Last Updated on December 14, 2023

Cryopreservation is necessary for the long-term preservation of biological materials, enabling researchers to store and study valuable samples over extended periods. It plays a pivotal role in various fields, from medical advancements and stem cell research to biodiversity conservation, ensuring the availability of resources and knowledge for future generations. Two primary freeze-down methods for cryopreservation exist: isopropanol (IPA) freezing container and controlled rate freezing. Both serve the critical purpose of preserving biological samples, but they differ significantly in their techniques and applications. In this blog post, we’ll compare the IPA cryopreservation method to using a controlled rate freezer (CRF), shedding light on their strengths and weaknesses.

IPA Cryopreservation Benefits:

  • Simplicity and Cost-Effectiveness: The IPA method’s simplicity and cost-effectiveness make it accessible to academic labs and smaller research facilities with limited resources. It is a relatively passive process that involves gradually cooling samples in an ispropanol container placed in a -80°C freezer. After the cells are chilled they can be stored in LN2 or kept in the -80°C.
  • Low Maintenance: This method requires minimal equipment and maintenance, reducing the potential for system failures. It’s an excellent choice for labs with limited technical expertise
  • Versatility: IPA cryopreservation method can be used for a variety of sample types, from cells and tissues to microorganisms and enzymes.

While the IPA method does have its place in research let’s explore some reasons why this may not be the best.

  • Limited Control: IPA cryopreservation offers minimal control over the freezing process, which can be problematic for temperature-sensitive samples requiring specific conditions.
  • Sample Variability: Inconsistent freezing conditions can lead to unpredictable results, making it challenging to reproduce experiments accurately.
  • Sample Volume: This method suits smaller volumes, while larger quantities become cumbersome to manage.
  • Resource Intensive: While cost-effective for small labs, it may be inefficient for high-volume or long-term storage needs.

Controlled rate freezers, on the other hand, provide a superior option for consistent and reliable freezing. Let’s explore some of the benefits.

    • Precision and Reproducibility: Controlled rate freezers offer precise control over the cooling process, ensuring samples freeze uniformly and at the desired rate, which is vital for preserving sensitive samples.
    • Suitable for Large Batches: These freezers can handle multiple samples simultaneously, ensuring consistent results, making them ideal for labs dealing with a high volume of samples.
    • Versatility: Controlled rate freezers are suitable for a wide range of biological samples, including stem cells, tissues, sperm, embryos, and more. More specifically, they allow users to program specific freezing profiles and cooling rates tailored to the specific requirements of the samples being preserved.


    • Record-Keeping: Controlled rate freezers feature built-in data logging systems that store essential information, ensuring traceability, reproducibility, and compliance with safety and regulatory standards. In fields like clinical research and cell therapy, controlled-rate freezers are often recommended or required to meet regulatory standards for sample handling and preservation.

    While controlled rate freezers offer numerous advantages in terms of precision and reliability, they are not without their drawbacks. It’s important to consider these limitations when deciding whether to use a controlled rate freezer for freezing down samples:

    • Cost: One of the most significant drawbacks of controlled rate freezers is their initial investment. These freezers can be a substantial investment for laboratories, particularly smaller ones with limited budgets. Many CRF’s use liquid nitrogen (LN2) as their cooling medium. The constant need for replenishing liquid nitrogen adds to operational expenses, making it an ongoing financial burden for laboratories.
    • Liquid Nitrogen: The logistics of procuring, storing, and handling liquid nitrogen can be a hassle, requiring dedicated storage infrastructure and regular refills, which can disrupt research workflows. Strex understood how prohibitive a LN2 CRF can be, so they developed the LN2-free CytoSAVER CRF to help researchers save time and money.
    • Space Requirements & Limited Portability: Controlled rate freezers are typically larger and bulkier than an isoprpanol freezing container, occupying valuable laboratory space. For smaller labs with limited space, accommodating these freezers may be a challenge. Luckily, Strex kept this in mind while developing the CytoSAVER, this unit is made to be small, compact, and portable.
    • Maintenance: Controlled rate freezers require regular maintenance and qualification to ensure they function correctly. This includes periodic calibration, cleaning, and servicing. Neglecting maintenance can lead to equipment malfunctions and compromised sample preservation.
    • Sample Size Constraints: Some controlled rate freezers may have limitations on the size and type of samples they can accommodate. This can be restrictive for researchers working with diverse sample types or larger quantities of samples. The Strex CytoSAVER, however, addresses this issue by providing interchangeable vial racks.

    In summary, while the IPA freezing containers are a useful and cost-effective tool for some applications, it has limitations in terms of control, reproducibility, and throughput. Careful consideration of your specific research needs and sample types is essential when choosing between the IPA method and controlled rate freezing. For those seeking an advanced controlled rate freezing solution, the Strex CytoSAVER liquid-nitrogen free controlled rate freezer emerges as a compelling option. This freezer offers solutions to some of the common drawbacks of using controlled rate freezers.

    To learn more about the CytoSAVER contact us anytime for an online demo.