The components of cell culture media mainly include the following categories:

Nutrients

1. Carbohydrates

• Glucose is the most common carbohydrate in cell culture media and is the main source of energy for cells. Through metabolic pathways such as glycolysis and cellular respiration, glucose is broken down into pyruvate and then generates adenosine triphosphate (ATP) to provide energy for various activities of cells. For example, in rapidly proliferating cells like tumor cells, the demand for glucose is high to meet the energy requirements of their high metabolic rate.
• Besides glucose, some media may also contain other sugars, such as galactose and fructose. They can also provide energy for cells or play special roles in the metabolic processes of specific cell types.

2. Amino Acids

• Cell culture media must contain 20 common amino acids, which are the basic units for protein synthesis. Among them, some are essential amino acids that cells cannot synthesize by themselves and must obtain from the media, such as leucine, isoleucine, and valine. Although cells can synthesize some non-essential amino acids on their own, adding them to the media also helps cell growth and protein synthesis. For example, glutamine is an important non-essential amino acid. It is not only a raw material for protein synthesis but also plays a key role in cell energy metabolism and nitrogen metabolism, providing additional energy and nitrogen sources for cells.

3. Vitamins

• Vitamins play indispensable roles in cell metabolism. For example, the vitamin B complex (including vitamin B1, B2, B6, B12, etc.) participates in many enzymatic reactions within cells and is an important cofactor for cell energy metabolism and substance synthesis. Vitamin C is an antioxidant that can protect cells from free radical damage and is very important for maintaining the redox balance of cells. Folic acid is involved in the synthesis of DNA and RNA and is crucial for cell proliferation and the stability of genetic material.

4. Inorganic Salts

• Cell culture media contain various inorganic salt ions, mainly including sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), phosphate (PO₄³⁻), etc. These ions are essential for maintaining the osmotic pressure balance of cells. For example, Na⁺ and Cl⁻ mainly maintain the osmotic pressure of extracellular fluid, while K⁺ mainly maintains the osmotic pressure of intracellular fluid. Ca²⁺ is an important second messenger in cell signal transduction and participates in many physiological activities of cells, such as muscle contraction and neurotransmitter release. Mg²⁺ is a cofactor for many enzymes (such as DNA polymerase, RNA polymerase, etc.) and is indispensable for processes such as nucleic acid synthesis and energy metabolism within cells.

Growth Factors

1. Epidermal Growth Factor (EGF)

• EGF is a small peptide that can stimulate the proliferation and differentiation of many cells (such as epithelial cells and endothelial cells). It activates intracellular signal transduction pathways by binding to the epidermal growth factor receptor (EGFR) on the cell surface, promoting cell mitosis and migration. EGF plays an important role in tissue repair and regeneration. For example, during skin injury repair, it can stimulate the proliferation of skin epidermal cells and accelerate wound healing.

2. Fibroblast Growth Factor (FGF)

• The FGF family includes multiple members, such as FGF-1 and FGF-2. They have important regulatory effects on the growth and differentiation of many cells, such as fibroblasts and neural stem cells. FGF can promote cell proliferation, migration, and angiogenesis. During embryonic development, FGF participates in the formation of multiple tissues and organs, such as the nervous system and skeletal system. In vitro cell culture, FGF is also an important additive component in many cell culture media, used to maintain cell growth and specific differentiation states.

3. Platelet-Derived Growth Factor (PDGF)

• PDGF is mainly derived from platelets and can stimulate the proliferation and migration of many cells (such as smooth muscle cells and fibroblasts). During wound healing, when platelets aggregate at the injury site, they release PDGF to stimulate the proliferation and migration of surrounding cells and promote tissue repair. In cell culture, PDGF can be used as an important growth factor for culturing cell types such as vascular smooth muscle cells.

Buffer System Components

1. Bicarbonate Buffer System (such as NaHCO₃ – H₂CO₃)

• This is one of the most commonly used buffer systems in cell culture media. Cells will produce acidic substances (such as lactic acid) and alkaline substances during metabolism. The bicarbonate buffer system can maintain the pH stability of the media through the following reactions: When cells produce acidic substances, H₂CO₃ will react with the acidic substances to generate more HCO₃⁻, thereby neutralizing the acidity; when cells produce alkaline substances, HCO₃⁻ will react with the alkaline substances to generate more H₂CO₃, thereby adjusting the pH. For example, during mammalian cell culture, the lactic acid produced by cell metabolism will cause the pH of the media to decrease, and the bicarbonate buffer system will play a role to maintain the pH within an appropriate range (usually 7.2 – 7.4).

2. HEPES (4-(2-Hydroxyethyl)-1-Piperazineethanesulfonic Acid) Buffer System

• HEPES is a zwitterionic buffer that has good buffering capacity within a relatively wide pH range (pH 6.8 – 8.2). Compared with the bicarbonate buffer system, the HEPES buffer system is less affected by the external carbon dioxide concentration. Therefore, in some cell culture environments with high requirements for pH stability or unstable carbon dioxide supply, the HEPES buffer system is a good choice. For example, in some closed cell culture devices or long-term cell culture experiments, adding HEPES can better maintain the pH stability of the media.

Other Components

1. Serum

• Serum is an important additive component in cell culture media. Common ones include fetal bovine serum (FBS), calf serum (CS), and horse serum (HS). Serum contains rich proteins, growth factors, hormones, lipids, and other nutrients. For example, fetal bovine serum contains albumin, which can provide nutrition for cells and maintain osmotic pressure. It also contains various growth factors such as EGF, FGF, and PDGF, which can stimulate cell growth and proliferation. It also contains hormones such as insulin, which can regulate cell glucose metabolism. However, the composition of serum is complex and there are batch-to-batch differences, which may have a certain impact on the reproducibility of experimental results.

2. Antibiotics and Antifungal Agents

• To prevent microbial contamination during cell culture, antibiotics and antifungal agents are usually added to the media. Common antibiotics include penicillin and streptomycin. They are usually used in combination. Penicillin mainly inhibits the synthesis of bacterial cell walls, while streptomycin mainly interferes with the synthesis of bacterial proteins, thereby inhibiting the growth of bacteria. Antifungal agents such as amphotericin B can inhibit the growth of fungi. However, when using these drugs, it is necessary to pay attention to controlling the dosage to avoid toxic effects on cells.