A Guide to Low-Temperature Storage of Biological Samples: How to Choose Safe and Reliable Freezing Bags?

 

In the fields of biotechnology, medical research, and cell therapy, freezing bags serve as the core tool for low-temperature preservation of biological samples. Their material properties, safety, and functionality directly impact the activity and stability of samples. The following are key information and selection suggestions regarding freezing bags:

 

I. Material and Process Characteristics

Freezing bags need to maintain flexibility and sealing performance in ultra-low temperature environments (e.g., -196°C). Currently, the mainstream manufacturing materials include:

1. Ethylene-vinyl acetate (EVA): It has excellent low-temperature resistance and is suitable for long-term storage of biological samples such as cells and tissues. Its low water permeability and shock-absorbing buffer design can effectively prevent sample damage during the freeze-thaw process.

2. Polyolefin-EVA hybrid material: Combining the high strength of polyolefin and the flexibility of EVA, it can maintain structural integrity at extremely low temperatures and is commonly used for samples that require frequent transfer or transportation.

3. Food-grade polyethylene (PE): Some freezing bags are made of high-purity PE material, meeting the safety standards of being free from harmful substances such as phthalates and bisphenol A (BPA), and are suitable for clinical-grade sample storage.

During the production process, high-end freezing bags are usually custom-processed in a Class C+A clean environment to ensure no microbial contamination, and their sealing performance and durability are verified through a strict quality control system.

 

II. Application Scenarios and Functional Design

1. Cell therapy and regenerative medicine: Freezing bags are widely used for the preservation of therapeutic cells such as CAR-T cells and hematopoietic progenitor cells (HPC). For example, bag types supporting an integrated filling tube design can simplify the cell filling process and reduce the risk of contamination.

2. Biological agent transportation: Through the design of membrane ports and label pockets, freezing bags can enable rapid sample identification and leak-proof transfer, meeting the needs of cross-regional transportation.

3. Construction of scientific research sample libraries: According to different capacity requirements, freezing bags are available in specifications ranging from 50 mL to 750 mL, supporting the classified storage of large-scale samples.

 

III. Core Purchase Points

1. Safety certification: Prioritize products that have passed biocompatibility tests and meet medical-grade standards to avoid the impact of material leachates on sample activity.

2. Sealing performance: Check the bag mouth sealing technology (such as heat sealing or compression bonding process) to ensure no liquid leakage or gas exchange during long-term low-temperature storage.

3. Freeze and shock resistance: In liquid nitrogen or ultra-low temperature freezers, the bag body needs to withstand repeated freeze-thaw impacts to avoid sample loss caused by rupture.

4. Convenience design: Some freezing bags are equipped with pre-installed tubes or label areas, which can improve experimental operation efficiency and reduce human errors.

 

IV. Usage Precautions

- Pretreatment: Some freezing bags need to be pre-cooled or degassed according to the sample type to optimize the storage effect.

- Filling volume: It is recommended to leave 10%-20% of the space to prevent the bag from bursting due to sample expansion.

- Restrictions on reuse: Although some freezing bags can be reused with caution, single-use products are recommended for clinical-grade operations to avoid the risk of cross-contamination.

In today's era of rapid development in biomedicine, the technological innovation of freezing bags continues to promote the safety and convenience of sample storage. Through scientific selection and standardized operation, the activity of biological samples and the reliability of research data can be maximally ensured.