What are Biological Samples?
Biological samples are important resources for medical research. Pathological tissue and cell samples are common clinical biological samples, mainly in clinical operations, biopsies, puncture, and other operations. They can be used for pathological diagnosis by preparing sections, smears, and extracting biological macromolecules.
The sample is the basis of medical research, and its quality largely determines the accuracy and reliability of the research results. With the rapid advancement of research methods such as genomics, transcriptomics, and proteomics, various analytical techniques have put forward higher requirements for the quality of biological samples. Faced with this situation, Heal Force is ready to offer you help.
There is currently no unified standard for the quality identification of biological samples, but the quality control of biological macromolecules such as DNA, RNA, protein, and other extracted products is relatively mature.
Therefore, in order to evaluate the effect of each storage method, the quality of the biological sample can be indirectly measured by detecting the quality of the biomacromolecule extracted from the sample. At present, there are two main types of storage methods for biological samples and their extracted products: ultra-low temperature and normal temperature. For different scientific research needs, more samples are also kept in succession, but the storage efficiency of each method is different.
Most samples are stored at -86℃ ultra-low temperature, so the collected biological samples should be immediately stored as required, labeled with appropriate labels, and the state and location of the sample storage should be recorded to ensure the quality of the sample. The stored samples should be tracked in real-time and checked regularly, and the internal and external environment of the stored biological samples should be monitored.
9 Steps to Save Samples
· Selection of Temperature for Storing
When choosing the storage temperature, you should consider the type of sample, the expected storage time, the characteristics of the biomolecules in the sample, and the characteristics of different cells. The critical temperature of bacteria and cells is generally considered to be -140°C. At this temperature, all metabolic activities are stopped. For biological samples that can withstand storage at this temperature, it is recommended to choose storage below this temperature, which is conducive to long-term stable storage.
Compared with tissues fixed with a formaldehyde solution, biological macromolecules of higher quality can be extracted from cryopreserved tissues to meet the needs of modern detection technology.
However, some studies have shown that after cryopreservation at -25°C for about 1 year, protein activity in tissues has decreased significantly. In contrast, cryopreservation (-80℃～-196℃) of ultra-low temperature and deep cryopreservation has a better preservation effect and has become a widely accepted long-term preservation method of biological samples.
Some biological samples can not withstand such a low temperature, the storage temperature is generally -86 ℃, at this temperature, the metabolic activity has not completely stopped. -86℃ ultra-low temperature cryopreservation combined with nucleic acid stabilizer can also be used as an ideal biological sample storage method: in a biological sample library without liquid nitrogen storage conditions, you can also consider using -86℃ ultra-low temperature refrigerator instead of liquid nitrogen to save tissue samples.
So, what is the effect of cryopreservation at -86℃ on tissue preservation? Studies have found that tissues stored at -86℃ for a long period of time can well protect the internal protein components, and can also extract high-quality RNA, which is not significantly different from that in frozen liquid nitrogen at -150℃.
But studies have also found that the tissue freeze exists at -86°C in a deep low-temperature environment. Although its DNA yield, integrity, and RNA yield can be maintained for up to 7 years without significant changes, its RNA integrity begins to decline after 5 years of freezing. Therefore, some researchers suggest that the tissue should be divided into small portions, added with RNA-specific stabilizers, and then frozen at -86 ℃, which is more conducive to the preservation of RNA in the tissue.
· Freezing and Recovery of Biological Samples
Selecting the storage temperature requires freezing the collected biological samples before storing them in suitable containers and equipment. The appropriate cooling rate should be used during the freezing of biological samples to control the size of ice crystals and the speed of ice crystal formation, which will affect the recovery of cells in the sample. The uniform cooling rate is from room temperature to 1°C per minute down to -80°C, which is suitable for most cells.
The frozen samples are stored according to the required temperature conditions. Samples should be stored under stable conditions and repeated freezing and thawing should be avoided. Separately store the appropriate amount of biological samples to avoid unnecessary repeated freezing and thawing. When a freeze-thaw sample is required, the stability and quality of the sample should be ensured in accordance with standard procedures. When the frozen samples need to be aliquoted and then stored, necessary thawing and resuscitation are required. The lower the storage temperature, the longer the recovery time. When thawing from a frozen state, the best way is to use a 37°C water bath. The process should not be too long to avoid damage to the cells.
