A guide to successful mL to L scale vitrification and rewarming

Area of Science:

• Biomaterials Science
• Cryobiology
• Thermal Engineering

Background:

• Vitrification is key for cryopreserving cells, tissues, and organs by forming an ice-free glassy state.
• Major hurdles in vitrification include ice crystallization and thermal shock-induced cracking.
• Cryoprotective agents (CPAs) inhibit ice formation, with critical cooling rates (CCR) and critical warming rates (CWR) defining their efficacy.

Approach:

• Thermal modeling was used to analyze heat transfer in cylindrical geometries for common vitrification cocktails (VS55, DP6, M22).
• Calculated cooling/warming rates and temperature differences (deltaT) during convective and nanowarming were compared to critical thresholds.
• The study evaluated thermal stress and fracture potential using a simplified thermal shock equation.

Key Points:

• M22 demonstrated superior vitrification capability over VS55 and DP6 due to lower CCR and CWR across all volumes.
• Nanowarming (volumetric heating) resulted in smaller temperature differences and higher rates compared to convective (boundary) rewarming.
• Increasing biomaterial volume exacerbates challenges, particularly with convective rewarming, leading to higher failure rates.

Conclusions:

• The study provides a practical guide for vitrification success based on system size and cooling/warming conditions.
• Understanding thermal stresses and ice crystallization limits is crucial for scaling vitrification techniques.
• Optimizing rewarming methods, like nanowarming, is essential for preserving larger biomaterials.