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How to adjust the pH value with sodium bicarbonate?

As shown in the figure, the pH value of the culture medium increases parabolically with the increase of sodium bicarbonate content. When a certain amount of sodium bicarbonate is added, the pH change becomes smaller and smaller. The osmotic pressure value of the culture medium increases linearly with the increase of sodium bicarbonate content, and the larger the amount of sodium bicarbonate, the higher the osmotic pressure value.

If only a small amount of sodium bicarbonate is added to achieve the working pH value and osmotic pressure is ignored, it may not achieve buffering effect and cause drastic changes in pH value during cell culture. Additionally, it may make the culture medium a low osmotic solution, which can easily cause cell expansion and rupture during cell culture; If a large amount of sodium bicarbonate is added to achieve the desired pH value, it may be difficult to achieve the desired pH value, and the culture medium may become a hypertonic solution, which can easily cause cell shrinkage during cell culture.

It is best to find the appropriate amount of sodium bicarbonate to be added under the conditions of osmotic pressure and pH value through experiments in production, or to prepare according to the formula of the culture medium. If sodium bicarbonate solution is used to adjust the pH, an 8% sodium bicarbonate solution can be prepared in advance and added as appropriate. The following are the curves of sodium bicarbonate with pH and osmotic pressure for DMEM (HED) and MEM media. The most suitable pH for cell growth is 7.2-7.4, and the most suitable osmotic pressure is (300 ± 20) milliosmotic units.

(1) DMEM (HED) medium