Next-Generation Affinity Chromatography with PEGylated Ligands

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PrzybycienCBET 1159886This NSF award by the Chemical and Biological Separations program supports work by Professor Todd M. Przybycien to develop new separations technology for use in the biotechnology industry and to develop a corresponding laboratory and teaching module for secondary school chemistry students as an introduction both to separations technology and to the biotechnology industry. The separations technology development effort involves the modification of affinity chromatography media, commonly used in the production of pharmaceutical proteins such as monoclonal antibodies, so that it is more resistant to fouling by contaminant species, thereby increasing manufacturing efficiency. The secondary education module development effort involves the creation and deployment of a set of laboratory experiments and supporting lecture materials in affinity partitioning technology that can be used to augment current high school chemistry curricular materials in the area of the separation of matter by demonstrating the ideas of affinity and specificity in separation operations. These educational materials will also be used to provide exposure to the biotechnology industry, a key domestic industrial sector, as the experiments are motivated by and have applications to bioprocessing and bioseparations.Affinity chromatography is a premier bioseparations technology in which specific binding interactions are exploited to achieve selective recovery of a target biological macromolecule from a complex biological mixture. Monoclonal antibodies, or MAbs, are the dominant class of biologic products from the biopharmaceutical industry. Affinity chromatography using media with immobilized MAb-specific binding groups such as Stapylococcal Protein A, or SPA, is typically the central unit operation around which generic, or platform, MAb purification processes are developed. Our specific research approach is to modify SPA-based affinity chromatography media by chemically attaching poly(ethylene glycol), or "PEG", an inert polymer, to the SPA binding group. This chemical modification, or PEGylation, will improve media selectivity by decreasing non-specific binding interactions with SPA and will improve media robustness by increasing the stability/degradation resistance of SPA. That this approach should be successful is supported by the well-known use of PEGylation to impart stealthy characteristics to protein-based drugs without adversely affecting biological binding activity, to enhance the physical stability of proteins, and to improve the fouling resistance of surfaces towards proteins and other biologically-derived species. PEGylation strategies (size, extent, structure of attached PEG chains; masking of MAb-specific binding sites on SPA to preserve binding affinity) will be evaluated with respect to their impact on important chromatographic performance metrics including MAb binding capacity and MAb binding specificity in the presence of customary contaminants (CHO host cell protein, DNA and virus) and during many cycles of repeated use. If successful, a new class of high-performance affinity chromatography media based on ligand PEGylation will result.The proposed research aims to invoke a step-change in the selectivity and robustness of affinity chromatography media, and SPA-based media in particular, to enable a corresponding step-change improvement in chromatographic performance. PEGylated affinity chromatography media with increased specificity and robustness relative to current media can reduce process development time for new biological pharmaceuticals (improved specificity translates into fewer downstream purification steps to develop and validate) and can increase process throughput for new and existing biological pharmaceuticals (improved specificity translates into shorter, less-stringent wash and clean-in-place cycles and fewer downstream steps to operate; improved robustness translates into greater binding capacity retention, less ligand leaching and ability to use ligands with preferred specificity but decreased stability, and more operating cycles before media replacement). Greater speed-to-market and process throughput, particularly for the critical MAb class of biopharmaceuticals, can drive down treatment costs. The proposed research will comprise the research training of a Ph.D. student and several undergraduate engineering students, poising each for career opportunities in the domestic biopharmaceutical industry.