CO2 Incubators: Environmental Precision Gives Researchers More Control

New Environmental Precision Gives Researchers More Control

To culture cells reproducibly, scientists seek a consistently controlled environment. “At the end of the day, a customer just wants to grow cells,” says Uwe Ross, president at BINDER (Bohemia, NY).

The evolution of incubators started with the control of heat. Then, scientists wanted humidity control. The desire to control an incubator’s pH spawned CO₂ incubators. “Now, we’re in the middle of looking at a growing number of applications that need O₂ control,” says Ross. “If you run an experiment on organ tissue and expose it to ambient oxygen levels of about 20–21 percent or reduce the levels to around five percent, you get different results.” Tomorrow’s incubators could control even more parameters, but each one adds to the cost.

A customer’s checklist for an incubator also includes contamination concerns, says Leah Harris, chief marketing officer at Caron Products (Marietta, OH). “Being able to have an incubator that offers the best contamination controls and elimination options is always a concern.”

Judging the jacket

In the past, the best CO₂ incubators used a water jacket to control the temperature. “The water jacket was invented because a CO₂ incubator needs highly accurate uniformity,” says Ross. “Now, we have air-jacket units that are as good or better.” In fact, Ross points out some disadvantages of a water jacket. “You can’t heat the water over 100 degrees Celsius,” he says, “and a water-jacket incubator is hard to move because it’s so heavy.”

An air-jacket incubator provides the same temperature accuracy, according to Ross, and it can be sterilized up to 180 degrees Celsius. He adds, “An air-jacket unit is also easier to service if you have a problem.”

Some incubators even use a gel jacket. “An incubator with this type of jacket has the benefits of both air and water jackets,” says Harris. For example, Caron’s GelJacket, Harris says, “incorporates proprietary gel active insulation, which surrounds the incubator on all sides. It is lightweight, requires no maintenance, can withstand high temperatures for decontamination cycles, and has no risk of leaking.”

Technology at work

The lifetime of a CO₂ incubator depends largely on how it gets used and maintained. Ross says that an incubator should last 5 to 10 years, and most likely closer to the 10. Keeping it working right for a decade, though, takes maintenance. “You don’t just purchase a CO₂ incubator, set it up, and never touch it again,” he says. “You wouldn’t do that to your car, and you shouldn’t do it to your incubator.” So an incubator should be serviced to maintain accuracy and efficiency.

At the Wilmot Cancer Center at the University of Rochester in New York, Randall M. Rossi, director of the Translational Research Core Facility, uses CO₂ incubators to culture animal and human cell lines. When asked what he’d like to see changed in today’s technology, he says, “I’d love to have the cost drop.” He adds, “The reliability of the CO₂ and O₂ sensors, if an incubator has them, are quite important right now. Most of the incubators that are CO₂ and O₂ are too large to maintain accurate O₂ levels.” Systems that do a good job of maintaining both gas levels, says Rossi, are “very expensive and not practical for general lab use.”

Other experts also find some of the dual-gas units challenging. From the Stem Cell and Flow Cytometry Core at the University of California, Santa Cruz, facilities manager Bari Holm Nazario reports, “We just opened a new building and we have been battling with a dual-gas unit.” She even notes they are in discussions with the manufacturer to “rewrite some firmware.” She also says that “one unit has had three post-installation visits for the engineers to stabilize things.”

Adding volume

Volume also matters. “We’re getting more requests and calls for high-volume cell culture,” says Harris. “More people are doing cell-culture applications with shakers, stirrers, and roller bottles.” Often, these devices only fit in large incubators.

Adding devices inside incubators creates other needs. For one thing, the incubator might need more shelves. In addition, the shelves must be strong enough. “The incubator must also isolate vibration so the shakers don’t move around,” Harris explains.

Adding instruments inside a CO₂ incubator can also increase the need for refrigeration. “Shakers let off some heat, so you need cooling to reach the set point desired for the cells in culture,” says Harris. “When a customer wants to do these higher-end applications that put off heat, we always quote refrigerated models, because only those units will give the precise set points that the scientist needs.”

As units get bigger, users consider energy consumption more than ever. “Some units are over-designed,” says Harris, “but you can get units that even plug into a 115-volt outlet, and that can save money.”

Corralling contamination

“Contamination is a bigger and bigger issue,” says Ross. “The number of contaminated CO₂ incubators out there is really staggering.” So in selecting an incubator, consider its anti-contamination features.

Sterilizing an incubator depends on the type of heating. With a water-jacket incubator, inside components get removed and autoclaved, and the remaining inside surfaces get washed down with alcohol. “With air jackets,” says Ross, “you just hit a button that heats up the unit to 180 degrees Celsius, and everything in there is killed.”

Sterilization could become even more critical as CO₂ incubators move into more applications. For example, Ross says, “The manufacturing trend is just starting.” Rather than just using CO₂ incubators in research labs, they also appear increasingly in manufacturing environments. “More and more, companies grow cartilage for knees or grow skin after a burn,” says Ross.

In any situation, though, sterile culturing conditions will stay on the incubator checklist.