It can be difficult to maintain colonies for your colony-forming unit (CFU) assay while you are away from the bench. Depending on how developed the colonies are, the following steps may help you to extend the life of your CFU assay:

• Make sure your incubators have lots of water in their pans and that you are using secondary containment plates around your 35 mm dishes, with additional open water dishes to maintaine humidity. Read more about maintaining humidity in CFU assays.
• Put your CFU assays in an incubator at 33°C to slow colony growth but maintain appropriate levels of CO₂. This will help preserve them until you can count the colonies: if they are at 12 - 14 days (human cultures) or past day 6 (mouse and rat cultures), moving to 33°C can help extend the ability to count colonies for up to 7 days, depending on the cell source (average 3 - 5 days).

Note: Do not put CFU cultures into 4°C, this will liquify the methylcellulose and you will not be able to count colonies in the assay. It is better to keep them as hydrated as possible and in 33°C to slow growth.

While we cannot guarantee that these steps will help CFU assays that are at less than 12 - 14 days of development, they may be worth trying if there is no alternative. Please refer to our website for more information on MethoCult™ methylcellulose-based media products optimized for human, mouse, and rat hematopoietic CFU assays.

For further assistance and information, please contact techsupport@stemcell.com.