reproductive medicine

The cryobank of Nadezhda hospital

A cryobank is a unit for the long term storage of various biological materials – cells and tissues – at low and ultralow temperatures (such as the temperature of liquid nitrogen –196°C).


It is recommended that cryobanks are located below ground level of buildings, as during cryogenic storage, the only environmental factor likely to have a minimal negative effect on tissues and cells is radiation, including solar radiation. That is why at Nadezhda, the cryobank is located underground, at level –1, in separate dedicated premises. Card readers restrict access to the cryogenic halls. Access to cryo tanks is also limited to qualified staff specifically authorised. 

Accoring to regulatory requirements, all specimens stored in the cryobank have to be clearly identified and separate cryotanks have to be used for storing different types of of cell or tissue specimens. Freshly frozen specimens are not allowed to be stored together with specimens in long storage. Freshly frozen specimens are temporarily stored in a separate quarantine tank for a certain time period depending on specific requirements. This is done as a precautionary measure to avoid cross-contamination (infection) of stored specimens by a potentially infectious one until all tests come clean.

At Nadezhda IVF’s cryobank, primarily sperm, eggs and embryos are stored. We also keep ovarian tissue in cryogenic storage from cancer patients who could not freeze eggs for some reason. In Bulgaria, the re-transplantation of cryopreserved ovarian tissue is not yet regulated by legislation, and such procedures are currently not performed, but patients have the chance to use stored tissue in a country with acting regulations on the matter.

Cryo tanks contain special metal canisters or shelves that have unique address positions for each specimen. Information for each specimen and its address in the cryo tank is entered and stored in a digital registry. A unique identification number (UIN) is allocated to every patient’s specimen, which is then registered with the Executive Agency Medicinal Audit, the competent authority overseeing assisted reproduction and biobanks.

The methos for freezing, storage and monitoring of cells and tissues at Nadezhda’s cryobank are identical to those employed by the world’s leading biobanks.

The release of stored embryos, eggs and sperm from Nadezhda’s Cryobank requires the patient’s signed informed consent. The competent authority is also notified to take the specimen out of the registries after the release.

Delivery of frozen specimens from abroad usually entails donor sperm. Courier companies with special authorisation carry out the transportation.

If frozen specimens from another cryobank have to be delivered, it is important that they are transported at the exact same or similar temperatures as during storage. When cells from other cryobanks are delivered to Nadezhda, they travel in a cryogenic transport tank loaded with liquid nitrogen at – 196 °C. To make this possible, the patient has to file a request to transfer the stored specimen to Nadezhda both with the original cryo bank and with us. On the scheduled day and time of transfer, a representative of the original cryobank, staff of Nadezhda cryobank, as well as the patients themselves need to be present. The participation and presence of the three parties are mandatory.

The cryobank of Nadezhda hospital is equipped with a centra system for continuous 24/7 monitoring of the cryogenic tanks, which are connected to temperature sensors inside every single one of them. Temperature readings are logged every 5 minutes. An intelligent alarm system can make automated calls round the clock to the on-duty team if there are specific actions needed.

See also

Egg freezing
Sperm freezing
"Keep Hope Alive"
Fertility preservation