Questions about serum's role in medium - (Aug/02/2006 )
Please forgive me if my questions are too naive. I am a newbee in the tissue culture world. When I read papers and protocols, I always see that serum is supplemented to the medium for cell lines. Sometimes 10%, sometimes 3%. Sometimes heat-inactivated serum. sometimes no serum at all. Can anyone tell me what serum can do when supplemented to the medium? And when is heat inactivation needed sometimes? It would be great if a link for beginners is given. Thanks!
When scientist were attempting to grow primary cells in vitro, they found that serum induces cell multiplication and when medium is depleted of serum, cells enter quiescence in G1 phase of cell cycle. Cells can be again induced to re-enter cell cycle by addition of serum.
Serum is not completely defined medium. But it contains large number of growth promoting activities such as contains peptide hormones or hormone-like growth factors that promote healthy growth, undefined effects on the interaction between cells and substrate, buffering toxic nutrients by binding them, neutralizes trypsin and other proteases,
Serum concentration can be changed according to cell type but generally it varies from 5 to 20%. With the changing methods of serum collection and processing heat inactivation is no more required. Like if you buy good quality serum from Hyclone, you don't need to heat inactivate serum. But people still use this practice to make sure that factors like complement factors are inactivated which can interfere in some assays, though not all. Heat inactivation for long time can reduce the nutritional content of the serum.
People do prefer serum free medium for few applications but in this case medium is supplemented with the essential nutritional requirements.
You might want to refer to atcc and hyclone web-site for some nice literature. Hope it helps.
I agree with exploresci.
There r way too many proteins and supplements in the serum to describe them.
I have been told that adherent cells will not adhere to plates without serum. The serum contains adhesive glycoproteins. For certain experiments, I have done serum-starvation. The serum-free medium is supplemented with BSA. Serum also contains albumin, growth factors, lipids, insulin, etc. Serum should not have any formed elements of blood (RBCs, leukocytes, platelets). Basically, I understand cell culture medium with serum as bathing cells in interstitial fluid.