Biological samples are an important resource for medical research, and their quality largely determines the accuracy and reliability of clinical results. Currently, there are two main types of preservation methods for biological samples and their extraction products: deep cryogenic and ambient. For different research needs, more sample preservation methods have been introduced. In this paper, we will analyze and summarize the commonly used methods of sample preservation and their effects, and provide feasible suggestions for the preservation of clinical biological samples and provide theoretical basis for obtaining high quality samples.

1. -196℃, -150℃ deep cryopreservation is the ideal sample preservation method: Currently, liquid nitrogen (-196℃) is recognized as the most reliable sample preservation method, however, because samples are completely submerged in liquid nitrogen, free tissue fragments may bring the potential risk of cross-contamination, therefore, the preservation method of vapor phase liquid nitrogen (-150℃) has been developed, which is to place samples above liquid nitrogen and surrounded by vapor phase liquid nitrogen. envelope, which can well avoid the risk of cross-contamination. Alternatively, a cryogenic effect of -150°C can be achieved through electric refrigerator cooling, which can meet the long-term preservation needs of samples. Because -137℃ is the water vitrification temperature, all the biochemical reactions that can lead to the degradation of the contents in the cells are inactivated when the temperature is lower than this, so that the long-term preservation requirements can be met.

2. -80℃ is a more ideal sample preservation method for freezing nucleic acids: In biological sample banks that do not have liquid nitrogen preservation conditions, you can also consider using -80℃ deep cryogenic refrigerator to preserve tissue samples. It has been shown that DNA yield, integrity, and RNA yield can be maintained at -80°C for up to 7 years without significant change, but RNA integrity begins to decline after 5 years of cryopreservation. Therefore, it is recommended to preserve tissues with fractionation and then freeze at -80°C after adding RNA-specific stabilizers to better preserve RNA in tissues. Regarding the preservation of proteins, deep cryopreservation is also currently used, which can well protect their stability.

3. Ambient preservation: In view of the inconvenience of transportation and operation of deep cryopreservation, the method of ambient preservation has come into being. The principle of room temperature preservation technology can be analogous to the phenomenon of nematode dehydration dormancy, using some special techniques or containers to place the dehydrated and dried samples in an airtight environment, or adding protective agents to biological samples to inactivate the relevant enzymes, so as to achieve the purpose of protecting the samples under room temperature environment.