A complete guide to cell cryopreservation

Cell cryopreservation is a fundamental technique in life sciences, biopharmaceuticals, and cell therapy. By storing cells at ultra-low temperatures (typically –80°C or in liquid nitrogen at –196°C), cellular metabolic activities are significantly slowed or halted, enabling long-term preservation. With the rapid development of biobanking and precision medicine, cryopreservation is no longer just about storage—it now emphasizes safety, traceability, and standardized management, making the selection of proper consumables and protective equipment essential.

Principles of Cryopreservation

During cryopreservation, cells are exposed to extremely low temperatures (typically –80°C or as low as –196°C in liquid nitrogen). If not properly controlled, this process can cause severe cellular damage due to ice crystal formation, osmotic stress, and disruption of cellular membranes. Therefore, a well-controlled cryopreservation process is essential to maintain cell viability and functionality.

The primary sources of cell injury include intracellular and extracellular ice formation during freezing. Ice crystals can physically damage cell membranes and organelles. In addition, extracellular freezing increases solute concentration, leading to osmotic imbalance, which causes cell dehydration and potential irreversible damage. To minimize these risks, cryopreservation follows several key principles:

1. Controlled Slow Cooling (~1°C/min)
A gradual cooling rate allows water to move out of the cells before freezing occurs, reducing intracellular ice formation. This is typically achieved using controlled-rate freezers or passive freezing containers (e.g., isopropanol-based freezing boxes) that ensure a consistent cooling rate.

2. Use of Cryoprotectants (e.g., DMSO)
Cryoprotective agents such as dimethyl sulfoxide (DMSO) or glycerol penetrate the cell membrane and help reduce ice crystal formation by lowering the freezing point. They also mitigate osmotic stress and protect membrane integrity. However, due to their potential cytotoxicity, they must be used at appropriate concentrations (typically 5–10%) and handled quickly, especially at room temperature.

3. Control of Dehydration and Osmotic Balance
During freezing, water exits the cell, leading to dehydration. Proper cooling rates and cryoprotectants help maintain osmotic balance, preventing excessive shrinkage or swelling that could damage the cell structure.

4. Rapid Thawing
After storage, cells should be thawed rapidly, usually in a 37°C water bath. Rapid thawing minimizes ice recrystallization, which can otherwise cause additional damage to cellular structures during the warming process.

The fundamental principle of cryopreservation is “slow freezing and rapid thawing,” combined with the use of cryoprotectants to control ice formation and osmotic stress. This approach maximizes post-thaw cell survival and preserves biological function.

Essential Consumables for Cell Cryopreservation

In cryopreservation workflows, the selection of consumables and equipment directly impacts cell viability, sample safety, and data reliability. High-quality materials not only ensure stability under ultra-low temperatures but also minimize risks such as contamination, leakage, and misidentification, forming the foundation of a standardized cryopreservation system.

Cryovials

Cryogenic tubes are the primary containers for long-term cell storage. They are typically made from high-purity polypropylene (PP), which provides excellent resistance to ultra-low temperatures, including liquid nitrogen conditions. High-quality cryovials are designed for safety and reliability in storing cells, tissues, and biological samples.

Key Features:

Resistant to temperatures as low as –196°C
Leak-proof sealing to prevent contamination and evaporation
Explosion-resistant design for safety under cryogenic conditions
Available in internal or external thread designs
DNase/RNase-free and non-pyrogenic

Cryogenic vials / cryovial tubes are laboratory consumables specially used for storing biological samples at ultra-low temperatures (usually -80°C to -196°C liquid nitrogen environment). It is usually made of high-strength, low-temperature resistant polypropylene (PP) material, and has the characteristics of low-temperature resistance, sealing and leak-proof, sterile and non-pyrogenic.

Why use cryotubes?

Resistant to extremely low temperatures, ensuring sample activity: Ordinary plastic containers cannot withstand -80°C or liquid nitrogen (-196°C) environments and are prone to brittle cracking and failure. Cryogenic tubes are made of low-temperature resistant materials to ensure that they remain strong and unbreakable at extremely low temperatures, maintaining the activity of cells or biological samples.
Sealed and leakproof to prevent contamination: The sealing cap and silicone ring of the cryotube can prevent liquid leakage, prevent liquid nitrogen from entering the tube, and prevent the sample from being contaminated by the outside world, which is the basis for safe storage.
Support information labeling and management
: The tube body usually has scales, a writable area or a pre-printed barcode (such as three-in-one cryopreservation tubes), which facilitates the laboratory to carry out sample numbering, information traceability and digital management.
Compatible with cryo boxes and freezing racks: The size of cryo tubes is standardized and can be neatly stored in cryo boxes and freezing racks, achieving efficient and orderly space management and batch operation.
Widely used in scientific research and medical treatment: Whether it is storing cell lines, serum, tissue samples, or vaccines, proteins, DNA, etc., special cryopreservation tubes must be used to ensure the quality of samples in the long term.

