Living cells yield much more information
Not too long ago, for visualization by high-resolution microscopy, cells were typically killed, fixed, stained for specific components and embedded in resin. However, imaging living cells yields much more information:
- living cells may go through division
- migrate
- interact to form tight monolayers just like living (cancer) cells in our body. Only with living cells, we can get a grasp of the dynamics of the internal biochemical processes.
A whole range of colored Fluorescent Proteins (picture 1) are available that enable us to label a single protein species and learn what we want to know about that protein. The trick is, to keep those cells alive and healthy on the microscope.
On the microscope, cells are kept in a glass bottom dish filled with DMEM medium: a bloodplasma-like salt solution with vitamins and nutrients. In the early days, we just kept them at room temperature in dishes in free air (~20 % O2, 80 % N2, 0.05% CO2). However, that does not mimic the atmosphere in our bodies at all, and consequently, results were not as expected.