Because the serum is collected and processed quickly at low temperatures, some fibrinogen is still in a dissolved state during the treatment process. After the final filtration and aliquot, fibrin precipitation will condense in the bottle and cause fibrin precipitation.

fetal bovine serum and other serums may be present in the following types of precipitates:

1. Fibrin: It is a large precipitate that often appears, can reach 1-2mm and can be observed with the naked eye. Because the serum is collected and processed quickly at low temperatures, some fibrinogen (soluble precursor to form floc fibrin) are still in a soluble state during the treatment process. After the final filtration and aliquot, fibrin precipitation will condense in the bottle and cause fibrin precipitation. 2. Calcium phosphate : It is also a common precipitate, which usually causes turbidity in serum and increases when cultured at 37°C. This precipitate looks like small black dots under an inverted microscope . These small black dots are often mistaken for microbial contamination because Brownian motion looks mobile. 3. cholesterol , fatty acid esters and some protein . They are also a common cause of serum precipitates. The most common precipitate of is the precipitate that sometimes occurs during serum melting. The serum contains floc precipitate, which contains fibrin and lipoprotein . To remove the precipitate, centrifuge the serum (400g, 1-2 minutes) or simply let it precipitate at the bottom of the bottle and carefully transfer the serum to another sterile bottle (filtration is generally not recommended to remove the precipitate, because the precipitate will clog the filter membrane and cannot be filtered). In most cases, the precipitation is gently shaken and heated to 37°C and then dissolved again. Therefore, when using the product, shake and heat the serum to 37°C, and the precipitation will disappear naturally.

The production of precipitation can be avoided as follows:

(1) When thawing serum/packing and freezing, it must be shaken evenly to make the temperature and ingredients uniform, and reduce the occurrence of precipitation. (2) Do not place the serum at 37°C for too long, otherwise the serum will become turbid, and many more unstable components in the serum will be damaged, thereby affecting the quality of the serum. (3) The heat inactivation of serum is very likely to cause an increase in precipitates. If necessary, this step is not required.

serum precipitation is a normal feature of serum. Serum of major brands has precipitation. According to many years of experience in cell culture, the amount of serum precipitation has no inevitable relationship with the effect of serum use. It is recommended to replace the new batch of serum and take a small amount of cells for testing and culture to determine whether it affects the subsequent growth of cells in .

Precipitation is not a hard indicator for serum testing, but for the sake of accurate experiments, beautiful experiments and convenient experiments, the production of precipitation should be minimized. Mastering the correct method of thawing and using serum, plus an excellent serum of stable quality, is crucial for cell experiments.

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