Elucidation of Compression-Induced Surface Crystallization in Amorphous Tablets Using Sum Frequency Generation (SFG) Microscopy
To investigate the effect of compression on the crystallization behavior in amorphous tablets using sum frequency generation (SFG) microscopy imaging and more established analytical methods.
Tablets containing neat amorphous griseofulvin with/without excipients (silica, hydroxypropyl methylcellulose acetate succinate (HPMCAS), microcrystalline cellulose (MCC) and polyethylene glycol (PEG)) were prepared. They were analyzed upon preparation and storage using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM) and SFG microscopy.
Compression-induced crystallization occurred predominantly on the surface of the neat amorphous griseofulvin tablets, with minimal crystallinity being detected in the core of the tablets. The presence of various types of excipients was not able to mitigate the compression-induced surface crystallization of the amorphous griseofulvin tablets. However, the excipients affected the crystallization rate of amorphous griseofulvin in the core of the tablet upon compression and storage.
SFG microscopy can be used in combination with ATR-FTIR spectroscopy and SEM to understand the crystallization behaviour of amorphous tablets upon compression and storage. When selecting excipients for amorphous formulations, it is important to consider the effect of the excipients on the physical stability of the amorphous formulations.
KEY WORDSamorphous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy compression crystallization griseofulvin scanning electron microscopy (SEM) sum frequency generation (SFG) microscopy
Attenuated total reflectance Fourier transform infrared
Differential scanning calorimetry
Hydroxypropyl methylcellulose acetate succinate
Nuclear magnetic resonance
Optical parametric oscillator
Scanning electron microscopy
Sum frequency generation
Second harmonic generation
X-ray powder diffractometry
ACKNOWLEDGMENTS AND DISCLOSURES
This study was partially supported by the Pharmacy Grant 2013 (University of Helsinki). Elman Poole Travelling Fellowship and the University of Otago Doctoral Scholarship are gratefully acknowledged for providing Pei Ting Mah with financial support. Timo Laaksonen acknowledges funding from the Academy of Finland grant no. 258114.
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