Based on the results above and experiences reported in literature on convective
interaction media (CIM) discs, it is obvious that macroporous chromatographic
materials have good potential for isolation of virus particles [64].
8 Chromatography of Biomolecules
Cryogels have an open structure and therefore produce low back-pressure when
used in chromatographic applications (Fig. 13). This positive feature is
counteracted by the fact that the large pores also result in a low capacity for
adsorption of proteins. Thus, in many comparisons, gels like Sepharose may be at
least ten times better with regard to capacity. The ability to operate with a high
flow-rate favors use of the cryogels. Still, the low capacity is a problem when the
gels are used for separation of proteins or other biomolecules. Much effort has gone
into improving the capacity of the cryogels and some different strategies are
presented next.
Means of increasing the binding capacity include: grafting, formation of composites, crosslinked nanoparticles with affinity, and double cryogel networks.
8.1 Grafting
It is possible to graft polymer chains to the pore walls of cryogels. This can be done
either by having a pre-made polymer that is attached to the pore wall, or by
initiating polymerization at the pore wall and then feeding monomers to build the
polymer from the pore wall and out.
Savina et al. have mainly focused on building the polymer from the pore wall
and out into the pore lumen. To achieve this, one needs to use an initiator that will
start the polymerization. Savina et al. used diperiodatocuprate(III) complex as
initiator. It was possible to first treat the pore wall with the initiator and then add
the monomers after removing excess initiator [66–69]. It was possible to graft more
than 100 % (w/w) of the weight of the polymer backbone. If the initiator was added
concomitantly with the monomers, then a lot of soluble polymers were obtained.
Therefore, a two-step procedure was utilized: first treating the polymer wall with
initiator and then introducing the monomers.
Studies on the grafting of charged polymers made it clear that the density of
polymers on the polymer backbone has a strong influence on the behavior of the
ion-exchange adsorbent obtained [66–69]. With a large amount of initiator, a lot of
short polymers were grafted, whereas when a lower amount of initiator was used,
less but longer polymer chains were formed. When adsorbing small molecules (e.g.,
the dye Orange G) to an anion exchanger, there were no differences in the amount
of small molecules bound if the amount of polymer was the same, even if there were
differences with regard to polymer chain length. However, when it came to proteins
(e.g., bovine serum albumin, BSA), it was found that the long polymer chains were
Cryogels for Biotechnological Applications
263
interaction media (CIM) discs, it is obvious that macroporous chromatographic
materials have good potential for isolation of virus particles [64].
8 Chromatography of Biomolecules
Cryogels have an open structure and therefore produce low back-pressure when
used in chromatographic applications (Fig. 13). This positive feature is
counteracted by the fact that the large pores also result in a low capacity for
adsorption of proteins. Thus, in many comparisons, gels like Sepharose may be at
least ten times better with regard to capacity. The ability to operate with a high
flow-rate favors use of the cryogels. Still, the low capacity is a problem when the
gels are used for separation of proteins or other biomolecules. Much effort has gone
into improving the capacity of the cryogels and some different strategies are
presented next.
Means of increasing the binding capacity include: grafting, formation of composites, crosslinked nanoparticles with affinity, and double cryogel networks.
8.1 Grafting
It is possible to graft polymer chains to the pore walls of cryogels. This can be done
either by having a pre-made polymer that is attached to the pore wall, or by
initiating polymerization at the pore wall and then feeding monomers to build the
polymer from the pore wall and out.
Savina et al. have mainly focused on building the polymer from the pore wall
and out into the pore lumen. To achieve this, one needs to use an initiator that will
start the polymerization. Savina et al. used diperiodatocuprate(III) complex as
initiator. It was possible to first treat the pore wall with the initiator and then add
the monomers after removing excess initiator [66–69]. It was possible to graft more
than 100 % (w/w) of the weight of the polymer backbone. If the initiator was added
concomitantly with the monomers, then a lot of soluble polymers were obtained.
Therefore, a two-step procedure was utilized: first treating the polymer wall with
initiator and then introducing the monomers.
Studies on the grafting of charged polymers made it clear that the density of
polymers on the polymer backbone has a strong influence on the behavior of the
ion-exchange adsorbent obtained [66–69]. With a large amount of initiator, a lot of
short polymers were grafted, whereas when a lower amount of initiator was used,
less but longer polymer chains were formed. When adsorbing small molecules (e.g.,
the dye Orange G) to an anion exchanger, there were no differences in the amount
of small molecules bound if the amount of polymer was the same, even if there were
differences with regard to polymer chain length. However, when it came to proteins
(e.g., bovine serum albumin, BSA), it was found that the long polymer chains were
Cryogels for Biotechnological Applications
263