Industry focus on freeze-drying bottled technology
During the freeze-drying process of pharmaceuticals, the freezing stage plays a crucial role in determining both the morphology of the frozen material and the final structure of the lyophilized product. This step is not only essential but also one of the most challenging to control due to the unpredictable nature of nucleation during freezing. Additionally, the freezing process can be damaging to biological materials, potentially leading to a loss of protein activity. In this study, the author analyzed experimental data from standard formulations used to stabilize pharmaceutical proteins during freeze-drying, focusing on ice crystal morphology and sublimation rates.
First, the study examined how different bottle configurations—such as molded versus tubular bottles, fill height, and bottle size—affect ice crystal formation. Using a light microscope within the freeze-drying chamber, the author observed and recorded ice crystal sizes under various freezing conditions. The results showed that ice crystal size distribution depends not only on the freezing rate but also on the bottle type and fill level. This behavior can be attributed to the overcooling effect, which typically leads to irregular and uneven ice crystal growth. However, controlled annealing was found to significantly improve homogeneity and increase the average size of ice crystals.
Secondly, the authors developed an ultrasound system to regulate ice nucleation in standard formulations such as mannitol, bovine serum albumin, and sucrose. The system enabled precise control of the nucleation temperature during supercooling. Experimental results confirmed that ultrasonically induced nucleation led to more uniform ice crystal structures, which in turn improved the drying efficiency during the lyophilization process.
The findings highlight that controlling the freezing step—particularly the nucleation process—is key to optimizing the morphology of freeze-dried matrices. The use of an optical microscope in the freeze-drying chamber allows for easy and effective visualization of ice phase morphology through reflection. The structure of the ice phase directly influences the sublimation rate and the final texture of the dried product.
Experiments also demonstrated that ultrasonically controlled nucleation can effectively initiate ice formation in glass bottles with different sizes and types, which are commonly used in industrial freeze-drying of pharmaceutical proteins. By setting a specific nucleation temperature, the system enables varying degrees of supercooling and ice crystal growth rates. A large number of frozen samples confirmed that this method produces more uniform ice crystal structures, resulting in a more porous and permeable lyophilized matrix, ultimately reducing sublimation time.
The author aims to further develop this system for pilot and industrial applications, with the goal of enhancing the quality and efficiency of the freeze-drying cycle for pharmaceutical products.
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