Cracking the Reproducibility Code: Sera Is a Key Component | Corning

Cell culture can be tough on sensitive cells. Researchers pipette them from dish to dish; freeze, thaw, and add digestive enzymes to detach them from substrates; and more. Cells may also be subjected to pH changes, heavy metal ions, endotoxin, and proteolytic activity. Fetal Bovine Serum (FBS) can be used as a media supplement to help cells thrive under these conditions and is commonly used at 5–10 percent of the cell culture media by volume to achieve the best results.

FBS provides many compounds that satisfy metabolic requirements for cells in culture, including hormones, vitamins, minerals, and lipids. Sera include thousands of distinct proteins originating from a variety of cells and tissues, as well as thousands of small-molecule metabolites. As a result, there are many undefined components.

FBS is a liquid extract from clotted cow blood, which is collected from abattoirs when pregnant cows are slaughtered. The serum is incredibly complex and can change with factors such as diet, geographical location, time of year, whether the animal received hormones or antibiotics, and the gestational age of the fetal calves. These factors lead to lot-to-lot variability, even for FBS lots that come from the same slaughterhouse and receive the same processing treatments. This variability has undoubtedly contributed to the number of published cell culture studies that can't be replicated, even by the original lab in some cases.

While the ideal solution might be chemically defined, serum-free media, the currently available options only work for some cell types in some applications. Serum will remain popular for the foreseeable future because it allows researchers to grow cells without knowing all of their requirements. The issue of lot-to-lot variability can be mitigated with careful planning and checking, so you can improve reproducibility and conduct your experiments with confidence.

Choose the Right Sera from the Start

Experimental assays are as unique as the cells involved, so you can start a study off strong by carefully considering the specific serum treatments that make the most sense for your assays.

Corning^® FBS is available with a variety of treatment options. These options include no additional treatment beyond being triple 0.1 micron sterile filtered and passing tests for sterility, mycoplasma, industry-monitored viruses, cell growth performance, and more. Researchers can also choose the country of origin for their sera, which includes the United States, Australia, and New Zealand.

Other popular FBS treatment options include heat inactivation at 56°C for 30 minutes. This is done prior to final filtration and bottling or by request for individual vials and serves to reduce precipitate and improve homogeneity. FBS is also available with gamma irradiation for viral inactivation, including mycoplasma inactivation. The irradiation dose can be customized to fit your specific needs, with the understanding that radiation also damages growth proteins and bioactive molecules that can help cells thrive. Another standard FBS formulation includes both heat inactivation and gamma irradiation.

Corning FBS is available as charcoal dextran stripped, which selectively removes hormones that can affect cell culture growth. Another option is dialyzed FBS, which removes small molecules such as amino acids, hormones, and cytokines while avoiding the precipitation of serum proteins. Tetracycline-negative FBS is also available for researchers using tetracycline-inducible gene expression systems and other applications when the presence of tetracycline is not desired. Finally, ultra-low Immunoglobulin G (IgG) FBS uses affinity chromatography to reduce IgG levels to <=5 ug/mL. This is useful for IgG antibody production and other work that would be hindered by the presence of IgG.

Whatever treatment option you choose, you'll want to pick the right partner to work with to ensure you can continue your work long-term. You can count on Corning's vertically integrated serum supply chain to provide a consistent supply of FBS, even during times of regional supply constraints. Corning's direct relationship with abattoirs ensures that collectors use the proper tools and training and adhere to strict aseptic techniques for blood collection at government-approved facilities. Corning Life Sciences is certified for traceability by the International Serum Industry Association (ISIA) and every lot is tested to confirm origin. You can be confident in the source of material from Corning.

Test Lots and Stock Up

Once you choose an appropriate serum treatment, you may want to test multiple lots to find one that works best for your experiments. This may be different than selecting a treatment and lot that results in the fastest cell growth. For example, different lots of dextran-stripped FBS will still contain trace amounts of steroid hormones. The sensitivity of your cells and your specific application will determine how many lots you need to test and what those tests will involve.

One of the best defenses against lot-to-lot variability is to stock up on a serum lot that works well for your application. Depending on how much cell culture your lab does, this might involve having a freezer dedicated to storing serum. Ideally, there will be enough serum to last for an entire study. When those stocks start to run low — but well before you run out — you should order and test multiple lots. The goal is to find a lot that produces results similar to your current lot for critical assays. Then, stock up again. These steps will help your experiments run consistently and ultimately save time.

When it's time to test a new lot of serum, all other reagents and supplies should stay the same. You should also have enough of the old serum lot on hand to do side-by-side comparisons. This is especially important because the best way to see how your cells are responding on a day-to-day basis is often just to look at them. Best practices include documenting what you see and plotting a cell growth curve. Researchers should also record the information provided by the manufacturer, including lot numbers. Finally, document your process for selecting a serum lot so other researchers can replicate your work.

Looking for the right sera for your applications? Explore Corning's wide variety of FBS options.