SOP-022: Storage and Retrieval of Cryopreserved Cells in Liquid Nitrogen
Purpose
To ensure the safe storage, retrieval, and handling of cryopreserved mammalian cells maintained in liquid nitrogen storage systems.
Scope
This SOP applies to all cryovials stored in liquid nitrogen freezers or vapor-phase liquid nitrogen storage systems for long-term preservation of mammalian cell cultures.
Responsibilities
The operator is responsible for:
- Maintaining accurate cryostorage records.
- Handling cryovials safely.
- Minimizing exposure of stored samples to ambient temperatures.
- Reporting damaged or missing samples.
Required Materials
Equipment
- Liquid nitrogen storage vessel
- Cryogenic gloves
- Face shield or safety goggles
- Laboratory coat
- Cryogenic forceps or retrieval tool
- Cryoboxes and storage racks
- Sample inventory records
Procedure
1. Verify Sample Information
Before opening the storage vessel:
- Confirm sample identity.
- Determine the storage location.
- Verify the required cryovial.
Avoid unnecessary searching while the vessel is open.
2. Prepare for Retrieval
Wear appropriate cryogenic personal protective equipment (PPE).
Gather all required materials before opening the storage vessel.
3. Retrieve the Cryovial
Open the storage vessel only for the minimum time required.
Locate the cryobox or storage rack.
Retrieve the required cryovial quickly using an appropriate retrieval tool.
Return the remaining samples to storage immediately.
4. Transfer the Sample
Transfer the retrieved cryovial directly to the next processing step according to the laboratory thawing protocol.
Avoid allowing cryovials to warm unintentionally during handling.
5. Return Remaining Samples
Ensure all cryoboxes and storage racks are returned to their correct positions.
Securely close the storage vessel after use.
6. Update Records
Document:
- Sample retrieved
- Date
- Operator
- Storage location changes (if applicable)
Acceptance Criteria
| Parameter | Acceptance Criterion |
|---|---|
| Sample identification | Verified before retrieval |
| Storage location | Correctly maintained |
| Cryovials | Intact without visible damage |
| Exposure time | Minimized during retrieval |
Critical Control Points
- Prepare all required materials before opening the storage vessel.
- Minimize exposure of stored samples to ambient temperatures.
- Return unused samples to storage immediately.
- Handle cryovials carefully to avoid physical damage.
- Maintain accurate inventory records.
Documentation
Record the following:
- Date
- Cell line
- Cryovial identification
- Storage location
- Operator initials
- Any abnormalities observed
Quality Control
Verify:
- Cryovials remain properly labeled.
- Storage locations are accurate.
- Cryoboxes are returned to their original positions.
- No damaged cryovials are returned to storage.
- Inventory records are updated after retrieval.
Troubleshooting
| Observation | Possible Cause | Corrective Action |
|---|---|---|
| Cryovial cannot be located | Incorrect inventory record | Verify storage records and update inventory after retrieval |
| Cryovial label unreadable | Label deterioration | Replace the sample label according to laboratory procedures if possible |
| Damaged cryovial | Mechanical damage during storage or handling | Do not use the sample; report the damage immediately |
| Prolonged storage vessel opening | Poor preparation before retrieval | Locate the storage position before opening the vessel |
Safety Considerations
- Wear cryogenic gloves, eye protection, and a laboratory coat when handling liquid nitrogen.
- Never allow liquid nitrogen to contact exposed skin.
- Use cryogenic forceps or approved retrieval tools.
- Handle cryovials carefully, as they may rupture if damaged.
- Use liquid nitrogen only in well-ventilated areas to minimize the risk of oxygen displacement.