Author Gary Brown, LN2 Product Specialist, Haier Biomedical, discusses the preservation and handling of precious biological materials.
Liquid nitrogen (LN2) plays a crucial role in the world of assisted reproductive technology, as the go-to cryogenic agent for storing precious biological materials, including eggs, sperm and embryos. LN2 ensures the long-term preservation of these delicate specimens by providing extremely low temperatures to maintain cellular integrity. However, handling LN2 poses unique challenges, due to its extremely cold temperature, rapid expansion rate and the potential risks associated with oxygen displacement. Recent changes to UK fertility laws – extending the amount of time that gametes and embryos can be stored – will only increase the use of LN2 to meet the growing demand for storage, making essential safety measures and best practices even more important to maintain a secure and efficient cryopreservation environment, safeguarding staff and the future of fertility treatments.
In modern fertility clinics, the storage of biological material primarily relies on LN2, due to its established efficacy and reliability. Its ultra-low temperature – typically around -196 °C – halts all biological activity to preserve the viability and integrity of cells indefinitely. This is commonly achieved through vitrification, a rapid freezing technique that prevents the formation of ice crystals that could damage cellular structures. This ensures that embryos and gametes remain viable for future use, providing individuals and couples with the opportunity to achieve pregnancy at a time of their choosing, whether due to medical treatments, personal choice, or other circumstances.
Figure 1: Cryogenic tanks containing LN2 provide long term- storage of eggs and gametes at ultra-low temperatures
The need to scale up
In the UK, the Health and Social Care Act 2022 included changes to fertility laws that extended the time that gametes and embryos can be kept from 10 years to 55 years – providing the patient reconsents every 10 years [1]. As a result, fertility clinics need to plan for significant increases in demand for storage, including expanding and modernising their LN2 cryostorage solutions. Currently, a standard centre will typically use a number of medium-sized aluminium dewar in a cryopreservation room. Each dewar will contain locator racks and box system capable of holding up to 6,000 samples, and these containers require daily LN2 top ups using a manual hose to ensure that samples are kept at appropriately low temperatures.
To increase storage, many clinics are now looking to scale up and consolidate sample storage into larger containers. Modern stainless steel storage containers come in various sizes, and can be capable of storing between 13,000 and 95,000 samples in 2 ml vials. For example, the YDD-370-326 from Haier Biomedical, can store around 2,000 individual patient samples in a customised racking system that clips goblets into columns for secure straw storage. These containers are designed to maximise storage capacity while minimising consumption of LN2. Some are also capable of automated refilling from an attached replenishment tank, removing the need for manual daily top ups and minimising the risks associated with spending time in the cryopreservation room and handling liquid nitrogen. The development of smart liquid