(319c) Interfacial Rheology of Monoclonal Antibodies

Monoclonal antibodies (MAbs) encounter a range of physical and chemical stresses during development, manufacturing, transportation, and storage. Such stresses can promote different aggregation mechanisms in bulk solution and at solid-liquid, liquid-liquid, and vapor-liquid interfaces. Aggregation in bulk solution has been studied extensively in a mechanistic context, but the understanding of surface-mediated aggregation remains largely speculative, in part because of the limitations of its experimental study. This talk will focus on mechanistic insight into surface-mediated aggregation of MAbs by improved techniques for studying protein behavior at interfaces. Interfacial rheology was introduced as a suitable technique for measuring the properties of protein layers adsorbed to the air-liquid interface. A Langmuir trough was used to improve the practicality of interfacial shear rheology measurements for MAb systems by accelerating meso-equilibration and reducing the preparation time for each experiment from several hours to approximately 30 minutes. Creep measurements and oscillatory strain and frequency sweep measurements revealed that an adsorbed MAb layer on the air-water interface resembles a soft solid. For each condition (pH, concentration), the creep compliance from different applied stresses could be superimposed in time onto a master curve. The viscoelastic moduli, creep compliance, and superimposed master curves of the MAb layers were dependent on solution pH and bulk concentration in a manner that indicated that adsorbed MAbs form stronger interfacial films as the solution pH approaches the pI of the MAb, and at higher bulk concentrations.