Gibco RPMI 1640 is a cell culture medium, a liquid designed to support cell growth in a laboratory. Gibco is the brand, now part of Thermo Fisher Scientific, that produces the medium. “RPMI 1640” designates the formulation created in 1966 at the Roswell Park Memorial Institute, now the Roswell Park Comprehensive Cancer Center. This medium was initially developed to grow human leukemic cells, a type of cancer cell found in the blood and bone marrow.
Core Composition and Function
RPMI 1640 is a chemically defined medium, meaning its exact molecular makeup is known. The base formula contains a precise mixture of components for cell survival and proliferation, including a set of essential amino acids and various vitamins. The formulation is distinct from other media like Eagle’s Minimal Essential Medium because it includes biotin, vitamin B12, and high concentrations of inositol and choline.
A primary component of the medium is glucose, which serves as the main energy source for the cells. To maintain a stable pH, RPMI 1640 uses a sodium bicarbonate buffer system. This system works with a controlled atmosphere of 5-10% carbon dioxide (CO2) in an incubator to mimic physiological conditions. The original formula also contained the reducing agent glutathione. This composition was optimized for growing human leukemic cells that float in suspension.
The basic RPMI 1640 formulation does not contain proteins, lipids, or growth factors, so it requires supplementation before use. The most common addition is Fetal Bovine Serum (FBS), usually at a concentration of 10%. FBS provides a complex mix of growth factors and other molecules that promote cell division and viability.
Common Applications and Cell Types
The application of RPMI 1640 has expanded significantly since its original design. It is now widely used to culture a variety of mammalian cells, especially those of the immune system. Lymphocytes, including T cells and B cells, grow well in this medium, making it a staple in immunological research where scientists study responses to pathogens and vaccines.
The medium is also frequently used for specific, well-established cell lines. Jurkat cells, an immortalized line of human T lymphocytes, are grown in RPMI 1640 to study T cell signaling and activation. Other common examples include HeLa cells (a cervical cancer line), MCF-7 cells (a breast cancer line), and peripheral blood mononuclear cells (PBMCs), which are a mix of immune cells isolated from blood.
Beyond basic cell propagation, RPMI 1640 is instrumental in cancer biology and virology. Researchers use it to grow various carcinoma and hematopoietic (blood-forming) cancer cells to test new therapies. It is also suitable for culturing hybridomas, which are engineered cells that produce monoclonal antibodies. The medium’s versatility allows for the cultivation of both suspension cells and some adherent cells.
Formulations and Modifications
To suit diverse experimental needs, the standard RPMI 1640 medium is available in numerous modified formulations. A common variation relates to L-glutamine, which is necessary for cell growth but is unstable in liquid media, breaking down into potentially toxic byproducts. To address this, Gibco offers formulations with GlutaMAX™, a stable dipeptide that cells can metabolize to release L-glutamine as needed.
Another frequent modification is the inclusion or exclusion of Phenol Red. Phenol Red is a pH indicator that gives the medium its characteristic pink-orange color. It provides a visual cue of the culture’s health; a change to yellow indicates acidic conditions, while a turn to purple signals alkalinity. For certain experiments, like fluorescence microscopy or flow cytometry, Phenol Red can interfere with optical measurements, prompting researchers to choose a formulation without it.
Some versions of RPMI 1640 contain HEPES, a chemical buffering agent that provides additional pH stability for cells handled for extended periods outside a CO2 incubator. This is useful during complex procedures like cell sorting or imaging. Researchers also add their own supplements, most commonly antibiotics like Penicillin-Streptomycin to prevent bacterial contamination.
Handling and Storage Best Practices
Proper handling and storage are necessary to maintain the integrity of RPMI 1640 medium. Liquid formulations must be stored at a temperature between 2°C and 8°C. This refrigeration slows the degradation of sensitive components. Freezing the medium is not recommended as it can cause salts and other solutes to precipitate out of the solution, altering its composition.
The medium must also be protected from light. Several components, particularly vitamins like riboflavin, are light-sensitive and can break down upon exposure, reducing the medium’s effectiveness. For this reason, it is supplied in bottles that are either amber-colored or are stored in protective boxes. When working with the medium, it is best to minimize its exposure to direct laboratory light.
The shelf life of the medium changes significantly after it is opened and supplemented. An unopened bottle of RPMI 1640 has a shelf life of several months to a year. Once supplements like Fetal Bovine Serum and antibiotics are added, the usable life of the complete medium is much shorter, typically two to four weeks when stored properly at 2-8°C, as the added components are also prone to degradation.