The important role of guanidine salt RNA sample transport media in nucleic acid detection

The new coronary pneumonia in 2020 caused fear, not only claimed the lives of many people, but also disrupted the pace of life. Due to an epidemic, China's GDP has plummeted, and the economy has directly returned to a decade ago. Even though the epidemic is relatively under control, experts cannot guarantee that it has been completely controlled, and it will even make a comeback. Nucleic acid testing is currently the main method of diagnosis and control of new coronary pneumonia. However, nucleic acid testing also encounters endless problems. For example, the test results are a large number of false negatives. For this problem, RNA sample transport media provides great help.

Virus transport media (inactivated and non-inactivated)

Before extracting the sample nucleic acid, the common sample transport media needs to put the sample in an environment above 56°C to inactivate the virus. This inactivation process undoubtedly protects the personnel in the inspection from virus exposure, but it also destroys the integrity of the viral nucleic acid, causing some samples to not be detected normally, which is one of the reasons for the high false negative rate.

High temperature heating will increase the degradation of RNA and reduce the amount of sample detection. Using RNA transport media can effectively inhibit the degradation of RNA. Regarding the preservation after the virus sample is collected, for example, after the pharyngeal swab is sampled, the sample is packaged and then put into the sampling tube. Not all sterile sampling tubes can be used to store viruses, at least one RNA sample transport media is required to save. For virus storage, non-inactivated virus transport medias are generally used.

The components of the non-inactivated virus transport media are: Hanks liquid foundation, gentamicin, fungal antibiotics, BSA (V), cryoprotectant, biological buffer and amino acids. The combination of multiple antibiotics has anti-bacterial and anti-fungal effects. Bovine serum albumin (BSA) as a protein stabilizer can form a protective film in the virus protein shell, making it difficult to decompose and ensure the integrity of the virus. The neutral environment constructed by Hanks buffer helps increase the survival time of the virus and the stability of infection. Its advantage is that it can effectively preserve the activity of the virus. It is convenient for the subsequent isolation and cultivation of the virus, but the premise is that it must be stored at a low temperature.

RNA is easily degraded, and RNase is simply the natural enemy of RNA extraction. RNase has a wide range of sources and can include various organisms in nature. Therefore, it is difficult to guarantee that RNase will not be mixed in the samples you collect. RNase also degrades RNA at room temperature, so we need to store samples at 4° (short-term) or -70° (medium-long term). If we want to store RNA virus for a long time, we need to use liquid nitrogen. In many cases, the extraction experiment requires rapid lysis of the sample after recovery, and even operation on ice can reduce the rate of RNA degradation. If there are few viral RNA samples collected in the original sample, it will become less after a period of RNase degradation. After the temperature is heated to 56°, the activity of the enzyme increases. At 92°, the enzyme will not be denatured, but the efficiency will be further improved. Then the degradation phenomenon will be more serious.

Is there any way to save the virus without being broken down by RNase? The answer is the guanidine salt RNA virus transport media, which is the virus inactivation transport media.

Guanidine salts generally include guanidine hydrochloride, guanidine nitrate, cyanoguanidine and the like, which can effectively denature proteins. RNase is also a protease that will be denatured and lose its original role. The virus shell is also made of protein, so the guanidine salt can also inactivate the virus. The 56° heating process can be omitted.

The virus inactivation transport media can inactivate viruses and reduce the infectivity of virus samples, while eliminating the process of high temperature heating greatly improves the accuracy of nucleic acid detection. Since the epidemic, Desheng has been working hard to develop virus transport medias to facilitate nucleic acid detection. Desheng virus transport medias are inactivated and non-inactivated, and nasal and pharyngeal swabs are also available.