How to choose sterile cryovials?

1. Look at the material

Cryopreservation tubes are generally made of non-cytotoxic plastic materials, which can be roughly divided into PP (polypropylene), PE (polyethylene) and PETE (polyethylene). Among them, PP material has better chemical resistance and temperature stability. In liquid ammonia gas environment, it can withstand low temperatures down to 196°C in winter, which can be said to be “blindly accepted”.

2. Look at the specifications

Cryogenic tubes generally have specifications such as 0.5ml, 1 ml cryovials, 2.0ml, and 5 ml cryovials. Generally, 2.0ml cryogenic tubes are widely used. The specific selection of appropriate cryogenic tubes depends on the size of the frozen sample.

3. Look at the composition

The cryotube is generally composed of a tube cap and a tube body, and is divided into an inner screw cap and an outer screw cap. The inner screw cap is generally used for freezing biological samples in liquid nitrogen. The silicone pad at the tube mouth enhances the sealing of the cryotube and can effectively prevent liquid nitrogen from penetrating; the outer screw cap is used for freezing samples in the refrigerator. The outer screw cap is convenient for sample labeling and can reduce the probability of contamination when handling samples.

Internally threaded vs externally threaded cryovials

Internal thread cryovials

Advantages: In terms of the tube cap and tube structure, liquid nitrogen in the internal-screw cryotube is easier to be discharged when it vaporizes than in the external-screw cryotube. And for cryotubes of the same quality, the sealing of the internal-screw cryotube is better than that of the external-screw cryotube, which reduces the possibility of tube explosion.

Disadvantages: The bottom of the internal-screw cap may contact the sample in the tube, increasing the risk of sample contamination. In addition, the internal volume of the same specification internal-screw cryotube is usually smaller than that of the external-screw cryotube.

External thread cryovials

Advantages: The externally twisted cap design reduces the risk of sample contamination, and the volume inside the tube is relatively large.

Disadvantages: The sealing of the externally twisted cryotube is relatively poor, and the gas is discharged slowly when the liquid nitrogen vaporizes, which increases the possibility of tube explosion.

Causes of cryopreservation tube explosion

Cryotube bursting usually occurs in liquid nitrogen cryopreservation experiments. The temperature of the gaseous layer of the liquid nitrogen tank is between -140℃ and -180℃, and cells can be stored in the gaseous layer or immersed in liquid nitrogen for a long time. Experimental users often cause tube bursts due to improper operation. The root cause is that liquid nitrogen remains in the tube. When the cryotube is taken out of the liquid nitrogen tank, the temperature rises rapidly, the residual liquid nitrogen in the tube vaporizes rapidly, and the volume expands rapidly (1 volume of liquid nitrogen can be vaporized into 646.4 volumes of nitrogen gas). If the cryotube cannot discharge these gases in time, the internal pressure will increase rapidly, causing the tube to rupture.

General tips for reducing the risk of pipe bursts

1. Give priority to internally spiral tubes: Give priority to internally spiral cryovials with better sealing performance to reduce the probability of liquid nitrogen infiltration.

2. Increase the volume of cryopreservation liquid: Add more cryopreservation liquid to the cryopreservation tube to reduce the gas space (for example, add 1.8mL of cryopreservation liquid to a 2mL cryopreservation tube).

3. Tighten the tube cap: Make sure the cryopreservation tube cap is tightened to reduce the infiltration of liquid nitrogen.

4. Post-processing after removal: After removing the cryopreservation tube from the liquid nitrogen tank, immediately place it horizontally or invert it for tens of seconds, and wait for the liquid nitrogen to flow out before performing the resuscitation operation.

5. Use cryopreservation tube sleeves: Cryopreservation tube sleeves can isolate direct contact between liquid nitrogen and cryopreservation tubes, reducing the possibility of liquid nitrogen infiltrating into the tube.

6. Storage in the gaseous layer of liquid nitrogen: Store the cryopreservation tube in the gaseous layer of the liquid nitrogen tank to prevent liquid nitrogen from directly entering the tube.

