Acoustic Anomalies and Fast Relaxation Dynamics of Amorphous Progesterone as Revealed by Brillouin Light Scattering.

Tae Kim,Jae-Hyeon Ko,Hyojong Yoo

doi:10.3390/ma10121426

Tae Kim, Jae-Hyeon Ko + Show 1 more

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https://doi.org/10.3390/ma10121426

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Journal: Materials	Publication Date: Dec 14, 2017
Citations: 1	License type: CC BY 4.0

Affiliation: Agency for Defense Development, Hallym University

Abstract

The amorphous state of pharmaceuticals has attracted much attention due to its high bioavailability and other advantages. The stability of the amorphous state in relation with the local molecular mobility is important from both fundamental and practical points of view. The acoustic properties of amorphous progesterone, one of the representative steroid hormones, were investigated by using a Brillouin inelastic light scattering technique. The Brillouin spectrum of the longitudinal acoustic mode exhibited distinct changes at the glass transition and the cold-crystallization temperatures. The acoustic dispersions of the longitudinal sound velocity and the acoustic absorption coefficient were attributed to the fast and possibly the secondary relaxation processes in the glassy and supercooled liquid states, while the structural relaxation process was considered as the dominant origin for the significant acoustic damping observed even in the liquid phase. The persisting acoustic dispersion in the liquid state was attributed to the single-molecule nature of the progesterone which does not exhibit hydrogen bonds in the condensed states.

Highlights

Amorphous pharmaceuticals have attracted great attention because of their potential advantages, such as better bioavailability due to higher solubility, easy production and packaging, etc. [1,2].They do not have any drawbacks caused by polymorphism, i.e., varied bioavailabilities due to two more crystallographically distinct structures
The progesterone crystals were melted at 408 K, which is above the melting point (Tm ~403 K), and quenched to 77 K to generate amorphous or glassy state
These spectra correspond to the states of progesterone starting from the quenched glassy state (203 K) to the ultraviscous state (313 K) and to the crystalline state (353 K)

Summary

Introduction

Amorphous pharmaceuticals have attracted great attention because of their potential advantages, such as better bioavailability due to higher solubility, easy production and packaging, etc. [1,2].They do not have any drawbacks caused by polymorphism, i.e., varied bioavailabilities due to two more crystallographically distinct structures. Amorphous pharmaceuticals have attracted great attention because of their potential advantages, such as better bioavailability due to higher solubility, easy production and packaging, etc. Glassy pharmaceuticals in the nonequilibrium state have higher free energy than crystalline ones. It indicates that aging, i.e., time dependence of physical properties, or recrystallization may limit the shelf life of pharmaceuticals [3,4]. Local molecular mobility remnant in the glassy and supercooled-liquid states might trigger or facilitate the recrystallization process. In this respect, it is important to investigate molecular mobility in their amorphous and ultraviscous (supercooled liquid) states in detail as a function of temperature [5]

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