Serum is a purely natural medium containing various nutrients required for cell growth and proliferation, such as proteins and polypeptides. It is widely used in cell culture and in the production of biological products and diagnostic reagents.
The main components of serum are proteins such as albumin, globulin and fibronectin (which promotes cell attachment), α2-macroglobulin (which inhibits trypsin activity), hormones, insulin (which promotes glucose and amino acid uptake and cell division), insulin-like growth factor (which binds insulin receptors expressed by cells, producing effects similar to insulin), growth hormone (cell proliferation), fetuin (promotes cell attachment) and transferrin (binds iron ions and reduces their toxicity). The composition and content of serum are often related to the sex, age, physiological condition and nutritional status of the donor animal. Below are some basics about serum.
1. How to choose a serum suitable for cell growth?
For primary cells or normal cell lines, Wanrui serums of different grades are recommended; for cells and stem cells with demanding growth requirements, Wanrui Superior/Ultra fetal bovine serum, or fetal bovine serum specially for embryonic stem cells, can be selected.
Because of batch-to-batch variation and differences among cell types, we recommend customers apply for a trial sample before purchasing. Once a satisfactory serum lot is identified through screening, bulk stock can be reserved according to project needs, ensuring consistent serum quality for the project and eliminating the impact of different serum lots on experiments.
2. How should serum be stored properly? What is its shelf life?
Serum intended for long-term storage must be kept in a -20 °C freezer (unopened serum has a shelf life of 5 years). If stored at 4 °C, do not exceed 1 month. If a bottle cannot be used up at once, aseptically aliquot and freeze the serum.
3. How should serum be thawed?
Serum should be thawed gradually: move the serum from the -20 °C freezer to a 2-8 °C refrigerator to partially thaw (no more than 24 hours), then move it to room temperature and aliquot after it has fully thawed. During thawing, gently swirl continuously (taking care not to create bubbles) to reduce precipitate formation. Never move serum directly from -20 °C to 37 °C to thaw, because too large a temperature difference easily causes protein precipitation and inactivation of some active factors.
4. What color should fetal bovine serum normally be?
Because fetal bovine serum has a complex composition, appearance color may vary somewhat between batches. Generally, the color may be yellow, reddish, or amber-like brown, or between these three.
5. Does newly purchased serum need to be filtered?
Serum is produced under Class C+A conditions, is filtered three times through 0.1 μm filters, and is tested before release using more than three cell lines for culture testing and sterility testing, so the probability of contamination is very low. Cell contamination can arise from many possible sources; based on analytical testing carried out with users, results show that the vast majority of contamination is caused by human operational error. Therefore, purchased serum does not need to be filtered again.
