Mechanisms, Applications, and Future Directions

Cryopreservation is a cornerstone technology in modern biotechnology, regenerative medicine, and cell therapy, enabling the preservation of cells, tissues, and other biological materials by freezing and storage at ultra-low temperatures, ranging from −80 °C to below −130 °C depending on the intended duration and application.  

 Rather than relying on a single compound, effective cryopreservation typically depends on carefully designed formulations that combine different classes of cryoprotective agents to mitigate the physical and osmotic stress associated with freezing and thawing.

Among these, dextran has played an important role as an extracellular cryoprotectant. By remaining outside of the cell, dextran supports cell survival during freezing and thawing through mitigation of the extracellular environment, contributing to reduced ice-related damage and osmotic stress

Cryopreservation: A Brief Scientific Context

To understand the role of dextran in cryopreservation, it is useful to first consider the fundamental challenges associated with freezing biological systems.

The primary challenge in cryopreservation arises not from the storage temperature itself, but during cooling and thawing through intermediate subzero — approximately between −15 °C and −60 °C — where ice crystal formation, recrystallisation and osmotic stress are most damaging.

As extracellular ice forms, the concentration of solutes in the unfrozen fraction increases, creating osmotic pressure that drives water out of cells. If cooling occurs too rapidly, insufficient water can leave the cell, leading to intracellular ice formation, which is often lethal. Conversely, if cooling is too slow, excessive dehydration and high intracellular solute concentrations can also damage cellular structures.

Cryoprotective agents are therefore used to:

• Reduce ice crystal formation

• Moderate osmotic stress

• Stabilise cellular structures and extracellular environment

These principles underpin the distinction between different classes of cryoprotectants.

Intracellular vs. Extracellular Cryoprotectants

Intracellular Cryoprotectants

Intracellular cryoprotectants, such as dimethyl sulfoxide (DMSO) and glycerol, readily penetrate the cell membrane. Their primary role is to reduce ice formation inside the cell by lowering the amount of freezable water within the cell, thereby protecting intracellular structures during freezing and thawing.

Although highly effective, intracellular cryoprotectants can adversely affect cells in a concentration-, time-, and cell-type–dependent manner. In clinical and translational settings, concerns related to cytotoxicity and patient exposure have driven growing interest in reducing their concentration or complementing them with alternative cryoprotective strategies.

Extracellular Cryoprotectants

Extracellular cryoprotectants remain outside the cell and exert their protective effects by modifying the extracellular environment. Their function includes:

• Modifying ice crystal growth and morphology in the extracellular space

• Mitigating osmotic stress during freezing and thawing

• Increasing solution viscosity and glass-forming tendencies

• Providing physical support that helps preserve cellular and tissue integrity

Dextran belongs to this category and is widely used as an extracellular cryoprotectant, often in combination with intracellular agents to achieve effective cryoprotection while reducing reliance on high concentrations of permeating cryoprotectants.

The Role of Dextran in Cryopreservation

Dextran is a naturally derived polysaccharide known for its biocompatibility, water solubility, and well-established safety profile. When used in cryopreservation, dextran functions as an extracellular cryoprotectant, supporting cell survival during freezing and thawing while remaining outside the cell.

Its protective effects arise from several complementary mechanisms:

• Occupies physical space in the extracellular solution

• Reduces the amount of freely mobile water

• Limits how far and how fast molecules and ice crystals can move

• Limits the mobility of water molecules and solutes in the extracellular space

As a non-penetrating cryoprotectant, dextran exerts its protective effects by stabilising the extracellular environment. Depending on the cell type and application, dextran can be used alone or in combination with intracellular cryoprotectants, enabling effective cryoprotection while, where appropriate, reducing reliance on high concentrations of permeating agents.

This flexibility has contributed to dextran’s long-standing use in cryobiology.

Benefits and Possible Downsides

Benefits

• Enhanced Cell Viability: Dextran reduces ice-related damage during freezing and thawing, contributing to improved post-thaw cell viability crystal formation, which is crucial for maintaining cell viability during freezing and thawing.

• Biocompatibility: Dextran has a well-established safety profile and is widely tolerated in biomedical and clinical applications.

• Versatility: Dextran can be used in combination with other cryoprotectants to optimize preservation protocols for different cell types and tissues.

• Stability during freezing: It provides structural stability to cells, minimizing damage during the cryopreservation process.Dextran contributes to the physical stabilisation of cells during cryopreservation, helping to minimise damage associated with ice formation and osmotic stress.

Possible Downsides

• Concentration Sensitivity: The effectiveness of dextran as a cryoprotectant can vary depending on its concentration, requiring optimization for specific applications.

• Viscosity Considerations: At higher concentrations, dextran solutions can become viscous, potentially complicating handling and processing.

Use Cases of Dextran Cryopreservation

Dextran-based cryoprotectants have been used across a range of applications, including:

• Preservation of cells for regenerative medicine and cell therapy

• Tissue cryopreservation for downstream organoid generation

• Cryopreservation of complex cellular systems, including hematopoietic and immune cells

• Organ and tissue preservation solutions where extracellular stabilisation is critical

As cryopreservation continues to evolve, dextran remains a valuable component of multi-component cryoprotective systems, particularly where safety, biocompatibility, and extracellular protection are priorities.

