Fetal bovine serum

Fetal bovine serum or FBS (or fetal calf serum) is the portion of plasma remaining after coagulation of blood, during which process the plasma protein fibrinogen is converted to fibrin and remains behind in the clot. Fetal bovine serum comes from the blood drawn from a bovine fetus via a closed system of collection at the slaughterhouse (aka abattoir). Fetal bovine serum is the most widely used serum-supplement for the in vitro cell culture of eukaryotic cells. This is due to it having a very low level of antibodies and containing more growth factors, allowing for versatility in many different cell culture applications.

The globular protein, bovine serum albumin (BSA), is a major component of fetal bovine serum. The rich variety of proteins in fetal bovine serum maintains cultured cells in a medium in which they can survive, grow, and divide.

Production

Fetal Bovine serum is a by-product of the meat industry. Fetal bovine serum, as with the vast majority of animal serum used in cell culture, is produced from blood collected at commercial slaughterhouses from cattle bred to supply meat destined for human consumption.

The first stage of the production process for fetal bovine serum is the harvesting of blood from the bovine fetus. The blood is collected aseptically into a sterile container or blood bag and then allowed to clot. The normal method of collection is cardiac puncture, where they take a needle and insert in between the ribcage into the heart. This minimizes "the danger of serum contamination with micro-organisms from the fetus itself, and the environment". It is then centrifuged to remove the fibrin clot and the remaining blood cells from the clear yellow (straw) colored serum. The serum is frozen prior to further processing that is necessary to make it suitable for cell culture.

The second stage of processing involves filtration, typically with a sterile 0.1 micrometre membrane filter. When processed by a reputable commercial serum supplier, the sterilized fetal bovine serum is subjected to stringent quality control testing and is supplied with a detailed Certificate of Analysis. The certificate gives full test results and information concerning the origin of the serum. Certificates of Analysis vary between commercial suppliers, but each usually includes the following details: filtration statement, country of origin, cell growth performance testing, microbial sterility testing, screening for mycoplasma and virus, endotoxin, haemoglobin, IgG and total protein assays.

Ethics

Ethical questions have been raised regarding the blood collection process with special emphasis on any potential discomfort caused to the fetus. Respected scientific investigation [1][2]has shown that the loss of blood circulation in the dam (mother animal) results in death within seconds of slaughter and that the fetus will be dead within a few minutes of the slaughter of the dam due to oxygen deprivation. In comparison, fetal bovine blood is collected from the bovine fetus only after the pregnant uterus has been removed from the slaughtered cow which, in a typical commercial slaughterhouse, means a delay of around 20 minutes from the time of slaughter. The time between maternal death and the start of fetal blood harvesting is relatively long and therefore means that there is minimal possibility of brain activity in the fetus at the time of blood harvesting and hence minimal possibility of discomfort. Of course, it is important to balance the ethical concerns surrounding the welfare of the donor animal against the highly significant benefits that the use of fetal bovine serum brings to human and animal health.

Serum use

Fetal bovine serum is commercially available from many manufacturers, and because cells grown in vitro are highly sensitive, customers usually test specific batches to check for suitability for their specific cell type. When changing from batch to batch it is usual to adapt the cells to the new batch of material, for example, by mixing 50% of the old serum with 50% of the new serum and allowing the cells to acclimatise to the new material.

Serum is stored frozen to preserve the stability of components such as growth factors. When serum is thawed, some precipitation may be seen. This is a normal phenomenon and it does not compromise the quality of serum in any way. The precipitate may be removed by transferring the serum to sterile tubes and centrifuging for 5 minutes at 400 x g.

To limit the amount of precipitation, it is recommended that the serum is thawed in a refrigerator at 2-8˚C. The serum should be regularly mixed during this process. Repeated freeze/thaw cycles should be avoided and it is advisable to dispense the serum into single use aliquots before freezing.

Source history

Serum produced for use in the biotechnology industry and research sectors is highly regulated. The collection and movement of all animal derived products globally is strictly controlled. Veterinary control of animal derived products largely follows the regulations set by the EU (DG SANCO) and the US (USDA). The current regulation concerning the importation of animal by-products into the EU is covered by Regulation (EU) 1774/2002 and various derogations and amendments. This regulation will be replaced in March 2011 by Regulation (EU) 1069/2009 which was published on October 21, 2009.

FBS is a product collected worldwide with the main collections being centered in the United States, Australia, New Zealand, Canada, Central America, South America and Europe.

Global sales

Sales of FBS in 2008 were estimated to be 700,000 litres globally.

Major companies that collect and sell FBS globally are members of the ISIA, the International Serum Industry Association. Member companies are listed on the ISIA website. Full contact details are available through this portal and the ISIA will be able to answer any questions concerning the collection and use of this important resource.

The International Serum Industry Association, was incorporated June 2006. The ISIA promotes and assures quality and standards to a previously unstandardized industry. The ISIA Mission Statement: “The ISIA shall establish, promote and assure compliance with uncompromised standards of excellence and ethics in the business practices of the global animal serum and blood products supply industry. Our primary focus will be on safety and safe use of serum and animal derived products through proper origin traceability, truth in labeling and appropriate standardization and oversight.”

See also

Laboratory use of serum

References

[1] Opinion of the Scientific Panel on Animal Health and Welfare on a request from the Commission related to the welfare aspects of the main systems of stunning and killing the main commercial species of animals, The EFSA Journal (2004), 45: 1-29

[2] Mellor DJ and Gregory NG (2003). Responsiveness, behavioural arousal and awareness in fetal and newborn lambs: experimental, practical and therapeutic implications, New Zealand Veterinary Journal, 51(1): 2-13.