Fetal Bovine Serum (FBS) is a supplement derived from the blood of bovine fetuses. It is widely used in biological research and biomanufacturing to support the growth of eukaryotic cells in vitro. The serum is valued for its rich mixture of molecules that promote cellular growth. When added to a culture medium, FBS provides the necessary components for cells to multiply and function in a laboratory setting.
The Role of FBS in Cell Culture
Fetal Bovine Serum is an additive in cell culture media because it supplies substances that support cell life. It delivers a complex blend of growth factors and hormones that stimulate cells to divide and proliferate. This serum also contains transport proteins, such as albumin, which bind to and deliver nutrients and other small molecules to the cells.
The serum’s composition helps maintain the balance required for cells to thrive in an artificial environment. It provides nutrients, vitamins, and trace elements that may be absent from the basal media. FBS also helps protect cells from various stresses, including significant shifts in pH and damage from enzymes or toxins that can accumulate in the culture.
Sourcing and Processing Standards
The consistency and purity of FBS are linked to the reliability of scientific experiments. Suppliers follow strict collection and processing standards to ensure a high-quality product. The process begins with the aseptic collection of blood to prevent microbial contamination. The raw serum then undergoes filtration to remove unwanted particles and microorganisms.
Suppliers often employ a triple 100-nanometer (nm) sterile filtration process. This small pore size is effective at removing bacteria and other potential contaminants while allowing beneficial proteins and growth factors to pass through. Following filtration, each batch of serum is extensively tested for quality control. Key indicators include low levels of endotoxin, a component of bacterial cell walls that can negatively impact cell growth, and hemoglobin. Reputable suppliers also provide traceability, documenting the geographic origin of the serum.
Variations of Fetal Bovine Serum
To meet the needs of specific research applications, standard FBS is often modified to create specialized variations.
- Heat-inactivated FBS: The serum is heated to 56°C for 30 minutes. This treatment destroys the complement system, a group of proteins that can cause certain sensitive cell types, particularly those from the immune system, to lyse or burst.
- Dialyzed FBS: This variant has undergone a process to remove small molecules below a certain molecular weight, such as amino acids and hormones. Researchers use this type to study the effect of a specific small molecule by adding it back into the culture.
- Charcoal-stripped FBS: Treated with activated charcoal to remove nonpolar molecules like steroid hormones. This variation is used for endocrinology research where the influence of specific hormones on cells is being investigated.
- Stem Cell Qualified FBS: This version is specifically tested to confirm it supports the growth of stem cells without inducing differentiation, making it available for those working with pluripotent cells.
Handling and Storage Guidelines
Proper handling and storage are necessary to maintain the quality of FBS. The serum must be kept frozen at temperatures of -20°C or colder to preserve its complex components. When the serum is needed, it should be thawed slowly to prevent the degradation and precipitation of proteins. The recommended method is to place it in a refrigerator at 2°C to 8°C overnight.
For quicker thawing, the bottle can be placed in a 37°C water bath, with gentle swirling. Repeated cycles of freezing and thawing can damage the growth factors and proteins within the serum. To avoid this, it is best practice to aliquot the newly thawed serum into smaller, single-use volumes using sterile techniques. These smaller tubes can then be refrozen, preserving its performance.