Paola Casucci
Ottergemsesteenweg 460
B-9000 Gent (Belgium)
Tel.: +32-9-264.8068
E-mail: Paola.Casucci@UGent.be
Education: Chemical Engineer
Applications of annealing on continuous freeze-drying
Annealing is an optional process step between freezing and primary drying in which samples are maintained at a specific subfreezing temperature for a pre-defined period of time. It is often used in lyophilization to increase the sublimation speed and thus reduce the duration of primary drying, as consequence of ice crystal growth, and to enhance the complete crystallization of certain compounds in the formulation. This thermal treatment of frozen solution improve influencing properties such as pore size and collapse temperature.
The study focused on the application of annealing to the continuous freeze-drying technology developed by LPPAT, which enables faster and better controlled formulation and process development compared to conventional batch freeze-drying. During the process, the vials filled with liquid solution are rapidly spun along its longitudinal axis during the freezing step, hence, a thin, cylindrical, frozen product layer is obtained. Subsequently the pressure in the chamber is lowered and the vial is continuously rotated at low rpm (e.g. 5 to 10) in front of a IR-heater supplying the required energy for sublimation and desorption. This approach has a multitude of advantages over conventional freeze-drying, such as reduced vial-to-vial variability, reduced process time and possibility of controlling and setting a broad range of cooling and freezing (crystallization) rates independently from each other.
The research aims to continue the goal of the research group to transform freeze-drying from the traditional batch process to a continuous process, including the annealing step.
Finally, the application of the annealing step in combination with spin freezing is planned for several APIs.