Cell Culture Medium Liquid

I. Definitions

Cell Culture Medium Liquid refers to a liquid formulation specifically designed to provide the necessary nutrients, growth factors, and environmental conditions for the growth, proliferation, and maintenance of cells in an in – vitro culture environment.

II. Composition

1. （Carbon Sources）
   • Glucose is a common carbon source. It is metabolized by cells through glycolysis and other pathways to generate energy in the form of ATP.
   • In some specialized cell cultures, other sugars like galactose or fructose may be used according to the specific metabolic requirements of the cells.
2. （Nitrogen Sources）
   • Amino acids are essential nitrogen sources. There are 20 common amino acids, and some are essential amino acids that must be supplied in the medium because cells cannot synthesize them.
   • In addition to amino acids, some small – molecule nitrogen – containing compounds may also be present to support cell growth.
3. （Vitamins）
   • B – group vitamins, such as thiamine (B1), riboflavin (B2), and pyridoxine (B6), play crucial roles in cellular metabolism. They act as co – factors for many enzymatic reactions.
   • Vitamins like ascorbic acid (vitamin C) are also important for some cell types, especially those involved in extracellular matrix synthesis.
4. （Inorganic Salts）
   • Sodium, potassium, calcium, and magnesium ions are present. Sodium and potassium ions are important for maintaining cell membrane potential.
   • Calcium ions are involved in cell signaling, cell adhesion, and many other cellular processes. Magnesium ions are co – factors for many enzymes.
   • Phosphate ions are necessary for energy metabolism (as part of ATP) and nucleic acid synthesis.
5. （Growth Factors）
   • Epidermal growth factor (EGF) promotes cell proliferation, especially for epithelial cells.
   • Fibroblast growth factor (FGF) is crucial for the growth and differentiation of fibroblasts and many other cell types.
   • Platelet – derived growth factor (PDGF) is involved in wound healing and cell proliferation.
6. Other Additives
   • Serum
     • Fetal bovine serum (FBS) is widely used. It contains a large number of proteins, growth factors, hormones, and other bioactive substances that support cell growth.
     • However, the use of serum has some disadvantages, such as batch – to – batch variation and the potential for introducing contaminants.
   • （Buffers）
     • To maintain a stable pH, buffers like HEPES (4 – (2 – hydroxyethyl) – 1 – piperazineethanesulfonic acid) or bicarbonate – CO2 systems are used.
   • （Antibiotics）
     • Antibiotics like penicillin and streptomycin are often added to prevent bacterial contamination.

III. Types

1. （Basic Media）
   • Minimal Essential Medium (MEM) is a well – known basic medium. It contains the essential nutrients required for the growth of many cell types but may need additional supplements for some cells.
   • Dulbecco’s Modified Eagle Medium (DMEM) is an enhanced version of MEM with higher concentrations of some nutrients, suitable for a wider range of cell cultures.
2. （Serum – free Media）
   • These media are formulated to replace serum with defined components. They are designed for applications where serum – related issues need to be avoided, such as in biopharmaceutical production.
   • Some serum – free media are specifically developed for particular cell types, providing the necessary growth factors and nutrients in a more controlled manner.
3. （Media for Special Purposes）
   • For example, neural stem cell medium contains specific growth factors and nutrients to support the growth and differentiation of neural stem cells.
   • Media for cancer cell cultures may have different compositions to meet the unique metabolic and growth requirements of cancer cells.

IV. Preparation and use

1. （Preparation）
   • First, the dry powder or concentrated form of the medium is usually obtained.
   • Then, it is dissolved in distilled water according to the manufacturer’s instructions. The appropriate amounts of other additives like serum, antibiotics, and growth factors are added.
   • The pH of the medium is adjusted to the appropriate range, usually between 7.2 and 7.4, using acid or base.
2. （Usage）
   • The prepared medium is filtered through a sterile filter with an appropriate pore size (usually 0.22 μm) to remove any particulate matter or contaminants.
   • The medium is then dispensed into sterile cell culture vessels such as flasks, plates, or dishes.
   • Cells are seeded into the medium – filled vessels at an appropriate density, and the cultures are incubated in a controlled environment with appropriate temperature (usually 37°C), humidity, and gas composition (usually 5% CO2).

V. Quality control and storage

1. Quality Control）
   • The composition of the medium is verified by chemical analysis to ensure that the concentrations of all components are within the specified ranges.
   • Tests for sterility, endotoxin levels, and mycoplasma contamination are carried out. Sterility tests ensure that there is no microbial growth in the medium. Endotoxin tests are important for applications where the medium will be in contact with cells that are sensitive to endotoxins. Mycoplasma contamination can affect cell growth and experimental results, so regular testing is necessary.
2. （Storage）
   • Most cell culture medium liquids are stored at 4°C in the dark. This helps to maintain the stability of the components.
   • Some media with more labile components may need to be stored at lower temperatures, such as – 20°C or – 80°C, and should be thawed properly before use.