- Fetal bovine serum (FBS) has historically been a foundational supplement in cell culture media due to its rich content of growth factors, hormones, adhesion molecules, lipids, and nutrients that support a wide range of cell types. However, its use has raised numerous concerns including ethical issues related to animal welfare, high batch-to-batch variability, potential contamination with bovine pathogens (such as viruses, mycoplasma, and prions), and the risk of immunogenic reactions when cells grown in FBS are used for clinical applications. In response, researchers and clinicians have turned toward a variety of FBS alternatives that aim to support cell growth while mitigating these concerns.
- One of the most prominent alternatives is human platelet lysate (HPL). HPL is derived from the lysis of human platelets, typically obtained from outdated or surplus blood donations. It contains a cocktail of growth factors—such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and transforming growth factor-beta (TGF-β)—that promote cell proliferation and survival, especially in human mesenchymal stromal/stem cells (MSCs), fibroblasts, and endothelial cells. Because it is human-derived, HPL reduces the risk of xenogeneic immune reactions and is increasingly used in clinical-grade, good manufacturing practice (GMP)-compliant cell expansion protocols. However, HPL presents challenges including the need for anticoagulants (e.g., heparin) to prevent gel formation, and variability among donor batches, which necessitates standardization procedures.
- Another important class of FBS alternatives includes chemically defined media, in which all ingredients are known and controlled in concentration. These media are free of animal-derived components and typically contain amino acids, vitamins, trace elements, and recombinant proteins such as insulin, transferrin, and albumin. Chemically defined media eliminate batch variability and are ideal for reproducible research, high-throughput screening, and therapeutic manufacturing. Their use is particularly prevalent in culturing pluripotent stem cells, T cells, and Chinese Hamster Ovary (CHO) cells used in biopharmaceutical production. However, they often require optimization for specific cell types and may not always replicate the full supportive effects of FBS without tailored supplementation.
- Serum-free media formulations are also widely used as FBS alternatives. These are typically customized for specific cell lines or applications and may include synthetic growth factors, lipids, and attachment factors. While some serum-free media are chemically defined, others contain undefined supplements such as hydrolysates or yeast extracts. Serum-free systems offer better experimental control, and when properly designed, can support high levels of cell growth and viability. Their adoption is growing, particularly in the pharmaceutical and stem cell industries, where precise control over cellular behavior is essential.
- For regenerative medicine and clinical applications, xeno-free media—which contain only human-derived or recombinant components—are especially important. These media reduce the risk of transmitting animal pathogens and mitigate immune compatibility issues. Xeno-free media are frequently used in the expansion of MSCs, neural stem cells, and other human therapeutic cell types. They are often used in combination with HPL or recombinant supplements to provide a supportive culture environment without animal components.
- Emerging approaches include plant-based and synthetic serum alternatives, which are being developed to provide a more ethical, scalable, and sustainable option. These include hydrolysates from soy, rice, or wheat, as well as algal extracts and fully synthetic formulations. While still in development or niche use, these supplements offer promise in reducing the environmental impact of cell culture and ensuring consistent performance in industrial bioprocessing.
- In conclusion, the search for and application of FBS alternatives in cell culture is driven by the need for ethical sourcing, clinical safety, and experimental reproducibility. While no single alternative universally replaces FBS across all cell types, a wide array of options—including HPL, chemically defined media, serum-free and xeno-free formulations, and emerging synthetic supplements—can now be selected and tailored based on specific cell culture requirements. The ongoing refinement of these alternatives is key to advancing both basic research and clinical translation in cell-based technologies.
