Serum is the amber fluid rich in protein that is separated from coagulated blood. Serums like newborn or fetal bovine serums are commonly used in cell culture media to provide nutrients and growth factors that promote survival and growth of cells. Alternative sources of cell growth and survival factors to animal serums and particularly fetal bovine serum (FBS) are being developed for a number of reasons, to suit research, therapeutic and food industries.
The use of serum poses safety concerns when used in production of therapeutic cells or therapeutic proteins produced by cells due to risk of pathogen contamination . Contamination and variability between serum batches can affect the quality and reproducibility of results from cell culture experiments . Ethical concerns surround the extraction of FBS during slaughtering of pregnant cows because this could potentially cause suffering to the fetus . FBS is expensive and is one of the hurdles for bringing down the cost of cultured meat . The clean meat industry also seeks to eliminate the inclusion of animal products, aside from the initial cells from which their meat cultures grow .
Serum-free media is more consistent between batches and the amount of protein is lower making it easier for applications where proteins will be purified from cultured cells . Serum-free media contains substances that promote cell adherence, growth factors, enzyme inhibitor, binding proteins and trace elements . As cells grow and fill up tissue culture dishes, trypsin is an enzyme used to detach cells from the surface of the culture dish in order to split the culture into more culture dishes. In the process, trypsin is inactivated by protease inhibitors found in animal serum so that cells can reattach to the surface . The plant-based soybean trypsin inhibitor is an enzyme used in serum-free media .
Ultroser G is a commercially available serum-free media which contains growth factors adhesion factors binding proteins, vitamins minerals and hormones . Mushroom extract has also been used to make a serum-free media . Companies focused on developing more consistent serum-free media that provides better growth are ThermoFisher Scientific, Athena Environmental Sciences, Inc., Pan Biotech UK Ltd., Bichrom, Irvine Scientific, Cellular Technology Ltd., Biological Industries, Sigma-Aldrich Co. LLC, CellGenix GmbH and HiMedia Laboratories .
EGF, bFGF, FGF, ECGF, IGF-1, PDGF, NGF, TGF-alpha and TGF-beta are growth factors used in serum-free media and each are appropriate for specific cell types . Purified growth factors or hormones may be derived from plants and animals or using recombinant DNA technology to produce proteins in bacteria or yeast . Most stem cells are cultured in serum-free media with specific factors to promote either self-renewal or differentiation into specific cell types .
Finless foods, a San Francisco company culturing tuna is working on growing fish cells without serum using microbial fermentation, algal or fungal extracts . Clean meat company, Just, Inc. (previously Hampton Creek) is analysing different plants for their ability to supply growth factors and nutrients . Aleph Farms is and Israel-based company growing meat in 3D culture with serum-free media .