Protein purification alternatives

Protein purification, often referred to as downstream processing, is the most costly and time-consuming process in the manufacture of bio-molecules. EU-funded researchers integrated materials science with process development to produce novel low-cost materials and methods for selective purification with a focus on chromatography, membrane separation and extraction.

Purification is somewhat like passing sand and pebbles through a sieve except that separation is not dependent on gravity and relative size of components and holes. Instead, separation depends on chemical and electrical interactions between the biological fluid and specific binders (ligands) through which it passes.

Among the many proteins purified by the pharmaceutical industry are human immunoglobulin G (IgG) and monoclonal antibodies (MAbs), both important in immunity and thus disease therapy. The most common method for purifying IgG and MAbs is the use of protein A resin. However, pharmaceutical companies are increasingly concerned about the supply of protein A materials.

The 'Advanced interactive materials by design' (AIMS) project thus sought to develop alternatives to protein A technology for the purification of proteins. The investigators developed excellent modelling tools enabling assessment of interactions among support, linker, ligand and product promoting efficient and effective design of new materials.

The researchers created a new SartoAims protein A affinity membrane with enhanced affinity for IgG, providing an important alternative to protein A for IgG purification. In addition, the investigators studied two alternatives to protein A technology for purification of MAbs, one using much less expensive ion exchange resins in a Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) form of chromatography and one using aqueous two-phase extraction.

The researchers also developed new materials for use in ion exchange chromatography, a technique that relies on charge interactions for separation. In fact, the chromatographic resin FractoAims demonstrated superior mechanical stability and can be tailor-made based on bead size, pore size, surface area and ligand density.

The new process concepts were tested in a mini-plant to evaluate performance with respect to protein A technology. A combination of two MCSGP units operating with different parameters enabled reduction in operating costs by a factor of three in total MAb purification costs.

The AIMS project outcomes will have significant impact on the protein purification process that has until now been the most costly part of bio-molecule development in the pharmaceutical, chemical and biotechnology industries. Commercialisation of the new technologies promises to improve the European position in the huge global chemicals and pharmaceuticals market.

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