Skip to main content

SOP-006: Routine Culture Medium Change

Purpose​

To safely replace spent culture medium with fresh complete medium while maintaining sterility and minimizing disturbance to cultured mammalian cells.

Scope​

This SOP applies to routine medium replacement for adherent mammalian cell cultures maintained in flasks, dishes, or multiwell plates.

Responsibilities​

The operator is responsible for:

  • Maintaining aseptic technique throughout the procedure.
  • Using the correct complete culture medium.
  • Minimizing disturbance to the cell monolayer.
  • Recording medium changes according to laboratory policy.

Required Materials​

Reagents​

  • Fresh complete culture medium
  • 70% ethanol

Equipment​

  • Class II Biosafety Cabinet
  • Serological pipettes
  • Pipette aid
  • Micropipettes (if required)
  • Biohazard waste container

Procedure​

1. Preparation​

Confirm:

  • Correct cell culture vessel
  • Appropriate complete medium
  • Medium is at the recommended working temperature
  • No evidence of contamination

Disinfect all materials before placing them inside the biosafety cabinet.

2. Inspect the Culture​

Before changing the medium, examine the culture microscopically for:

  • Cell morphology
  • Confluency
  • Cell attachment
  • Evidence of contamination

Do not proceed if contamination is suspected.

3. Remove Spent Medium​

Carefully aspirate the spent medium without disturbing the cell monolayer.

Avoid allowing the cell surface to dry.

Dispose of waste according to institutional biosafety procedures.

4. Add Fresh Medium​

Slowly dispense fresh complete medium against the wall of the culture vessel.

Avoid directing the medium stream onto the cells.

Ensure the cells are completely covered by medium.

5. Return Culture to Incubator​

Replace the vessel cap or lid securely.

Return the culture to the incubator promptly.

Avoid unnecessary exposure to room temperature.

Acceptance Criteria​

ParameterAcceptance Criterion
Cell attachmentMaintained after medium change
Cell morphologyNormal for the cell line
Medium appearanceClear without contamination
MonolayerUndisturbed

Critical Control Points​

  • Work aseptically throughout the procedure.
  • Minimize the time cultures remain outside the incubator.
  • Prevent the cell monolayer from drying.
  • Add fresh medium gently to avoid detaching cells.
  • Confirm the correct medium is used for the cell line.

Documentation​

Record the following:

  • Date
  • Cell line
  • Passage number
  • Medium used
  • Operator initials
  • Any abnormal observations

Quality Control​

Verify:

  • Fresh medium was used.
  • No contamination is present.
  • Cells remain attached.
  • Medium volume is appropriate for the culture vessel.
  • Incubator conditions are restored promptly.

Troubleshooting​

ObservationPossible CauseCorrective Action
Cells detach after medium changeMedium added too rapidlyAdd medium slowly against the wall of the vessel
Cells appear stressedMedium temperature unsuitableUse medium at the recommended working temperature
Medium becomes cloudy shortly after changePossible contaminationDiscontinue culture and investigate contamination source
Cells begin drying during procedureDelay in adding fresh mediumMinimize handling time and add fresh medium immediately

Safety Considerations​

  • Handle all cultures as potentially biohazardous material.
  • Wear appropriate personal protective equipment (PPE).
  • Perform all procedures in a certified Class II Biosafety Cabinet.
  • Dispose of biological waste according to institutional guidelines.
  • Disinfect work surfaces before and after the procedure.