How to plot growth curves for cells in a cell factory

 The cell growth curve is a common method for determining the absolute growth number of cells, an important indicator for determining cell viability, and one of the basic parameters for the biological characteristics of cultured cells. The cell factory is mainly used for the culture of adherent cells, so how to draw the cell growth curve?

Generally, after the cells are passaged, they are suspended for a short time and then adhere to the wall, and then spend different incubation periods of different lengths, that is, they enter the exponential growth phase of massive division. After the cells reach saturation density, they stop growing, enter the plateau phase, and then degenerate and die. In order to accurately describe the dynamic changes of cell numbers in the whole process, a typical growth curve can be divided into four parts: a slow-growing latent period, an exponential growth period with a large slope, a plateau-shaped flat-top period, and degeneration and decay. The growth curve was obtained by plotting the number of viable cells (10,000/mL) against the culture time (h or d).

1. Incubation period: Digestion and passage have an effect on the cells, so the treated cells need to be re-adapted to the new growth environment. Primary cells need at least 24-96 hours, and immortal cells need 6-24 hours;

2. Logarithmic growth phase: The number of cells in this phase shows a logarithmic growth trend. The logarithmic growth period varies according to different cell types, generally 3-5 days;

3. Stasis phase: Generally speaking, the cells will eventually grow to form a monolayer. When the contact environment and the number of cells reach a mutually suitable level, the cells will no longer grow and the activity will be in the stagnating phase.

By observing the growth curve of cells in the cell factory, we can understand the growth process of cells, so as to analyze the proliferation rate of cells, and determine the time of cell passage, cryopreservation, and drug addition.