Abstract
Purpose: The physical state of excipients in freeze-dried formulations directly affects the stability of the active pharmaceutical ingredient (API). Crystallization of trehalose and mannitol in frozen solutions has been shown to be a function of composition. However, to date a detailed study of the effect of concentrations of the API and other excipients on the crystallinity of mannitol and trehalose in frozen solutions has not been reported. Methods: The crystallinity of mannitol and trehalose in frozen solutions was characterized by Differential Scanning Calorimetry, X-ray diffractometry, and FTIR spectroscopy. The secondary structure of BSA was probed by FTIR, and Circular Dichroism spectroscopy in frozen and thawed solutions, respectively. Results: Trehalose crystallization was accompanied by unfolding of BSA. BSA delayed and reduced the extent of mannitol and trehalose crystallization. Similar effects were observed upon adding D2O (≥5% w/w) and low concentrations of polysorbate 20 (≤0.2% w/w) with retention of BSA in its native conformation. At high BSA to trehalose mass ratio, the protein could stabilize itself in the frozen state, but unfolded upon thawing. Conclusions: The API and other excipients, in a concentration-dependent manner, influenced the physical state of the freeze concentrate as well as the stability of the API.
Original language | English (US) |
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Pages (from-to) | 462-478 |
Number of pages | 17 |
Journal | Pharmaceutical research |
Volume | 34 |
Issue number | 2 |
DOIs | |
State | Published - Feb 1 2017 |
Bibliographical note
Funding Information:This research was funded by an NSF grant (CBET-1335936) to A.A. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program.
Publisher Copyright:
© 2016, Springer Science+Business Media New York.
Keywords
- crystallization
- freeze-drying
- glass transition
- mannitol
- trehalose