Tri-code Cryovials

Three-in-one cryogenic tubes integrate QR code, digital code and barcode on the basis of cryogenic tubes. They can be scanned and entered into the system, and can also be recognized by naked eyes and recorded manually.

Compared with ordinary cryogenic tubes, three-in-one cryogenic tubes have the following features:
✔️ Scan code to enter, avoiding manual input errors
✔️ Quickly trace the source, batch and storage time of samples
✔️ The tube body is wear-resistant and low-temperature resistant, and the logo is not easy to fade
✔️ Can be used with cryogenic boxes and freezing racks for standardized storage

It not only meets the ultra-low temperature storage needs of -80°C to -196°C, but also plays a greater role in information management.

Cryoboxes

Cryoboxes are mainly used to store sample containers such as cryopreservation tubes and three-in-one cryopreservation tubes. Through grid design and number identification, they help experimenters quickly locate the sample position.

✔️ Suitable for cryopreservation tubes of different specifications such as 1.5ml, 2ml, and 5ml
✔️ Can withstand -80°C or even liquid nitrogen temperature
✔️ The box body is antifreeze, waterproof, and corrosion-resistant
✔️ The box cover is transparent or translucent for easy observation

The combination of “one box for multiple tubes, one rack for multiple boxes” realizes the full-link management of samples from tubes to boxes and from boxes to racks.

How to choose the size and material of the cryopreservation box?

Taking into account the cost and safety issues, we can usually choose paper or plastic cryoboxes when storing samples in an ultra-low temperature freezer at -80℃, while in a liquid nitrogen environment at -196℃ we need to use cardboard freezer storage boxes or PC cryoboxes. It should be noted that PP cryoboxes will become fragile and easy to crack in a liquid nitrogen environment, so it is not recommended to store PP cryoboxes in a liquid nitrogen environment.

In terms of height, cryo boxes are usually divided into 1 inch, 2 inches and 3.75 inches. In terms of the number of commonly used holes, cryo boxes are usually divided into 100 grids and 81 grids.
1 inch 100 grids are suitable for 0.5ml cryo tubes, 2 inches 81 grids are suitable for 2ml internal and external rotation cryo tubes, 2 inches 100 grids are suitable for 1.5ml cryo tubes, and 3.75 inches 81 grids are suitable for 5ml cryo tubes. Simply put, 100 grids are suitable for 0.5ml and 1.5ml cryo tubes, and 81 grids are suitable for 2ml internal and external rotation cryo tubes.

How to use cryogenic boxes with cryogenic tubes, three-in-one cryogenic tubes, and freezing racks？

Cryoboxes and cryotubes are the “best partners”. When using three-in-one cryotubes, the plastic boxes for freezer storage can not only fix the tube body, but also facilitate batch scanning of QR codes or barcodes into the system.

For example: A 100-grid cryobox can store 100 2ml cryotubes. Low-temperature labels can be pasted on the box body and the box cover to ensure that the label will not fall off in a low-temperature environment. Scan the QR codes of the box body and cryotubes with a barcode scanner to quickly update the database and trace samples, greatly improving information management efficiency.

In order to efficiently utilize space in -80°C refrigerators or liquid nitrogen tanks, laboratories often use cryogenic racks with cryo boxes.

Cryogenic racks are customized according to the size of cryo boxes and can accommodate 10-20 boxes. Different materials (stainless steel, aluminum alloy) adapt to different low temperature environments. Convenient access to the entire box, reducing opening time and reducing sample exposure.

As a “module unit” in the cryo rack, the cryo box ensures the “structuring” and “labeling” of laboratory storage.

The rack for freezer is specially designed for storing cryo boxes and can be used in -80°C ultra-low temperature freezers and liquid nitrogen tanks. Through layered and column management, the cryo boxes can be stored in an orderly manner, greatly saving freezing space, making it easy to access and avoiding sample confusion or loss.

Different laboratories have different requirements for freezing racks. When purchasing, it is recommended to pay attention to:

Whether the size of the freezer shelves are suitable for existing refrigerators and liquid nitrogen tanks.
Whether it is compatible with the existing cryobox size (common standards 133×133mm, etc.).
Material selection (stainless steel is more corrosion-resistant, aluminum alloy is lighter).
Whether the number of layers and capacity can meet future expansion.

