Nanocrystalline cerium dioxide reduces recrystallization in cryopreservation solutions

Nanocrystalline cerium dioxide is able to protect living cells from oxidative stress under the influence of various stress factors, in particular under the one of low temperatures. This study investigates the phase-structural transformations in aqueous solutions containing CeO₂ nanoparticles (NPs) and their impact on the cryopreservation process. Differential scanning calorimetry and thermomechanical analysis were used to analyse the phase transitions in aqueous suspensions of CeO₂ NPs and aqueous solutions of the cryoprotectant dimethyl sulfoxide (Me₂SO) with CeO₂ NPs. Various concentrations of CeO₂ NPs were tested to observe their effects on the crystallization and melting behaviours. The addition of CeO₂ NPs significantly altered the temperatures and enthalpies of melting and crystallization in water. Low concentrations of CeO₂ NPs promoted crystallization, while higher concentrations inhibited it, reducing supercooling and recrystallization during thawing. In Me₂SO solutions, CeO₂ NPs raised the glass transition temperature and affected the recrystallization process, with higher concentrations leading to more pronounced vitrification and reduced recrystallization. We also investigated the regularities of the effect of CeO₂ NPs on phase transitions in combined cryoprotective media with Ham's F12, fetal bovine serum and Me₂SO, which can be used in future to design the cryopreservation protocols. In the complex media, CeO₂ NPs decreased the metastability and altered eutectic crystallization patterns, indicating potential cryoprotective effects. In conclusion, CeO₂ NPs modulate the thermophysical properties of cryoprotective solutions, enhancing vitrification and reducing recrystallization, which could improve cryopreservation efficiency. Optimizing NP concentrations is crucial for practical applications in cryopreservation.