Animal-Derived Products
Animal-derived products (ADPs) are materials sourced from animals widely used in a range of research and clinical applications, from in vitro cell culture to disease diagnosis.
Despite their widespread use, concerns exist regarding their reproducibility, reliability, and, in some cases, relevance of the data they generate. Additionally, ethical and environmental issues related to the production and use of ADPs are significant.
Common animal-derived products used in research
Animal Serum
Animal serum is a widely used additive in laboratory cell culture research providing essential nutrients, growth factors, and other molecules that support cell survival, proliferation, and differentiation. It is typically extracted from the blood of animals who are slaughtered for meat. Examples include foetal calf serum (FCS), also known as foetal bovine serum (FBS), which is taken from unborn calves by cardiac puncture, or newborn calf serum (NBCS) which is taken from calves up to 20 days of age.
Scientific concerns surrounding animal serum include questions about its physiological relevance, batch-to-batch variation, and the potential risk of contamination with viruses and pathogens.
Serum-free media options are now widely available, alongside many protocols to humanise common cell lines. Researchers can explore serum-free media compositions for hundreds of commonly used cell lines using the FCS-Free Database.
Another option is the use of human serum which has advantages over animal serum that include direct translatability into human-specific, clinical applications, and no risk of external pathogen transmission. As human serum is harvested from volunteer donors, a consistent supply is ensured. However, as it is collected from multiple sources batch-to-batch variation is an issue and due to its limited supply, costs tend to be higher.
Antibodies
Antibodies are widely used tools, vital for research, monitoring, diagnostics, and therapeutics.
For more information on the classifications of antibodies, the role of animals in their discovery and production, and information on animal-free alternatives visit our Recombinant Antibodies & Mimetics Database.
Bovine Serum Albumin
Bovine serum albumin (BSA) is purified from bovine serum using methods such as cold-organic solvent fractionation, heat shock, or ion exchange chromatography. It is widely used in experiments such as western blotting and immunohistochemistry as a blocking agent or to prevent non-specific binding, as well as in cell culture applications.
While each purification method produces BSA that meets standard specifications, there are several attributes which are often overlooked such as fatty acid and hormone profiles, contaminants and the presence of IgG, transferrin, and other peptides. These factors can significantly impact the performance of BSA in certain applications. This contributes to batch-to-batch and supplier variability in the BSA market.
Innovative alternative blocking solutions are now available from several suppliers including VectorLabs and Cell Signalling Technology.
Cell Culture Dissociation Enzymes
Trypsin is a protease-based dissociation regent, typically derived from porcine pancreas in slaughterhouses. It is commonly used to detach cells from culture vessels with minimal damage to cell membranes.
Issues around this ADB include contamination, impurities, and the spread of porcine viruses.
Alternatives to trypsin are commercially available, including TrypZean solution, a recombinant animal-free dissociation reagent expressed in corn.
Growth Factors & Cytokines
Growth factors and cytokines are important additives in cell culture and cell-based assays. Many cell lines need specific growth factors to promote proliferation and maintain their relevant phenotype for applications such as disease modelling and drug discovery. Stem cell cultures require growth factors to maintain pluripotency and for differentiation into specific lineages.
Animal-derived recombinant growth factors are purified from animal (including human) cell lines over-expressing the protein of interest. Mammalian cells contain the necessary mechanisms for protein folding and post-translational modification which can be important for the bioactivity of recombinant proteins.
Scientific concerns over mammalian-expressed recombinant proteins mainly centre around growth factor purity, as similar endogenous growth factors can be co-purified with the over-expressed growth factor. This can lead to activation of off-target signalling pathways, and can lead to incorrect scientific conclusions, particularly when studying novel systems. In cell cultures growth factor impurities cannot be controlled for and will vary from batch to batch preventing reproducibility. These proteins are often derived from cell cultures which use large volumes of foetal calf serum and there is the potential risk of contamination with mammalian viruses and pathogens.
Animal origin-free growth factors and cytokines, such as those expressed in Escherichia coli have the advantage of being free of trace animal components and can be purer. They also are more suitable for scale-up as they can be produced in bulk for lower cost. For some complex growth factors advanced protein engineering is required to ensure they fold correctly and are bioactive.
Scaffolds
Scaffolds play a pivotal role in 2D and 3D cell cultures, enabling cellular support, cell adhesion, nutrient transport, and the facilitation of cell migration.
Collagen is widely used as a scaffold and is derived from animals including cows, pigs, rats, and even jellyfish.
Another widely used scaffold is Matrigel™ (also known as Geltrex™ or Cultrex™) derived from the reconstituted basement membrane of an Engelbreth-Holm-Swarm mouse sarcoma. Matrigel™ is a hydrated gel (hydrogel) composed of extracellular matrix proteins that form a 3D network.
Both collagen and Matrigel™ have significant limitations, including batch-to-batch variation, poor reproducibility, and high production costs. The exact chemical composition of Matrigel is unknown, making it impossible to determine which specific components might be influencing experimental outcomes.
Animal-free and synthetic alternatives include those sourced from plant-based materials, fibrin derived from human plasma, alginate sourced from brown algae, and synthetic polymers.
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