Ice nucleation temperature influences recovery of activity of a model protein after freeze drying

The objective of this study was to determine whether a relationship exists between ice nucleation temperature and recovery of activity of a model protein, lactate dehydrogenase, after freeze drying. Aqueous buffer systems containing 50 µg/mL of protein were frozen in vials with externally mounted thermocouples on the shelf of a freeze dryer, then freeze dried. Various methods were used to establish a wide range of ice nucleation temperatures. An inverse relationship was found between the extent of supercooling during freezing and recovery of activity in the reconstituted solution. The data are consistent with a mechanism of inactivation resulting from adsorption of protein at the ice/freeze–concentrate interface during the freezing process. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3495–3498, 2009