Historical Use of Dextran in Cryopreservation

The use of dextran in cryopreservation traces back to the mid-20th century, arising soon after its introduction as a plasma volume expander in the 1940s.¹ Dextran’s biocompatibility, water solubility, and stabilising properties — first recognised in clinical volume-expanding therapies — made it an attractive candidate for early cryobiological studies focused on preserving tissues and complex cellular systems.1

Over time, dextran has been applied to:

• Preservation of cells for regenerative medicine and cell therapy

• Tissue cryopreservation for downstream organoid generation

• Stabilisation of proteins and vaccines during freezing and storage

• Organ preservation and transport solutions

Advances in polymer chemistry and analytical control have since enabled the development of dextran grades with defined molecular weights and substitution profiles, expanding their relevance in modern cryopreservation strategies.

Recent Developments & Innovation

Recent developments in cryopreservation increasingly focus on reducing reliance on high concentrations of intracellular cryoprotectants, particularly DMSO, while maintaining or improving post-thaw recovery and functional performance.

Although DMSO is highly effective at suppressing intracellular ice formation, its use can impair post-thaw viability and recovery, particularly at higher concentrations or with prolonged exposure. These effects may compromise cellular function and, in therapeutic settings, influence clinical performance.  In addition to these technical considerations, DMSO is also associated with clinically relevant safety concerns, with reported adverse events ranging from mild reactions to more severe outcomes, including cardiac arrest, respiratory complications, neurotoxicity, and epileptic seizures.2

As awareness of these cytotoxic and clinical risks continues to grow, one emerging strategy is the use of low–molecular weight dextran–based extracellular cryoprotectants, designed to provide effective extracellular protection while improving handling and flexibility.

PentaHibe® is an example of this next-generation approach. Built on a low–molecular weight dextran backbone, PentaHibe® functions as an extracellular cryoprotectant and is formulated to support cryopreservation with reduced or in some formulations, no DMSO.

By combining extracellular protection from dextran with optimised formulation design, such approaches enable:

• Reduced overall DMSO exposure

• Improved post-thaw cell recovery and functionality

• Enhanced suitability for translational and clinical workflows

Importantly, these innovations do not rely on new dextran-specific molecular pathways. Rather, they build on established cryobiological principles—including modulation of extracellular ice formation, osmotic buffering, and physical stabilisation of the extracellular environment.3,4,5 This formulation-driven approach supports the rational development of more robust, application-specific cryopreservation protocols.

Frequently Asked Questions (FAQ)

What is the primary role of dextran in cryopreservation?

 Dextran acts as a cryoprotectant, reducing ice crystal formation and osmotic shock during freezing and thawing, thereby preserving cell viability and functionality.

How does dextran compare to other cryoprotectants?

 Dextran is biocompatible and versatile, making it suitable for a wide range of applications. It can be used alone or in combination with other cryoprotectants to optimize preservation outcomes.

Are there any limitations to using dextran in cryopreservation?

The main limitations include the need for precise concentration optimization and potential cost considerations, especially for high-purity dextran.

Can dextran be used for all types of cells and tissues?

 While dextran is effective for many cell types and tissues, specific protocols may need to be developed to optimize its use for particular applications.

What are the recent trends in dextran cryopreservation research?

 Recent trends include exploring novel formulations, understanding the molecular mechanisms of dextran's protective effects, and developing personalized cryopreservation protocols for regenerative medicine and other advanced therapies.

In conclusion, dextran cryopreservation is a vital technique with broad applications across medicine, biotechnology, pharmaceuticals, and research. Its continued development and optimization hold significant promise for advancing the preservation of biological materials in various fields.

References:

1 - Litvan, H., Casas, J.I., Villar-Landeira, J.M. (1998). Volume Replacement Therapy with Dextrans: Are Dextrans Still Useful in Volume Replacement?. In: Baron, JF., Treib, J. (eds) Volume Replacement. Springer, Berlin, Heidelberg.

 2 -  Svalgaard JD et al. (2016). Transplantation and Cellular Engineering, Low Molecular Weight Carbohydrate Pentaisomaltose May Replace Dimethyl Sulfoxide As A Safer Cryoprotectant For Cryopreservation Of Peripheral Blood Stem Cells; Vol 56(5): 1088-1095

3 -  Mazur P. Freezing of living cells: mechanisms and implications. American Journal of Physiology. 1984 Sep;247(3 Pt 1):C125-42. PMID: 6383068.

4 - Memon, Kashan, Zhang, Bing, Fareed, Muhammad Azam and Zhao, Gang. "Encapsulation for efficient cryopreservation" Frigid Zone Medicine, vol. 5, no. 2, 2025, pp. 73-80. 

5 -  Cryopreservation – Wikipedia (Cryoprotectant overview) — Authoritative summary of cryoprotectant categories and mechanisms, establishing the conceptual basis for extracellular polymer effects such as ice modulation and osmotic control – last edited on 6 February 2026