pH - Adjust the pH when the pH falls below normal range; glucose concentration should remain above 1.0 - 1.5 g/L.

CO₂ If the CO₂ concentration at incubation has been set to 0, add buffer or change the medium. For cultures that extend over weeks or months, exchange the medium once a day. Replace the medium with 500 mL each day to keep cells in an optimal state. If the media is rich enough and does not require frequent replenishment, monitor the pH and adjust the CO₂ concentration to NaHCO3, 1 M HEPES. If working with insect cells, adjust with 1 M Bis-Tris.

Estimating Number of Cells:
You may estimate the viable cell count during culture in either of three ways. The cell densities should be periodically measured:

Nucleus Count - Each FibraStage system includes 500 mL of crystal violet dye (CVD) for estimating the number of cells using the nucleus count method. Aseptically remove a few samples of the FibraCel disks using the sterilized long-arm forceps provided, and estimate the cell population by crystal violet dye (CVD) nucleus count method, which is further described in our FibraStage operating manual. Each FibraStage bottle contains 10 grams of disks, equaling 2,210 disks, 1%.

Glucose Uptake Rate (GUR) - Estimate the cell growth by calculating the GUR, which should be proportional to the total cell volume. We recommend you measure glucose concentration every day or approximately 6 to 8 hours after medium replenishment. Use this equation:

GUR = (C_{Glu, t2} C_{Glu, t1}) x V_solu / (t
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