(313e) Membrane-Based Hybrid Method for Purifying Pegylated Proteins

PEGylated proteins are value-added pharmaceutical products obtained by conjugating poly (ethylene glycol) or PEG with proteins. PEGylation improves the therapeutic efficacy of biopharmaceutical proteins by increasing their biological half-life, reducing their immunogenicity and increasing their stability. A range of synthetic methods is available for carrying out protein PEGylation After the reaction, the PEGylated protein is purified from unreacted protein and other species present in the reaction mixture, typically using chromatographic methods. While very pure products can be obtained using these chromatographic methods, they suffer from binding capacity and scalability limitations. The large-scale production capability for PEGylated proteins could be significantly enhanced through the use of a high-throughput, non-chromatographic purification step. However, there has been considerably less work done in the area of non-chromatographic purification of PEGylated proteins. PEG is an LCST polymer, i.e. it undergoes phase transition from a hydrophilic state to a mildly hydrophobic state when temperature is increased. Phase transition can be made to occur at ambient temperature by the addition of lyotropic salts such as sodium chloride and ammonium sulphate. Further increase in salt concentration leads to the formation of micelle like structures. Preliminary studies showed that a majority of these micelles were several microns in size. Based on this, a membrane-based hybrid technique involving formation, microfiltration, and dissolution of PEG micelles for purifying PEGylated proteins was developed. The results obtained are discussed.