A cell culture incubator is a device that provides a stable temperature (37°C), stable CO2 level (5%), constant acidity (pH: 7.2-7.4), and high relative saturated humidity (95%) to culture cells/tissues in vitro. So nowadays, why do most cell cultures need a CO2 cell incubator, let me explain it to you below.
Typically, cell culture solutions have a ph value between 7.0 and 7.4. Most culture fluids maintain the stability of ph through the carbonate pH buffer system, as it is a physiological pH buffer system that is Z-important in human blood. When configuring culture solutions, it is often necessary to add a certain amount of sodium bicarbonate to the culture solution.
In order to keep the ph stable, for the culture solution with carbonate as the pH buffer system, the concentration of dissolved carbon dioxide in the culture solution is maintained by keeping the proportion of carbon dioxide in the incubator between 2-10%. In order to facilitate gas exchange, then a certain degree of permeability is necessary for cell culture vessels. So if other pH buffer systems are used, is a CO2 cell culture incubator still needed, the answer is yes, of course. The carbon dioxide concentration in the air is very low, the HCO3- in the culture solution will be quickly depleted, the buffer system will lose its effect, if no longer cultured in the carbon dioxide incubator, then it is difficult for the cells to grow normally, the carbon dioxide incubator is very necessary for the cultivation of many animal cells.
In order to increase the buffering capacity of pH, other pH buffer systems are often attached to the cell culture solution, such as HEPES buffer system, when the ph is between 7.2-7.4, the buffering capacity of HEPES is very strong. When the culture vessel is taken out of the CO2 incubator, the CO2 concentration in the air is very low, the HCO3- in the culture medium will be depleted very quickly, and the carbonate buffer system in the culture medium will lose its effect. However, the pH remains stable because the HEPES buffer system acts as a buffer.