Serum is one of the most important elements in cell culture. Note and handling methods in laboratory operations: 1. Serum storage: It is recommended that the serum should be stored at -5 ℃ to -20 ℃. However, if stored at 4 ° C, do not exceed one month. If you are unable to use up one bottle at a time, it is recommended that you aseptically dispense the serum into an appropriate sterilized container, and then put it back into the freezing. 2. Method of thawing serum: It is recommended that you remove the serum from the freezer and put it in the refrigerator at 2 ～ 8 ℃ to melt it, and then melt it at room temperature. But it must be noted that during the melting process, it must be shaken regularly and evenly. 3. After the serum is thawed, there are flocculent precipitates. What should I do? There are many reasons for the appearance of the precipitates in the serum, but the most common reason is that the fibrin (formation One of the coagulated proteins) will also be present in the serum after the serum is thawed, which is also one of the main causes of the precipitate. But these flocculent precipitates do not affect the quality of the serum itself. If you want to remove these flocculent precipitates, you can divide the serum into a sterile centrifuge tube and centrifuge it at 400g. The supernatant can then be added to the medium and filtered together. We do not recommend that you remove these flocculent sediments by filtration, as it may clog your filter membrane. 4. Why heat inactivate serum? Heating can inactivate the complement system. Activated complement participates in lysis of cells, stimulates smooth muscle contraction, cells and platelets release histamine, and activates lymphocytes and macrophages. In immunological studies, heat-inactivated serum is recommended when culturing ES cells, insect cells, and smooth muscle cells. 5. Is it necessary to do heat inactivation? Experiments have shown that properly processed heat inactivated serum is unnecessary for most cells. After this treatment, the serum only slightly promotes the growth of the cells, or has no effect at all, and even because the high temperature treatment affects the quality of the serum, the cell growth rate is reduced. In the heat-treated serum, the formation of precipitates will increase significantly. These precipitates are observed under an inverted microscope, such as "small black spots", which often makes researchers mistakenly think that the serum is contaminated and put the serum in 37 In the ℃ environment, this sediment will increase more, which makes the researchers mistakenly believe that it is the division and expansion of microorganisms. Therefore, we recommend that you do not need to do heat treatment if not necessary. In this way, not only save your precious time, but also ensure the quality of the serum! 6. Why does the fetal bovine serum stored in the refrigerator appear to precipitate? The fetal bovine serum is not pre-aged. Various proteins and lipoproteins (such as cold agglutinin, fibrinogen, vitronectin, etc.) may aggregate to form a precipitate or visible turbidity. This should not affect the quality of the serum. It is recommended to store fetal bovine serum at -20 ° C to avoid repeated freezing and thawing. 7. How to avoid the precipitation? When thawing the serum, please follow the recommended stepwise thawing method (-20 ℃ to 4 ℃ to room temperature). If the serum changes too much temperature (eg -20 ℃ to 37 ℃) , The experiment shows that it is very easy to produce precipitates. When thawing serum, please shake it evenly at any time to make the temperature and composition uniform and reduce the occurrence of precipitation. Do not leave the serum at 37 ℃ for too long. If left at 37 ° C for too long, the serum will become cloudy, and many less stable components in the serum will be damaged as a result, affecting the quality of the serum. The heat inactivation of serum is very easy to cause the increase of precipitates. If not necessary, this step is not necessary. If the serum must be thermally inactivated, please observe the principle of 56 ° C for 30 minutes and shake it evenly at any time. If the temperature is too high, the time is too long or the shaking is uneven, it will cause the increase of sediment.
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