Storing tissue safely
We provide tissue in three formats: freeze dried, frozen and cryopreserved in gas phase nitrogen
All tissue undergoes stock management to ensure the oldest product (with the closest expiry) is used first (this may not necessarily be the most recent delivery).
Freeze dried tissue e.g. bone
This tissue has undergone a freeze drying process, meaning it does not need special storage temperatures. This means normal ambient or room temperature is all that is required and no monitoring or alarm systems are required. The packaging must be kept dry and must not be exposed to direct sunlight as this can make the packaging brittle and prone to damage. We therefore recommend that the tissue is stored in a secure, controlled access, dark, dry place e.g. a drawer or cupboard. The expiry date is indicated on the pack (normally 3 years from donation).
Frozen tissue e.g. bone, tendons, amnion
This tissue must be stored in a dedicated, alarmed freezer/refrigerator. This means a compartment with:
- Continual temperature recording (e.g. chart recorder or electronic format) which should be checked and authorised against the required temperature limit at least once per week.
- An audible and visual alarm that indicates when the freezer is out of specification – this alarm must be in a place, or linked to a system, that is manned 24/7.
- A system in place to respond to alarms 24/7 (either in a 24/7 manned location or linked to an on-call system)
Cryopreserved tissue e.g. skin, heart valves
This tissue is stored in vapour phase nitrogen at below -135°C at Tissue and Eye Services and is usually supplied in dry ice (-79°C). It should not be returned to nitrogen storage (if you need to do this, please contact us for advice). This product can be stored in a dedicated alarmed freezer running at -80°C (please see requirements above in frozen tissue section) until the expiry date (permitted 6 months storage). Once thawed, it can be placed in a +4°C refrigerator for up to 24 hours. Do not re-freeze.
The temperature for storage will depend on the tissue:
- Bone and tendons need to be stored below -40°C for the full shelf life (3 years from donation). However they can be stored between -20° and -40°C for up to 3 months. When you place your order, we will ask you for the temperature of the freezer you are intending to use, to ensure the correct labelling and expiry date is printed on the product prior to supply. Once thawed, tissues can be placed in a +4°C refrigerator for up to 24 hours. Do not re-freeze.
- Amnion must be stored below -40°C as the high concentration glycerol it is stored in liquefies above this temperature. Once thawed, they can be placed in a +4°C refrigerator for up to 24 hours. Do not re-freeze.
Looking after tissue
Donated human tissue is a valuable resource and should be used appropriately and with minimal wastage. Hence stock levels should be kept to a minimum to avoid time expiry. Expired tissue must not be used and must be discarded (customers must not use tissue for non-transplant purposes without prior arrangement as lawful consent may not be in place).
Storage temperatures, further information and expiry date is given on pack inserts. The EU Tissue and Cells Directive requires that storage is documented in Standard Operating Procedures. We recommend, where possible, that blood transfusion laboratories assume responsibility for this task. These types of department are familiar with the need to track products and are equipped with the storage and tracking of human derived material. They are also familiar with the reporting of adverse events and reactions and they are audited to quality systems e.g. CPA.