Solvent effects on the controlled dense gas precipitation of model proteins

Protein was precipitated from organic and aqueous solutions using carbon di oxide and ammonia as antisolvents. The gas antisolvent precipitation proces s (GAS) was used to produce lysozyme, insulin and myoglobin powders. Protei n powders were produced with narrow size ranges, and particle size was cont rolled between 0.05 mu m and 2.0 mu m by changes to the solvent system. Typ ically the stronger the protein solvent the larger the precipitate size. Th e GAS process, although ideal for the micronisation of stable protein powde rs, was limited by the number of suitable protein solvents that were miscib le with dense carbon dioxide and that did not irreversibly affect protein c onformation. As a result, GAS precipitation from aqueous solutions was also assessed. Insulin was precipitated from aqueous solutions as discrete 0.2- 0.3 mu m spheres using ammonia as an antisolvent. (C) 2000 Society of Chemi cal Industry.