Animal Derived Biomaterials

Animal-derived Biomaterials

Animal Free Research UK funds innovation pilot grants to support researchers to transition to NAMs (New Approach Methodologies) and highlight the power of human-focused research.

Animal-derived biomaterials (ADB) are consumables used for many applications in biomedical research, from in vitro cell culture to disease diagnosis in the clinic.

ADBs are commonplace in most research environments, however there is a clear need to change these practices to further the progress of human-specific research and reduce unnecessary animal involvement. In addition to the well documented ethical and environmental issues around the production of animal-derived antibodies and foetal bovine serum (FBS, also known as foetal calf serum, or FCS), there are real scientific concerns about the reproducibility and reliability of data generated using these and other animal derived products. Despite numerous studies highlighting problems associated with ADB use, most researchers still use them without considering animal-free alternatives.

To help modern science move in the right direction for the greater benefit of patients, Animal Free Research UK supports researchers in firstly recognising the need to change their tools, and secondly, embracing the vast number of animal-free products available for research use.

Two young female scientists doing experiments in lab - Animal Free Research UK

Our research funding viewpoint

We appreciate that it is essential for scientists to validate their tools before moving forward with experiments and ensure their results are reliable. We also understand that some highly valuable animal-free research projects might, therefore, require the use of some ADBs, with the ultimate aim of fully replacing them. In these particular circumstances, Animal Free Research UK may approve the use of animal-derived biomaterials, however the grants we award cannot be used to fund the purchase of any animal-derived biomaterials. Further information can be found in our Terms & Conditions.

We always require robust scientific justification from scientists for approval of temporary and limited animal-derived biomaterial use to support the transition to fully animal-free research.

Common animal-derived biomaterials used in research

Polyclonal antibodies

Polyclonal antibodies are produced in animals, often rabbits and mice, which have antigens from other species (including humans) injected into them. Within a few weeks and following repeated immunisation, the animal’s immune system produces high levels of antibodies specific for the antigen. After an incubation period of typically around two months, the antibodies are then harvested through bleeding and purified. Animals are often subjected to repeats of this process, raising welfare concerns.

Aside from the unethical process of using an animal to create a polyclonal antibody, there are also many other issues including long production times, off-target reactivity and batch-to-batch variation.

Millions of animals are killed each year for the routine production of antibodies. The number of animals used varies considerably and depends on the species used, the amount of antibody required and the success of immunisation. A minimum of 2 rabbits or guinea pigs or 5-10 rats or mice are commonly used for each batch of polyclonal antibody and typically, 5 mice are immunised per hybridoma protocol for monoclonal antibody production, creating just 1-3mg of antibody.

Developing and producing polyclonal antibodies always involves using live animals, which is why Animal Free Research UK does not allow their use in our funded research.

Serum

Animal serum is a commonly used additive for laboratory cell culture research to grow and maintain cells under controlled conditions.

Animal serum is extracted from the blood of animals who are killed in slaughterhouses for meat. Foetal calf serum (FCS) is taken from live unborn calves by cardiac puncture without any form of anaesthesia. Calves are likely to feel pain and discomfort during the procedure. Aside from these clear ethical concerns, scientific concerns around the batch-to-batch variability and high risk of contamination with viruses and pathogens mean that the use of FCS can affect experimental outcomes.

Animal Free Research UK does not allow the use of any animal serum in our funded research, and there are now many replacements which can be used instead.

There is now a wide range of serum-free media options available for purchase, alongside many protocols to humanise common cell lines. Animal Free Research UK supports the FCS-free database, a useful resource to find serum-free cell culture protocols from both industry and individual research groups for hundreds of commonly used cell lines.

Professor Lorna Harries, Animal Free Research UK funded researcher at the University of Exeter has created a humanisation guide for human-relevant tissue culture without the use of animal-derived biomaterials, which can be accessed here.

