Influence of compression on water sorption, glass transition, and enthalpy relaxation behavior of freeze-dried amorphous sugar matrices

Koreyoshi Imamura, Ryo Kagotani, Mayo Nomura, Kazuhiro Tanaka, Kohshi Kinugawa, Kazuhiro Nakanishi

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

An amorphous matrix comprised of sugar molecules are frequently used in the pharmaceutical industry. The compression of the amorphous sugar matrix improves the handling. Herein, the influence of compression on the water sorption of an amorphous sugar matrix was investigated. Amorphous sugar samples were prepared by freeze-drying, using several types of sugars, and compressed at 0-443 MPa. The compressed amorphous sugar samples as well as uncompressed samples were rehumidified at given RHs, and the equilibrium water content and glass transition temperature (Tg) were then measured. Compression resulted in a decrease in the equilibrium water content of the matrix, the magnitude of which was more significant for smaller sized sugars. Diffusivity of water vapor in the sample was also decreased to one-hundredth by the compression. The T g value for a given RH remained unchanged, irrespective of the compression. Accordingly, the decrease in Tg with increasing water content increased as the result of compression. The structural relaxation of the amorphous sugar matrices were also examined and found to be accelerated to the level of a non-porous amorphous sugar matrix as the result of the compression. The findings indicate that pores contained in freeze-dried sugar samples interfere with the propagation of structural relaxation.

Original languageEnglish
Pages (from-to)76-83
Number of pages8
JournalInternational Journal of Pharmaceutics
Volume408
Issue number1-2
DOIs
Publication statusPublished - Apr 15 2011

Keywords

  • Amorphous sugar
  • Compression
  • Freeze-drying
  • Glass transition temperature
  • Structural relaxation
  • Water sorption

ASJC Scopus subject areas

  • Pharmaceutical Science

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