Influence of polyvinyl alcohol on the non-equilibrium phase and state transition behaviors of trehalose solutions

BACKGROUND: Cryopreservation and freeze-drying are commonly-used techniques for the longterm preservation of liable biological materials. The understanding of the non-equilibrium phase transition behavior of cryoprotectant solutions is crucial for optimizing preservation protocols with the precise control of phase transition behaviors. OBJECTIVE: To investigated the effect of polyvinyl alcohol (PVA) on the phase transition dynamics of trehalose solutions, particularly the cooling rate effect on crystallization. MATERIALS AND METHODS: Differential scanning calorimetry (DSC) was used to examine real-time crystallization behavior during cooling of trehalose-PVA solutions as temperature-dependent and time-resolved thermal transitions. Trehalose concentration varied from 0 to 0.8 M, and cooling rates from 1 to 20°C/min. The effect of PVA molecular weight on crystallization kinetics was also analyzed. RESULTS: The increasing of trehalose concentration accelerates and enhances crystallization. Higher cooling rates promote earlier crystallization and lead to sharper exothermic peaks. PVA molecular weight also alters the crystallization process, and crystallization is inhibited by large PVA molecules. The complex interaction between cooling rate and PVA molecular weight influences crystallization kinetics and amorphous stability. CONCLUSION: These findings provide valuable insights into the stabilization mechanisms of cryoprotectant formulations and have important implications for improving cryopreservation and lyophilization protocols.