An efficient laboratory low-temperature storage system is inseparable from the perfect combination of refrigerator freezer racks, cryo boxes, and cryo tubes:

The freezer rack shelf provides a three-dimensional structure, which is convenient for placing cryo boxes in multiple layers.
The cryo box is a basic unit that can store cryo tubes of different specifications such as 81 grids and 100 grids.
Cryo tubes or three-in-one cryo tubes can be used for different marking and tracking needs.

Through the hierarchical management system of cryo freezer racks → cryo boxes → cryo tubes, experimenters can quickly locate samples, reduce exposure time, and improve work efficiency. With a barcode scanner, the information of the three-in-one cryo tubes can be entered, making data management more convenient.

Cryogenic Labels

Standard labels may fail under extreme temperatures, leading to loss of critical sample information. Cryogenic labels are specifically designed to withstand harsh conditions.

Key Features:

Resistant to liquid nitrogen and ultra-low temperatures
Waterproof and chemical-resistant
Strong adhesion, no peeling or detachment
Long-term readability
Suitable for various containers and surfaces

Tips for choosing and using cryogenic laboratory labels

When purchasing cryogenic labeling, it is recommended to consider the following factors in combination with experimental needs:

Temperature range: confirm whether it can withstand the lowest temperature of your experiment (-80°C / -196°C).
Adhesive material: confirm whether it is suitable for cryogenic tubes and polypropylene (PP) surfaces.
Size and layout: select the appropriate cryogenic freezer labels size according to the size of cryogenic tubes and cryogenic boxes.
Printing compatibility: confirm whether it can be printed with a label printer or barcode printer.

Usage suggestions:

Stick the clear cryogenic labels before freezing the sample to ensure that the surface is dry and frost-free.
Press the cryogenic container labels with your thumb for 5-10 seconds after sticking it to increase adhesion.
It is recommended to use it with cryogenic boxes and freezing racks to build a complete labeling management system.

Freezer Racks

Cryovial racks are used to hold, organize, and transport cryovials during handling and storage processes.

Advantages:

Improves workflow efficiency
Keeps samples well-organized
Minimizes handling errors
Facilitates batch processing
Suitable for both room temperature and cryogenic environments

Microtubes

Sample tubes are essential laboratory consumables used for sample collection, preparation, and short-term storage. In cryopreservation workflows, they are often used for pre-processing or aliquoting samples.

Applications and Features:

Available in various volumes (e.g., 0.5 mL, 1.5 mL, 2.0 mL)
High transparency for easy observation
Secure sealing to prevent contamination or evaporation
Suitable for centrifugation and mixing
Available in sterile and nuclease-free options

Cryopreservation Workflow

Cryopreservation is a delicate laboratory procedure that involves multiple steps, each requiring precise control to maximize cell viability and function. A standard cryopreservation workflow generally includes the following stages:

1. Cell Harvesting and Viability Assessment

Before freezing, healthy cells in the logarithmic growth phase are collected from culture flasks or plates. Key steps include:

Observing cell morphology to ensure no contamination, over-confluency, or apoptosis
Counting cells and assessing viability using trypan blue exclusion or an automated cell counter
Selecting only healthy, high-viability cells for cryopreservation to ensure maximum post-thaw survival

2. Preparation of Freezing Medium and Mixing with Cells

Freezing medium typically contains culture medium, serum (e.g., FBS), and cryoprotectants (e.g., DMSO). Procedure:

Prepare the freezing medium under sterile conditions according to the protocol
Gradually add freezing medium to the cell suspension and gently mix to avoid mechanical damage
Adjust cell concentration and total volume according to cryovial size and experimental needs

3. Aliquoting into Cryovials

Dispense the mixed cell suspension into pre-labeled cryovials
Fill each vial with the appropriate volume (e.g., 1 mL or 2 mL), avoiding overfilling or underfilling
Securely close the vial caps to prevent leakage and contamination

4. Controlled-Rate Freezing

Slow, controlled cooling is critical for cell survival:

Use a programmable controlled-rate freezer or an equivalent cooling system
Recommended cooling rate is approximately 1°C per minute, gradually lowering temperature from room temperature to –80°C
During cooling, cells slowly dehydrate, reducing the risk of intracellular ice formation
Cryovials can be placed in isopropanol-based freezing boxes for simplified controlled freezing

5. Transfer to Liquid Nitrogen Storage

After cooling to –80°C, transfer the cryovials into liquid nitrogen tanks (-196°C) for long-term storage
Ensure sufficient liquid nitrogen levels and periodically check vial labels and integrity
Liquid nitrogen storage maintains long-term cell viability and allows rapid physiological recovery upon thawing

Safety Protection and Best Practices

Handling liquid nitrogen involves significant risks, including extreme cold burns, splashes, and potential container rupture. Therefore, strict safety measures must be implemented to protect personnel and maintain a safe laboratory environment.

