Biotechnological and Biomedical Applications of Magnetically Stabilized and Fluidized Beds - Porous Media: Applications in Biological Systems and Biotechnology - page 471

12.5 Main Biotechnological and Biomedical
Applications
As referred in the introduction, several applications, at laboratorial and
industrial scale, of the MFBs and MSBs in the areas of biotechnology and
biomedicine have been developed through the years (mainly cell, antibody,
and protein removal/ processing, fermentation, and cell/enzyme immobiliza-
tion). The major applications will be detailed in this chapter. We start by
describing generically the type of magnetic particles that may form the MSBs
and MFBs in this type of processes.
12.5.1 Particles (Beads)
Magnetic stabilized and fluidized beds require the use of particles/substances
possessing suciently high values of magnetic susceptibility and/or perme-
ability. Two main types of systems have been developed: those that use 100%
magnetic particles and those that use a mixture of magnetic and nonmagnetic
particles. The systems having only magnetic particles proved to be superior
in recently developed applications, when the fulfillment of all the goals of
separation and reaction are considered (Seibert et al. 1998; Hristov 1999).
The magnetic beads used in MSFBs may assume many forms and composi-
tions, but they usually consist of a central core made of magnetite, maghemite,
or any other kind of strong paramagnetic or ferromagnetic material, which is
then covered by some kind of polymeric adsorbent or resin that is usually later
functionalized and surface modified to have higher adsorption and active sites,
and that will be responsible for the interaction with the biological media. This
interaction may be directly on the substances we are interested in removing,
modifying, or purifying, or it may be indirect by the attachment of biological
material to the surface of the beads (e.g., enzymes, zeolites, etc.), which will
then interact with the desired biological substances.
Some reviews on magnetic beads used in MSFBs may be found in literature
(e.g., Hristov 1999; Tanyolac and Ozdural 2000).
As examples of magnetic beads we may point out: Fe 3 O 4 /(alginate or
activated carbon) particles (see Figure 12.7) (Bohm and Pittermann 2000;
Al-Qodah and Al-Shannag 2006); polymeric adsorbent magnetic particles
(Seibert et al. 1998) like the highly used mPHEMA beads (magnetic polyhy-
droxyethylmethacrylate) (Basar et al. 2007; Ozturk et al. 2007), mPEGDMA
beads (magnetic polyethyleneglycoldimethylcrylate) ( Ozturk et al. 2007),
PAM beads (polyacrylamide/magnetite) (Cocker et al. 1997), mPVB beads
(polyvinylbutyral) (Tanyolac and Ozdural 2000), P(GMA-MMA) beads (poly
glycidylmethacrylate-methylmethacrylate) (Bayramoglu and Arica 2008); and
ferromagnetic beads with immobilized enzymes or catalysts (Al-Hassan et al.
1991; Ivanova 1996 Bayramoglu and Arica 2008). These magnetic beads are