Incubators are heated, controlled-climate chambers used mainly to grow cells or microorganisms. Together with the culture medium, conditions inside incubators are meant to mimic a cell’s natural physiological conditions. Industries most likely to use incubators are pharmaceutical, biotechnology, and health care.
Although incubators operate at much lower temperatures than ovens, they resemble ovens in their requirements for temperature uniformity (ensuring even temperature throughout the unit) and precision (the ability to maintain a specific temperature). These values should be less than 1ºC for high-quality incubators. Units achieve uniform heating either through fans or as a result of internal designs that promote circulation.
Two main categories
Cell culture incubators, also known as carbon dioxide (CO2) incubators, are by far the largest group in terms of sales and application. CO2 incubators support cell culture work in basic research and in the biotechnology industry. Diagnostics and pharmaceutical firms also use these incubators to grow test cells.
Most incubators have an internal CO2 concentration of approximately 5 percent. Other gases, such as nitrogen, can be used to reduce oxygen levels for hypoxic cell cultures. CO2 is used to control the pH of cell culture media and to provide a more lifelike environment in which cells can grow.
“Heat only” incubators, the other major product category, are used to grow bacteria and yeast. In some laboratories, these devices support the growth and propagation of microorganisms for research purposes; hospitals use them to culture environmental bacteria swipes for contamination control and patient samples for diagnosing infectious diseases.
CO2 and heat-only incubators come in two basic sizes. Benchtop models tend to be small (6 to 7 cubic feet in volume) and stackable. Anywhere from one to half a dozen lab workers might use a single unit. Reach-in floor-model incubators are larger (up to about 30 cubic feet) and might hold samples from up to several dozen workers or an entire department. Floor models are popular in hospitals, which require high-volume incubators to meet demand for patient testing and sample segregation. Pharmaceutical and biotech companies also use large incubators to support cell line development, clone selection, and cell culture seeding for biomanufacturing, or to create cultures of test cells.
Benchtop incubators outsell reach-ins by about 20:1.
Contamination is the single most devastating occurrence in cultured cells. Contamination can delay critical diagnoses in hospitals, destroy tissues in fertility clinics, ruin basic research work on cells that may have taken months to develop, or delay a cell-based manufacturing project by months. Contamination arises from the lab environment, the researcher, or the medium being used.
Users employ several approaches to avoiding and resolving contamination, according to Scott Christensen, VP for North American Sales at NuAire (Plymouth, MN).
Some manufacturers line the insides of incubators with copper to reduce bacterial growth; others employ HEPA filtration to prevent contaminants from entering. Incubators are usually kept free of contaminating bacteria through a combination of HEPA filtration and manual cleaning. Hand cleaning can disinfect and decontaminate an incubator, but it does not sterilize it. Sterilization is achieved by heating the unit to between 140ºC and 180ºC, which kills all pathogenic organisms present.
Which contamination control approach is most effective? “There has been a lot of discussion on that subject,” Christensen tells Lab Manager Magazine. “Our approach is to prevent contamination in the first place.” NuAire utilizes HEPA filtration in all models, resulting in an ISO Class 5 environment. Some units also use heat to periodically decontaminate the chamber, including the HEPA filter.
By contrast, BINDER’s (Great River, NY) incubators do not incorporate HEPA filtration. According to Dave Craig, senior regional sales manager, filters can be expensive and require periodic maintenance or removal. “Plus, HEPA housings, fittings, and screws are perfect places for microorganisms to grow.”
BINDER instead utilizes a heating cycle, which sterilizes incubators at 180ºC. Note that while heat will kill pathogenic agents lurking inside the incubator cabinet, it will not clean dirt and spills present on the inside surface.
Drying out is another serious issue that destroys cell cultures. Some units today employ steam generators to replenish humidity to close to 100 percent within the incubator. Steam pans—containers filled with water— are more common.
With so much of biomedical research now based on cells, one could argue that incubators have become an enabling technology for translational medicine. That’s the view of Craig, who cites basic cancer research and in vitro fertilization as examples. “Human cell research is at the forefront of taking basic science from several sources and bridging it with other disciplines to optimize patient care.”
For additional resources on incubators, including useful articles and a list of manufacturers, visit www.labmanager.com/incubators
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