Transfect Expi293F™ Cells in a 3L Bioreactor1. Subculture and expand Expi293F™ cells until they reach a density of 3–5 × 106viable cells/mL in a culture volume that will yield at least 9 × 108 viable cells toinoculate one bioreactor.Note: Allow cells to recover for at least three passages after thaw beforetransfecting.2. Calibrate DO and pH probes and add to assembled bioreactor.3. Sterilize bioreactor and allow to cool to room temperature.