Improving Incubation

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Anyone working with cells in culture needs an incubator. Scientists working in this area range from researchers in academic and government labs to personnel in biotechnology, the pharmaceutical industry, and others. The key question is: What should scientists consider when shopping for a new CO2 or cell culture incubator?

According to Christian Haberlandt, marketing manager at Eppendorf (Hamburg, Germany), the top thing that an incubator should ensure is cell safety. As he asks: “Do the cells find optimal growth conditions?” Those conditions should exist throughout an incubator, creating a consistent environment, such that cells grow the same in all locations, including the top shelf. Creating such an environment depends on multiple temperature sensors. Plus, those sensors should be positioned to experience the same conditions that the cells face.

To get that needed uniformity, Mary Kay Bates, senior application scientist at Thermo Fisher Scientific (Waltham, MA), says, “Look for a cell culture incubator with active airflow circulation that provides uniformity throughout the chamber and recovery of all parameters in 10 minutes or less.”

Despite keeping the air moving to maintain consistent conditions, the environment needs to be stable. Haberlandt poses the question: “Are there any additional potential interference sources inside that cause, for example, vibration or turbulence?”

To be certain that an incubator provides the required consistency, a customer must rely on data from the vendor. In the end, the manufacturer must verify the uniformity of its incubators—for example, at 27 spots inside based on the DIN ISO 12880.

Cleaning options

“Contamination control features are critical in today’s cell culture, and these functions should be independently proven effective according to the U.S. Pharmacopeia, which requires a 12-log ‘overkill’ of the prescribed biological indicator organism,” Bates says. “For example, for a sterilization function, it’s not about the temperature or time, but that at least one million Bacillus subtilis bacterial spores were shown to be eliminated, and then that exposure is doubled.”

In addition, filtration can be part of the process that keeps an incubator clean. “HEPA filtration in the chamber to provide ISO Class 5 cleanroom conditions should meet this threshold in 5 minutes following a 30-second door opening,” Bates says. “This performance captures all airborne particles regardless of size, protecting cultured cells from circulating microorganisms.”

Everything, though, comes with some ups and downs. As Haberlandt notes, “Internal HEPA filters must be replaced twice yearly and do not withstand internal sterilization.”

The construction of an incubator also impacts how reliably and easy it is to clean. The chamber surface should be as smooth as possible and include a minimal number of internal parts to eliminate places that can’t be easily cleaned. Overall, as Haberlandt points out, downloadable performance protocols should be available to document the decontamination process.

For an overview, download the whitepaper “CO2 Incubator: Proper Use and Preventative Maintenance” from NuAire (Plymouth, MN).

Improving options

The high demand for cell culture incubators drives manufacturers to keep improving the platforms. At the end of 2018, for example, Eppendorf launched the CellXpert C170i and C170 Co₂ incubator. Haberlandt says that these incubators include “improvements in many of the points mentioned above.” When asked about the main benefits of these new incubators, he says, “Mainly to improve reproducibility of experiments and reliably reduce recurring costs and time investments.”

Eppendorf’s CO₂ incubators offer filterable USB-downloadable performance charts and recurring tasks. (Image courtesy of Eppendorf.)

In Eppendorf’s CO₂ incubators, temperature uniformity is verified inside at 27 positions. (Image courtesy of Eppendorf.)

Also in 2018, Thermo Fisher Scientific introduced its Thermo Scientific Cell Locker System. “Incorporated into our popular Thermo Scientific Heracell VIOS 160i CO₂ incubators, the Cell Locker System consists of six individual chambers that subdivide the incubator chamber, providing enhanced culture stability and protection for sensitive, critical cultures like stem cells, primary cells, viral clones, neural-derived tissues, and more,” says Bates.

With the Thermo Scientific Cell Locker System, scientists can open one chamber without disturbing the other five. (Image courtesy of Thermo Fisher Scientific.)

When asked about the key benefits from this technology, Bates says, “Fragile cultures which require more care represent a bigger loss when contaminated, so the Cell Locker System segregates cultures or projects, preventing cross-contamination of cultures.” Plus, a scientist can open one Cell Locker chamber without opening the other five. Given that “the remaining five chambers do not experience the door opening,” says Bates, “these sensitive cells remain in their ideal environment.”

In addition, “The Cell Locker System is designed to reduce gas use and evaporation by 50% or more, based on average usage and door openings,” says Bates. “If needed, an individual Cell Locker chamber can be carried to the work station or even a neighboring lab, protecting cultures from circulating airborne microorganisms.”

NuAire also offers a collection of CO₂ incubators. For example, the Model NU-5700 includes a “highly selective single source dual wave infrared (IR) sensor [that] allows for incredibly sensitive and accurate CO₂ control (within ±0.1%).” Some of NuAire’s CO₂ incubators, such as the Model NU-5710, include dual sterilization cycles: one at 145 °C dry and another at 95 °C humidified. The company also makes specific incubators aimed at using less energy. For example, NuAire’s In-VitroCell ES (Energy Saver) model NU-8600 CO₂ incubator, “uses heated water that surrounds the growth chamber to create uniform temperature conditions for cell culture growth,” the company explains.

Vendors often build incubators that control CO₂ and O₂. German-based BINDER’s CB series of CO₂ incubators come with or without O₂ control. For the ones with O₂ control, the range is 0.2–20% by volume.

As noted above, it’s not just the air in an incubator, but how it moves, too. The CO₂ Cell Incubators from BMT (Seattle, WA), for example, use a patented bi-directional air movement system. The company notes that this provides “precise uniformity of both humidity and temperature.”

Cost over time

Beyond what it costs to buy a particular cell culture incubator, it’s worth considering ongoing costs. These include the energy needed to run the device. So, it’s worth getting an efficient one.

Haberlandt also recommends considering a couple of other potential costs. He asks: “How much gas does the incubator consume? How much real usable space does the incubator offer?” He also suggests getting an idea of what internal parts, like HEPA filters, might need regular replacement and what it would cost. Last, he poses: “Is the manufacturer reliable and offers, for example, quality service?” Customers should consider all of these potential additional costs and concerns.

There’s nothing easy about culturing cells and keeping them in the most physiologically relevant conditions, but a sophisticated incubator makes it far easier. In many cases, the value of the samples far surpasses the cost of purchasing and running the incubator. So, it pays off very quickly to get the very one that a lab needs.

Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]