(368h) The Influence of High Hydrostatic Pressure on Structure-Viscosity Relationships in Protein Formulations

High hydrostatic pressure, an increasingly prevalent processing tool for foods and pharmaceuticals, can have significant effects on the stability and rheological properties of protein formulations. Despite this, pressure effects on molecular protein behavior are not well understood. Building on our recent work, which revealed for the first time an empirical connection between short-time effects of pressure and dissolved salt on protein-protein interactions (PPIs), the current study exploits small-angle neutron scattering (SANS) and light scattering microrheology, or diffusing wave spectroscopy (DWS), to explore long-time formulation behavior under high pressure and reversibility of pressure effects, and connects interaction trends to macroscopic rheological properties. In situ high-pressure small-angle neutron scattering (HP-SANS) is performed on solutions of ovalbumin, a model protein, in the presence of ammonium sulfate under long pressure equilibrations. PPIs determined from fits to HP-SANS data confirm the synergistic effect of pressure and salt suggested by prior short-time experiments, and reveal enhanced attraction with longer pressurization time. Pressure effects are shown to be reversible after equilibration at ambient pressure, with slower relaxation for formulations close to a known aggregation boundary. Complementary viscosity trends were collected via in situ high-pressure diffusing wave spectroscopy (HP-DWS) on identical formulations. Viscosity increases with applied pressure across the investigated conditions, and rheological properties from HP-DWS correlate well with interaction behavior from HP-SANS. The results provide rigor to the previously determined empirical model by incorporating long-time effects and establishing reversibility, and develop a connection between microscopic interaction behavior and macroscopic solution properties across a large range of formulation conditions.

Research Interests

During my doctoral studies, I have gained significant experience in the characterization of protein-derived complex fluids, with the goal of expanding our fundamental understanding of how processing conditions affect protein formulation behavior. My career goal is to apply this knowledge to help develop the next generation of biotherapeutics in an industrial research setting. Colloidal and conformational stability are key indicators of macroscopic behavior, and the careful application of scattering techniques, rheology, and spectroscopy can provide the means to optimize product quality and process performance.