Frequently Asked Questions (FAQs)

Why do cell and tissue cultures need serum?

Serum is vitally important as a source of growth and adhesion factors, hormones, lipids and minerals for the culture of cells in basal media. In addition, serum also regulates cell membrane permeability and serves as a carrier for lipids, enzymes, micronutrients, and trace elements into the cell. Serum is added as a supplement to culture media at a concentration of 2-10% to provide that mixture of nutritional, hormonal, growth and attachment factors. Serum also acts as a buffer to the cell culture system against a variety of disruptions to cell growth and toxic effects such as pH change, proteoloytic activity, or the presence of heavy metals.

How is serum processed?

Serum delivered frozen to a processing facility is thawed and tested for the presence of bacteria, virus, endotoxin and for hemoglobin content. The serum is then filtered through a sequence of membrane filters, terminating with a 0.1 micron pore filtration under aseptic conditions. After filtration, aseptic conditions are maintained as serum is dispensed into sterile bottles, quickly frozen to -20˚C and quarantined until all lots have met or exceeded quality control standards. A certificate of analysis for each lot is available upon request.

How is serum shipped?

All fetal bovine serums and frozen materials are shipped via overnight carriers. Packed in an adequate supply of dry ice to remain frozen until receipt unless otherwise specified by the purchaser. Truck shipments are handled by experienced, refrigerated carriers and will be kept frozen until delivered.

What is the recommended storage temperature for serum?

The recommended storage temperature for serum is between -10°C and -20°C, as it is most stable when stored frozen until needed. Storing serum in a frost-free freezer is not recommended, because temperature cycling may cause bottles to crack, contributing to contamination or deterioration of the product.

How should serum be thawed?

Serum should be thawed overnight at 2-8°C to prevent degradation; or, it may be thawed at room temperature with periodic agitation to resuspend the contents. Thawed serum should be mixed thoroughly before being added to cell culture medium. As repeated freeze-thaw cycles may significantly impact serum quality, we recommend aliquoting the thawed serum for single use, and to store aliquots at -20°C. If serum is stored between 2-8°C, it should be used within 2-4 weeks.

If serum arrives partially thawed, can I still use it?

Serum is packaged in dry ice and it should arrive frozen. However, if serum is partially thawed due to delay, it can still be used. Thaw the serum completely and aliquot into single-use aliquots for storage and further use.

Why does the thawed serum appear cloudy?

In most every instance, the serum IS NOT contaminated, it is fine or flakey precipitate. This is not an uncommon occurrence and most FBS will contain small amounts upon thawing. How quickly the blood is processed into raw serum usually dictates the amount of precipitate, the longer the amount of time allowed for the red cells to clot, the less precipitates. This is because the fibrin is not completely clotted out and even though the raw serum is filtered during final processing it remains in solution. When the serum is frozen and then thawed, the fibrin can come out of solution giving rise to fine or flakey precipitates.

What is Mycoplasma?

Mycoplasma species belong to the Mollicutes class, which includes Acholeplasma and Ureaplasma amongst others. Mollicutes are Gram-positive bacteria but unlike other species, they lack a cell wall and thus can adopt various different shapes. For convenience, the term Mycoplasma is often used to refer to all species of the Mollicutes class. Mycoplasma species are widespread in nature as parasites of mammals (including humans), reptiles, insects, and plants. They are the smallest and simplest self-replicating prokaryotes at just 0.2 – 0.8 µm in size. With a genome of only 0.58 – 2.20 Mb, Mycoplasma species have limited biosynthetic capabilities and are therefore dependent on their hosts for most nutrients. Contamination of cell cultures with Mycoplasma species can affect your cells in numerous ways, most of which will reduce the reliability, reproducibility, and consistency of your experimental results. The type and severity of these effects will often depend on the cell type you are using. Some of the general effects observed in eukaryotic cells can include:  Alterations to the levels of protein, RNA, and DNA synthesis due to nutrient deprivation. • Changes in cellular morphology.  An increase (or decrease) in cytokine expression Contamination with certain Mycoplasma species can also cause cytopathic effects, characterized by stunted, abnormal growth and degenerated cells, likely due to the promotion or inhibition of apoptosis1. This is a major problem for research, as well as during the manufacturing and processing of biological products and biopharmaceuticals because contamination can result in reduced yields or loss of an entire product batch. In addition, hybridoma cells, typically generated to support applications like antibody manufacturing, can show characteristic effects when contaminated with Mycoplasma, such as inhibition of cell fusion and a lower yield of monoclonal Our proprietary filtration scheme utilizes three separate 0.1 micron membranes which effectively removes mycoplasma from our sera. In addition, every lot is tested for mycoplasma using the method from FDA Points to Consider for the Mycoplasma testing of Cell Cultures and Biologicals derived from cell substrates.

What is Endotoxin?