A further alternative is the use of human serum, which can be used to grow a range of cell types. Human serum has many advantages over FCS, including direct translatability into human experiments, clinical applications and no risk of external pathogen transmission. As human serum is harvested from volunteer donors, a consistent supply can be gained without inflicting unnecessary suffering on animals. Although due to the nature of collection of human serum from multiple sources there is a risk of some variation, risk is minimised by pooling and standardisation of samples. While there is a smaller supply of this product available, resulting in higher costs, human serum is of high quality and more valuable for human-relevant research.

Bovine Serum Albumin

Bovine serum albumin (BSA) is commonly used for blocking steps in experiments such as western blotting and immunohistochemistry to prevent non-specific binding, and also in cell culture applications.

BSA is purified from bovine serum using one of three different purification methods: cold-organic solvent fractionation, heat shock or ion exchange chromatography. Each method produces BSA that can meet standard specifications, but there are several attributes in each standard Certificate of Analysis which are often ignored. This results in a lack of heterogeneity in the BSA market, linked to performance variability both batch-to-batch and between suppliers. These attributes include fatty acid and hormone profiles, contaminants and the presence of IgG, transferrin and other peptides which can be critical to the performance of BSA in a particular application.

Innovative animal-free blocking solutions are now available from several suppliers including VectorLabs and Cell Signalling Technology, to replace the use of BSA. This switch would not only reduce animal use in research, but likely also improve the overall consistency and reliability of results.

Bovine Pituitary Extract

Cell culture media additives such as Bovine Pituitary Extract (BPE) are often added to supplement serum free media and provide growth factors and hormones to encourage cell proliferation. BPE is harvested from healthy calves between 18-22 months old, while other additives are often derived from mice and rats. Aside from the moral issues of using animal derived growth factors, there are risks of disease transmission from these types of products, such as the recent epidemic of bovine spongiform encephalopathy (mad cow disease), which temporarily halted the production of BPE, alongside the lack of translational relevance to human research.

While direct animal-free alternatives to BPE are difficult to come by, alternatives such as human serum, fibroblast growth factors (FGF) and other BPE-free media have been explored for use in some cell types.

Monoclonal antibodies

In 1975, a technique was developed where cells from the spleens of immunised mice were fused together with immortal myeloma cancer cells to form a perpetually growing ‘hybridoma’. The original method of monoclonal antibody production is known as the in vivo, or mouse ascites, method. This method involves continual propagation of hybridomas expressing the target antibody, which are then screened and selected for injection into the peritoneal cavity of a prepared mouse, causing a tumour to develop. Fluid containing the antibody of interest is excreted by the tumour and is collected then purified for research use. Welfare concerns were raised with this method as the mice likely experience pain and distress induced by excessive accumulation of fluid in the abdomen and the invasion of the viscera. A number of countries including Australia, Canada, Germany, the Netherlands, Switzerland and the UK have restricted or banned the production of antibodies via the ascites method due to these animal welfare concerns; however, this method can still used when it can be ‘scientifically justified.’

Most monoclonal antibodies are now produced using in vitro tissue culture instead, which does not require any additional animal use once the hybridoma has been created. This method is however more difficult, expensive and time consuming. Many commercial monoclonal antibodies produced using hybridoma technology will state they are animal-free; however, while this method does reduce animal use in monoclonal antibody production, a cell or gene source will have been used from an immunised animal to create the initial hybridoma.

Currently, monoclonal antibodies remain a central element in medical research as they are highly specific for one target of interest with less cross-reactivity compared to polyclonal antibodies. However, limitations with in vitro production methods include that some hybridomas do not grow well or are lost in culture conditions, reproducibility issues, risk of genetic drift, antibody concentrations are generally low and only small amounts are produced at a time, and culture generally requires the use of foetal bovine serum (FBS) leading to a risk of contamination and further concerns over animal welfare issues related to FBS use.

Animal Free Research UK will only allow the use of monoclonal antibodies in our funded research when it has been proven that there are no alternative options available. Fortunately, these antibodies can be increasingly replaced by synthetics, known as recombinant antibodies.

Recombinant antibodies

There are now a wide range of animal-free antibodies available commercially which have been produced by utilising gene libraries (human or synthetic genes), or through other methods including display methods (such as phage, bacterial, ribosome, yeast) computer-assisted 3D modelling and synthetic antibodies generated with molecularly imprinted polymers (MIPs).

