Immobilized affinity adsorbents adsorption

Mathematical Modeling of Bioproduct Adsorption Using Immobilized Affinity Adsorbents... 

The use of small affinity adsorbent particles immobilized in hydrogel beads has been investigated for whole broth processing (1). The adsorbent particles can contain biospecific ligands covalently attached to a porous solid support. A mathematical model was developed to study bioproduct adsorption using immobilized affinity adsorbent beads in batch operation. 

The fractionation and purification of deteriorated proteins is undoubtedly one of the least successful techniques. This is simply because all of the methods that have been developed, with very few exceptions, are directed toward purifying the undeteriorated protein. The methods available are usually based on some particular biochemical activity of the protein, usually enzyme activity, and sometimes an affinity column or affinity adsorbent could be used to separate the native protein from the deteriorated one. Quite often a good affinity adsorbent is unavailable. This procedure, however, does not always work properly even when an adsorbent is available, because the deteriorated protein may possess some activity or an affinity for the adsorbent even though it has lost its natural enzyme activity (see Figure 24). The antigen-antibody reaction can also be used by means of precipitation with antibodies against the native proteins or adsorption on the immobilized antibodies. But here again, the specific antibody must be available, and the deteriorated protein may retain so much affinity for the antibody that differential separations will be impractical in some cases. 

The performance of immobilized and freely suspended affinity adsorbents was compared by calculating adsorption rates and selectivities for four different bead geometries. Simulation results indicate that the performance of finely ground adsorbent particles immobilized in hydrogel beads is superior compared to freely suspended adsorbents. The mathematical model was further used for simulation studies to investigate the effect of bead design parameters on product adsorption. 

Since many metallic catalysts have high adsorption affinities, we often find that certain poison molecules are adsorbed in an immobile form after only a very few collisions with the catalyst surface. In this situation, the outer periphery of the catalyst particle will be completely poisoned while the inner shell will be completely free of poison. The thickness of the poisoned shell grows with prolonged exposure to poison molecules until the pellet is completely deactivated. During the poisoning process, the boundary between active and deactivated regions is relatively sharp. 

At present, a wide range of solid substrates are available for protein immobilization. According to the protein attachment strategies, namely, adsorption, affinity binding, and covalent binding, all these substrates can be separated into three main parts. Surfaces like ploy(vinylidene fluoride) (PVDF), poly(dimethylsiloxane) (PDMS), nitrocellulose, polystyrene, and poly-1-lysine coated glass can adsorb proteins by electrostatic or hydrophobic forces. A potential drawback of such substrates is the difficulty... 

Another way to attach the specific antibody is dry-adsorption on GEC. Like many other biomolecules that were previously dry-adsorbed on GEC (Protein G, Protein A, IgG, DNA, Avidin), antiatrazine antibodies can be easily adsorbed on GEC by dry-adsorption while keeping its specific binding capacity [54], However, dry adsorption on GEC does not provide a well-oriented layer of specific antibodies while dry-assisted affinity immobilization on ProtA-GEB provides a compact and well-oriented layer of specific antibodies. 

Immunoadsorption, an advanced therapeutic modality, focuses on detoxification of patient blood rich in high-molecular-weight pathogenic substances, mostly abnormal autoantibodies such as rheumatoid factors in rheumatoid arthritis (RA) and anti-DNA autoantibodies in systemic lupus erythematosus (SLE). Detoxification of these pathogens will be accomplished through extracorporeal perfusion of the patient plasma or whole blood over an affinity column made of immunoadsorbents. These adsorbents perform their function through the same mechanism as conventional affinity adsorption, where proteins in the liquid phase are adsorbed on the specific ligands immobilized onto an insoluble support. 

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