are more resistant to fouling, diffusional limitations, and
attrition than porous supports [1, 29]. There are many ways to immobilize the
cells or compounds of interest and practically all the standard procedures used
in affinity chromatography can be used for this purpose. Again, similar to the
chromatography methods, a spacer must often be inserted between the
magnetic particle and the ligand to overcome steric hindrance at the cell
surface. Several microorganisms have been immobilized on magnetic carriers
or have been entrapped in biopolymers containing magnetic material. These
methods are useful in applications where suspended particles and viscous
substances are present in the fermentation medium. The magnetic material
usually does not interfere with the catalytic function of the cells, as shown for
Saccharomyces cerevisiae immobilized in calcium alginate together with
magnetite [30]. HGMS of yeast cells by means of irreversible adsorption of very
fine particles of maghemite (gamma-Fe 2 O 3 ) on the cell wall was reported [31].
Binding of paramagnetic erbium ions on various surface structures of
microbial cells also leads to the formation of magnetized microorganisms [32].
Many other applications in different biorelated areas, apart from the specific
ones given in this section, are discussed by Safarik and Safarika [33], in an
excellent review article on magnetic separations.
Gravity-dependent phenomena associated with separation processes have
been studied in the low-gravity environment of space flight [34]. Magnetic
field-based separations, on the other hand, have not been pursued in microgravity research. In general, gravity assists the separation of magnetized from
unmagnetized separands [35], or magnetic stabilization is designed to avert
effects of gravity [36, 37]. Flowing systems [38] can be considered relatively
gravity independent. However, certain gradient-dependent separations have a
meaningful gravitational component, and Owen’s work suggests that enhanced
separation could be achieved in a ferrofluid relieved of the gravity vector [39].
The method of cell separation using a magnetic field has been implemented
as a binary separation between cells that have and have not bound magnetic
microspheres on the basis of a cell receptor (a specific type of surface ligand),
as shown in Fig. 1.
Apart from the above-mentioned interests in low-gravity research applied to
separation science and technology, there is an interest in performing separations in support of low-gravity biotechnology, immunology, cytology, serology,
microbiology, and chemical procedures on the International Space Station
Multistage Magnetic and Electrophoretic Extraction of Cells, Particles and Macromolecules
147
polysaccharides or structure containing sugar moities. This technique has been
used for the isolation of various microbial cells from culture media [24].
Immunomagnetic particles – magnetic particles bearing immobilized specific
antibodies against the target structures – can be used for the selective isolation
of specific cells such as prokaryotic and eukaryotic [25, 26].
Magnetic modifications of standard immunoassays can be successfully used
for the determination of microbial cells [26], parasites [27], and viruses [28].
Cells to which magnetic carriers are attached can be removed from the system
simply by using an external magnetic field, or can also be targeted to the desired
place. Non-porous magnetic supports with a diameter of 1 mm or smaller are
advantageous as they are more resistant to fouling, diffusional limitations, and
attrition than porous supports [1, 29]. There are many ways to immobilize the
cells or compounds of interest and practically all the standard procedures used
in affinity chromatography can be used for this purpose. Again, similar to the
chromatography methods, a spacer must often be inserted between the
magnetic particle and the ligand to overcome steric hindrance at the cell
surface. Several microorganisms have been immobilized on magnetic carriers
or have been entrapped in biopolymers containing magnetic material. These
methods are useful in applications where suspended particles and viscous
substances are present in the fermentation medium. The magnetic material
usually does not interfere with the catalytic function of the cells, as shown for
Saccharomyces cerevisiae immobilized in calcium alginate together with
magnetite [30]. HGMS of yeast cells by means of irreversible adsorption of very
fine particles of maghemite (gamma-Fe 2 O 3 ) on the cell wall was reported [31].
Binding of paramagnetic erbium ions on various surface structures of
microbial cells also leads to the formation of magnetized microorganisms [32].
Many other applications in different biorelated areas, apart from the specific
ones given in this section, are discussed by Safarik and Safarika [33], in an
excellent review article on magnetic separations.
Gravity-dependent phenomena associated with separation processes have
been studied in the low-gravity environment of space flight [34]. Magnetic
field-based separations, on the other hand, have not been pursued in microgravity research. In general, gravity assists the separation of magnetized from
unmagnetized separands [35], or magnetic stabilization is designed to avert
effects of gravity [36, 37]. Flowing systems [38] can be considered relatively
gravity independent. However, certain gradient-dependent separations have a
meaningful gravitational component, and Owen’s work suggests that enhanced
separation could be achieved in a ferrofluid relieved of the gravity vector [39].
The method of cell separation using a magnetic field has been implemented
as a binary separation between cells that have and have not bound magnetic
microspheres on the basis of a cell receptor (a specific type of surface ligand),
as shown in Fig. 1.
Apart from the above-mentioned interests in low-gravity research applied to
separation science and technology, there is an interest in performing separations in support of low-gravity biotechnology, immunology, cytology, serology,
microbiology, and chemical procedures on the International Space Station
Multistage Magnetic and Electrophoretic Extraction of Cells, Particles and Macromolecules
147