As the genetic modification of mice is increasingly used in medical and biological research, so too is the need for an efficient way to transport cryopreserved embryos and sperm.
For the preservation of the frozen embryos/sperm, liquid nitrogen is used to keep the temperatures in the transport containers below −150 °C. These containers, which are like a dry sipper with liquid nitrogen absorbers embedded inside, are heavy and often expensive, especially when used for short distance transportation.
In this study, a macroporous silicone gel  was tested for its ability to retain liquid nitrogen and its properties. Researchers packed the marshmallow-like gel (MG) into a commercially available vacuum-insulated water bottle and tested its absorption of liquid nitrogen. They found that the gel was able to keep the temperature inside the container below -150 °C for 10 hours (Figures 1 and 2).
As a further test, the researchers placed mouse embryos in the container with the gel for nine hours and found no clear decrease in the embryos' survival rate.
Figure 1. Photograph of the container packing a MG.
Figure 2. Temperature change of a container made with a MG, compared with containers packed with a cloth.
Since the marshmallow-like gel showed little deterioration after exposure to the liquid nitrogen,  the container can be used repeatedly. The process of fabricating MGs is also simple and can be prepared DIY-style by users without experience in chemical synthesis.
These research results were published online in Applied Materials Today on November 1, 2017. The work was supported by the JSPS KAKENHI and the Sasakawa Scientific Research Grant from the Japan Science Society.
- Publication Details:
Title: Marshmallow-like silicone gels as flexible thermal insulators and liquid nitrogen retention materials and their application in containers for cryopreserved embryos
Authors: Gen Hayase, Yasutaka Ohya
Journal: Applied Materials Today
Frontier Research Institute for Interdisciplinary Sciences