Cryopreservation is the process of freezing biological material at extreme temperatures; most common -196 °C/-321 °F in liquid nitrogen (N2). At these low temperatures, all biological activity stops, including the biochemical reactions that lead to cell death and DNA degradation. This preservation method in theory makes it possible to store living cells as well as other biological material unchanged for centuries.
The challenge of cryopreservation is to help cells to survive both cooling to extreme temperatures and thawing back to physiological conditions. Intracellular ice formation in particular is a critical issue that has to be controlled to keep the cell membrane intact and the cells alive. The crucial elements to prevent this are the freezing rate (degrees per minute) and the composition of the freezing medium used. The freezing medium generally consists of a diluter, (sometimes) a protein source, as well as a cryoprotectant compound. The choice of most suitable cryoprotectant will influence the preservation result and will be different between different cells and different species.
Cryopreservation technology is important in breeding programs to preserve desired genes, but also provides an opportunity to save endangered species.
Cryogenetics perform their cryopreservation services in specially designed laboratories, located at Puerto Montt in Chile, Vancouver Island and New Brunswick in Canada, Woburn, MA in the USA, Tasmania in Australia and Trondheim and Hamar in Norway.
Clients ship the milt or, in the case of zebrafish, the live fish, to their nearest Cryogenetics facility where the cryopreservation is performed. The process includes all the steps from quality evaluation, dilution, packing in storage containers and freezing in liquid Nitrogen.
After the milt/sperm is cryopreserved in liquid Nitrogen, you the client can choose how you would like the material to be stored with us or, if you want, the material can be returned for storage at your own site.
You only need notify Cryogenetics when the material is needed for fertilization and then we will organize the return shipment. Training is provided for the milt thawing and fertilization process.
Just as important as having the correct cryopreservation protocol, is to have the best possible container in which to store the frozen sperm. Each container needs to be tailored to its application; an optimal volume, biosecure, non-toxic, practical, space-saving and aid the fertilization process after thawing. Based on these design principles, Cryogenetics has developed two specialized and patented receptacles; the SquarePack® for and a “Micro-straw”.
The SquarePack® volume is 12.5 ml and is designed for freezing of milt in large volumes. This is an important factor in providing effective reproduction and would be used for Atlantic salmon for example. One salmon male can give more than 1 liter of diluted milt which means that traditional 0.5 ml straws are far too small for such larger scale production needs.
The “Micro-straw” was developed for fish at the opposite end of the scale, such as Zebrafish who give sperm in a volume of approximately 1-3 µl. The “Micro-straw” holds volumes up to 50 µl of diluted sperm which is a much more suitable container for these smaller species.