Cryogenic Gloves

Cryogenic gloves are the most basic protective equipment for liquid nitrogen handling. They protect hands from frostbite while maintaining dexterity and grip.

Key Features:

Frostbite Protection: Can withstand ultra-low temperatures (-196°C) to prevent direct contact of liquid nitrogen or frozen samples with skin.
Splash Resistance: Provides protection against splashes during pouring or transferring liquid nitrogen.
Grip and Dexterity: Ensures safe handling of cryovials or other laboratory tools without compromising dexterity.

Usage Tips:

Gloves should cover wrists and part of the forearm for complete protection.
Inspect gloves regularly for wear, tear, or moisture and replace as needed.

Cryogenic Apron

Cryogenic aprons are essential protective gear during ultra-low temperature operations, especially when handling large volumes of liquid nitrogen or transferring samples.

Key Features:

Splash Protection: Prevent accidental splashes of liquid nitrogen onto the body, reducing the risk of frostbite.
Anti-Permeation: Special materials resist liquid nitrogen penetration, keeping the body dry and warm.
Core Body Protection: Provides targeted protection for vulnerable areas such as the chest, abdomen, and waist.

Usage Tips:

Always wear during pouring, transferring, or handling liquid nitrogen.
Combine with cryogenic gloves and safety goggles for full-body protection.
Select apron size suitable for lab work and body size to avoid restricted movement.

How to choose cryogenic gloves suitable for the laboratory?

Different experimental scenarios have different protection requirements for tempshield cryogenic gloves. It is recommended to pay attention to the following factors when purchasing:

Whether the temperature resistance range (-20°C / -80°C / -196°C) meets the experimental needs.
Whether it is waterproof and impermeable, suitable for liquid nitrogen operation.
Whether the cold storage gloves length (short/medium-long/long) meet the operation depth.
Comfort and flexibility, avoid cryogenic safety gloves that are too hard and cause inconvenience in grasping.

For example, it is recommended to use long cryogenic gloves when handling liquid nitrogen tanks, and the protection range covers the forearm; while for daily -80°C refrigerator operation, you can choose medium-long gloves for dry ice handling.

Industry Trends

With the rapid development of life sciences, stem cell research, and precision medicine, cell cryopreservation is evolving toward greater automation, efficiency, and standardization. Key future trends include:

1. Automated Cryopreservation Systems
Traditional freezing relies heavily on manual operation, which can introduce variability and errors. Automated systems—including robotic aliquoting, programmed cooling, and automated liquid nitrogen transfer—are increasingly adopted to improve consistency, efficiency, and reliability of sample handling.

2. Intelligent Sample Tracking
Accurate sample management is critical for reproducible research outcomes. Future approaches use barcodes, RFID chips, and Laboratory Information Management Systems (LIMS) to track samples throughout collection, freezing, transport, and thawing, ensuring full traceability and data integrity.

3. High-Throughput Biobanks
Growing demand for large-scale biological samples drives the development of high-throughput, standardized biobanks. Integrated with automated storage devices, intelligent management software, and environmental monitoring, these biobanks enable efficient storage, retrieval, and management of massive sample collections, supporting research and clinical applications.

4. Environmental and Safety Optimization
Safety and environmental considerations in cryopreservation are increasingly emphasized. Future improvements include eco-friendly liquid nitrogen use, enhanced personal protective equipment (PPE) such as low-temperature gloves and aprons, and standardized operating procedures to minimize risks to both personnel and samples.

5. Innovative Cryoprotectants and Techniques
New cryoprotective agents and optimized freezing strategies continue to emerge, such as reducing DMSO toxicity, developing low-temperature stabilizing protein additives, and improving rapid freezing and thawing methods. These innovations enhance post-thaw cell survival and preserve cell function.

Summary

Cell cryopreservation is not merely a technical procedure; it is a comprehensive system encompassing consumable selection, standardized workflows, safety protocols, and information management. Only by combining high-quality consumables, rigorous standard operating procedures, proper safety protection, and intelligent management can long-term sample stability and post-thaw functionality be ensured. This integrated approach provides a reliable foundation for scientific research, stem cell therapies, and biobank development.