The Six Main Ingredients in Cell Culture Medium

Cell culture is one of the major technologies in the life sciences. It is a general term used to remove cells, tissues or organs from animals or plants and place them in an artificial environment conducive to their survival and/or proliferation. The basic environmental requirements for optimal cell growth are: controlled temperature, substrate for cell attachment, appropriate growth medium and incubator to maintain correct pH and osmolarity. The most important and critical step in cell culture is the selection of an appropriate growth medium for in vitro culture.

A growth medium or medium is a liquid or gel designed to support the growth of microorganisms, cells or small plants. Cell culture media typically contain appropriate energy sources and compounds that regulate the cell cycle. A typical medium consists of amino acids, vitamins, inorganic salts, glucose, and serum as a source of growth factors, hormones, and attachment factors. In addition to nutrients, the medium helps maintain pH and osmolarity.

Natural media consist only of naturally occurring biological fluids. Natural media are very useful and convenient for a wide range of animal cell cultures. The main disadvantage of natural media is poor reproducibility due to lack of knowledge of the exact composition of these natural media.

Artificial or synthetic media are prepared by adding nutrients (organic and inorganic), vitamins, salts, O2 and CO2 gas phases, serum proteins, carbohydrates, cofactors. Different artificial media have been designed to serve one or more of the following purposes: 1) immediate survival (balanced salt solution, with specific pH and osmolarity); 2) prolonged survival (supplementation with various organic compounds and/or or serum's balanced salt solution); 3) infinite growth; 4) specialized functions.

Serum containing medium

Fetal bovine serum is the most common additive in animal cell culture media. It is used as a low-cost supplement to provide an optimal medium. Serum provides a carrier or chelator for unstable or water-insoluble nutrients, hormones and growth factors, protease inhibitors, and binds and neutralizes toxic moieties.

Serum-free medium

The presence of serum in culture media has many disadvantages and can lead to serious misinterpretations in immunological research. Various serum-free media have been developed. These media are often specifically formulated to support the culture of single cell types, as well as Stem Cell Technologies [6]'s mTESR media for stem cells, and incorporate defined quantities of purified growth factors, lipoproteins, and other proteins otherwise typically produced by Serum delivery. These media are also referred to as "determined culture media" because the components in these media are known.

Chemically defined media

These media contain contamination-free ultrapure inorganic and organic components and may contain pure protein supplements such as growth factors. Their ingredients are produced in bacteria or yeast through genetic engineering and are fortified with vitamins, cholesterol, specific amino acids and fatty acids.

Protein-free medium

Protein-free media do not contain any protein, only non-protein components. Using protein-free media improves cell growth and protein expression compared to serum-supplemented media, and facilitates downstream purification of any expressed products. Formulas such as MEM, RPMI-1640 are protein free and provide protein supplementation when needed.

The choice of cell culture medium is extremely important and can significantly affect the success of your cell culture experiments. The choice of medium depends on the type of cells to be cultured as well as the purpose of the culture and the resources available to the laboratory. Different cell types have highly specific growth requirements, therefore, the most suitable medium for each cell type must be determined experimentally.

Primary cell cultures provide unique and valuable research data, but cell numbers are the limitation most of the time. For such critical samples, especially those from diseased human biopsies, high-quality media are required. This reduces the risk of contamination and saves time, labor and money by eliminating required preparation steps and replenishment. In addition, all of these media undergo extensive quality control testing, and each batch is routinely tested for growth promotion, absence of cytotoxicity, and physical parameters such as osmolarity and pH.

The complexity of cell culture media composition presents many challenges in optimizing the individual components of the media. Most classical media are designed for small-scale, low-density cultures, often requiring serum as a key nutrient. However, in the biotechnology industry where high cell densities need to be maintained and cell productivity increased, the development and optimization of media is critical.