Serum Thawing & Heat Inactivation

(Chris Cohick from JRH Biosciences catalogue)

How to thaw serum:

Serum that is stored at -10º C to -40º C is stable for extended periods of time. It is neither necessary or desirable to store serum at -70º C, as it does not prolong the shelf life of the product and will often damage the bottles. Particular care should be taken when thawing material for use to protect the integrity of the product and to prevent breakage of the bottles.

1. Remove bottles from the freezer and place in a refrigerator or cold room where the temperature is 2º C to 8º C.

2. Allow serum to thaw completely and to reach the temperature of the environment. Overnight exposure is usually adequate.

3. Remove serum and allow to reach room temperature prior to use. After serum has reached room temperature, it can be prewarmed to 37º C for mixing with medium, or it can be heat inactivated (see below).

4. Serum should never be taken from a frozen or refrigerated state and placed in a water bath to expedite thawing or warming. Such handling compromises the quality of the serum and may cause the bottle to break.

How to heat inactivate serum:

Many cell culture products use serum that has been heat inactivated to destroy complement that may lead to cell lysis by antibody binding.

1. Thaw the serum slowly (see above).

2. Prepare a water bath large enough to accommodate the number of bottles being treated. Water temperature should be 56º C.

3. Place bottles of thawed serum in the water bath. Include a bottle of water of the same size as the bottles of serum; place a calibrated thermometer in this bottle.

4. Bottles should be agitated gently during the heat inactivation process to ensure uniform heating throughout the serum.

5. When the temperature of the bottle of water has reached 56º C, begin timing the heat inactivation. Continue to agitate the serum.

6. After 30 minutes of treatment at 56º C, remove the serum from the water bath. Prolonged treatment will cause deterioration of some components of the serum.

7. Heat inactivated serum frequently contains flocculent material. This is lipoprotein; its appearance is a normal phenomenon and not an indication that the quality of the serum has been compromised in any way.