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Early stage phase separation in pharmaceutical solid dispersion thin films under high humidity: improved spatial
Sheng Qi1, Jonathan G Moffat, Ziyi Yang
1School of Pharmacy, University of East Anglia , Norwich, Norfolk, NR4 7TJ, United Kingdom. sheng.qi@uea.ac.uk
Molecular Pharmaceutics
|January 17, 2013
Summary
Phase separation in pharmaceutical thin films under humidity differs from dry conditions. Amorphous drug domains form in the bulk, then migrate to the surface, with PVP minimizing crystallization.
Area of Science:
- Pharmaceutical Science
- Materials Science
- Physical Chemistry
Background:
- Phase separation in pharmaceutical solid dispersions is critical for drug delivery.
- Understanding submicrometer-scale behavior in thin films under humidity is challenging.
- Previous studies focused on dry conditions, leaving high humidity effects poorly understood.
Purpose of the Study:
- To investigate the submicrometer-scale phase separation of felodipine-PVP K29/32 solid dispersion thin films under high humidity.
- To elucidate the mechanisms and spatial distribution of phase separation.
- To evaluate the role of PVP in mitigating drug crystallization.
Main Methods:
- Spin-coating was used to prepare model felodipine-PVP K29/32 thin films.
- Probe-based techniques including atomic force microscopy (AFM), nanothermal analysis (TNA), and photothermal infrared microspectroscopy (PTIR) were employed.
- These methods allowed for three-dimensional nanoscale characterization.
Main Results:
- Phase separation under high humidity differs significantly from dry conditions.
- Initial phase separation occurs in the bulk, forming amorphous drug domains.
- Increased humidity promotes drug migration to the film surface.
- Polyvinylpyrrolidone (PVP) does not prevent phase separation but reduces amorphous felodipine crystallization.
Conclusions:
- High humidity induces bulk-initiated phase separation and surface migration of felodipine in PVP K29/32 thin films.
- Nanocharacterization techniques provide valuable 3D insights into pharmaceutical thin film behavior.
- PVP plays a role in stabilizing amorphous drug domains against crystallization under humid conditions.
