When it comes to conducting laboratory research in the life sciences, scientists must create appropriate conditions to accommodate the survival and/or growth of living cells.
Cell cultures require certain environmental conditions. For optimal growth and proliferation, cells require:
- Temperature control
- Appropriate pH and osmolality
- A substrate for cellular attachment
- A certain type of culture medium
- An incubator to maintain stable conditions
This article will delve into one of these critical components: cell culture media. We will explain what cell culture media is, what its components are, the different types, and what to look for when selecting an appropriate cell culture medium.
What is cell culture media?
Cell culture media, also known as growth media, is an umbrella term that encompasses any gel or liquid created to support cellular growth in an artificial environment.
When scientists remove cells, organs, or tissues from living creatures, they must keep them in an appropriate artificial environment. A culture medium plays an integral role in cell culture technology, supporting in vitro cellular research.
It is the medium that supplies the nutrients necessary for cell cultures to survive and proliferate. The growth media also provides the correct osmolality and pH.
Scientists must consider their cell type when choosing an appropriate growth medium. There are a variety of different types of cell culture media that accommodate cells from mammals, plants, insects, bacteria, yeast, viruses, and more.
The choice of cell culture medium directly impacts the results of an experiment, and as such, must be carefully considered.
What are the components of cell culture media?
Cell culture media are comprised of a combination of compounds and nutrients designed to support cellular growth. Common components of cell culture media include:
- Amino acids: Every cell culture media contains a mixture of amino acids, the building blocks of protein. Both essential and nonessential amino acids may be used to boost cell viability and growth.
- Vitamins: Vitamins are included to facilitate cellular growth and proliferation. Serum is used as the source of many vitamins in serum-containing media, but vitamins must be added to serum-free media.
- Carbohydrates: Carbohydrates provide an energy source for living cells. Glucose is commonly used, but other carbohydrates, such as galactose, fructose, or maltose, are available.
- Inorganic salts: Inorganic salts are needed to regulate membrane potential and osmolality.
- Basic and trace elements: Cells need elements like iron, potassium, magnesium, and zinc to grow.
- Serum: Serum contains growth factors and inhibitors, hormones, protease inhibitors, chelators, amino acids, carbohydrates, lipids, vitamins, trace elements, minerals, and more that are needed for cellular growth. Bovine serum is commonly used.
- Hormones: Certain hormones may be added to influence cell function, growth, and proliferation.
- Buffering systems: Buffering systems regulate pH.
- Supplements: Supplements like hormones, enzyme inhibitors, and trace elements are sometimes added to cell culture media that cater to the cell-type and research goal.
- Antibiotics: Antibiotics are added to cell culture media to inhibit fungal and bacterial growth. Antibiotics are best suited for serum media thanks to proteins that bind some of the antibiotic load. In contrast, cells in serum-free media are at a greater chance of antibiotic toxicity.
What are the different types of cell culture media?
Cell culture media can be broken into two primary categories: natural media and synthetic media.
Natural media are those that are derived from tissue extraction or animal body fluids, such as plasma, lymph, and serum. Natural media can be broken down into three groups:
- Biological fluids: Examples include serum, plasma, lymph, and amniotic fluid.
- Tissue extracts: Examples include embryo, bone marrow, tumour, and liver extracts.
- Clots or coagulants: Examples include plasma clots and coagulants.
Serum is the most common natural medium. Serum is even used as a supplement in synthetic medium cultures. Bovine serum is popular thanks to numerous advantages, including ample resources and a long application time.
Synthetic media (also known as artificial media) are those created using a variety of organic and inorganic compounds. Synthetic media include:
- Serum-containing media: Synthetic media where supplemental serum is used.
- Serum-free media: Serum-free media (SFM) offer greater consistency than serum-containing media, allowing researchers to support cellular growth and proliferation without the need for serum.
- Chemically defined media: Chemically defined media are contamination-free, consisting of only purified organic and inorganic components.
- Protein-free media: Protein-free media contain no protein. Protein supplements are added on an as-needed basis.
