Cell culture incubators allow researchers to propagate mammalian cells by mimicking in vivo growth conditions. However, precious cell cultures can easily be destroyed as a result of contamination. Here, we share some tips for decontaminating cell culture incubators and suggest features to look for when selecting a cell culture incubator for your lab.
Cell culture incubators provide a stable environment for growing mammalian cells by controlling several critical parameters. These include temperature, which is typically set at 37oC, and CO2 concentration, which is usually kept at 5% to ensure cell culture media remains at the correct pH. Humidification is generally achieved using a removable pan containing sterile distilled water. To help protect against microorganisms such as bacteria, molds, and yeasts, cell culture incubators are fitted with various contamination control methods.
Routine cleaning of cell culture incubators is essential to minimize the risk of contamination. It often involves both manual and automatic methods, which will vary depending on the incubator model.
If manual cleaning will be performed, step number one is to switch the cell culture incubator off so that it cools to room temperature. Don’t worry that it will take a long while to return to 37oC; while this is often the case for older, water-jacketed cell culture incubators, modern air jacketed incubators often take little more than one hour to get back to operating temperature.
Next, turn off the CO2 supply at the tank. While the tank should theoretically still be full at the end of the cleaning process, any small leaks in the lines can result in levels being depleted. If the gauge reads less than 200 pounds, make sure you have a replacement tank available. Cell culture incubators that have an automatic tank switcher fitted are often preferred to avoid breaks in the CO2 supply.
Once everything is switched off, you will need to remove the water pan since standing water is an ideal place for contaminants to breed. If your cell culture incubator has a water pan with a raised lip, great—this will reduce the chances of spillage. Once you’ve emptied the water, wipe the pan and clean it with 70% ethanol. Don’t be tempted to use 100% ethanol as this evaporates too quickly for bacteria to be effectively killed.
Following this, you should autoclave the shelves, interior components, and water pan to destroy any microorganisms that might be lurking in difficult to reach areas. It is also important to wipe down the inner chamber of the cell culture incubator with 70% ethanol, not forgetting the inner door gasket, latch, and glass, as well as any hinges and fasteners.
If your cell culture incubator offers a decontamination cycle, you can run this at the same time as autoclaving. While UV decontamination cycles can take up to 24 hours, some newer cell culture incubators now use hydrogen peroxide (H2O2) vapor for high-speed decontamination, a process taking less than three hours. An advantage of H2O2 decontamination is that it precludes the need for autoclaving.
Although the cleaning frequency will vary according to factors such as the types of cells being cultured and the number of researchers using the cell culture incubator, at the very least the water pan should be cleaned and refilled once a week. Other recommended best practices to prevent contamination include positioning the cell culture incubator appropriately in the lab (e.g., away from air conditioning vents and doorways); ensuring end users are properly trained (e.g., wearing suitable PPE, using correct aseptic technique when handling cells, minimizing door openings); and performing preventive maintenance based on the manufacturer’s instructions (e.g., replacing air inlet and gas supply line filters in a timely fashion).
When selecting a cell culture incubator for your lab, it is worth finding out which features are available to help keep cells free of contamination. In addition to optional high-speed decontamination, these might include passive decontamination mechanisms such as construction from germicidal copper enriched stainless steel or the use of concealed UV lamps for decontaminating circulated air and the contents of the water pan. Manufacturers will be able to help you identify a model that best fits your experimental workflow and budget.
PHC Corporation offers a broad selection of CO2 and multi-gas incubators for precise cell culture reproducibility. To learn more, visit phchd.com/cell-culture-incubators