Overview
Standardised procedure for transferring cells into culture vessels at defined densities. Covers adherent and suspension cell types, cell counting, density calculation, and initial culture setup.
This protocol does not presuppose a specific cell line. Consult product documentation for line-specific parameters including growth medium, CO₂ requirements, and recommended seeding densities.
Published under CC BY 4.0. Free to use, adapt, and republish with attribution to Cellindex.
Cell source — active culture, freshly thawed vial, or newly established line
Culture vessel appropriate to the cell type and assay format
Complete growth medium, pre-warmed to 37 °C
Cell counter (haemocytometer or automated)
Sterile pipettes and tips
Incubator set to the appropriate conditions for the cell type
Procedure
8 steps
Choose a vessel format appropriate to cell type, assay requirements, and required surface area. Common formats include T-flasks, multi-well plates, and dishes.
For adherent cultures, seeding density is expressed as cells per cm² of growth surface. For suspension cultures, it is expressed as cells per mL of medium. Target density depends on cell line, doubling time, and the interval before the next manipulation.
Harvest cells from source culture by the appropriate method for the cell type — enzymatic dissociation for adherent lines, direct transfer for suspension lines. Resuspend in fresh pre-warmed medium to yield a homogeneous suspension.
Determine cell concentration and viability using a haemocytometer with an exclusion dye, or an automated cell counter. Cultures with viability below 90% should not be used as the basis for a timed experiment.
Divide the target cell number by the measured cell concentration to determine the volume of suspension to transfer. Target cell number = desired seeding density × available growth surface area (or volume for suspension cultures).
Pipette the calculated volume of cell suspension into the culture vessel. Add sufficient complete medium to reach the final working volume.
Place the vessel in a pre-equilibrated incubator at the conditions required for the cell type — commonly 37 °C, 5% CO₂, and controlled humidity. Record all conditions in the experiment log.
For adherent cultures, examine the vessel 2–6 hours after seeding to confirm attachment. Continue monitoring for morphology and confluency at regular intervals as defined in the culture maintenance schedule.
Seeding density and confluency
Incorrect seeding density is one of the most common sources of culture variability. Cells seeded too densely exhaust medium rapidly and may enter growth arrest prematurely. Cells seeded too sparsely may fail to establish or exhibit abnormal growth behaviour. Vary seeding density systematically until consistent growth rates and yields are achieved for your specific cell line and vessel format, and record the validated density in the culture log.
Subculturing and passage tracking
Cells should be subcultured while still in logarithmic growth phase, before reaching confluency. Allowing cells to reach or exceed confluency can induce contact inhibition in normal lines or genetic instability in transformed lines. Maintain a detailed culture log recording seeding densities, passage numbers, medium changes, morphological observations, and any deviations. Track passage number carefully — repeated subculture can alter key biological properties over time.