Thawing Biological Samples in Advanced Therapies: Key Considerations for Preserving Cell Viability

The development of advanced therapies has transformed regenerative and oncological medicine over the past decade. Yet behind every therapeutic product lies a chain of processes that largely determines its clinical efficacy, and the thawing of biological samples is one of its most critical links. Unlike freezing, where parameters are highly controlled, thawing in advanced therapy settings still relies in many laboratories on manual, poorly standardized procedures. If not performed with the required rigor, the thawing process can irreversibly compromise cell viability and functionality.

Biological Sample Thawing Protocols in Advanced Therapies: Critical Process Variables

A robust cell thawing protocol must have at least four process variables under control and documentation, each identified as a determinant of final cell viability:

• Temperature: the 37 °C water bath is the most widely documented thawing method in clinical trials. The optimal warming rate is approximately 45 °C/min, enabling a rapid transition to ambient temperature while minimizing cell damage.
  
  
• Thawing rate: slow thawing increases the risk of recrystallization and prolongs cell exposure to high extracellular cryoprotectant concentrations, reducing viability. Rapid thawing is the recommended strategy.
  
  
• Cryoprotectant dilution: gradual DMSO removal through stepwise addition of pre-warmed culture medium is the standard approach to prevent osmotic shock and preserve post-thaw cell stability. This procedure has been shown to improve cell survival by at least 15%.
  
  
• Time to processing: must be kept to a minimum. In CAR T cell therapies, clinical guidelines establish that cells must be administered to the patient within 30–90 minutes of thawing, given the progressive cytotoxicity of DMSO at ambient temperature.
  
  

Standardization of these variables is the foundation of any rigorous biological process control system within the regulatory context of advanced therapies.

Thawing Methods for Cryopreserved Cells: Impact on Cell Viability and Functionality

Thawing methods used in research and advanced therapy manufacturing environments can be classified based on whether the process is controlled or manual:

• The 37 °C water bath has been the reference method for decades due to its simplicity and accessibility. However, it presents notable limitations: uneven temperature distribution within the vial, operator-introduced variability, and risk of contamination of the exterior of the cryogenic vial. While still valid in basic research settings, it is insufficient for processes governed by formal regulatory requirements.
  
  
• Controlled thawing systems (dry baths or electronically regulated temperature devices) offer reproducibility and traceability. Some are specifically designed for integration into regulated workflow environments, with automated temperature curve logging that facilitates procedure validation.
  
  

The joint optimization of the freezing and thawing phases has a synergistic effect on cell recovery: the combination of an appropriate cryoprotectant, a controlled warming rate, and a post-thaw-specific culture medium can significantly increase the viability and adhesion capacity of recovered cells.

Managing Cell Stress During Thawing: Risks and Control Strategies

Thawing-induced cell stress is a leading cause of viability and functionality loss that is not always captured by standard quality controls, with direct implications for the efficacy of the final therapeutic product.

The main mechanisms of cell damage are:

• Osmotic stress: caused by DMSO and abrupt changes in ionic concentration during the phase transition. Controlled cryoprotectant dilution is the primary mitigation strategy.
  
  
• Delayed apoptosis: cells that physically survive the thawing process may activate apoptotic pathways in the following hours. The use of apoptosis inhibitors during the first hours of post-thaw culture has shown positive results in certain cell types.
  
  
• Recrystallization damage: the formation of secondary ice crystals during slow or interrupted thawing is mechanically destructive. It is one of the strongest arguments in favor of rapid, continuous thawing processes.
  
  
• DMSO toxicity at ambient temperature: DMSO is cytotoxic above 4 °C under prolonged exposure. Once thawing begins, contact time must be minimized and transfer to culture medium carried out without delay.
  
  

Key good laboratory practices to mitigate these risks include pre-warming all media and reagents before starting the process, handling samples under controlled temperature conditions, and systematically documenting the parameters of each thawing run.

Handling Cryogenic Vials and Transferring to Operational Conditions After Thawing

Sample handling begins the moment the vial is removed from the storage system. The quality of prior custody conditions directly affects thawing outcomes. Proper biological sample management also includes verifying vial integrity, documenting time since retrieval, and using appropriate personal protective equipment.

Post-thaw transfer to operational conditions must follow a validated protocol encompassing centrifugation for cryoprotectant removal, resuspension in the appropriate medium, and viability assessment before continuing the process. In advanced therapies, this step is frequently a critical control point (CCP) requiring thorough documentation and predefined acceptance criteria.

Working with a provider that offers both thawing systems and prior sample custody under the same quality standard significantly simplifies this chain of responsibility.

At Bexen Bioservices, we offer comprehensive cold chain management solutions for advanced therapies, designed for processes that require reproducibility, traceability, and compatibility with regulated environments. Our product range includes thawing systems for vials and bags, biopreservation media, cell thawing media, and solutions for cell processing and maintenance. We also operate a network of four biorepositories that ensures optimal sample custody conditions until the moment of use.

Contact our team and let us help you define the right solution for your process.

References

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Browne DJ, Miller CM, Doolan DL. Technical pitfalls when collecting, cryopreserving, thawing, and stimulating human T-cells. Front Immunol. 2024 May 15;15:1382192. doi: 10.3389/fimmu.2024.1382192. 

Gostage J, Domingo-Lopez DA, Tarpey R, Duffy GP, Levey RE. From cold chain to ambient: Benefits, risks, and evidence across cell therapy logistics. Mol Ther Methods Clin Dev. 2025 Oct 11;33(4):101613. doi: 10.1016/j.omtm.2025.101613. 

Li R, Johnson R, Yu G, McKenna DH, Hubel A. Preservation of cell-based immunotherapies for clinical trials. Cytotherapy. 2019 Sep;21(9):943-957. doi: 10.1016/j.jcyt.2019.07.004. 

Uhrig M, Ezquer F, Ezquer M. Improving Cell Recovery: Freezing and Thawing Optimization of Induced Pluripotent Stem Cells. Cells. 2022 Feb 24;11(5):799. doi: 10.3390/cells11050799.