Correlating\nDifferences in the Surface Activity to\nInterface-Induced Particle Formation in Different Protein Modalities:\nIgG mAb Versus Fc-Fusion Protein

The propensity of protein-based biologics to form protein\nparticles\nduring bioprocessing can be related to their interfacial properties.\nIn this study, we compare the surface activity and interfacial film\nproperties of two structurally different biologics, an IgG and Fc-fusion,\nin the absence and presence of interfacial dilatational stresses,\nand correlate these differences to their tendency to form interface-induced\nprotein particles. Our results show that interface-induced particle\nformation is protein-dependent, with the Fc-fusion demonstrating greater\ninterfacial stability. This observation can be correlated with faster\nadsorption kinetics of the Fc-fusion protein, and formation of a less\nincompressible film at the air–liquid interface. The addition\nof polysorbate 80 (PS80), commonly added to mitigate protein particle\nformation, led to a surfactant–dominant interface for quiescent\nconditions and coadsorption of protein and surfactant for the Fc-fusion\nwhen exposed to interfacial stress. On the other hand, for the IgG\nmolecule, the surface always remained surfactant dominant. Image analysis\ndemonstrated that PS80 was more effective in mitigating particle formation\nfor the IgG than Fc-fusion. This suggests that a surfactant–dominant\ninterface is necessary to prevent interface-induced protein particle\nformation. Further, while PS80 is effective in mitigating particle\nformation in the IgG formulation, it may not be the best choice for\nother protein modalities.