Dry powders of stable protein formulations from aqueous solutions prepared using supercritical CO2-assisted aerosolization

We report on the use of a new supercritical carbon dioxide-assisted aerosolization coupled with bubble drying technology to prepare stabilized, dry, finely divided powders from aqueous protein formulations. In this study, the feasibility of this new technology was tested using two model proteins, lysozyme and lactate dehydrogenase (LDH). In the absence of excipients, lysozyme was observed to undergo perturbations of secondary structure observed by solid-state infrared spectroscopy. In the presence of sucrose, this unfolding was minimized. Lysozyme did not, however, undergo irreversible loss of activity, as all lysozyme powders generated by supercritical CO2-assisted aerosolization (with or without excipients) regained almost complete activity on reconstitution. The more labile LDH suffered irrecoverable loss of activity on reconstituting after supercritical CO2-assisted aerosolization and bubble drying in the absence of carbohydrate stabilizers. LDH could be stabilized throughout the nebulization, drying, and rehydration processes with the addition of sucrose, and almost complete preservation of activity was achieved with the further addition of a surface active agent, such as Tween 20, to the aqueous formulation prior to processing. (C) 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:785-797, 2001.