Don’t Panic for Precipitate serum

2018-07-14 10:02:51 GMT+0800

Obviously it is a bottle of good serum.

However, there has been precipitation.

Is it related to serum quality?

Will it affect cell culture?

How to avoid sedimentation?

How to deal with precipitation?

Q: The precipitation in the serum is too much. Is it not good quality? What are these sediments?

A: These are just fibrins in the serum. As they evolve over time, they have no nutritional value.

Q: Why is there so much  in serum,whilethere is little in other serum?

A: It mainly consists of two factors:

1: The preservation time: there is no precipitationis not precipitated in serum whenit is produced.The longer the time it lasts, themore precipitation it precipitates;

2: After the blood is the store and transport process after ceux: each freeze-thaw of the serum will precipitate protein precipitation. Therefore, the serum of raw materials with more freezing and thawing times will be less precipitated when finished.

Now let's take a look at the characteristics of domestic and imported serum sedimentation:

Domestic serum: precipitation is very less, because the time after production to the customer's hands is very short, at the same time, the temperature during storage and transportation of raw materials is not constant, and even more frequent freezing and thawing.

Imported serum: precipitation is relatively high, which is associated with a longer preservation time, and the whole transport process is more standardized after blood collection.

So, the amount of sedimentation is not related to the quality of the serum. So, how do you deal with the more precipitated serum?

1: After the cryopreserved serum was taken out, the refrigerator was set at 4°C to stand still overnight.

2: After the serum is thawed, turn it upside down and mix gently to continue at 4°C for 2-3 hours.

3: Gently absorb the upper serum, sub-packed, left and right under about 50ml.

4: Centrifuge at low speed for 5 minutes to remove precipitate.

In addition, we have to distinguish between serum deposition and serum contamination. After the former is at rest for a while, the supernatant is clear and translucent, and the latter always has a certain degree of turbidity. The contrast between the two is even more pronounced. How much of the serum is precipitated is determined by the serum itself, and contamination often occurs during the dispensing process. There is also a reason why we don't know it – the transport link. Melting of serum during transportation (especially in the summer), under constant jostling, the probability of contamination was greatly increased, with an initial estimate of 0.5%.

Q: What is serum precipitation?

A: There are often visible precipitates in the serum. There are many types of components in the serum. There are many reasons for this, mainly fibrin, calcium phosphate, and some other components.

1. Fibrin

Most of the precipitates visible in the serum are of this type. Due to the fact that during the production process, serum collection, filtration (3 0.1 μm filtration) and filling are performed rapidly under low temperature conditions, in which serum Fibrinogen is in a dissolved state. However, after thawing, serum fibrinogen tends to agglutinate, forming a visible precipitate.

The following figure shows the agglutination of fibrinogen due to repeated freezing and thawing of serum.

2. Calcium Phosphate

This is a common precipitate component that usually causes cloudiness in the serum. This phenomenon is particularly noticeable when the product is stored at 37°C. The presence of small black spots can be observed under an inverted microscope. These black spots are swimming around under the influence of Brown's movement and are often mistaken for microbial contamination.

3. Other ingredients

Other components in the serum also form precipitates, such as cholesterol droplets and other protein precipitates.

Q: Does precipitation of serum affect cell culture?


1.Cell growth

We will conduct a series of quality tests on the serum before leaving the factory to ensure that the serum quality meets stringent standards. Serum test and cell culture experience also showed that its precipitated components do not affect the performance of serum as a cell culture additive. This has been confirmed by numerous customers and other serum suppliers. After thawing, fibrinogen in the serum tends to agglutinate, forming a macroscopic precipitate.

2. Suspected of pollution

Calcium phosphate particles are often used as microbiological contamination and cause unnecessary concerns. Under normal circumstances, when the operator notices that the turbidity is cloudy after thawing the serum, it is often stored in a refrigerator at 4°C and considered whether to continue using it. However, this will further increase the precipitation, which will make the serum more turbid, and thus mistakenly believe there is serum contamination. In addition, under the inverted microscope, the small black spots (Brownian movement of calcium phosphate particles) that move around in the serum can be observed, and it is more likely that people think that there is microbial contamination.

In order to prevent such misunderstandings from happening, we do not recommend that customers culture sera to verify the presence of contamination. Instead, the serum is directly inoculated on a bacterial culture medium to observe the proliferation of bacteria. Also, gram staining was performed and observed under an oil lens (100 x 10 times) to directly confirm the presence of microbial contamination.

Q: How can we avoid sedimentation?


1. Thaw correctly

First, the thawed serum should be correctly thawed in the way of gradual thawing: After being taken out of -20°C, it is slowly thawed in a refrigerator at 4°C and finally left to thaw at room temperature. If you directly thawed from room temperature at -20 °C or 37 °C water bath, it is very easy to produce precipitation. During the thawing process, please note that shaking the bottle slowly from time to time reduces the production of precipitates. To avoid repeated freezing and thawing, it is recommended that you use separate sera.

2. Use and save precautions

Serum precipitation is difficult to predict and avoid. There is no need to worry about precipitation. This does not affect serum quality. Serum deposition is known to increase in the following conditions:

1) Heat inactivation;

2) 37 °C culture;

3) Repeated freezing and thawing;

4) Gamma irradiation;

5) Long-term storage at 2-8°C;

6) Stored in a refrigerator that can be automated for long periods of time (temperature instability).

The mechanism of formation of serum precipitates is diverse and the specific mechanism is not yet clear. We cannot accurately predict and control the production of serum precipitates. Currently, all brands of serum products on the market have precipitation phenomena, which can be confirmed on the declaration of sedimentation on the official website of each brand.


Precipitation in serum products is a common phenomenon, but it does not affect the quality of the serum. There is no problem with cell culture. We can use it with confidence!

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