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Flash-and-Freeze: A Novel Technique to Capture Membrane Dynamics with Electron Microscopy
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Spin Freezing and Its Impact on Pore Size, Tortuosity and Solid State
Joris Lammens1, Niloofar Moazami Goudarzi2,3, Laurens Leys4
1Laboratory of Pharmaceutical Technology, Department of Pharmaceutics, Ghent University, Ottergemsesteenweg 460, B-9000 Gent, Belgium.
Pharmaceutics
|December 28, 2021
Summary
Spin freezing rate significantly impacts freeze-dried product characteristics. Fast spin freezing creates lamellar structures with low mass transfer resistance, enhancing drying efficiency.
Area of Science:
- Materials Science
- Chemical Engineering
- Pharmaceutical Technology
Background:
- Spin freeze-drying offers higher drying rates and process control than batch methods.
- The influence of spin freezing rate on dried product properties remains unclear.
Purpose of the Study:
- To investigate the relationship between spin freezing rate and key characteristics of the freeze-dried product layer.
- To understand how spin freezing affects pore size, pore shape, mass transfer resistance, and solid state.
Main Methods:
- High-resolution X-ray micro-computed tomography (µCT) for detailed structural analysis.
- Scanning electron microscopy (SEM) to visualize surface morphology.
- Thermal imaging and X-ray diffraction (XRD) to assess thermal properties and solid state.
Main Results:
- Slow spin freezing rates led to highly tortuous structures.
- Fast spin freezing rates resulted in lamellar structures.
- Tortuosity and mass transfer resistance were significantly higher in slow-frozen samples.
Conclusions:
- Spin freezing rate is a critical parameter controlling the microstructure of freeze-dried products.
- Fast spin freezing optimizes pore structure, reducing mass transfer resistance and improving drying efficiency.
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