Type of cryopreservation methods

Slow-rate freezing

The most widely used approach in research laboratories is slow-rate freezing, whereby cells are cooled at a rate of approximately one degree Celsius per minute. This gradual process is important because it enables water molecules inside the cell to migrate into the extracellular space, thereby reducing the risk of large ice crystals forming within the cytoplasm. These ice crystals are one of the main causes of mechanical damage to membranes and organelles during freezing. By minimizing their formation, slow-rate freezing generally leads to higher survival rates.

To achieve this controlled cooling profile, laboratories often rely on specialised programmable freezers. However, many researchers opt for more accessible solutions, such as the Mr Frosty™ freezing container, which uses isopropanol to control the cooling process at –80 °C. This simple device provides a consistent cooling rate of around –1 °C per minute, making it a convenient and cost-effective tool for routine cryopreservation. Following the initial freezing step, samples are usually transferred to liquid nitrogen for long-term storage.

Despite its advantages, the success of slow-rate freezing still depends heavily on the cryopreservation medium. Without an optimised protective solution, cells remain susceptible to osmotic stress and other types of freezing-related damage, even under ideal cooling conditions.

Vitrification

At the forefront of cryobiology is vitrification, a method designed to prevent the formation of ice crystals entirely. Unlike slow-rate freezing, where water gradually leaves the cell during controlled cooling, vitrification relies on ultra-rapid cooling combined with higher concentrations of cryoprotectants. This combination transforms water inside and around cells into a glass-like, solidified state instead of crystalline ice. Because no ice crystals form, cells are spared from the mechanical damage that usually threatens their survival during freezing.

In practice, the cell suspension is loaded onto specialised carriers, such as cryoloops, cryotops or thin straws, which can hold only microlitres of solution. These carriers are then either plunged directly into liquid nitrogen (LN₂) or exposed to LN₂ vapour. Due to the small sample volume, heat transfer is almost instantaneous, enabling cooling rates of thousands of degrees per minute. This rapid quenching prevents ice crystals from forming and preserves the internal structures of the cells.

Vitrification has proven especially valuable in fields where cell integrity is critical, such as reproductive medicine for preserving oocytes and embryos, and in advanced stem cell research where maintaining differentiation potential is essential. However, the technique requires highly precise handling, rapid cooling equipment, and the use of cryoprotectant concentrations that can be toxic to some cells if not carefully managed. For these reasons, vitrification is considered a specialized method, often applied in high-stakes or highly sensitive applications, rather than in routine laboratory cryopreservation.

Role of cyoprotectants

All cryopreservation methods rely on the use of cryoprotective agents (CPAs), which are essential for mitigating freezing damage. Dimethyl sulfoxide (DMSO) is the most widely used CPA as it effectively prevents the formation of large ice crystals and stabilizes cellular structures during cooling. Traditionally, it has been combined with fetal bovine serum (FBS) for added protection.

However, there are serious limitations to serum-based solutions. Not only do they carry the risk of contamination with animal-derived pathogens, but their undefined composition also introduces variability from batch to batch, which undermines reproducibility. In clinical and translational research, serum also raises ethical and regulatory concerns. These shortcomings have led to a shift towards serum-free, chemically defined cryopreservation media, which provide safer, more reliable and consistent conditions for research and clinical applications.

Where Bambanker™ makes the difference

Our Bambanker™ series was developed in response to these exact challenges. As a serum-free, ready-to-use cryopreservation medium, Bambanker™ eliminates the variability and risks associated with serum, while delivering consistently high cell viability across a wide range of cell types. Unlike traditional protocols that demand controlled-rate freezers, Bambanker™ performs reliably even with standard laboratory freezers, making effective cryopreservation accessible to every lab.

Researchers around the world rely on Bambanker™ for applications ranging from hybridoma storage to stem cell research and primary cultures. By providing a chemically defined, reproducible solution, it not only safeguards valuable cell lines but also ensures that results remain consistent across experiments, institutions, and countries. This global trust has established as a standard tool in modern cryopreservation.

Cryopreservation is essential for safeguarding valuable cells, but traditional approaches often demand specialized equipment, serum-based media, and complex protocols. Modern serum-free solutions like Bambanker™ make this process far more straightforward, enabling reliable cell preservation without the need for controlled-rate freezing devices. By simplifying the workflow while ensuring consistently high viability, Bambanker™ allows researchers to focus on their science.

🔗 Learn more about Bambanker™: https://www.nippongenetics.eu/en/product-category/cell-biology/freezing-media/

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