There are many types of fetal bovine serum on the market, mixed with good and bad, and many researchers, especially those who have just been exposed to cell culture, find it difficult to distinguish the quality of serum. Based on more than ten years of experience in serum production and sales, the summary is as follows:

一、 Appearance

When you receive serum, the first thing you come into contact with is the appearance of the serum. For those who lack experience in cell culture, judging the appearance is particularly important

1. Color

According to the different levels of hemoglobin content, fetal bovine serum can appear yellow or red. The standard for cell culture serum in China is not higher than 20mg/dl. In fact, the level of hemoglobin content has no direct impact on serum. The significance of this indicator is to reflect the rigor and standardization of the blood collection process, and good operation can reduce serum hemolysis.

The blood collection points for domestic serum are very scattered, mostly collected by immediate centrifugation after slaughter, so there is rarely hemolysis, showing a bright waxy yellow color. Of course, domestic serum also rarely has standard fetal bovine serum.

Imported fetal bovine serum is more or less prone to hemolysis, as genuine fetal bovine serum has poor coagulation function and red blood cells are prone to rupture.

Overall, domestically produced serum presents a waxy yellow color. The imported serum has the best quality and presents a pale yellow or slightly red color, such as Gibco 16000, and almost appears orange or bright red. Of course, heat inactivated serum or improperly stored serum may appear dark red or even coffee colored due to the destruction and oxidation of hemoglobin.

2. Precipitation

Many serum customers may find precipitation in imported serum and suspect the quality of the serum, which is unfounded.

The precipitation in serum is generated by the aggregation of fibrin and has no effect on serum quality. There are many reasons for the formation of precipitation, which are closely related to the processing and production methods of manufacturers.

Most of the domestically produced serum comes from the north, and due to its low price and poor storage environment, it undergoes multiple freeze-thaw cycles from blood collection, freezing, transportation to production. Each freeze-thaw process results in the precipitation of some fibrin, making the filtered serum product appear more "clean" with minimal precipitation.

Imported fetal bovine serum rarely undergoes repeated freezing and thawing before filtration and packaging, and the finished product is also clear after production. However, over time, a large amount of fibrin in the serum will precipitate and form a precipitate. Of course, imported newborn bovine serum is generally around 2 weeks old, and the levels of various proteins in the serum are significantly higher. After production, the serum may become cloudy and even have a large amount of sediment.

Of course, the purchased serum is in a frozen state and needs to be melted during use. The melting process is best carried out slowly at a lower temperature, otherwise there will be relatively more precipitation. Although precipitation does not directly affect the quality of serum, it has certain obstacles to microscopic observation of cells.

3. Clarity degree

Imported fetal bovine serum, due to its low content of protein and lipids, appears thin and light, while domestically produced serum, as the vast majority is newborn bovine serum, is relatively more viscous and slightly darker in color, which is difficult for those who have initial contact with serum to judge. However, comparing the two can easily distinguish them.

2、 Main technical indicators

The current quality standard for serum in China is the 2005 edition of the Pharmacopoeia of the People's Republic of China, with the following main indicators:

1. Endotoxin

The standard is not higher than 5EU/ml. Endotoxins are components of the cell wall after bacterial fragmentation, and therefore the level of endotoxin content can reflect the aseptic operation during a series of processes from blood collection to production. At present, domestic serum can basically meet this requirement, and many imported fetal bovine serum have even higher endotoxin levels, such as Gibco 26140, which only requires no more than 50EU/ml, which is 10 times higher than China's standard. Even if it is 16000, it still requires 10EU/ml, and the serum quality has not been affected. It can be seen that a high endotoxin content does not affect quality, unless the content is extremely high, indicating contamination.

2. Total protein content

The general range of fetal bovine serum is 30-40mg/ml. If the value is too high, it indicates that the cow used for blood collection is older than the fetal cow. If the value is too low, it suggests that the serum may have been mixed with water.

3. Hemoglobin

The standard is not higher than 20mg/dl, the redder the color, the higher the value, and vice versa, the lower the value.

4、pH

Domestic serum is mostly above 7.5, while imported fetal bovine serum is mostly below 7.5. The specific reason is unknown and may be related to the age of the cattle. This can also be used to preliminarily identify the source of the serum.

5. Microorganisms

Including bacteria, fungi, mycoplasma, bacteriophages, various pathogenic viruses, etc. With the improvement of production conditions for domestic serum manufacturers, "large" microorganisms such as bacteria and molds can be almost 100% controlled, and mycoplasma can be mostly eliminated after 0.1um filtration. The contamination of Escherichia coli bacteriophages is still quite serious, mainly introduced during the production process and cannot be filtered, making it difficult to completely remove, but it has little impact on serum quality. Pathogenic viruses, especially BVDV, are present in almost 90% of domestic serum, and these microorganisms are one of the important factors affecting the quality of domestic serum. Imported fetal bovine serum is basically well controlled.

6. Immunoglobulin

Domestic serum is only qualitatively tested, and the results are also very inaccurate. Imported fetal bovine serum is mostly quantitatively tested. The value of immunoglobulin can fully reflect the age of the cattle at the time of blood collection. Domestic serum is mostly from newborn cattle, which are prone to produce IgM and have high levels of IgG. Imported fetal bovine serum does not contain IgM and has low levels of IgG.

7. Other

Both domestic and imported serum are not tested for antibiotics (except for tetracycline free fetal bovine serum). Abroad, the use of antibiotics is very strict and the dosage is also very small. Each cow's product, including serum, can be traced back, so it is possible to ensure that fetal bovine serum does not contain antibiotics or has extremely low levels; In China, the abuse of antibiotics has become a common phenomenon, with high residual levels in serum that are extremely detrimental to cell culture. This is the fundamental reason for the poor quality of domestically produced serum.

3、 Blood source

The serum sources on the market are mainly divided into China, North America, South America, and Australia.

1. The poor quality of domestic serum is widely recognized, and the main reason is not the responsibility of the manufacturer, but the poor natural environment and the extensive use of antibiotics. The domestic environment is severely polluted, and antibiotics are extremely abused during the breeding process. Toxic and harmful substances will remain in the serum in large quantities, ultimately hindering cell growth.

2. There are many sources of South American serum, such as Bioind's Panama, Gibco's Uruguay, Brazil, etc. Due to the uncontrollability of blood collection, the quality of these sera varies greatly. Of course, compared to domestic sera, they are much better. In addition, most of the South American serum sold domestically is bright red in color, such as Bioind, Gibco, Hylone and other brands, but the serum from Argentina is an exception, which may be related to the blood collection and production processes of various countries.

3. North American serum mainly comes from the United States and Canada, such as SH30396, SH30070, SH30071 for Hclone, 16000-044, 26140-079 for Gibco, etc. This type of serum has a lighter color with higher grades, appearing as light yellow with a hint of red. The comparison between SH30070 and SH30396 is very obvious, and special grade fetal bovine serum can basically be used for stem cell culture. Another significant feature of North American serum is that each bottle of serum can be traced, which is particularly important for some large vaccine and pharmaceutical factories.

4. Australian serum, mainly sourced from New Zealand and Australia, entered the Chinese market after the North American serum embargo and generally does not have traceability functions. Due to production, transportation, and other reasons, the price is relatively expensive. Compared to Gibco's 10099 and 16000, the latter has a higher quality level, lighter colors, and higher cost-effectiveness.