SOP-007: Cell Seeding
Purpose
To uniformly seed mammalian cells into culture vessels at the desired density for routine maintenance or experimental applications.
Scope
This SOP applies to the seeding of adherent and suspension mammalian cell cultures into flasks, culture dishes, and multiwell plates.
Responsibilities
The operator is responsible for:
- Preparing a viable single-cell suspension.
- Calculating the required seeding density.
- Maintaining aseptic technique throughout the procedure.
- Ensuring even cell distribution.
- Recording seeding information.
Required Materials
Reagents
- Cell suspension
- Complete culture medium
- Sterile PBS (if required)
Equipment
- Class II Biosafety Cabinet
- Micropipettes and sterile tips
- Serological pipettes
- Pipette aid
- Cell culture vessels
- Inverted microscope
Procedure
1. Prepare the Cell Suspension
Obtain a well-mixed, single-cell suspension.
If required, determine cell concentration and viability before seeding.
2. Calculate the Required Cell Volume
Calculate the volume of cell suspension needed to achieve the desired seeding density.
Refer to the Cell Seeding Calculation Guide for calculation methods.
3. Prepare the Cell Suspension
Dilute the cell suspension with complete culture medium to the desired final concentration.
Mix gently to maintain a homogeneous suspension.
4. Dispense Cells
Add the calculated volume of cell suspension into each culture vessel.
Dispense gently to minimize bubble formation.
For multiwell plates, use the same technique and dispensing speed for each well.
5. Mix the Culture Vessel
Immediately after seeding, gently move the vessel in a front-to-back and side-to-side ("north-south" and "east-west") motion to distribute cells evenly.
Avoid circular swirling, which may concentrate cells in the center.
6. Incubate
Place the culture vessel carefully into the incubator.
Avoid unnecessary movement until cells have attached (for adherent cultures).
Acceptance Criteria
| Parameter | Acceptance Criterion |
|---|---|
| Cell suspension | Homogeneous with minimal clumping |
| Cell distribution | Even across the culture surface |
| Seeding density | Matches experimental design |
| Culture vessel | Properly labeled |
Critical Control Points
- Thoroughly mix the cell suspension immediately before dispensing.
- Calculate the correct seeding density.
- Keep the suspension mixed when seeding multiple vessels.
- Avoid generating bubbles during dispensing.
- Distribute cells evenly before incubation.
Documentation
Record the following:
- Date
- Cell line
- Passage number
- Culture vessel type
- Seeding density
- Medium used
- Operator initials
Quality Control
Verify:
- Cell viability meets laboratory requirements.
- Cell suspension is free of excessive clumping.
- Uniform cell distribution after seeding.
- Correct labeling of all culture vessels.
Troubleshooting
| Observation | Possible Cause | Corrective Action |
|---|---|---|
| Uneven cell distribution | Inadequate mixing | Gently mix the suspension before and during seeding |
| Cell clumping | Poor dissociation | Improve dissociation before preparing the suspension |
| Variable cell numbers between wells | Suspension settled during dispensing | Resuspend cells frequently while seeding |
| Poor attachment after seeding | Cells disturbed before attachment | Minimize movement of culture vessels after incubation |
Safety Considerations
- Handle all cultured cells as potentially biohazardous.
- Wear appropriate personal protective equipment (PPE).
- Perform all procedures in a certified Class II Biosafety Cabinet.
- Dispose of biological waste according to institutional biosafety guidelines.
- Disinfect work surfaces before and after the procedure.