(53h) How pH Can Impact the Interfacial Properties of a Monoclonal Antibody and How This Can Lead to Aggregation during Bioprocessing

Protein stability during manufacturing, storage, transportation, and administration to a patient is essential in protein therapeutics, especially for monoclonal antibodies (mAbs). Undesired submicron and subvisible particles in a mAb solution, in the size range of 0.1-100 μm, has the potential to cause adverse effects on product safety and efficacy and is of extreme concern in the formulation of biopharmaceuticals. Recently, the air-liquid interface has been associated with protein particle aggregation. When mechanical agitation is applied to a mAb solution, it has been shown that protein particle formulation often occurs. However, the effect of pH on these stressed interfacial properties remain unclear and is still highly debated today. To better understand the effect of pH on mechanical agitations, a Langmuir trough is used in this study to apply controlled dilatational stress to the interface of the unstable mAb, Molecule C (MC), solution. Any protein particles formed at the interface or in the bulk solution were characterized using atomic force microscopy (AFM) and micro-flow imaging (MFI). The MC solution was first allowed to equilibrate unstressed for two hours to reach maximum adsorption to the interface before being subjected to 750 interfacial compression-expansion cycles at a rate of 150 mm/min for 6 hours. To determine the effect of pH on the interfacial properties of both the unstressed and stressed conditions, a solution at a higher and lower pH were compared respectively. At each pH, the adsorption curves and isotherms followed a similar trend. However, the lower pH exhibited the highest hysteresis in surface pressure versus area isotherms, the highest surface activity when allowed to equilibrate, and the highest increase in particles at the air-liquid interface when subjected to interfacial stresses. The higher pH did increase interfacial activity as well but followed a closer trend to the original solution. The higher pH did however exhibit the highest particle increase in the bulk solution comparatively. These results suggest that while the air-liquid interface does serve as a nucleation site for initiating protein aggregation, the number of protein particles in both the bulk and interface are dependent upon mechanical agitation as well as pH.