The Case for Serum - Free Media

Use of serum-free media and the related genera of animal-free and protein-free media has increased significantly over the past 15 years. This is particularly true in industrial applications, in which the use of serum presents a safety hazard and a source of unwanted contamination in the production of biopharmaceuticals (1). As the name suggests, serum-free media are prepared without animal serum, but it may contain serum constituents or substitutes thereof. Animal-free media are similar to serum-free except that the components are derived from nonanimal sources. Recombinant proteins replace native proteins, and the nutrients are obtained from synthetic, plant, or microbial sources. By contrast, protein-free (or chemically defined) media are devoid of protein, although few formulations can be 100% protein free without loss of function. A more accurate definition of such a medium would describe it as low in protein, with minimal quantities of small mass proteins used. The three types of media can be thought of in a gradient of complexity. After true serum-based media, serum-free media are the most complex compositions designed for universal use in culturing mammalian cell lines. Animal-free and protein-free media formulations are less complex and more defined but limited to the cultivation of specific cell types. Thus, selection of one medium over another depends on its intended use. For most research applications, serum-free medium is the best choice because it provides broadspectrum utility and enables good control of the composition. By contrast, in the manufacture of protein-based drugs, potential contaminants and production costs play a more significant role in the selection of more defined medium compositions.