Quick answer
Passage cells based on growth state, culture type, and cell-line guidance
Routine cell passaging, also called subculturing cells or cell splitting, is essential for maintaining healthy cultures over time. As cells proliferate, they consume nutrients, accumulate metabolic waste, and eventually reach densities that can alter growth and cell behavior.
For adherent cultures, passaging usually involves detaching cells from the culture surface and reseeding them into fresh vessels. Suspension cells generally do not require enzymatic detachment and can instead be diluted into fresh medium at an appropriate density.
The exact passage frequency and split ratio depend on the cell line. When cell-specific guidance is available, follow your lab's standard protocol rather than applying a universal schedule.
Protocol boundary
Use this as general guidance
Cell-line-specific instructions, supplier recovery notes, institutional biosafety requirements, and your lab's validated SOP should take priority when they differ from this general workflow.
Materials
Materials and reagents
Complete culture medium appropriate for the cell line
Cell culture flasks
Adherent growth, expansion, passaging, and recovery culture.
Shop cell culture flasksWorkflow step
Step 1: Prepare Media and Workspace Before Passaging
Warm the required complete medium and, when appropriate, dissociation reagent to the conditions specified for the cell line. Prepare fresh culture vessels before beginning.
For adherent cells, assess morphology and confluency before passaging. Many commonly cultured adherent cell lines are passaged before reaching complete confluence, often around 70–90% confluency, although the optimal range is cell-line dependent.
For suspension cells, evaluate cell density, viability, and signs of excessive clumping before dilution.
Workflow step
Step 2: Remove Old Media and Rinse with PBS (Adherent) or Assess Cell Density (Suspension)
Adherent Cells
Aspirate the spent medium and gently rinse the monolayer with PBS to remove residual serum and loosely associated debris. Serum proteins can inhibit trypsin activity, so an effective rinse supports more consistent detachment.
Avoid allowing the cell layer to dry during this process.
Suspension Cells
Mix the culture gently to obtain a representative suspension, then determine viable cell density.
Compare the result with the recommended growth range for the cell line. Many suspension cultures are maintained by diluting cells back to a defined starting concentration before they reach excessive density.
Workflow step
Step 3: Detach Cells with Trypsin-EDTA (Adherent) or Dilute Cell Suspension (Suspension)
Adherent Cells
Add enough trypsin-EDTA to cover the cell layer and incubate until the cells begin to round up and detach. For many common cell lines, detachment takes approximately 2–5 minutes at 37°C, but sensitive cells may require shorter exposure.
Gently tap the vessel if necessary. Once cells have detached, add complete medium containing serum, when applicable, to neutralize trypsin.
Avoid prolonged trypsin exposure. Over-digestion can damage cell-surface proteins, reduce viability, and impair subsequent attachment.
Suspension Cells
Suspension cultures generally do not require enzymatic treatment. Calculate the volume of the existing culture needed to establish the desired starting density, then dilute it with fresh complete medium.
If substantial debris or dead cells have accumulated, centrifugation and resuspension may occasionally be appropriate, but routine passaging often requires only dilution.
Workflow step
Step 4: Plate Cells and Resume Culture
Transfer the desired number of cells into fresh culture vessels containing complete medium.
Adherent cells are commonly split using ratios such as 1:3 to 1:10, depending on growth rate and experimental requirements. These ratios should not be treated as universal; cell-line-specific recommendations take priority.
Distribute adherent cells evenly by gently moving the vessel after seeding. For suspension cultures, ensure cells are thoroughly but gently mixed.
Return cultures promptly to their appropriate incubation conditions.
Expected Results
Expected Results
Within several hours after passaging, healthy adherent cells should begin attaching and spreading. By approximately 24 hours, morphology should resemble the expected appearance of the cell line.
Healthy suspension cultures should show a relatively uniform cell distribution, acceptable viability, and limited debris. Cell density should increase predictably during subsequent culture.
Troubleshooting
Common problems to check
Cells Are Not Detaching
Residual serum may be inhibiting trypsin, or the exposure time may be insufficient. Confirm that the monolayer was rinsed properly and that the dissociation reagent is active.
Cell Clumping
Incomplete dissociation or excessive cell density can promote clumping. Gently pipette the suspension after detachment without introducing unnecessary shear stress.
Low Viability After Passaging
Possible causes include overly aggressive pipetting, excessive centrifugation, inappropriate split ratios, or prolonged exposure to dissociation reagent.
Over-Digestion
Excessive trypsin exposure can damage membrane proteins and reduce attachment. Monitor cells during detachment rather than relying only on a fixed incubation time.
FAQ
Common questions
How often should cells be passaged?
Passage frequency depends on growth rate and starting density. Fast-growing lines may require passaging every few days, while slower cultures require longer intervals.
Should adherent cells reach 100% confluency before splitting?
Usually not. Prolonged over-confluence can alter growth and phenotype in many cell lines. Follow the recommended confluency range for your cells.
Do suspension cells need trypsin?
Generally, no. Suspension cells grow freely in the medium and usually can be passaged by dilution.
What split ratio should I use?
Common ratios range from approximately 1:3 to 1:10, but the correct ratio depends on the cell line and desired culture schedule.
Products
Products used in this workflow
Cell culture flasks
Adherent growth, expansion, passaging, and recovery culture.
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