“Slow freezing and quick thawing” is the basic principle of cell cryopreservation and resuscitation, which is essential for maximizing cell viability. At present, glycerin or dimethyl sulfoxide (DMSO) is often used as a protective agent for cell cryopreservation. These two substances can improve the permeability of cell membranes to water.
It is the key to reduce the generation of ice crystals in cells during cell cryopreservation and recovery. Slow freezing can make the water inside the cell seep outside the cell, reduce the formation of ice crystals in the cell, and thus reduce the physical damage of the ice crystal to the cell. Resuscitated cells use a rapid melting method to ensure that the extracellular crystals melt in a very short period of time, to avoid the damage caused by the slow melting of water into the cells and the formation of intracellular recrystallization.
· Selection of Biological Samples Container
The sample storage container must be stable and all samples are strictly stored in suitable containers. The container used to store the sample should be able to withstand the sudden temperature drop to ultra-low temperature, can be sealed at low temperature, and stored at low temperature for a long time. Any container used under the ultra-low temperature of -86℃ should have a calibrated service temperature.
· The Choice of Storage Equipment
When biological samples need to be refrigerated (2-8°C for a short time), but does not require low-temperature freezing, the storage temperature of the refrigerator should always be kept within the range of 2-8°C.
It is recommended to use Heal Force Pharmacy Refrigerator.
When the sample needs to be cryopreserved, according to the characteristics of the biomolecules in biological samples and the characteristics of different cells, some specially processed samples can be stored under low-temperature conditions, the storage temperature is -25 ℃, -40 ℃, -86 ℃.
At those temperature, the recommended low-temperature products of Heal Force are:
· Identification of Sample Storage
All stored samples, storage containers and equipment should be properly labeled. The information identified by each sample must be specific. Generally, a set of codes is used to represent unique identity information or tracking number. The coded information should be able to be linked to the database sample information. The sample library uses a QR code to identify all samples.
Each sample storage container should have a unique identification, clear and easy to read, to accurately position the container and ensure storage conditions. Establish contact with the information system and record the storage location information of each storage sample on the freezer or shelf.
· Sample Inventory Tracking
Sample inventory tracking can reflect the location information of the sample storage and storage information in real time, reasonably allocate the location of the sample storage, and reduce the impact on the sample storage environment during the retrieval process.
· Inventory Verification
As an important part of quality control, inventory verification is used to determine whether samples are stored in the correct location. The verification procedure is based on the sample storage location information recorded by the information system.
· External Quality Control
Ensuring the quality of the stored samples requires not only storing the samples at the appropriate temperature and container equipment, a good external storage environment, but also the necessary equipment monitoring and maintenance. The external storage environment includes the air, lighting, and temperature of the sample storage room, as well as the installation and placement of the facility.
- If the site chooses the basement to consider ventilation and drainage, on the upper floor, the floor needs to be strengthened, the bearing capacity is more than 300kg/m, and the ground is laboratory PVC ground, which is dust-proof and corrosion-resistant.
- Does the floor height meet the equipment height +40cm? The frozen storage equipment is placed against the load-bearing wall, with a distance of 30cm between the equipment and the wall, and a distance of 30cm between the equipment and the equipment.
- The power load is calculated based on the upper limit of the maximum power of the refrigerator × 2 (the starting instantaneous current is large), and the total demand is calculated. Each socket should be tripped independently. According to the equipment, confirm whether the socket is 10A or 16A. The circuit design uses a double circuit protection design, which burns out the circuit. There is always a backup circuit.
- Due to the large heat generated by the refrigerator, the air conditioner must be turned on when the temperature exceeds 32°C. The central air conditioner is warm in winter and cool in summer, and the central air conditioner should be turned off in winter.
- Install video surveillance facilities, require no dead ends, have access control systems, and require entry and exit registration.
- Specimen safety considerations should be carried out by a special person, and the refrigerator should be equipped with a lock. Monthly maintenance of ultra-low temperature refrigerators, including the use of vacuum cleaners for filter cleaning and dust removal, prolongs the life of frozen storage equipment, early detection of possible problems, and important samples are stored separately in multiple refrigerators during storage.
- Installation of a cold chain monitoring system, SMS intelligent alarm. Equipped with a spare refrigerator to keep it open normally to prevent the refrigerator from malfunctioning and the temporary cooling is too late
- It is not recommended to install automatic fire sprinklers and should be equipped with non-corrosive gas fire extinguishers.
- A sewage purification system shall be provided for the sewage in the specimen reservoir.
- Biological sample banks should be divided into the specimen storage area, specimen working area, and office area.