Best Practices for Using CO2 Incubators

CO₂ incubators are essential pieces of laboratory equipment, designed to provide an optimal environment for cell growth. This is critical to the success of both routine propagation and cell-based screening. However, because CO₂ incubators are typically a shared resource, it is wise to make sure they are being used correctly. In this article, we share some best practices to reduce the risk of cells becoming contaminated within the CO₂ incubator and ensure that cell-based screening data can be trusted.

Take care during installation and set-up

If you’re lucky enough to have recently acquired a CO₂ incubator, you’ll want to make sure you install it correctly. This means positioning it away from direct sunlight and drafts (e.g. those coming from air-conditioning ducts or the exhaust vents of ultralow temperature freezers) that can interfere with growth chamber conditions. It is also important to confirm that the laboratory environment aligns with manufacturer specifications for maintaining stable incubation at 37^oC.

Additionally, it is recommended that CO₂ incubators be placed on leg-leveling casters rather than directly on the floor. As well as making them easier to move during cleaning, casters help prevent dust and dirt from entering the growth chamber when opening and closing the incubator door. It is also sensible, during installation, to check that the CO₂ incubator is level. “An uneven incubator can have a significant impact on cell growth that can compromise screening data,” comments Amy Emery, research associate at the University of Cambridge. “For example, where adherent cells are more concentrated at one side of the microplate wells than the other, they may respond differently to treatment with chemical compounds, thereby skewing results.”

Once the CO₂ incubator has been positioned appropriately and connected to power and gas supplies, it should be thoroughly cleaned and disinfected prior to use. Many newer models are fitted with an automatic self-sterilization program that should always be run where available. It is also recommended that the CO₂ incubator be allowed to stabilize overnight before any cells are introduced.

Implement a regular cleaning schedule

Regular cleaning is essential for CO₂ incubators to operate effectively. Where contaminants such as bacteria, fungal spores, or viral particles are allowed to accumulate, they can infiltrate cell cultures and can increase the risk of transmission to end users. Cleaning should involve wiping down external surfaces with a solution of mild detergent in single distilled water, and treating the inner chamber with a noncorrosive disinfectant like 70% isopropyl alcohol or 70% ethanol. Particular attention should be given to frequent contact points (e.g. door handles) and to areas that are more prone to harboring contamination (e.g. door gaskets). “It is also good practice to disinfect the water tray and refill it with fresh distilled water on a weekly basis,” adds Emery. “The water tray is vital to prevent cells from cell drying out but it can be a major contamination source.”

Modern CO₂ incubators are often easier to clean than older models. For example, many newer systems feature a seamless interior surface to eliminate any joins where contaminants could become trapped. Others incorporate flanges rather than brackets for shelf support or may be equipped with removable, autoclavable door gaskets. Cleaning protocols should be adapted to suit the incubator in question, with the cleaning frequency being dictated by factors including the number of users and the type of material being handled.

Perform routine preventive maintenance

Routine preventive maintenance is key to timely identification and resolution of any potential problems with CO₂ incubator function. Where fitted, HEPA filters should be changed regularly—typically every 3–6 months for inlet filters and every couple of years for air capsule filters. Likewise, gas supply line filters (CO₂ and N₂) should also be swapped out; it is common practice to do this every fifth tank or whenever the filter is discolored. Other useful checks include regular visual assessments to confirm displays and indicator lights are working normally; evaluation of the incubator’s ability to recover to correct gas % within a specified time; and inspection for any water leaks.

Be mindful when opening and closing the incubator door

CO₂ incubators can undergo numerous door openings during the working day, but it pays to minimize these so that growing cells are not stressed. Keeping the contents of the incubator organized will reduce the length of time the door remains open, and can easily be achieved by limiting the number of operatives using the incubator and assigning shelves to a particular cell line or researcher. “It is especially important to keep the incubator door shut when screening,” comments Emery. “This ensures that data generated on different days can be compared without having to worry about varying experimental conditions. CO₂ incubators with split doors can be a valuable asset to screening labs, allowing microplates to remain undisturbed in one section of the incubator while researchers proceed with routine cell passaging.”

NuAire offers an extensive selection of CO₂ incubators that deliver reliable performance for optimum cell growth. To learn more, visit nuaire.com