Endotoxin is a complex lipopolysaccharide (LPS) found in the outer cell membrane of gram-negative bacteria, typically water borne. Bacteria shed endotoxin in large amounts upon cell death and when they are actively growing and dividing. Endotoxin is measured in Endotoxin Units per milliliter (EU/mL). One EU/mL equals approximately 0.1 to 0.2 ng/mL. Endotoxin is directly related to the quality of collection and processing of serum, the more endotoxin, the more exposure to gram-negative bacteria. The typical industry standard for endotoxin in fetal bovine serum is less than 10 EU/mL and even at that level it is suitable for most cell culture applications. Some exceptions are production of vaccines and injectables in which case the lowest levels are desirable. If your application does not require these low levels you can probably save some money by using our Choice or Cornerstone grades.

What is the shelf life of serum products?

The shelf life of serum is five years from the date of manufacture.

How long can I store media once I have added serum and all the supplements?

If aseptic handling is carefully observed, serum-supplemented media may be stored up to six weeks at 2-8°C. Media should be discarded using appropriate institutional biosafety protocols if it becomes cloudy, regardless of storage duration.

Are serum products free of Bovine Spongiform Encephalopathy (BSE)?

Yes. All sera have been sourced from countries that are free of or at low risk for BSE. The intergovernmental World Organization for Animal Health (OIE) fights animal disease at the global level by monitoring country compliance with OIE guidelines and standards.

Why do we see lot-to-lot variability in serum?

As serum is a solution extracted from biological sources, its composition may vary from lot to lot. To minimize application variability, we perform rigorous quality testing of each lot, and can provide lot samples to our customers for testing in their labs. We reserve material from the test batch during the customers’™ lot qualification process.

The color of the FBS is not the same as my previous lot. Does this affect serum performance?

The color of the serum depends on hemoglobin concentration, and variation in this parameter will not affect serum performance.

Why is the origin of serum important?

The origin of serum (also sometimes referred to as the “source”) is the country where the unrefined blood was collected. This is not to be confused with the country where the serum was separated, filtered, or otherwise processed, which may differ. The certificate of origin documents from the serum supplier should clearly state the serum source and processing information.

What is the difference between USDA-origin and U.S.-origin serum?

U.S.-origin serum is collected from facilities within the United States of America that undergo continuous inspection by the United States Department of Agriculture (USDA). USDA-origin serum is collected from facilities outside the U.S. in countries that have been approved for import to the U.S. by the USDA. These can include Australia, Canada, Mexico, New Zealand, Chile, and Central America.

How do traceability and origin impact the cost of serum?

While “origin” refers to the country in which serum was collected, the term “traceability” refers to the documents that trace the serum from origin through manufacturing and distribution. Serum is a commodity product for which price varies among countries of origin. For example, the cost of serum originating from Australia and New Zealand may be higher than that from other countries, due to lower supply and/or higher costs associated with collection.

Can fetal bovine serum be filtered?

It is not necessary, since commercial FBS is usually triple filtered through 0.1 µm filters.

How does fetal bovine serum work?

Because of its high quantity of hormones, carrier proteins and macromolecular proteins, fetal bovine serum is frequently present in culture medium used in in vitro fertilization. In this process, embryonic stem cells are transferred into the culture medium; this results in growth of the cells.

Where does fetal bovine serum come from?

Fetal bovine serum is a by-product of the dairy industry. Fetal bovine serum, as with most of the animal serum used in cell culture, is produced from blood collected at commercial slaughterhouses from dairy cattle that also supply meat intended for human consumption.

Why fetal bovine serum is used?

Serum is commonly used as a supplement to basal growth medium in cell culture. The most common type of serum is fetal bovine serum (FBS) because of its high content of embryonic growth promoting factors. Serum also adds buffering capacity to the medium and binds or neutralizes toxic components.

How is fetal bovine serum made?

After slaughter and bleeding of the cow at an abattoir, the mother’s uterus containing the calf fetus is removed during the evisceration process and transferred to the blood collection room. A needle is then inserted between the fetus’s ribs directly into its heart and the blood is vacuumed into a sterile collection bag. This process is aimed at minimizing the risk of contamination of the serum with micro-organisms from the fetus and its environment. Only fetuses over the age of three months are used otherwise the heart is considered too small to puncture. Once collected, the blood is allowed to clot at room temperature and the serum separated through a process known as refrigerated centrifugation.

Is fetal bovine serum used in vaccines?

When most people think about vaccines, they do not think about cows. But fetal bovine serum (FBS), a blood byproduct of the meat industry, is a crucial building block for vaccines.

Which vaccines contain fetal bovine serum?

Bacteria and cells to grow viruses for some vaccines need a growth medium to provide optimal nutrition and moisture conditions. Some growth mediums use bovine serum albumin or fetal calf serum from cow blood to provide the nutrition the bacteria and cells need. Some components in the following vaccines have been exposed to bovine-derived materials in growth medium or milk-derived materials, such as bovine serum albumin, fetal calf serum, or casein: Act-HIB®, ADT™ Booster, Boostrix®, Hiberix®, Infanrix®-hexa, Infanrix®-IPV, IPOL®, NeisVac-C®, M-M-R® II, Priorix®, Rotarix® and RotaTeq®, to name a few.