Glass Transition Curves of Aqueous Solutions for the Freeze-Drying of Biomaterials
Freeze-drying is a common process for the long-term preservation of biological material, such as therapeutical and diagnostical proteins. The maintenance of a glassy state is generally believed to guarantee long-term stability of the freeze-dried material. In order to yield high recovery rates, it is common practice to add stabilizers to the biomaterial. In this study, a large number of carbohydrate and macromolecular stabilizers are analyzed with respect to their glass transition temperatures. Aqueous solutions of these stabilizers were prepared and subjected to the freeze-drying process. It was found that the glass transition temperatures of these solutions increase during the drying process. They also tend to increase with increasing molecular weight of the stabilizer. In contrast, the addition of salts leads to a depression of the glass transition temperature. The resulting glass transition curves are described using a thermodynamic model. A rationale is presented to allow for the selection of stabilizers which have favorable properties with respect to glass formation.
KeywordsGlass Transition Glass Transition Temperature Lactic Acid Bacterium Specific Heat Capacity Hydroxyethyl Starch
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