(303a) Effect of Freezing Rate and Geometry On Protein Frozen Storage Stability

Freezing processes are of interest in storage stability as they can increase product stability and shelf life, decrease microbial growth and eliminate foaming during transport, allowing flexibility in the manufacturing process. However, bulk freezing processes can lead to protein aggregation over time as a result of unfolding at ice-solution interfaces, phase separation or crystallization of solutes, pH changes, and cryo-concentration. The main objective of this study was to demonstrate that varying the freezing rate influences the stability of the protein during storage.

A 20 mg/ml monoclonal antibody solution was studied in 50 ml stainless steel vessels. By varying the coolant phase, temperature, and convection, various linear freezing rates, above and below the 2 μm/s dendritic ice front limit, were generated. Freezing temperature profiles giving ice front velocities and freeze-concentration profiles were measured to understand the stresses experienced by the protein during the freezing process. Protein structural stability, measured by ELISA, tryptophan fluorescence, size exclusion chromatography, and optical density, shows that vessels frozen rapidly above the dendritic freezing rate limit are more stable over 1 year of frozen storage than those frozen fully or partially below the dendritic linear ice front velocity limit.