- Balanced salt solutions (BSS): BSS on their own are used to keep cells alive. BSS are enriched with nutrients and other compounds to create culture media capable of supporting cellular growth and proliferation. As such, BSS form the foundation of many types of complex media.
Serum-free media (SFM) are often categorized as either basic/basal or complex. Basal mediums are those without supplements. Once growth supplements are added to a basal medium, it becomes a complex medium.
Below is a list of some common culture media.
|Media Name||Media Type||Description|
|MEM (Minimum Essential Medium)||Basal media||Also known as Eagle’s minimal essential medium (EMEM), this medium is used for primary and diploid cultures. MEMs contain only vitamins, non-essential amino acids, inorganic salts, and glutamine. |
|DMEM (Dulbecco’s Modified Eagle’s Medium)||Basal media||Similar to MEM, but with additional amino acids and vitamins. Contains no growth promoters or proteins.|
|IMDM (Iscove’s Modified Dulbecco’s Medium)||Complex media||A modified version of DMEM with more amino acids and vitamins. It contains no iron but does have selenium and ferric nitrate. Suitable for high-density cultures. |
|RPMI-1640 ||Complex media ||A medium that works for most types of mammalian cells. One of the most used mediums. |
|Ham’s F-10 and F-12||Serum-free media||Ham’s F-10 was the original Ham nutrient mixture, designed for use with Chinese hamster ovary (CHO) cells. It’s suitable for use with human diploid cells. Ham’s F-12 is more complex, suited for rat prostate epithelial and rat hepatocyte cells. |
What to look for in a cell culture media
The most important step is determining what type of cell culture medium to use. With so many commercial mediums available, finding the right choice can be intimidating.
Start by researching the cell line you will be using to determine what different culture mediums are recommended. You may then select a few and try them out to see what works best. Here are some factors to consider.
1. Media preparation
Cell culture media varieties come in three forms:
1. Powdered medium: Powdered media are the least expensive but must be sterilized and prepared by the researcher.
2. Concentrated medium: Concentrated media only need to be diluted by the researcher.
3. Working solution: Working solutions are the easiest type of media. They are designed to be used without any manipulation by the researcher.
2. Type of media to use: natural vs synthetic media
All cell culture media belong to one of two categories: natural media or synthetic media. Each has its own pros and cons which direct investigators on which medium to choose.
Serum media are created by removing hemaleucin from plasma. The resulting mixture contains a combination of components that is valuable for cellular growth and proliferation. The benefits of serum media include that they:
- Consist of a wide variety of cellular nutrients, such as amino acids, vitamins, minerals, and fatty acids.
- Provide components that allow for cell adherence.
- Contain a variety of growth factors and hormones.
But there are downsides to serum media. When it comes to its drawbacks, serum media:
- Lack compositional uniformity, making it poorly suited for large-scale experiments.
- Contain a mixture of compounds, some of which can be harmful to or inhibit the growth of certain cell types.
- Have a greater risk of contamination when compared to artificial media.
- May complicate the isolation of cell culture products.
- Can be expensive.
Synthetic media have the distinct advantage of consistency. Investigators can be sure that they are using the same culture medium, even when scaling their research. Additionally, artificial media are typically less expensive than serum-based media.
Yet, there are downsides to using a serum-free medium. These cultures are more sensitive to extremes, including those of temperature, pH, and osmolality.
3. Which specific medium to use
Once you have chosen between natural and artificial media, you must select a specific medium. Many labs utilize commercial media, allowing quality and consistency with minimal effort.
To find the best one, you must ask yourself:
- What types of cells will you be using, and what are their requirements?
- What are the capabilities and limitations of your lab?
- What is the purpose of the experiment?
For instance, stem cells require media that can facilitate maintenance, differentiation, expansion, and downstream applications. Because stem cells are pluripotent, their media conditions must be closely monitored so that investigators do not end up with something other than their target. There are certain commercial media designed for use with stem cells, such as RPMI-1640, that work well with certain types of stem cells.
If you are unsure which medium is best, media companies can help you narrow down your options. Be sure that you understand your cells, goals, and lab specifications so that you select the best fit.