Cell lines are populations of cells established to grow and divide indefinitely outside the body under controlled laboratory conditions. These cells are invaluable tools used globally for drug screening, vaccine development, and modeling complex human diseases like cancer. Working with cell lines requires strict adherence to safety-related work practices (SRWPs) to protect personnel from potential biological hazards and prevent culture contamination. These safety protocols ensure the integrity of scientific results and comply with regulatory requirements.
Assessing Biological Hazard and Risk Classification
The necessity for stringent safety practices stems from the inherent biological risks associated with cell lines, particularly those derived from human or primate tissues. Even seemingly safe cell lines may harbor latent viruses or uncharacterized pathogens. Many human cell lines must be treated as potentially infectious for bloodborne diseases like HIV and Hepatitis B and C viruses, and the potential for oncogenicity also contributes to the hazard profile.
The primary system for formal risk categorization is the Biosafety Level (BSL) framework, which ranges from BSL-1 to BSL-4. This classification, guided by the CDC’s Biosafety in Microbiological and Biomedical Laboratories (BMBL), determines the minimum required containment. Most work involving cell lines falls under Biosafety Level 2 (BSL-2) because it involves agents that pose moderate risk to personnel and the environment. BSL-2 is specifically recommended for all human and non-human primate cell lines unless documented to be free of recognized bloodborne pathogens.
Mandatory Practices for Primary Containment
Primary containment focuses on the procedures and physical barriers that protect the worker from the cell line and the cell line from environmental contamination. This begins with the mandatory use of Personal Protective Equipment (PPE), which creates a barrier against hazardous material. Personnel must wear buttoned lab coats or gowns with cuffed sleeves and disposable gloves, changing them immediately if contaminated or compromised. Eye and face protection, such as safety glasses or face shields, is required whenever a procedure may create splashes or aerosols outside of an engineering control.
The most critical engineering control is the Biological Safety Cabinet (BSC), typically a Class II Type A2 cabinet, which provides personnel, product, and environmental protection. Work involving open containers of cell lines must be performed within the clean, HEPA-filtered airflow zone of the BSC. This prevents the escape of aerosols and maintains the sterility of the culture. Proper aseptic technique requires surfaces within the BSC to be decontaminated before and after use with a suitable disinfectant like 70% ethanol or bleach.
Equipment control mandates practices to minimize the generation of infectious aerosols, which pose the greatest inhalation risk. Procedures that impart energy into the cell culture, such as vortexing, sonication, or centrifugation, must be performed with sealed vessels or tubes. When using a centrifuge, tubes must be capped securely, and rotors should be loaded and unloaded entirely within the BSC. Mouth pipetting is strictly prohibited; filtered pipette tips and mechanical devices are required to prevent accidental ingestion or aerosol formation.
Facility Requirements and Administrative Controls
The BSL designation defines work practices and dictates the requirements for the laboratory structure, known as secondary containment. A BSL-2 facility must have self-closing doors and restricted access when work is in progress. Surfaces must be easily cleanable and resistant to disinfectants, and floors must be non-porous to facilitate decontamination. Handwashing sinks are required near the exit.
Waste management protocols require the inactivation of biological material before final disposal. Contaminated liquid waste, such as culture media, must be treated with a chemical disinfectant, like a 10% bleach solution, or sterilized by autoclaving. Solid contaminated waste, including plasticware and gloves, must be collected in properly labeled biohazard bags and often requires autoclaving or incineration. Sharps, such as needles and broken glass, must be placed immediately into puncture-proof, leak-proof containers labeled with the universal biohazard symbol.
Administrative controls are the essential framework for maintaining compliance and a culture of safety. These include developing detailed Standard Operating Procedures (SOPs) for all tasks involving cell lines, documenting specific hazards and controls. Mandatory, documented training is required for all personnel to ensure they understand the risks, proper work practices, and emergency procedures. Personnel working with human or primate cell lines must comply with the OSHA Bloodborne Pathogens Standard, which includes specific training and access to a medical surveillance program.