The four pillars of cell culture integrity

Daily monitoring of cell cultures using phase contrast microscopy enables you to recognize any unusual changes at an early stage. Each day that you examine your cells for confluency, take a closer look at your cells according to the following checklist:

What does the medium look like?

Increased turbidity, as well as a rapid color change of medium containing phenol red as a pH indicator, strongly suggests a contamination. Watch out for bacteria, fungal colonies floating on the medium surface as well as ovoid bright particles between the cells, indicating a yeast contamination.

Do cells proliferate?

Cells undergoing mitosis assume a round shape and partly detach from the surface. The occurrence of these cells in your cell culture is a sign of a healthy culture.

Do you see cells swimming in the medium?

An increased number of cells swimming in the medium can be a sign of a cell culture that has become overly confluent and which actually needs to be passaged. Cells start to die off and detach from the surface. Depending on the extent of die-off, a healthy culture may not be recoverable.

Vacuoles or granules?

Cytoplasmic vacuolation, as well as granules around the nucleus, indicate an unhealthy culture due to cellular damage, oxidative stress etc. Change of medium might be sufficient to remedy the problem, whereas in other cases cultures will have to be discarded due to serious causes (e.g. microbial contamination, senescence of the cell line, or inadequate medium or serum).

Check your cell culture by microscope on a daily basis! It just takes a few minutes and contributes to the maintenance of consistent and optimized culture conditions, resulting in high reproducibility of your experimental data.