As recombinant antibodies are produced using synthetic genes or antibody fragments, immunisation of an animal or cultivation of hybridomas for production is not required. However, the initial antibody discovery process may have an involved animal immunisation step and development could also have involved the use of animal-derived biomaterials such as FCS and bovine serum albumin (BSA).

Recombinant antibodies have several advantages over both polyclonal and monoclonal antibodies, in that they are genetically stable and highly specific, can be produced in great quantities and have no issues with batch-to-batch variation, as would be found in antibodies derived from an animal. As recombinant antibodies are produced based on a known and defined gene sequence, large scale commercial production is highly reproducible and low cost.

Dissociation enzymes

The most common protease-based dissociation regent for the detachment of cells from a culture vessel is Trypsin, which coupled with EDTA, can remove cultures with minimal damage to cell membranes. Trypsin is usually derived from the pancreas of pigs in slaughterhouses, with significant issues reported around contamination and impurities in the product, alongside the spread of porcine viruses. Many alternatives to Trypsin are commercially available, including TrypZean Solution, a recombinant animal-free dissociation reagent expressed in corn.

Extracellular matrices and hydrogels

Scaffolds play an important role in cell culture. Collagen is widely used to develop these structures as it enables cells to be fixed to a surface, can transport nutrients to cells as they grow and also allows cell migration. Most collagen is derived from animals including cows, pigs, rats and even jellyfish. Completely animal-free sources of collagen are difficult to find, as even products which are marketed as ‘animal-free’ have often been made with the initial step involving a skin sample from an animal. The only method of traditional collagen production which is truly animal free is that using human collagen, but this is generally more expensive.

Many alternatives to collagen scaffolds are now available, including hydrogels, which are 3D network structures which can absorb large amounts of fluid. These structures form the basis for many types of research including growth of tissue and cells, testing drug delivery and applications in regenerative medicine. Due to their versatility and variety of uses, hydrogels have also become commonplace in the development of NAMs. However, many components of commonly used hydrogels and matrices such as Matrigel™ (also known as Geltrex™ or Cultrex™), are derived from animals.

Matrigel™ is the most widely used material to mimic the extracellular matrix, which is made from the reconstituted basement membrane of an Engelbreth-Holm-Swarm mouse sarcoma. As an animal-derived product, significant limitations including as batch-to-batch variation and poor reproducibility are commonly encountered, alongside high production costs.

As NAM technologies using these products continue to develop and progress, attention is being turned to the creation of synthetic, animal-free alternatives to Matrigel™ and other animal-derived hydrogels, with many options now available. Other alternatives include fibrin, which is sourced from human plasma, or alginate, sourced from brown algae. Hybrid polymers also exist, some of which are animal-free. A list of suppliers of animal-free hydrogels and other biomaterials can be found here.

Making the transition to animal-free

We strongly encourage scientists to avoid all animal-derived biomaterials; however, we recognise that transitioning to new reagents can be a tricky and time-consuming process, requiring confirmational studies to assess whether experiments are functioning as expected. This is why we are working hard to facilitate these efforts and have several tools to assist with the transition to animal-free research:

The Animal-Free Biomaterial Providers database is a useful repository of companies offering animal-free products including serum free media, antibodies, hydrogels and proteins.
The NAMs Companies Interface is a database providing animal-free biomaterials, information and training.
The NAMs Resources Database contains links to organisations and companies offering training in NAM protocols, safety and alternatives to animal-derived biomaterials.
The FCS-free Database can be used to find serum-free media compositions for hundreds of commonly used cell lines. Many humanisation methods are also available from published literature.

At Animal Free Research UK, we believe that developing and using human models of disease provides the best chance of finding treatments which can make a real difference for patients.

Completely animal-free research can be difficult to achieve at present given the prevalence of animal-derived biomaterials within scientific research. However, we are working with industry, academia and policymakers to phase out this hidden animal use and empower scientists to end the use of animals in research.