Biotechnological and Biomedical Applications of Magnetically Stabilized and Fluidized Beds - Porous Media: Applications in Biological Systems and Biotechnology - page 457

in terms of selectivity and in terms of recovery). However, among other
disadvantages, in fact, technique is not able to handle samples containing par-
ticulate material (typically present in early stages of the isolation/purification
of biological materials when suspended solid and fouling components exist),
and therefore, alternative separation processes, such as magnetic anity, ion
exchange, hydrophobic or adsorption batch separations, magnetically stabi-
lized fluidized beds (MSFBs), and magnetically modified two-phase systems,
have shown their usefulness (Safarik and Safarikova 2004).
Magnetic methods are very promising for the purification and isolation of
substances, especially when allied with the new magnetic tagging and carrying
technologies, because they have a low cost, and are very effective. This is
even more the case when every day new methods to create and effectively
manipulate magnetic tags and carriers are being developed.
In the case of biomedical and biotechnological applications the principle
of magnetic separation is very simple (Safarik and Safarikova 2004): magnetic
carriers with some sort of anity, hydrophobic ligands, or specially chosen
ion-exchange groups are mixed with a sample containing target compound(s)
(e.g., crude cell lysates, whole blood, plasma, ascites fluid, milk, whey, urine,
cultivation media, wastes from food and fermentation industry); after the nec-
essary incubation period for the target compound(s) to attach to the magnetic
particles, the resulting magnetic complex is easily and rapidly removed from
the sample by using a magnetic separator. Then, after washing out the contam-
inants, the treated sample can be eluted and the isolated target compound(s)
further processed.
Details on the main advantages of application of magnetic methods can be
found in this chapter and also in Safarik and Safarikova (2004).
Magnetically stabilized fluidized beds exhibit a unique combination of the
properties of packed and fluidized beds (Hausmann et al. 2000). They have
been one of the key magnetic separation techniques used during the last decade
to achieve the purification of biological materials. In MSFBs the magnetic
particles (magnetic carriers or other type of tags) are placed under the influ-
ence of an external magnetic field that is capable of sustaining them against
flow velocities higher than those verified in packed beds. These magnetic par-
ticles have some artificially manipulated anity that enables them to col-
lect/adsorb/attach the target biological substance from the media that flows
through them.
In this chapter, the applications of MSFBs to biotechnology and biomedicine
will be addressed. First it will be given an historical overview of the develop-
ments and applications of MSFBs in the biotechnological and biomedical areas.
Next, the main principles behind MSFB technology will be reviewed, includ-
ing the behavior of MSFB's as porous media. Then, the theory that supports
MSFB applications, including the supporting theory for applications such as
biorreactions and bioadsorptions will be presented. The main current and past
applications of MSFB in the areas of biotechnology and biomedicine are described
in detail in a subsequent section. Detail on the type of particles used to form these
beds, are also given. The main advantages and disadvantages of this technique,