Gibco Iscove’s Modified Dulbecco’s Medium, or IMDM, is a specialized and highly enriched cell culture medium used for biological research. It is a modification of a simpler medium, designed specifically to grow cells that have high nutritional demands or that grow at a high density. Researchers use this liquid growth medium to sustain specific cell types outside of a living organism, in a laboratory setting.
IMDM Formulation and Key Components
Iscove’s Modified Dulbecco’s Medium (IMDM) is defined by its complex and enriched formulation, which builds upon the foundation of Dulbecco’s Modified Eagle Medium (DMEM). IMDM contains an extensive list of amino acids and vitamins, present in higher concentrations than in many other media. These components are the fundamental building blocks for proteins and are necessary to support the rapid growth and division of cells. The medium is enriched with additional amino acids not found in standard DMEM, providing a more comprehensive nutritional profile.
A component in IMDM is the trace element selenium, which is added in the form of sodium selenite. Selenium is a component of certain enzymes and proteins that help protect cells from oxidative damage. The HEPES buffer is also included to maintain a stable pH, a measure of acidity, even when the culture is temporarily exposed to atmospheric conditions. This provides greater pH stability compared to media that rely solely on a sodium bicarbonate buffer system.
IMDM contains a high concentration of glucose for energy and sodium pyruvate, which serves as an additional carbohydrate source in cellular metabolism. Gibco offers IMDM in various formulations, including options with or without L-glutamine, an amino acid that can be unstable in liquid media. It is also available without phenol red, a pH indicator that can sometimes interfere with certain experimental assays.
Distinct Advantages and Modifications from DMEM
IMDM was developed by Harry Iscove to culture specific hematopoietic cells that could not be sustained in existing media like Dulbecco’s Modified Eagle Medium (DMEM). The modifications provide advantages for growing difficult cell types and support rapid cell proliferation at high densities.
The inclusion of selenium was a deliberate modification to support the growth of lymphoid cells and bone marrow progenitors, which have a specific requirement for this trace element for their survival and function. Another significant change from standard DMEM is the replacement of ferric nitrate with potassium nitrate as the iron source. The addition of HEPES buffer is also particularly advantageous in experimental setups where incubators have less precise CO2 control or when cultures are frequently handled outside the incubator.
Common Applications and Supported Cell Lines
The enriched nature of IMDM makes it particularly well-suited for the culture of hematopoietic cells, which are cells that give rise to all other blood cells. This includes various progenitor cells found in bone marrow, such as BFU-E (burst-forming unit-erythroid) and CFU-GM (colony-forming unit-granulocyte/macrophage). The medium’s composition supports the differentiation and proliferation of these early-stage cells.
IMDM is also widely used for growing both B lymphocytes and T lymphocytes, which are types of white blood cells central to the adaptive immune system. Researchers studying immune responses, lymphocyte activation, and cytokine production often rely on IMDM to maintain healthy lymphocyte populations in vitro. The medium’s ability to support these non-adherent, or suspension, cells at high density is an advantage.
Beyond immune cells, IMDM is a standard medium for the cultivation of hybridoma cell lines. These are engineered cells created by fusing a specific antibody-producing B cell with a myeloma (cancerous) cell, resulting in a line that can produce large quantities of a single, specific monoclonal antibody. Additionally, it supports the growth of certain adherent cell lines like COS-7 (a kidney cell line from a monkey) and macrophages.
Required Supplementation for Complete Media
While IMDM is a highly enriched basal medium, it is not a complete growth medium on its own and requires supplementation to support cell culture. The primary supplement is Fetal Bovine Serum (FBS). FBS provides a complex mixture of hormones, growth factors, and proteins that are not present in the basal formula but are needed for cell survival, proliferation, and attachment. The concentration of FBS used ranges from 10% to 20%, depending on the specific needs of the cell line being cultured.
To prevent bacterial and fungal contamination, which can quickly ruin a cell culture experiment, researchers add antibiotics to the complete medium. A common choice is a combination of penicillin and streptomycin, often sold as a premixed solution. This mixture effectively targets the most common types of laboratory contaminants.
If the specific IMDM formulation used does not already contain it, L-glutamine must be added as a supplement. L-glutamine is an amino acid that serves as a major energy source for many cultured cells. Because it is less stable than other amino acids in liquid solution, it is often added fresh to the medium just before use to ensure its availability to the cells.