Immunoadsorption is a powerful and generalizable method for protein purification that exploits the fine specificity of antigen-antibody interactions. In spite of its potential utility, the more widespread process scale use of immunoadsorption has been limited by the high cost of the antibody and the lack of gentle elution schemes that completely preserve the activity of both the immunoadsorbent and the eluted product. In this report, we review common chemical elution strategies such as pH, ionic strength, chaotropic salts, denaturants, and organic solvents as well as physical techniques such as pressure, electrokinetics, and temperature. In general, selection of elution strategies has largely been an empirical art, balancing stability of the immunoadsorbent and the eluted product and efficiency. The limitations of the available choices demonstrate that more attention must be placed on the antibody. Techniques which assist in the identification or creation of new antibodies with improved binding properties and resistance to degradation, e.g., screening and/or rational protein engineering, are also discussed.
A series of hydrogels with large pores was synthesized by the precipitation polymerization of 2-hydroxyethyl methacrylate (HEMA) with crosslinking agent in aqueous solution. Such gels are potentially useful for the controlled release of large-molecular-weight species such as proteins. In this study, the release behavior of lysozyme and alpha-amylase from hydrogels formed from HEMA or HEMA with a comonomer was studied. It was found that the polymer composition affected the total amount of lysozyme released and its activity. Effects were smaller with alpha-amylase. Charged gels, containing a phosphate moiety, released larger amounts of lysozyme at a reduced rate as a result of charge-charge interactions.
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