Storage and deposition of cell banks involve careful cryopreservation, thorough documentation, rigorous quality control, and adherence to regulatory requirements to ensure that the cells remain viable, authentic, and functional when needed for future use in research or production.
Overview of the processes involved:
Before storage and deposition, a master cell bank (MCB) is created from a well-characterized parental cell line. These cells are subjected to rigorous tests to confirm identity, stability, and freedom from contaminants like viruses or mycoplasma. After the MCB is established, working cell banks (WCB) are derived by expanding and cryopreserving aliquots for future use in production.
The primary goal of cell bank storage is to maintain the integrity and viability of the cells for as long as necessary. This is typically achieved through cryopreservation, which involves freezing cells at very low temperatures.
Cryopreservation: Cells are frozen in a controlled manner using cryoprotectants (e.g., dimethyl sulfoxide or DMSO) to prevent ice crystal formation that could damage the cells.
Temperature Requirements:
Master Cell Banks (MCB) and Working Cell Banks (WCB) are typically stored at temperatures ranging from -70°C to -196°C (liquid nitrogen temperatures, around -180°C) to ensure minimal metabolic activity and preserve cell viability.
Some cell types may be stored in ultra-low freezers at -80°C for short to medium-term storage, though liquid nitrogen storage is generally preferred for long-term preservation.
Accurate and detailed documentation is essential for tracking the identity, origin, and quality of cell banks. This includes:
- Cell bank lot numbers
- Donor/source information (if applicable)
- Test records (for identity, sterility, mycoplasma, endotoxins, and other quality controls)
- Freezing protocols
- Storage location details (e.g., cryovials, racks, and storage unit specifics)
Before storage, and periodically throughout their life cycle, the cell banks undergo a variety of quality control (QC) tests:
Identity tests: DNA fingerprinting, STR analysis, or other molecular methods confirm the cell line's authenticity.
Microbial testing: Cells are checked for contaminants like bacteria, fungi, or mycoplasma.
Stability testing: To ensure that the cell line retains its properties (e.g., productivity or function) over time.
Viability and potency assays: Confirm that the cells remain viable and functional after cryopreservation.
Regulatory authorities, including the FDA and EMA, require that cell banks meet strict standards regarding safety, traceability, and characterization. This includes:
- Compliance with Good Manufacturing Practices (GMP) for production and handling.
- Ensuring that biological materials used in cell bank creation (e.g., animal-derived components) meet safety standards.
- Ongoing monitoring for the absence of cross-contamination or genetic drift during long-term storage.
When a cell bank is needed for the production of biologic products, cells are re-thawed carefully under controlled conditions. The cells are then expanded in culture under optimized conditions to reach the desired cell density and functionality before being used in the production process.