Trypsin in Animal Cell Culture: A Gentle "Cellular Scissors"

Why do cells need to be "loosened"

In animal experiments, many studies require cells removed from animals and grown in culture flasks. These cells prefer to attach to the bottom of the flask and stay tightly packed together. When the cells form a confluent layer, they need to be separated and transferred to a new culture flask to continue growing. This process is called "passaging." Between cells and between cells and the flask wall, certain proteins act like "ropes" holding them together. The main function of trypsin is to cut these protein ropes, allowing the cells to temporarily loosen and become individual suspended cells.

Why trypsin is commonly used

Trypsin used in animal experiments usually comes from porcine or bovine pancreas, and after extraction and purification, it is made into powder or solution. Its advantage is that its action is relatively direct: as long as it contacts adherent cells at a suitable temperature, it can cause the cells to round up and detach within a few minutes. Laboratories generally prepare it as a 0.25% or 0.05% solution for use. These are common specifications, and the specific concentration can be adjusted according to cell type.

Digestion time requires careful observation

Digestion is not better the longer it lasts. If the time is too short, the cells have not yet loosened, and they are easily damaged during pipetting; if the time is too long, trypsin may continue to break down receptors or membrane proteins on the cell surface, affecting cell condition. A common practice is: when most cells are seen under the microscope to have rounded up and have bright edges, promptly add serum-containing culture medium to stop the reaction. Serum contains trypsin inhibitors, which can help the cells "brake."

Different animal cells have different temperaments

Even among adherent cells, animal cells from different sources have different sensitivities to trypsin. For example, some fibroblasts digest quickly, while epithelial cells or certain neural-derived cells may require a shorter time or lower concentration. Before the experiment, reading the recommendations in the instructions and first performing a small-scale preliminary experiment is a reliable practice that ordinary experimenters can also master.

How to judge whether digestion is appropriate

In addition to looking under the microscope, you can also gently tap the side of the culture flask. If the cells slowly slide down like fine sand, it indicates that digestion is basically sufficient. At this point, termination solution should be added quickly, and you should not wait until all cells have completely detached before processing. This is because the cells that detach first may already have been over-digested. In daily experiments, developing the habit of observing at fixed intervals is more reliable than mechanically adhering to a fixed time.

Summary

Trypsin is like a pair of scissors in animal cell culture, helping experimenters separate cells. As long as concentration, time, and termination timing are well controlled, cells can be passaged smoothly, providing cell material in good condition for subsequent animal experiments.